Long-term colonization of the solar system with 290,000 square feet per person

A 5 km settlement radius corresponds roughly to the sweet design spot where earthlike radiation shielding is produced for free by the required structural mass. The paper is by Pekka Janhunen.

Overall, the settlement concept satisfies the following generic requirements for long-term large-scale settling of the solar system:

1. 1g artificial gravity, earthlike atmosphere, earthlike radiation protection.
2. Large enough size so that internals of the settlement exceed a person’s lifetime-integrated capacity to explore.
3. Standard of living reminiscent to contemporary royal families on Earth, quantified by up to 25,000 m2 of urban living area and 2000 m2 of rural area per inhabitant (290,000 square feet per person).
4. Access to other settlements and Earth by spacecraft docking ports, using safe arrival and departure procedures that do not require impulsive chemical propulsion.

In particular, the proposed lighting geometry enables a long-term reliable architecture, i.e., a design that does not include large moving parts, is free of single failure points and exhibits passively stable rotation.

As a future refinement of the concept, one could consider more general orbits than 1 au circular, and a range of settlement sizes could be analyzed.

This cylindrical space settlement concept has sunlight is concentrated by cylindrical
paraboloid concentrators and reflected by semi-toroidal and conical reflectors and controlled by local blinders to simulate earthlike diurnal and seasonal illumination cycles. The rural wall living cylinder is divided into 20 (for example) z-directed valleys which are in different phases of the light cycles. No moving parts are needed other than numerous and easily accessible local blinders that regulate light input into the valleys. The settlement rotates as a rigid body and the mass distribution is such that the rotation is passively stable.

The geometry has natural spare volume at the equator where one can add multi-storey urban blocks without reducing the rural area. Adjacent to the urban blocks there is natural place where to install a zone of solar panels without reducing the amount of gathered light.

The inhabitant population is limited by the ability of the closed ecosystem of the sunlit rural areas to produce food. The naturally buildable total urban floorspace are

In conclusion, a requirement for settling the solar system in a large scale is that the habitats must be longterm reliable and they should provide a high standard of living compared to Earth. In the light of our analysis, the goals seem possible to reach, without essentially increasing the total mass consumption per inhabitant beyond what is required by radiation protection in any case.

Cylindrical kilometer-scale artificial gravity space settlements were proposed by Gerard O’Neill in the 1970s. The early concept had two oppositely rotating cylinders and moving mirrors to simulate the diurnal cycle. Later, the Kalpana One concept exhibited passively stable rotation and no large moving parts. Here Pekka Janhunen and others propose and analyze a specific light transfer solution for Kalpana One type settlements. Their proposed solution is technically reliable because it avoids large moving parts that could be single failure points. The scheme has an array of cylindrical paraboloid concentrators in the outer wall and semi-toroidal reflectors at the equator which distribute the concentrated sunlight onto the living surface. The living cylinder is divided into a number of ϕ-sections (valleys) that are in different phases of the diurnal and seasonal cycles. To reduce the mass of nitrogen needed, a shallow atmosphere is used which is contained by a pressure-tight transparent roof. The only moving parts needed are local blinders installed below the roof of each valley. they also find that settlements of this class have a natural location at the equator where one can build multi-storey urban blocks. The location is optimal from the mass distribution (rotational stability) point of view. If maximally built, the amount of urban floorspace per person becomes large, up to 25,000 m2 , which is an order of magnitude larger than the food-producing rural biosphere area per person. Large urban floorspace area per person may increase the material standard of living much beyond Earth while increasing the total mass per person relatively little.

The NSS Space Settlement Journal is a peer-reviewed, open access journal which may be found at http://space.nss.org/national-space-society-space-settlement-journal/

323 thoughts on “Long-term colonization of the solar system with 290,000 square feet per person”

  1. Space exploration is for robots not for humans Why a man should be interested in go live in a moon of Jupiter?

  2. Why noh really , why on Earth should someone be interested to live on the Moon? There are quite a few interesting places on Earth. Space “exploration” is for robots not for hmans

  3. I don’t like how the roof is only 50 m from the floor. That is shorter than a lot of normal trees. I mean it would be fine and liveable, but if we want luxury living “Standard of living reminiscent to contemporary royal families on Earth, quantified by up to 25,000 m2 of urban living area and 2000 m2 of rural area per inhabitant ” then a low ceiling and no big trees seems to be starting off on the wrong foot. Especially if you want birds and things living there. Now cranking it up to say 250 m of ceiling height only requires another (2000 sq.m x 200 m x 1.3 equals 520 tonnes of air/capita). Whereas the walls (errr.. floor) are supposed to be 10 tonnes/sq.m x 2000 sq.m equals 20 000 tonnes. So the extra air is trivial. I suspect they haven’t seen the work on atmospheric scoops that means that getting oxygen and nitrogen to earth orbit might be even easier and cheaper than asteroid material.

  4. Maybe our nuclear scientists can leap in here, but if you are relying on the structural mass of your construction to provide radiation shielding, then will the material properties of your structure be weakened by radiation, the way it happens in reactors?

  5. Nice revisiting of the High Frontier, with slightly less ambitious objectives (no full O’Neill cylinder, but close) and probably far more updated requirement calculations. Nevertheless, this still suffers from the same problem: who’t gonna pay for this in the beginning? My hope is that we can make a viable case for space settlement in orbit with far less ambitious plans. Like some labs and commercial facilities using rotational gravity in LEO, protected from radiation by Earth’s magnetosphere, for showing it can be done profitably. Having access to both gravity and weightlessness in a same factory/building ought to have some commercial value. If does for human habitation, so probably some orbital enterprise requiring human presence for some long periods will be the first one of giving a healthier environment to its employees. Or a space hotel, catering to tourists looking for a exotic getaway but without relinquishing all the comforts of Earthly life. But from that to this, there is a long road.

  6. I love the thinking behind this. What primarily drove European colonization of the Americas wasn’t a desire to explore but the opportunity to have a much higher standard of living than could be expected in Europe. Being able to offer that in off-world settlements will be key to driving migration. We too often get caught up in what would be the minimum viable option to enable settlements, but who wants to live at a minimal standard of living?

  7. Space exploration is for robots not for humans Why a man should be interested in go live in a moon of Jupiter?

  8. Why noh really why on Earth should someone be interested to live on the Moon? There are quite a few interesting places on Earth. Space exploration”” is for robots not for hmans”””

  9. I don’t like how the roof is only 50 m from the floor. That is shorter than a lot of normal trees.I mean it would be fine and liveable but if we want luxury living Standard of living reminiscent to contemporary royal families on Earth” quantified by up to 25″000 m2 of urban living area and 2000 m2 of rural area per inhabitant “” then a low ceiling and no big trees seems to be starting off on the wrong foot. Especially if you want birds and things living there.Now cranking it up to say 250 m of ceiling height only requires another (2000 sq.m x 200 m x 1.3 equals 520 tonnes of air/capita).Whereas the walls (errr.. floor) are supposed to be 10 tonnes/sq.m x 2000 sq.m equals 20 000 tonnes. So the extra air is trivial.I suspect they haven’t seen the work on atmospheric scoops that means that getting oxygen and nitrogen to earth orbit might be even easier and cheaper than asteroid material.”””

  10. Maybe our nuclear scientists can leap in here but if you are relying on the structural mass of your construction to provide radiation shielding then will the material properties of your structure be weakened by radiation the way it happens in reactors?

  11. Nice revisiting of the High Frontier with slightly less ambitious objectives (no full O’Neill cylinder but close) and probably far more updated requirement calculations.Nevertheless this still suffers from the same problem: who’t gonna pay for this in the beginning?My hope is that we can make a viable case for space settlement in orbit with far less ambitious plans. Like some labs and commercial facilities using rotational gravity in LEO protected from radiation by Earth’s magnetosphere for showing it can be done profitably. Having access to both gravity and weightlessness in a same factory/building ought to have some commercial value.If does for human habitation so probably some orbital enterprise requiring human presence for some long periods will be the first one of giving a healthier environment to its employees. Or a space hotel catering to tourists looking for a exotic getaway but without relinquishing all the comforts of Earthly life.But from that to this there is a long road.

  12. I love the thinking behind this. What primarily drove European colonization of the Americas wasn’t a desire to explore but the opportunity to have a much higher standard of living than could be expected in Europe. Being able to offer that in off-world settlements will be key to driving migration. We too often get caught up in what would be the minimum viable option to enable settlements but who wants to live at a minimal standard of living?

  13. It’s been a while since I ran any structural calculations on a O’Neil colony design, (Used to be a member of the L-5 society in college.) but, just off hand, a 5 km radius doesn’t sound crazy. Just running a quick calculation, if the structure were a silica fiber hoop 2m thick, you’d be looking at a 106MPa load. Not running the numbers for the air and everything, just the hoop. Since E glass has a tensile strength about thirty times that, the whole thing looks very feasible, just needs a lot of silica.

  14. As Jean Baptiste opines, its just too bad it’d cost so much. Per person. Living in a giant city sized cylinder (hey… if you think of an amount of land of just a flat patch of dirt 10 km in diameter… πr² = 3.14 × 5,000² → 78,000,000 m² or 7800 hectarea … per “level”. San Francisco is about 12,000 hectares. New York City about 75,000 hectares. So yah, these things as imagined are huge. But given that they’re not built on dirt just sitting there, on rivers not passing by, with air encircling the globe “for free”, and contained by gravity “for free” instead of drifting into deep space, the technological hurdles to overcome for a small city-in-space construction that needs to be nearly-perfectly-leak-free … Is HUGE. And “huge” near-always means “hugely expensive”. And that’s the problem. Time to reactivate that file — the Science Fiction file. This falls squarely into it. Just saying, GoatGuy

  15. I think the sentiment “it is much slower in space than a nuclear reactor” is actually the right factual answer. Humans do poorly at more than 1 REM per year, total absorbed radiation. What’s that, https:\en.[i]Wikipedia[/i].orgwikiSievert well, the Wikipedia (change backslashes to slashes) sez [i]NASA[/i] limits astronauts to 1 Sv over their entire career. By comparison, the neutron / gamma environment of a LPR reactor, at the containment wall, in operation, at 3 GW thermal is about 1 Sv per µs. And in interplanetary space, cosmic radiation flux is about 1 Sv/year. So… 60 sec × 60 min × 24 hr × 365.25 day / (1 ÷ 1,000,000) sec → 31 TRILLION times less radiation. Just saying. If enbrittlement happens in reactor-years, 31 trillion of them is quite a bit longer. Than I intend to live. LOL GoatGuy ( I could be off by a factor of a million … or ten … and it’d still be usefully instructive.)

  16. Generally we’re on the same page. 5 km radius to deliver 8 m/s² (N/kg) AT the rim of centripetal force rotates at 0.38 RPM → 23 revolutions per hour. Modeled (my design option) as a centripetal ring delivering ±10% of that 8 m/s² force, the radial range is 4,000 to 6,000 m; this of course just memorializes that F = ω²r or rotational rate squared times radius. Radius is linear related to centripetal force for fixed omega; I have a pretty detailed model for this (physics / structurally), but I have to say… in the end to me it seemed like 5 km radius is quite a bit larger than might reasonably be practical — even with nearly magical super strong low mass materials. For instance, figuring 150 MPa “section tether” tensile strength, with both radial and axial tension methods to handle the centripetal force of the whole contraption, at 1,250 m radius, the 150 radial spokes would each have diameters of 8 m² per. At 5,000 m radius, the 600 spokes would each need 120 m² area. The centripetal forces are prodigious: 1.1×10¹³ N … just of the outer rim attempting to fly away. Now granted, “my design” for a 10 km diameter job has an outer ring twice as “wide” as it is thick. 4000 m wide, 2000 m thick. 5,000 m radius. 23 RPH. 7.2 to 8.8 m/s² centripetal force. 10 kg/m³ mean density. 125,000,000,000 m³ total volume in ring. 1.2 billion tons. Room for 6,000,000 people, each having about 5,000 m³ of “volume share”. All in … Then you sit back with a nice Extra Special Bitter and watch the pipe smoke swirl about, and think, “Dâhmn! This is ridiculous!” Just saying, GoatGuy

  17. I did a quick search, and apparently metals and ceramics are fairly safe for long term use, centuries, in normal space radiation environments. Silica fiber is particularly good. OTOH, polymers don’t handle it so well. You’d probably want to avoid the use of polymers on the outside of the habitat, though they’d likely be ok for use inside.

  18. You’d have trouble fitting a Sequoia under a 50 meter roof. But a Sequoia would concentrate enough weight in one place to cause structural concerns anyway. A bit of quick research suggests at 250m of ceiling height would be serious overkill, 120 meters would do fine, it would only be needed if you were deliberately choosing unusually tall tree species.

  19. Ok, looking at it further, this does NOT look like a natural shape for a pressurized compartment. You could, of course, maintain a pressurized volume in this shape with enough internal stays. Approximately one 18mm Spectra rope per square meter would do the trick, but they wouldn’t have to be one to a square meter, you could space them at wider intervals if they were thicker, and distribute the load towards the end. But they don’t seem to envision living in a forest of ropes, and a quick scan didn’t turn up any mention of internal stays. However, the talk of reducing structural requirements by a shallow atmosphere only makes sense if the load from the roof is transferred to the floor. Further, the stays would contribute about 200 grams of mass per cubic meter of interior. OK, the air would be 6 times that, so you might indeed save weight by doing it this way. Structurally it looks like a feasible design, just with key details omitted. I really don’t like the lighting scheme, though.

  20. That just means it happens slower. Tensile structural materials are inherently vulnerable to radiation damage, and you’d want a habitat’s structure to last for centuries. How long is Spectra loaded to maybe 20% of it’s yield strength good for under typical radiation levels in space?

  21. up to 25,000 m2 of urban living area and 2000 m2 of rural area per inhabitant ” Are you sure you didn’t get those numbers swapped? Because I used to live in the country, and 2000 square meters would have fit in my front yard with room to spare, it’s a tiny space by rural standards,

  22. This is why I say the colonization of space on any significant scale demands that we develop Von Neumann machines. The per capita infrastructure requirements are just crazy.But if you get your factories self-reproducing and you don’t have enough factories you just give them a few more generations to double.

  23. Who says unmaintained? There’s a big difference between maintaining systems and maintaining a hull that’s in tension. You build a building you expect to reshingle the roof periodically but the foundation better be good for the life of the building.For an O’Neil colony the structural component of the hull is the foundation it’s very difficult to design one where you can replace that bit by bit.

  24. It’s been a while since I ran any structural calculations on a O’Neil colony design (Used to be a member of the L-5 society in college.) but just off hand a 5 km radius doesn’t sound crazy.Just running a quick calculation if the structure were a silica fiber hoop 2m thick you’d be looking at a 106MPa load. Not running the numbers for the air and everything just the hoop. Since E glass has a tensile strength about thirty times that the whole thing looks very feasible just needs a lot of silica.

  25. As Jean Baptiste opines its just too bad it’d cost so much. Per person. Living in a giant city sized cylinder (hey… if you think of an amount of land of just a flat patch of dirt 10 km in diameter… πr² = 3.14 × 5000² → 78000000 m² or 7800 hectarea … per level””. San Francisco is about 12″”000 hectares. New York City about 75000 hectares. So yah these things as imagined are huge. But given that they’re not built on dirt just sitting there on rivers not passing by”” with air encircling the globe “”””for free”””””””” and contained by gravity “”””for free”””” instead of drifting into deep space”””” the technological hurdles to overcome for a small city-in-space construction that needs to be nearly-perfectly-leak-free … Is HUGE.And “”””huge”””” near-always means “”””hugely expensive””””. And that’s the problem.Time to reactivate that file — the Science Fiction file. This falls squarely into it.Just saying””””GoatGuy”””””””

  26. I think the sentiment it is much slower in space than a nuclear reactor”” is actually the right factual answer. Humans do poorly at more than 1 REM per year”” total absorbed radiation. What’s that https:\\en.[i]Wikipedia[/i].org\wiki\Sievert well the Wikipedia (change backslashes to slashes) sez [i]NASA[/i] limits astronauts to 1 Sv over their entire career. By comparison the neutron / gamma environment of a LPR reactor at the containment wall in operation at 3 GW thermal is about 1 Sv per µs. And in interplanetary space cosmic radiation flux is about 1 Sv/year. So…60 sec × 60 min × 24 hr × 365.25 day / (1 ÷ 10000) sec → 31 TRILLION times less radiation. Just saying.If enbrittlement happens in reactor-years”” 31 trillion of them is quite a bit longer.Than I intend to live. LOLGoatGuy( I could be off by a factor of a million … or ten … and it’d still be usefully instructive.)”””””””

  27. Generally we’re on the same page.5 km radius to deliver 8 m/s² (N/kg) AT the rim of centripetal force rotates at 0.38 RPM → 23 revolutions per hour. Modeled (my design option) as a centripetal ring delivering ±10{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} of that 8 m/s² force the radial range is 4000 to 6000 m; this of course just memorializes that F = ω²r or rotational rate squared times radius. Radius is linear related to centripetal force for fixed omega; I have a pretty detailed model for this (physics / structurally) but I have to say… in the end to me it seemed like 5 km radius is quite a bit larger than might reasonably be practical — even with nearly magical super strong low mass materials. For instance figuring 150 MPa section tether”” tensile strength”” with both radial and axial tension methods to handle the centripetal force of the whole contraption at 1250 m radius the 150 radial spokes would each have diameters of 8 m² per. At 5000 m radius the 600 spokes would each need 120 m² area. The centripetal forces are prodigious: 1.1×10¹³ N … just of the outer rim attempting to fly away. Now granted”” “”””my design”””” for a 10 km diameter job has an outer ring twice as “”””wide”””” as it is thick. 4000 m wide”” 2000 m thick. 5000 m radius. 23 RPH. 7.2 to 8.8 m/s² centripetal force. 10 kg/m³ mean density. 12500000 m³ total volume in ring. 1.2 billion tons. Room for 60000 people each having about 5″”000 m³ of “”””volume share””””. All in … Then you sit back with a nice Extra Special Bitter and watch the pipe smoke swirl about”” and think”” “”””Dâhmn! This is ridiculous!”””” Just saying”””” GoatGuy”””””””

  28. I did a quick search and apparently metals and ceramics are fairly safe for long term use centuries in normal space radiation environments. Silica fiber is particularly good. OTOH polymers don’t handle it so well. You’d probably want to avoid the use of polymers on the outside of the habitat though they’d likely be ok for use inside.

  29. You’d have trouble fitting a Sequoia under a 50 meter roof. But a Sequoia would concentrate enough weight in one place to cause structural concerns anyway. A bit of quick research suggests at 250m of ceiling height would be serious overkill 120 meters would do fine it would only be needed if you were deliberately choosing unusually tall tree species.

  30. Ok looking at it further this does NOT look like a natural shape for a pressurized compartment. You could of course maintain a pressurized volume in this shape with enough internal stays. Approximately one 18mm Spectra rope per square meter would do the trick but they wouldn’t have to be one to a square meter you could space them at wider intervals if they were thicker and distribute the load towards the end.But they don’t seem to envision living in a forest of ropes and a quick scan didn’t turn up any mention of internal stays. However the talk of reducing structural requirements by a shallow atmosphere only makes sense if the load from the roof is transferred to the floor.Further the stays would contribute about 200 grams of mass per cubic meter of interior. OK the air would be 6 times that so you might indeed save weight by doing it this way.Structurally it looks like a feasible design just with key details omitted. I really don’t like the lighting scheme though.

  31. up to 25″000 m2 of urban living area and 2000 m2 of rural area per inhabitant “”Are you sure you didn’t get those numbers swapped? Because I used to live in the country”” and 2000 square meters would have fit in my front yard with room to spare it’s a tiny space by rural standards”

  32. And if GoatGuy’s math is correct to with in an order of magnitude, it’s a total non-issue, as my impression from read about the topic had been.

  33. I solved the problem of finding a chapter of the L-5 society at Michigan Tech by founding one. It was tense problem, but I got past it. The near Earth diurnal light cycle was, explicitly. achieved by putting Venetian blinds on a 24 hour timer… The colony is pointed towards the Sun so that the light doesn’t vary with its rotation. Personally, I prefer LED lighting, it can be tuned to optimize photosynthetic efficiency, and reduce waste heat, the bane of all space colonies, and you don’t need large transparent panels, also a bit of a problem. Mind, you could filter the light at a mirror to the same end, and focus it in vacuum into some pretty narrow light pipes, so maybe LEDs aren’t the way to go. But a colony with a circumference of 31km and a roof that’s only 50-100 meters up can just rotate the mirror to move “day” around the colony on a schedule that is unconnected to the main rotation rate. If your atmosphere is only 50-100 meters thick, and maintained by a roof that’s structurally connected to the floor, it’s comparatively easy to partition the colony space into lots and lots of individual bubbles all resting on the tension hoop base, if this is seen as necessary.

  34. I failed to “socially connect” (can engineer-types socially connect?) with UCBerkeley’s L–5 society chapter. Then again, its not clear that it had one in the mid 1970s. We were still trying to avoid the brontosaurs that infested the campus. One very old idea I’ve fostered — and remain attached to — is the idea of a non-cylinder design. Cylinders penalize all kinds of ordinary happens chance. They’re integral — and sure, they’re going to have hermetic isolation doors aplenty — but leaks are leaks for the (w)hole section. Mass movement isn’t such a penalty as the things get larger: proportionately the structure is growing in total terapascal budget, and relatively each moving mass is smaller compared to the whole. By cylinders also penalize non-uniformity: by definition they’re masses concentrated around a hub as a torus. And not any-old torus, but one that at least in part is semi-circular in cross section. To deal with air pressure. Over a LARGE area. The non-cylinder / torus idea I’ve had is to utilize tethers-and-blobs at the end of them. Visualize a really big condom quarter filled with 20 kg of mercury. What’s it going to look like, suspended from the ceiling? Blob at the bottom, teardrop shaped, suspended by a long, thin strand of condom rubber. If it holds. LOL. Yet, taken as the unit-of-fabrication of a space station, around a central hub of most any length, one could “string out” blobs-on-tethers co-rotating on the axis, in tension. There are a lot of cocktail napkin issues to address: they really cannot be untethered from each other because even small changes in inertial mass distribution would result in their rotational rate changing, then bumping into each other. And “bumping is bad”, so to say. But “tethers are cheap” too. So establishing a fixed inter-blob distance around the perimeter doesn’t sound all that hard in practice. Moreover, having them isolated like little seed pods of a dandelion also divides-and-conquors the w

  35. I really shouldn’t have said that, now I can’t stop thinking about how to do just that. One of the downsides of being an engineer, I guess.

  36. The numbers look good for steel and ceramics, but you wouldn’t want to use polymers for your O’Neil colony hull. And, of course, you have to consider the tensile loading, it’s going to aggravate the damage.

  37. This is why I say the colonization of space on any significant scale demands that we develop Von Neumann machines. The per capita infrastructure requirements are just crazy. But if you get your factories self-reproducing, and you don’t have enough factories, you just give them a few more generations to double.

  38. Who says unmaintained? There’s a big difference between maintaining systems, and maintaining a hull that’s in tension. You build a building, you expect to reshingle the roof periodically, but the foundation better be good for the life of the building. For an O’Neil colony, the structural component of the hull is the foundation, it’s very difficult to design one where you can replace that bit by bit.

  39. And if GoatGuy’s math is correct to with in an order of magnitude it’s a total non-issue as my impression from read about the topic had been.

  40. Here is the link to the 13 page paperhttp://space.nss.org/media/NSS-JOURNAL-Natural-Illumination-for-Rotating-Space-Settlements.pdf

  41. I solved the problem of finding a chapter of the L-5 society at Michigan Tech by founding one. It was tense problem but I got past it.The near Earth diurnal light cycle was explicitly. achieved by putting Venetian blinds on a 24 hour timer… The colony is pointed towards the Sun so that the light doesn’t vary with its rotation. Personally I prefer LED lighting it can be tuned to optimize photosynthetic efficiency and reduce waste heat the bane of all space colonies and you don’t need large transparent panels also a bit of a problem.Mind you could filter the light at a mirror to the same end and focus it in vacuum into some pretty narrow light pipes so maybe LEDs aren’t the way to go. But a colony with a circumference of 31km and a roof that’s only 50-100 meters up can just rotate the mirror to move day”” around the colony on a schedule that is unconnected to the main rotation rate.If your atmosphere is only 50-100 meters thick”” and maintained by a roof that’s structurally connected to the floor it’s comparatively easy to partition the colony space into lots and lots of individual bubbles all resting on the tension hoop base”” if this is seen as necessary.”””

  42. I failed to socially connect”” (can engineer-types socially connect?) with UCBerkeley’s L–5 society chapter. Then again”” its not clear that it had one in the mid 1970s. We were still trying to avoid the brontosaurs that infested the campus. One very old idea I’ve fostered — and remain attached to — is the idea of a non-cylinder design. Cylinders penalize all kinds of ordinary happens chance. They’re integral — and sure they’re going to have hermetic isolation doors aplenty — but leaks are leaks for the (w)hole section. Mass movement isn’t such a penalty as the things get larger: proportionately the structure is growing in total terapascal budget and relatively each moving mass is smaller compared to the whole. By cylinders also penalize non-uniformity: by definition they’re masses concentrated around a hub as a torus. And not any-old torus but one that at least in part is semi-circular in cross section. To deal with air pressure. Over a LARGE area. The non-cylinder / torus idea I’ve had is to utilize tethers-and-blobs at the end of them. Visualize a really big condom quarter filled with 20 kg of mercury. What’s it going to look like suspended from the ceiling? Blob at the bottom teardrop shaped suspended by a long thin strand of condom rubber. If it holds. LOL. Yet taken as the unit-of-fabrication of a space station around a central hub of most any length”” one could “”””string out”””” blobs-on-tethers co-rotating on the axis”” in tension. There are a lot of cocktail napkin issues to address: they really cannot be untethered from each other because even small changes in inertial mass distribution would result in their rotational rate changing”” then bumping into each other. And “”””bumping is bad”””””””” so to say. But “”””tethers are cheap”””” too. So establishing a fixed inter-blob distance around the perimeter doesn’t sound all that hard in practice. Moreover”” having them isolated like little seed pods of a dandelion also”

  43. I really shouldn’t have said that now I can’t stop thinking about how to do just that. One of the downsides of being an engineer I guess.

  44. The numbers look good for steel and ceramics but you wouldn’t want to use polymers for your O’Neil colony hull. And of course you have to consider the tensile loading it’s going to aggravate the damage.

  45. Right. Maybe the doctor was thinking 50 feet instead of meters. Trees growing above 160 feet are actually pretty rare.

  46. Follow-up to my previous post below – I followed the link to the PDF by Pekka Janhunen, the numbers are intentional. space nss org/media/NSS-JOURNAL-Natural-Illumination-for-Rotating-Space-Settlements.pdf

  47. I agree it’s doable if by “rural space” you mean “intensive agricultural space”. But then you look at the other half, and 25,000 square meters per person in a urban area? 40 people per square kilometer is normally considered to be a rural population density! But 2000 square meters per person? 500 people per square kilometer? That’s normally regarded as a comfortable or even spacious suburb. And, if you look at the illustration, most of the space in the habitat is labeled “rural”. I think the most likely scenario is that the numbers just got accidentally swapped.

  48. I saw that too, but chalked it up to his ideas that we apparently need to live like royalty to live in space, despite every sci fi movie or book, and despite real-world experience of people flocking to the cities to live in small apartments. Many people in urban areas like to stay within a few blocks radius for most of their experience. Add in VR, you certainly don’t need “enough space so that … the settlement exceed a person’s lifetime-integrated capacity to explore”. Having a (very) high ceiling at the surface level, and occasionally long sight lines would alleviate any feelings of claustrophobia. I’ve done a little research to show with intensive agriculture (and don’t need to worry about seasons), you would need maybe .1 or .2 hectares per person for decent food production. So 2000 sq. meters is indeed doable for what he calls rural space.

  49. My understanding from research I’ve read, is that it is a non-issue for metals and ceramics, (Including silica fibers.) somewhat of an issue for plastics, (Varies from one to another.) and a real killer for elastomers.

  50. Seems like multiple repeating layers of silica sand with the tops fused into thin glass sheets would distribute stress well and over the area involved tolerate a good deal of bending as well. With leakage retrieval pumps hoovering between layers, net losses would be very small over large areas.

  51. Right. Maybe the doctor was thinking 50 feet instead of meters. Trees growing above 160 feet are actually pretty rare.

  52. Follow-up to my previous post below – I followed the link to the PDF by Pekka Janhunen the numbers are intentional.space nss org/media/NSS-JOURNAL-Natural-Illumination-for-Rotating-Space-Settlements.pdf

  53. I agree it’s doable if by rural space”” you mean “”””intensive agricultural space””””. But then you look at the other half”” and 25000 square meters per person in a urban area? 40 people per square kilometer is normally considered to be a rural population density! But 2000 square meters per person? 500 people per square kilometer? That’s normally regarded as a comfortable or even spacious suburb.And if you look at the illustration”” most of the space in the habitat is labeled “”””rural””””. I think the most likely scenario is that the numbers just got accidentally swapped.”””

  54. I saw that too but chalked it up to his ideas that we apparently need to live like royalty to live in space despite every sci fi movie or book and despite real-world experience of people flocking to the cities to live in small apartments. Many people in urban areas like to stay within a few blocks radius for most of their experience. Add in VR you certainly don’t need enough space so that … the settlement exceed a person’s lifetime-integrated capacity to explore””. Having a (very) high ceiling at the surface level”” and occasionally long sight lines would alleviate any feelings of claustrophobia.I’ve done a little research to show with intensive agriculture (and don’t need to worry about seasons)”” you would need maybe .1 or .2 hectares per person for decent food production. So 2000 sq. meters is indeed doable for what he calls rural space.”””””””

  55. My understanding from research I’ve read is that it is a non-issue for metals and ceramics (Including silica fibers.) somewhat of an issue for plastics (Varies from one to another.) and a real killer for elastomers.

  56. Seems like multiple repeating layers of silica sand with the tops fused into thin glass sheets would distribute stress well and over the area involved tolerate a good deal of bending as well. With leakage retrieval pumps hoovering between layers net losses would be very small over large areas.

  57. Add the periods back in: space nss org/media/NSS-JOURNAL-Natural-Illumination-for-Rotating-Space-Settlements.pdf

  58. If you’re looking to maximize interior space per kg of structure (and shielding) and minimize unneeded atmosphere (at areas say, of less than .5G), then a torus becomes the most efficient structure. Having a lot of blobs, I guess circling a common axle, might be good for self-sufficiency and redundancy, but it wouldn’t be the most cost-effective approach. Might as well connect the blobs together and have yourself a torus.

  59. Add the periods back in:space nss org/media/NSS-JOURNAL-Natural-Illumination-for-Rotating-Space-Settlements.pdf

  60. If you’re looking to maximize interior space per kg of structure (and shielding) and minimize unneeded atmosphere (at areas say of less than .5G) then a torus becomes the most efficient structure. Having a lot of blobs I guess circling a common axle might be good for self-sufficiency and redundancy but it wouldn’t be the most cost-effective approach. Might as well connect the blobs together and have yourself a torus.

  61. Another issue that concerns me is how they are using high strength steel in their calculations. Indeed they keep referring to piano wire. I can’t say this is WRONG per se. But it makes me uneasy. 1. Piano wire is a very… childish? amatuerish? way to talk about high strength steel. It’s very much the sort of thing that you would choose to illustrate the concept to your grandmother. Assuming she didn’t know much about steel. Yes it’s strong, but it’s clearly not what you would make a space station out of. Much better to talk of submarine or ship hulls. But then they aren’t anywhere near as strong. It turns out that the very hard material drawn out into fine wires are very difficult to replicate in thick hulls. Both for engineering reasons and for reasons of basic physics. 2. Surely a much better option would be to look at nickel iron asteroids, and use that material as a guide. Neither of these are showstoppers, but it looks like the kind of thing a 2nd year engineering student would come up with and plug into some equations without a broader understanding. Like I said, not wrong as such, but the wrong flavour.

  62. Nah, I don’t think in feet. I’d actually have trouble visualising what a 50 foot tree looks like. (About 15 meters tall I’d guess.) My point isn’t that you’ll have all these trees hitting the ceiling (though I would prefer if my luxury gardens DID have some Mountain ash or something) but that you’ll have a ceiling that is clearly THERE. You’ll get echoes from it. Birds couldn’t fly at normal heights. The trees will be distorted (remember the light is coming from the side and being reflected down.) And more generally that you’ve spent astronomical resources to create this volume of radiation free, supported space, and then you are only using the surface of it.

  63. If you read the paper there was no swapping. The clear intent is a vast, enormous internal area and the minimum outside required to easily grow enough food for the population. And they did the calculations of each, so there was no accidental switching. The internal area is achieved by having multiple floors, which lets you stack much, much more floorspace into a given volume. One wonders why they didn’t try stacking the plant growing region into multiple floors. That would have given them much more area for a given about of outside wall (which is the vast majority of the structure and hence cost).

  64. Another issue that concerns me is how they are using high strength steel in their calculations. Indeed they keep referring to piano wire.I can’t say this is WRONG per se. But it makes me uneasy.1. Piano wire is a very… childish? amatuerish? way to talk about high strength steel. It’s very much the sort of thing that you would choose to illustrate the concept to your grandmother. Assuming she didn’t know much about steel. Yes it’s strong but it’s clearly not what you would make a space station out of. Much better to talk of submarine or ship hulls. But then they aren’t anywhere near as strong. It turns out that the very hard material drawn out into fine wires are very difficult to replicate in thick hulls. Both for engineering reasons and for reasons of basic physics.2. Surely a much better option would be to look at nickel iron asteroids and use that material as a guide.Neither of these are showstoppers but it looks like the kind of thing a 2nd year engineering student would come up with and plug into some equations without a broader understanding.Like I said not wrong as such but the wrong flavour.

  65. Nah I don’t think in feet. I’d actually have trouble visualising what a 50 foot tree looks like. (About 15 meters tall I’d guess.)My point isn’t that you’ll have all these trees hitting the ceiling (though I would prefer if my luxury gardens DID have some Mountain ash or something) but that you’ll have a ceiling that is clearly THERE. You’ll get echoes from it. Birds couldn’t fly at normal heights. The trees will be distorted (remember the light is coming from the side and being reflected down.)And more generally that you’ve spent astronomical resources to create this volume of radiation free supported space and then you are only using the surface of it.

  66. If you read the paper there was no swapping. The clear intent is a vast enormous internal area and the minimum outside required to easily grow enough food for the population. And they did the calculations of each so there was no accidental switching.The internal area is achieved by having multiple floors which lets you stack much much more floorspace into a given volume.One wonders why they didn’t try stacking the plant growing region into multiple floors. That would have given them much more area for a given about of outside wall (which is the vast majority of the structure and hence cost).

  67. Why would you want to live in Texas with all the snakes and bitty things and heat, Upper midwest with all the snow and insane temps, Florida and all the Humidity and ancient Crocs and snakes….. You get the point. I would hate to live in a boring place like California where the weather is so predictable and bland. I would hate New York with all those shops people love and such. Matheus, people are different and want different things.

  68. Good point on the radiators. Heat radiation is covered in their paper, and yes it is a significant issue as we all know. However, I suspect (no I’m not doing the calculations, I’m supposed to be reviewing a spreadsheet on my other screen) that if, as stated, the vast majority of structure and material (i.e. cost) is required to provide a stable, radiation shielded volume, then 1. Use the shielded volume as efficiently as possible (ie. multiple layers) 2. Use unshielded volume to put your radiators in. So, off the top of my head, you get something that looks like a jet turbine fan disk. The inner core, running out to maybe 2/3 of the total radius, is your shielded volume with the outer layers being ~ 1g living spaces and multiple layers on top of that (at lower g, but still fine for plants I guess, and of course fine for humans to go if they don’t live there) being the “outdoorsy” bits. Then, radiating out from there are the “fan blades”. Thin radiators built largely in tension for low mass. The only bit that makes it less than ideally elegant is that the radiators hang “down” so you can’t use natural convection.

  69. Why would you want to live in Texas with all the snakes and bitty things and heat Upper midwest with all the snow and insane temps Florida and all the Humidity and ancient Crocs and snakes…..You get the point. I would hate to live in a boring place like California where the weather is so predictable and bland. I would hate New York with all those shops people love and such.Matheus people are different and want different things.

  70. Good point on the radiators.Heat radiation is covered in their paper and yes it is a significant issue as we all know.However I suspect (no I’m not doing the calculations I’m supposed to be reviewing a spreadsheet on my other screen) that if as stated the vast majority of structure and material (i.e. cost) is required to provide a stable radiation shielded volume then1. Use the shielded volume as efficiently as possible (ie. multiple layers)2. Use unshielded volume to put your radiators in.So off the top of my head you get something that looks like a jet turbine fan disk. The inner core running out to maybe 2/3 of the total radius is your shielded volume with the outer layers being ~ 1g living spaces and multiple layers on top of that (at lower g but still fine for plants I guess and of course fine for humans to go if they don’t live there) being the outdoorsy”” bits.Then”””” radiating out from there are the “”””fan blades””””. Thin radiators built largely in tension for low mass. The only bit that makes it less than ideally elegant is that the radiators hang “”””down”””” so you can’t use natural convection.”””

  71. I really do not like this design. The basic concept of a cylindrical habitat with an atmosphere constrained to be shallow to conserve gases is fine. Sizing it so that the required structural mass serves the shielding purpose is fine. But the biggest problem in colony design after holding in the air, is getting rid of waste heat, and that fancy light plenum they’ve wrapped around the colony is like putting it in a giant thermos bottle! It greatly complicates the problem of moving heat out of the colony.

  72. I really do not like this design. The basic concept of a cylindrical habitat with an atmosphere constrained to be shallow to conserve gases is fine. Sizing it so that the required structural mass serves the shielding purpose is fine. But the biggest problem in colony design after holding in the air is getting rid of waste heat and that fancy light plenum they’ve wrapped around the colony is like putting it in a giant thermos bottle! It greatly complicates the problem of moving heat out of the colony.

  73. Pretty sure that’s meant total *per colony*. Which is what you get when you use such low population density as this paper suggests.

  74. It’s not that nobody wants to live in Antarctica. The great powers couldn’t decide how to split it up, so they agreed nobody would get it. If you try to colonize Antarctica, somebody will show up with guns and remove you.

  75. Pretty sure that’s meant total *per colony*. Which is what you get when you use such low population density as this paper suggests.

  76. It’s not that nobody wants to live in Antarctica. The great powers couldn’t decide how to split it up so they agreed nobody would get it. If you try to colonize Antarctica somebody will show up with guns and remove you.

  77. But the population density is driven by the agricultural productivity of the “rural” area, which in turn drives the illumination budget, and thus the heat rejection budget, thus dictating the size of the radiators. You can’t really stack the agricultural area much because the radiator area is roughly equal to it. Unless you’re doing so much energy intensive stuff that the agricultural heat load is a small fraction of your radiator requirements, but that just makes the colony larger in proportion to the population. Their absurdly low “urban” population density isn’t realistic, it’s really just a demonstration that living space isn’t constrained in this design. The size is driven by the farm area, not living space. Unless you use some sort of industrial chemistry production of calories, or engineer plants to be considerably more efficient, self-sufficient space colonies are stuck having fairly low population densities. Sure, cities on Earth aren’t so constrained, but that’s because they’re not self-sufficient, they’re dependent on food imports.

  78. But the population density is driven by the agricultural productivity of the rural”” area”” which in turn drives the illumination budget and thus the heat rejection budget thus dictating the size of the radiators. You can’t really stack the agricultural area much because the radiator area is roughly equal to it. Unless you’re doing so much energy intensive stuff that the agricultural heat load is a small fraction of your radiator requirements”” but that just makes the colony larger in proportion to the population.Their absurdly low “”””urban”””” population density isn’t realistic”” it’s really just a demonstration that living space isn’t constrained in this design. The size is driven by the farm area not living space.Unless you use some sort of industrial chemistry production of calories or engineer plants to be considerably more efficient self-sufficient space colonies are stuck having fairly low population densities. Sure cities on Earth aren’t so constrained but that’s because they’re not self-sufficient”” they’re dependent on food imports.”””

  79. Of course C2H5OH is alcohol, I meant to say C6H12O6 . DOH! But good point, if you are actually starting with sterile nutrient solutions (rather than an area of land) then vat-grown-meat looks easily viable. I wouldn’t expect you’d need to synthesize the amino acids and stuff, because you could grow yeasts and other cultures in big vats feeding them the simple sugars. The aim being to get away from needing flat 2D land, which occupies valuable protected space, and moving to 3D volumes where you can fit in so much more stuff for a given amount of radiation shielding. Even on earth, most people’s diets consist of 90% bland starches (rice, bread, pasta,potatoes, yams, tapioca… like you could even tell one from the other from a fully synthetic variant) with a little bit of interesting stuff on top. If the 90% grows in a vat then this spaces colony design get’s far more viable in person/$million sense.

  80. Nah. You are being too old fashioned. They just need to release a cyptocoin called spacecoin that operates on proof-of-work where the work required is… building a space colony. The problem solves itself.

  81. Starting from asteroid carbon, you’d either steam crack it to various hydrocarbons, or gasify it into CO, CO2, H2, and possibly H2O and CH4. These can be converted back into higher hydrocarbons if needed. From there, either make methanol and convert it to acetic acid via the Cativa process, or use propylene to make glycerol. (Acetic acid can be reduced to C2H5OH, ethanol.) Glycerol can be oxidized to glyceraldehyde, and then converted to the higher sugars through homologation (Kiliani-Fischer) or by other methods. There may be a way to convert two glycerols into glucose more directly. Or there may be better routes from the smaller molecules. The higher hydrocarbons, either obtained from steam cracking or synthesized from ethylene, can be converted to fatty alcohols or aldehydes (Ziegler process or similar), then oxidized into the fatty acids. These can be reacted with glycerol and other components to make fats and lipids. Fatty acids can also be made from acetic acid through homologation, but that’s more complicated. There are also various ways to synthesize amino acids and vitamins, which would be needed to complete a balanced diet. Amino acids will likely be the most expensive part, barring a breakthrough. All of this gets easier with nanotechnology. Biomimetic routes with enzymes and biosynthetic routes with microorganisms are also worth considering. Anyway, a large part of normal food is actually water. So the synthetic starches, sugars, etc can be condensed to some form of sweet crackers with a fatty filling, with a much lower water content. These can be quite tasty if done right, and would provide a balanced diet. They could be made in a variety of flavors, and supplemented with a small amount of grown food for psychological reasons, as you suggest. One last technology which may complete the picture is the plant equivalent of lab-grown meat: use tissue culture or other techniques to grow only the needed parts. Should be more efficient.

  82. One prediction from Jules Verne that hasn’t (in some fashion) happened yet is mass production of chemical foodstuffs. In his book (Paris in the Twentieth Century) he has the anti-hero spiralling into poverty and being forced to reduce his diet to hydrocarbon based bread, and eventually coal bread. Which makes sense. Turning say natural gas into sugar eg. C2H5OH, can’t be that difficult. From there even vats of yeast or something would make edible (if not desirable food) that could form the caloric base on which smaller amounts of actually grown food would provide a diet. If 90% of calories came from synthesized starches and sugars, and you used some of those to grow fish or something in water tanks, then you’d only need 5% of so of the calculated “land area” to grow the necessary tomatoes, chilis etc to keep the average person content. A google search for “artificial synthesis of sugar” shows a bunch of hits that start with raw H2 and CO2. But I didn’t spend enough time to see if there is data on how efficient this would be on an industrial scale.

  83. Maybe there was a reason that Christopher Columbus had to leave Italy and go to a more dynamic country to get them interested in leaving Europe?

  84. To a first approximation, if the roof is 1m thick steel, mass/area is 8000 kg/m^3 x 1 m equals 8000 kg/m^2. And the alternative is 5 km of air running to the middle of the cylinder, mass/area is 1.3 kg/m^3 x 5000 m equals 8000 kg/m^2. You don’t save anything by putting in a roof. And having 100 times as much air means that there is a huge amount of thermal and chemical inertia in your atmosphere. Makes it much easier to control any unwanted fluctuations.

  85. Of course C2H5OH is alcohol I meant to say C6H12O6 . DOH!But good point if you are actually starting with sterile nutrient solutions (rather than an area of land) then vat-grown-meat looks easily viable.I wouldn’t expect you’d need to synthesize the amino acids and stuff because you could grow yeasts and other cultures in big vats feeding them the simple sugars.The aim being to get away from needing flat 2D land which occupies valuable protected space and moving to 3D volumes where you can fit in so much more stuff for a given amount of radiation shielding.Even on earth most people’s diets consist of 90{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} bland starches (rice bread pastapotatoes yams tapioca… like you could even tell one from the other from a fully synthetic variant) with a little bit of interesting stuff on top. If the 90{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} grows in a vat then this spaces colony design get’s far more viable in person/$million sense.

  86. Nah. You are being too old fashioned. They just need to release a cyptocoin called spacecoin that operates on proof-of-work where the work required is… building a space colony.The problem solves itself.

  87. Starting from asteroid carbon you’d either steam crack it to various hydrocarbons or gasify it into CO CO2 H2 and possibly H2O and CH4. These can be converted back into higher hydrocarbons if needed. From there either make methanol and convert it to acetic acid via the Cativa process or use propylene to make glycerol. (Acetic acid can be reduced to C2H5OH ethanol.)Glycerol can be oxidized to glyceraldehyde and then converted to the higher sugars through homologation (Kiliani-Fischer) or by other methods. There may be a way to convert two glycerols into glucose more directly. Or there may be better routes from the smaller molecules.The higher hydrocarbons either obtained from steam cracking or synthesized from ethylene can be converted to fatty alcohols or aldehydes (Ziegler process or similar) then oxidized into the fatty acids. These can be reacted with glycerol and other components to make fats and lipids. Fatty acids can also be made from acetic acid through homologation but that’s more complicated.There are also various ways to synthesize amino acids and vitamins which would be needed to complete a balanced diet. Amino acids will likely be the most expensive part barring a breakthrough. All of this gets easier with nanotechnology. Biomimetic routes with enzymes and biosynthetic routes with microorganisms are also worth considering.Anyway a large part of normal food is actually water. So the synthetic starches sugars etc can be condensed to some form of sweet crackers with a fatty filling with a much lower water content. These can be quite tasty if done right and would provide a balanced diet. They could be made in a variety of flavors and supplemented with a small amount of grown food for psychological reasons as you suggest.One last technology which may complete the picture is the plant equivalent of lab-grown meat: use tissue culture or other techniques to grow only the needed parts. Should be more efficient.

  88. One prediction from Jules Verne that hasn’t (in some fashion) happened yet is mass production of chemical foodstuffs.In his book (Paris in the Twentieth Century) he has the anti-hero spiralling into poverty and being forced to reduce his diet to hydrocarbon based bread and eventually coal bread.Which makes sense. Turning say natural gas into sugar eg. C2H5OH can’t be that difficult. From there even vats of yeast or something would make edible (if not desirable food) that could form the caloric base on which smaller amounts of actually grown food would provide a diet. If 90{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} of calories came from synthesized starches and sugars and you used some of those to grow fish or something in water tanks then you’d only need 5{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} of so of the calculated land area”” to grow the necessary tomatoes”””” chilis etc to keep the average person content.A google search for “”””artificial synthesis of sugar”””” shows a bunch of hits that start with raw H2 and CO2. But I didn’t spend enough time to see if there is data on how efficient this would be on an industrial scale.”””

  89. Maybe there was a reason that Christopher Columbus had to leave Italy and go to a more dynamic country to get them interested in leaving Europe?

  90. To a first approximation if the roof is 1m thick steel mass/area is 8000 kg/m^3 x 1 m equals 8000 kg/m^2. And the alternative is 5 km of air running to the middle of the cylinder mass/area is 1.3 kg/m^3 x 5000 m equals 8000 kg/m^2.You don’t save anything by putting in a roof. And having 100 times as much air means that there is a huge amount of thermal and chemical inertia in your atmosphere. Makes it much easier to control any unwanted fluctuations.

  91. Personally, I’m convinced that we’re eventually going to re-engineer ourselves to be able to internally close our cycle given a source of energy and a bit of make up mass. At the very least, on the vitamin/protein side, and still use fats and starches with oxygen for energy. But, yes, I expect that most of the food in a real colony will come from vats, not farm fields, at much higher efficiency. Farming is horribly inefficient at turning light into calories. The remainder will likely come from edible plantings used as landscaping. People like to have living things around them.

  92. Actually, you do save something: You can find asteroids made of steel, but asteroids made of air are pretty hard to find. *You conserve volatiles,* always an important issue in colony design. Also, the low roof allowed them to divide the habitat into many isolated sections, “valleys” they called them, which would be capable of being independently pressurized in case of a leak I’ve already said, though, that I don’t like the colony design. It’s mostly about their ray-tracing project to design a light plenum to passively distribute the light, you wouldn’t really design a colony like that otherwise. And their plenum design is a bad idea because it puts the entire colony inside a thermos bottle. Even if I were going to design a colony with the confined atmosphere design contemplated here, I’d redesign the plenum to occupy only the interior of the torus. The roof could be much thinner than you suggest if connected to the floor by stays, because it wouldn’t provide shielding. That would be accomplished by terminating the plenum at one end with mirror chevrons, and the other with just a shielded mirror, at considerably less cost in mass. (The end caps having less area than the roof.) That way you don’t have a plenum surrounding the outer surface of the torus, and can hang your radiators directly “under” where the heat shows up. You still have the problem that the “gravity” and heat flow are opposed, denying you the use of passive heat pipes. But that’s basically inevitable in rotating space colonies, sadly. At least the heat flow paths become fairly short, on the order of a couple hundred meters rather than kilometers as in their design.

  93. Yes, I figured you probably meant sugar. Though if you did want to make ethanol, it can be made more directly from ethylene. I suspect that yeast etc would need a larger reactor volume and longer time per amount of product, compared to a chemical reaction. But it may be cheaper. Depends on the reaction and volume.

  94. Personally I’m convinced that we’re eventually going to re-engineer ourselves to be able to internally close our cycle given a source of energy and a bit of make up mass. At the very least on the vitamin/protein side and still use fats and starches with oxygen for energy. But yes I expect that most of the food in a real colony will come from vats not farm fields at much higher efficiency. Farming is horribly inefficient at turning light into calories.The remainder will likely come from edible plantings used as landscaping. People like to have living things around them.

  95. Actually you do save something: You can find asteroids made of steel but asteroids made of air are pretty hard to find. *You conserve volatiles* always an important issue in colony design. Also the low roof allowed them to divide the habitat into many isolated sections valleys”” they called them”” which would be capable of being independently pressurized in case of a leakI’ve already said though that I don’t like the colony design. It’s mostly about their ray-tracing project to design a light plenum to passively distribute the light you wouldn’t really design a colony like that otherwise. And their plenum design is a bad idea because it puts the entire colony inside a thermos bottle.Even if I were going to design a colony with the confined atmosphere design contemplated here I’d redesign the plenum to occupy only the interior of the torus. The roof could be much thinner than you suggest if connected to the floor by stays because it wouldn’t provide shielding. That would be accomplished by terminating the plenum at one end with mirror chevrons and the other with just a shielded mirror at considerably less cost in mass. (The end caps having less area than the roof.) That way you don’t have a plenum surrounding the outer surface of the torus”” and can hang your radiators directly “”””under”””” where the heat shows up.You still have the problem that the “”””gravity”””” and heat flow are opposed”” denying you the use of passive heat pipes. But that’s basically inevitable in rotating space colonies sadly. At least the heat flow paths become fairly short”” on the order of a couple hundred meters rather than kilometers as in their design.”””

  96. Yes I figured you probably meant sugar. Though if you did want to make ethanol it can be made more directly from ethylene.I suspect that yeast etc would need a larger reactor volume and longer time per amount of product compared to a chemical reaction. But it may be cheaper. Depends on the reaction and volume.

  97. Actually, not necessarily. In today’s economy, where a certain amount of scarce human labor must be devoted to any infrastructure project, cost matters a great deal, because you have to husband scarce resources. But, if we develop Von Neumann machines, (And I think we must to make this sort of thing feasible.) human labor ceases to be a limiting factor. The limiting factors become the availability of mass and energy, and how many doubling times you’re willing to wait for enough autofactories to become available. So, sure, there will still be costs, but on a hugely different scale and distribution. The second colony will be much, much cheaper than the 1st, for instance. For resources you’ll be competing with other grand projects like statite arrays to power interstellar launches, terraforming Mars, that sort of thing. So, now? Impossibly expensive, more than the world’s economy could supply in 20 years. Fifty years from now? About like building a new real estate development.

  98. Actually not necessarily. In today’s economy where a certain amount of scarce human labor must be devoted to any infrastructure project cost matters a great deal because you have to husband scarce resources.But if we develop Von Neumann machines (And I think we must to make this sort of thing feasible.) human labor ceases to be a limiting factor. The limiting factors become the availability of mass and energy and how many doubling times you’re willing to wait for enough autofactories to become available.So sure there will still be costs but on a hugely different scale and distribution. The second colony will be much much cheaper than the 1st for instance. For resources you’ll be competing with other grand projects like statite arrays to power interstellar launches terraforming Mars that sort of thing.So now? Impossibly expensive more than the world’s economy could supply in 20 years.Fifty years from now? About like building a new real estate development.

  99. Actually, not necessarily. In today’s economy, where a certain amount of scarce human labor must be devoted to any infrastructure project, cost matters a great deal, because you have to husband scarce resources. But, if we develop Von Neumann machines, (And I think we must to make this sort of thing feasible.) human labor ceases to be a limiting factor. The limiting factors become the availability of mass and energy, and how many doubling times you’re willing to wait for enough autofactories to become available. So, sure, there will still be costs, but on a hugely different scale and distribution. The second colony will be much, much cheaper than the 1st, for instance. For resources you’ll be competing with other grand projects like statite arrays to power interstellar launches, terraforming Mars, that sort of thing. So, now? Impossibly expensive, more than the world’s economy could supply in 20 years. Fifty years from now? About like building a new real estate development.

  100. Actually not necessarily. In today’s economy where a certain amount of scarce human labor must be devoted to any infrastructure project cost matters a great deal because you have to husband scarce resources.But if we develop Von Neumann machines (And I think we must to make this sort of thing feasible.) human labor ceases to be a limiting factor. The limiting factors become the availability of mass and energy and how many doubling times you’re willing to wait for enough autofactories to become available.So sure there will still be costs but on a hugely different scale and distribution. The second colony will be much much cheaper than the 1st for instance. For resources you’ll be competing with other grand projects like statite arrays to power interstellar launches terraforming Mars that sort of thing.So now? Impossibly expensive more than the world’s economy could supply in 20 years.Fifty years from now? About like building a new real estate development.

  101. Personally, I’m convinced that we’re eventually going to re-engineer ourselves to be able to internally close our cycle given a source of energy and a bit of make up mass. At the very least, on the vitamin/protein side, and still use fats and starches with oxygen for energy. But, yes, I expect that most of the food in a real colony will come from vats, not farm fields, at much higher efficiency. Farming is horribly inefficient at turning light into calories. The remainder will likely come from edible plantings used as landscaping. People like to have living things around them.

  102. Personally I’m convinced that we’re eventually going to re-engineer ourselves to be able to internally close our cycle given a source of energy and a bit of make up mass. At the very least on the vitamin/protein side and still use fats and starches with oxygen for energy. But yes I expect that most of the food in a real colony will come from vats not farm fields at much higher efficiency. Farming is horribly inefficient at turning light into calories.The remainder will likely come from edible plantings used as landscaping. People like to have living things around them.

  103. Actually, you do save something: You can find asteroids made of steel, but asteroids made of air are pretty hard to find. *You conserve volatiles,* always an important issue in colony design. Also, the low roof allowed them to divide the habitat into many isolated sections, “valleys” they called them, which would be capable of being independently pressurized in case of a leak I’ve already said, though, that I don’t like the colony design. It’s mostly about their ray-tracing project to design a light plenum to passively distribute the light, you wouldn’t really design a colony like that otherwise. And their plenum design is a bad idea because it puts the entire colony inside a thermos bottle. Even if I were going to design a colony with the confined atmosphere design contemplated here, I’d redesign the plenum to occupy only the interior of the torus. The roof could be much thinner than you suggest if connected to the floor by stays, because it wouldn’t provide shielding. That would be accomplished by terminating the plenum at one end with mirror chevrons, and the other with just a shielded mirror, at considerably less cost in mass. (The end caps having less area than the roof.) That way you don’t have a plenum surrounding the outer surface of the torus, and can hang your radiators directly “under” where the heat shows up. You still have the problem that the “gravity” and heat flow are opposed, denying you the use of passive heat pipes. But that’s basically inevitable in rotating space colonies, sadly. At least the heat flow paths become fairly short, on the order of a couple hundred meters rather than kilometers as in their design.

  104. Actually you do save something: You can find asteroids made of steel but asteroids made of air are pretty hard to find. *You conserve volatiles* always an important issue in colony design. Also the low roof allowed them to divide the habitat into many isolated sections valleys”” they called them”” which would be capable of being independently pressurized in case of a leakI’ve already said though that I don’t like the colony design. It’s mostly about their ray-tracing project to design a light plenum to passively distribute the light you wouldn’t really design a colony like that otherwise. And their plenum design is a bad idea because it puts the entire colony inside a thermos bottle.Even if I were going to design a colony with the confined atmosphere design contemplated here I’d redesign the plenum to occupy only the interior of the torus. The roof could be much thinner than you suggest if connected to the floor by stays because it wouldn’t provide shielding. That would be accomplished by terminating the plenum at one end with mirror chevrons and the other with just a shielded mirror at considerably less cost in mass. (The end caps having less area than the roof.) That way you don’t have a plenum surrounding the outer surface of the torus”” and can hang your radiators directly “”””under”””” where the heat shows up.You still have the problem that the “”””gravity”””” and heat flow are opposed”” denying you the use of passive heat pipes. But that’s basically inevitable in rotating space colonies sadly. At least the heat flow paths become fairly short”” on the order of a couple hundred meters rather than kilometers as in their design.”””

  105. Yes, I figured you probably meant sugar. Though if you did want to make ethanol, it can be made more directly from ethylene. I suspect that yeast etc would need a larger reactor volume and longer time per amount of product, compared to a chemical reaction. But it may be cheaper. Depends on the reaction and volume.

  106. Yes I figured you probably meant sugar. Though if you did want to make ethanol it can be made more directly from ethylene.I suspect that yeast etc would need a larger reactor volume and longer time per amount of product compared to a chemical reaction. But it may be cheaper. Depends on the reaction and volume.

  107. Of course C2H5OH is alcohol, I meant to say C6H12O6 . DOH! But good point, if you are actually starting with sterile nutrient solutions (rather than an area of land) then vat-grown-meat looks easily viable. I wouldn’t expect you’d need to synthesize the amino acids and stuff, because you could grow yeasts and other cultures in big vats feeding them the simple sugars. The aim being to get away from needing flat 2D land, which occupies valuable protected space, and moving to 3D volumes where you can fit in so much more stuff for a given amount of radiation shielding. Even on earth, most people’s diets consist of 90% bland starches (rice, bread, pasta,potatoes, yams, tapioca… like you could even tell one from the other from a fully synthetic variant) with a little bit of interesting stuff on top. If the 90% grows in a vat then this spaces colony design get’s far more viable in person/$million sense.

  108. Of course C2H5OH is alcohol I meant to say C6H12O6 . DOH!But good point if you are actually starting with sterile nutrient solutions (rather than an area of land) then vat-grown-meat looks easily viable.I wouldn’t expect you’d need to synthesize the amino acids and stuff because you could grow yeasts and other cultures in big vats feeding them the simple sugars.The aim being to get away from needing flat 2D land which occupies valuable protected space and moving to 3D volumes where you can fit in so much more stuff for a given amount of radiation shielding.Even on earth most people’s diets consist of 90{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} bland starches (rice bread pastapotatoes yams tapioca… like you could even tell one from the other from a fully synthetic variant) with a little bit of interesting stuff on top. If the 90{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} grows in a vat then this spaces colony design get’s far more viable in person/$million sense.

  109. Nah. You are being too old fashioned. They just need to release a cyptocoin called spacecoin that operates on proof-of-work where the work required is… building a space colony. The problem solves itself.

  110. Nah. You are being too old fashioned. They just need to release a cyptocoin called spacecoin that operates on proof-of-work where the work required is… building a space colony.The problem solves itself.

  111. Starting from asteroid carbon, you’d either steam crack it to various hydrocarbons, or gasify it into CO, CO2, H2, and possibly H2O and CH4. These can be converted back into higher hydrocarbons if needed. From there, either make methanol and convert it to acetic acid via the Cativa process, or use propylene to make glycerol. (Acetic acid can be reduced to C2H5OH, ethanol.) Glycerol can be oxidized to glyceraldehyde, and then converted to the higher sugars through homologation (Kiliani-Fischer) or by other methods. There may be a way to convert two glycerols into glucose more directly. Or there may be better routes from the smaller molecules. The higher hydrocarbons, either obtained from steam cracking or synthesized from ethylene, can be converted to fatty alcohols or aldehydes (Ziegler process or similar), then oxidized into the fatty acids. These can be reacted with glycerol and other components to make fats and lipids. Fatty acids can also be made from acetic acid through homologation, but that’s more complicated. There are also various ways to synthesize amino acids and vitamins, which would be needed to complete a balanced diet. Amino acids will likely be the most expensive part, barring a breakthrough. All of this gets easier with nanotechnology. Biomimetic routes with enzymes and biosynthetic routes with microorganisms are also worth considering. Anyway, a large part of normal food is actually water. So the synthetic starches, sugars, etc can be condensed to some form of sweet crackers with a fatty filling, with a much lower water content. These can be quite tasty if done right, and would provide a balanced diet. They could be made in a variety of flavors, and supplemented with a small amount of grown food for psychological reasons, as you suggest. One last technology which may complete the picture is the plant equivalent of lab-grown meat: use tissue culture or other techniques to grow only the needed parts. Should be more efficient.

  112. Starting from asteroid carbon you’d either steam crack it to various hydrocarbons or gasify it into CO CO2 H2 and possibly H2O and CH4. These can be converted back into higher hydrocarbons if needed. From there either make methanol and convert it to acetic acid via the Cativa process or use propylene to make glycerol. (Acetic acid can be reduced to C2H5OH ethanol.)Glycerol can be oxidized to glyceraldehyde and then converted to the higher sugars through homologation (Kiliani-Fischer) or by other methods. There may be a way to convert two glycerols into glucose more directly. Or there may be better routes from the smaller molecules.The higher hydrocarbons either obtained from steam cracking or synthesized from ethylene can be converted to fatty alcohols or aldehydes (Ziegler process or similar) then oxidized into the fatty acids. These can be reacted with glycerol and other components to make fats and lipids. Fatty acids can also be made from acetic acid through homologation but that’s more complicated.There are also various ways to synthesize amino acids and vitamins which would be needed to complete a balanced diet. Amino acids will likely be the most expensive part barring a breakthrough. All of this gets easier with nanotechnology. Biomimetic routes with enzymes and biosynthetic routes with microorganisms are also worth considering.Anyway a large part of normal food is actually water. So the synthetic starches sugars etc can be condensed to some form of sweet crackers with a fatty filling with a much lower water content. These can be quite tasty if done right and would provide a balanced diet. They could be made in a variety of flavors and supplemented with a small amount of grown food for psychological reasons as you suggest.One last technology which may complete the picture is the plant equivalent of lab-grown meat: use tissue culture or other techniques to grow only the needed parts. Should be more efficient.

  113. One prediction from Jules Verne that hasn’t (in some fashion) happened yet is mass production of chemical foodstuffs. In his book (Paris in the Twentieth Century) he has the anti-hero spiralling into poverty and being forced to reduce his diet to hydrocarbon based bread, and eventually coal bread. Which makes sense. Turning say natural gas into sugar eg. C2H5OH, can’t be that difficult. From there even vats of yeast or something would make edible (if not desirable food) that could form the caloric base on which smaller amounts of actually grown food would provide a diet. If 90% of calories came from synthesized starches and sugars, and you used some of those to grow fish or something in water tanks, then you’d only need 5% of so of the calculated “land area” to grow the necessary tomatoes, chilis etc to keep the average person content. A google search for “artificial synthesis of sugar” shows a bunch of hits that start with raw H2 and CO2. But I didn’t spend enough time to see if there is data on how efficient this would be on an industrial scale.

  114. One prediction from Jules Verne that hasn’t (in some fashion) happened yet is mass production of chemical foodstuffs.In his book (Paris in the Twentieth Century) he has the anti-hero spiralling into poverty and being forced to reduce his diet to hydrocarbon based bread and eventually coal bread.Which makes sense. Turning say natural gas into sugar eg. C2H5OH can’t be that difficult. From there even vats of yeast or something would make edible (if not desirable food) that could form the caloric base on which smaller amounts of actually grown food would provide a diet. If 90{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} of calories came from synthesized starches and sugars and you used some of those to grow fish or something in water tanks then you’d only need 5{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} of so of the calculated land area”” to grow the necessary tomatoes”””” chilis etc to keep the average person content.A google search for “”””artificial synthesis of sugar”””” shows a bunch of hits that start with raw H2 and CO2. But I didn’t spend enough time to see if there is data on how efficient this would be on an industrial scale.”””

  115. Actually, not necessarily.

    In today’s economy, where a certain amount of scarce human labor must be devoted to any infrastructure project, cost matters a great deal, because you have to husband scarce resources.

    But, if we develop Von Neumann machines, (And I think we must to make this sort of thing feasible.) human labor ceases to be a limiting factor. The limiting factors become the availability of mass and energy, and how many doubling times you’re willing to wait for enough autofactories to become available.

    So, sure, there will still be costs, but on a hugely different scale and distribution. The second colony will be much, much cheaper than the 1st, for instance. For resources you’ll be competing with other grand projects like statite arrays to power interstellar launches, terraforming Mars, that sort of thing.

    So, now? Impossibly expensive, more than the world’s economy could supply in 20 years.

    Fifty years from now? About like building a new real estate development.

  116. Maybe there was a reason that Christopher Columbus had to leave Italy and go to a more dynamic country to get them interested in leaving Europe?

  117. Maybe there was a reason that Christopher Columbus had to leave Italy and go to a more dynamic country to get them interested in leaving Europe?

  118. To a first approximation, if the roof is 1m thick steel, mass/area is 8000 kg/m^3 x 1 m equals 8000 kg/m^2. And the alternative is 5 km of air running to the middle of the cylinder, mass/area is 1.3 kg/m^3 x 5000 m equals 8000 kg/m^2. You don’t save anything by putting in a roof. And having 100 times as much air means that there is a huge amount of thermal and chemical inertia in your atmosphere. Makes it much easier to control any unwanted fluctuations.

  119. To a first approximation if the roof is 1m thick steel mass/area is 8000 kg/m^3 x 1 m equals 8000 kg/m^2. And the alternative is 5 km of air running to the middle of the cylinder mass/area is 1.3 kg/m^3 x 5000 m equals 8000 kg/m^2.You don’t save anything by putting in a roof. And having 100 times as much air means that there is a huge amount of thermal and chemical inertia in your atmosphere. Makes it much easier to control any unwanted fluctuations.

  120. Personally, I’m convinced that we’re eventually going to re-engineer ourselves to be able to internally close our cycle given a source of energy and a bit of make up mass. At the very least, on the vitamin/protein side, and still use fats and starches with oxygen for energy. But, yes, I expect that most of the food in a real colony will come from vats, not farm fields, at much higher efficiency. Farming is horribly inefficient at turning light into calories.

    The remainder will likely come from edible plantings used as landscaping. People like to have living things around them.

  121. Actually, you do save something: You can find asteroids made of steel, but asteroids made of air are pretty hard to find. *You conserve volatiles,* always an important issue in colony design. Also, the low roof allowed them to divide the habitat into many isolated sections, “valleys” they called them, which would be capable of being independently pressurized in case of a leak

    I’ve already said, though, that I don’t like the colony design. It’s mostly about their ray-tracing project to design a light plenum to passively distribute the light, you wouldn’t really design a colony like that otherwise. And their plenum design is a bad idea because it puts the entire colony inside a thermos bottle.

    Even if I were going to design a colony with the confined atmosphere design contemplated here, I’d redesign the plenum to occupy only the interior of the torus. The roof could be much thinner than you suggest if connected to the floor by stays, because it wouldn’t provide shielding. That would be accomplished by terminating the plenum at one end with mirror chevrons, and the other with just a shielded mirror, at considerably less cost in mass. (The end caps having less area than the roof.)

    That way you don’t have a plenum surrounding the outer surface of the torus, and can hang your radiators directly “under” where the heat shows up.

    You still have the problem that the “gravity” and heat flow are opposed, denying you the use of passive heat pipes. But that’s basically inevitable in rotating space colonies, sadly. At least the heat flow paths become fairly short, on the order of a couple hundred meters rather than kilometers as in their design.

  122. Yes, I figured you probably meant sugar. Though if you did want to make ethanol, it can be made more directly from ethylene.

    I suspect that yeast etc would need a larger reactor volume and longer time per amount of product, compared to a chemical reaction. But it may be cheaper. Depends on the reaction and volume.

  123. Of course C2H5OH is alcohol, I meant to say C6H12O6 . DOH!

    But good point, if you are actually starting with sterile nutrient solutions (rather than an area of land) then vat-grown-meat looks easily viable.

    I wouldn’t expect you’d need to synthesize the amino acids and stuff, because you could grow yeasts and other cultures in big vats feeding them the simple sugars.

    The aim being to get away from needing flat 2D land, which occupies valuable protected space, and moving to 3D volumes where you can fit in so much more stuff for a given amount of radiation shielding.

    Even on earth, most people’s diets consist of 90% bland starches (rice, bread, pasta,potatoes, yams, tapioca… like you could even tell one from the other from a fully synthetic variant) with a little bit of interesting stuff on top. If the 90% grows in a vat then this spaces colony design get’s far more viable in person/$million sense.

  124. Nah. You are being too old fashioned. They just need to release a cyptocoin called spacecoin that operates on proof-of-work where the work required is… building a space colony.
    The problem solves itself.

  125. Starting from asteroid carbon, you’d either steam crack it to various hydrocarbons, or gasify it into CO, CO2, H2, and possibly H2O and CH4. These can be converted back into higher hydrocarbons if needed. From there, either make methanol and convert it to acetic acid via the Cativa process, or use propylene to make glycerol. (Acetic acid can be reduced to C2H5OH, ethanol.)

    Glycerol can be oxidized to glyceraldehyde, and then converted to the higher sugars through homologation (Kiliani-Fischer) or by other methods. There may be a way to convert two glycerols into glucose more directly. Or there may be better routes from the smaller molecules.

    The higher hydrocarbons, either obtained from steam cracking or synthesized from ethylene, can be converted to fatty alcohols or aldehydes (Ziegler process or similar), then oxidized into the fatty acids. These can be reacted with glycerol and other components to make fats and lipids. Fatty acids can also be made from acetic acid through homologation, but that’s more complicated.

    There are also various ways to synthesize amino acids and vitamins, which would be needed to complete a balanced diet. Amino acids will likely be the most expensive part, barring a breakthrough. All of this gets easier with nanotechnology. Biomimetic routes with enzymes and biosynthetic routes with microorganisms are also worth considering.

    Anyway, a large part of normal food is actually water. So the synthetic starches, sugars, etc can be condensed to some form of sweet crackers with a fatty filling, with a much lower water content. These can be quite tasty if done right, and would provide a balanced diet. They could be made in a variety of flavors, and supplemented with a small amount of grown food for psychological reasons, as you suggest.

    One last technology which may complete the picture is the plant equivalent of lab-grown meat: use tissue culture or other techniques to grow only the needed parts. Should be more efficient.

  126. One prediction from Jules Verne that hasn’t (in some fashion) happened yet is mass production of chemical foodstuffs.

    In his book (Paris in the Twentieth Century) he has the anti-hero spiralling into poverty and being forced to reduce his diet to hydrocarbon based bread, and eventually coal bread.

    Which makes sense. Turning say natural gas into sugar eg. C2H5OH, can’t be that difficult. From there even vats of yeast or something would make edible (if not desirable food) that could form the caloric base on which smaller amounts of actually grown food would provide a diet.

    If 90% of calories came from synthesized starches and sugars, and you used some of those to grow fish or something in water tanks, then you’d only need 5% of so of the calculated “land area” to grow the necessary tomatoes, chilis etc to keep the average person content.

    A google search for “artificial synthesis of sugar” shows a bunch of hits that start with raw H2 and CO2. But I didn’t spend enough time to see if there is data on how efficient this would be on an industrial scale.

  127. To a first approximation, if the roof is 1m thick steel, mass/area is 8000 kg/m^3 x 1 m equals 8000 kg/m^2.

    And the alternative is 5 km of air running to the middle of the cylinder, mass/area is 1.3 kg/m^3 x 5000 m equals 8000 kg/m^2.

    You don’t save anything by putting in a roof. And having 100 times as much air means that there is a huge amount of thermal and chemical inertia in your atmosphere. Makes it much easier to control any unwanted fluctuations.

  128. But the population density is driven by the agricultural productivity of the “rural” area, which in turn drives the illumination budget, and thus the heat rejection budget, thus dictating the size of the radiators. You can’t really stack the agricultural area much because the radiator area is roughly equal to it. Unless you’re doing so much energy intensive stuff that the agricultural heat load is a small fraction of your radiator requirements, but that just makes the colony larger in proportion to the population. Their absurdly low “urban” population density isn’t realistic, it’s really just a demonstration that living space isn’t constrained in this design. The size is driven by the farm area, not living space. Unless you use some sort of industrial chemistry production of calories, or engineer plants to be considerably more efficient, self-sufficient space colonies are stuck having fairly low population densities. Sure, cities on Earth aren’t so constrained, but that’s because they’re not self-sufficient, they’re dependent on food imports.

  129. But the population density is driven by the agricultural productivity of the rural”” area”” which in turn drives the illumination budget and thus the heat rejection budget thus dictating the size of the radiators. You can’t really stack the agricultural area much because the radiator area is roughly equal to it. Unless you’re doing so much energy intensive stuff that the agricultural heat load is a small fraction of your radiator requirements”” but that just makes the colony larger in proportion to the population.Their absurdly low “”””urban”””” population density isn’t realistic”” it’s really just a demonstration that living space isn’t constrained in this design. The size is driven by the farm area not living space.Unless you use some sort of industrial chemistry production of calories or engineer plants to be considerably more efficient self-sufficient space colonies are stuck having fairly low population densities. Sure cities on Earth aren’t so constrained but that’s because they’re not self-sufficient”” they’re dependent on food imports.”””

  130. Pretty sure that’s meant total *per colony*. Which is what you get when you use such low population density as this paper suggests.

  131. Pretty sure that’s meant total *per colony*. Which is what you get when you use such low population density as this paper suggests.

  132. It’s not that nobody wants to live in Antarctica. The great powers couldn’t decide how to split it up, so they agreed nobody would get it. If you try to colonize Antarctica, somebody will show up with guns and remove you.

  133. It’s not that nobody wants to live in Antarctica. The great powers couldn’t decide how to split it up so they agreed nobody would get it. If you try to colonize Antarctica somebody will show up with guns and remove you.

  134. I really do not like this design. The basic concept of a cylindrical habitat with an atmosphere constrained to be shallow to conserve gases is fine. Sizing it so that the required structural mass serves the shielding purpose is fine. But the biggest problem in colony design after holding in the air, is getting rid of waste heat, and that fancy light plenum they’ve wrapped around the colony is like putting it in a giant thermos bottle! It greatly complicates the problem of moving heat out of the colony.

  135. I really do not like this design. The basic concept of a cylindrical habitat with an atmosphere constrained to be shallow to conserve gases is fine. Sizing it so that the required structural mass serves the shielding purpose is fine. But the biggest problem in colony design after holding in the air is getting rid of waste heat and that fancy light plenum they’ve wrapped around the colony is like putting it in a giant thermos bottle! It greatly complicates the problem of moving heat out of the colony.

  136. But the population density is driven by the agricultural productivity of the “rural” area, which in turn drives the illumination budget, and thus the heat rejection budget, thus dictating the size of the radiators. You can’t really stack the agricultural area much because the radiator area is roughly equal to it. Unless you’re doing so much energy intensive stuff that the agricultural heat load is a small fraction of your radiator requirements, but that just makes the colony larger in proportion to the population.

    Their absurdly low “urban” population density isn’t realistic, it’s really just a demonstration that living space isn’t constrained in this design. The size is driven by the farm area, not living space.

    Unless you use some sort of industrial chemistry production of calories, or engineer plants to be considerably more efficient, self-sufficient space colonies are stuck having fairly low population densities. Sure, cities on Earth aren’t so constrained, but that’s because they’re not self-sufficient, they’re dependent on food imports.

  137. Why would you want to live in Texas with all the snakes and bitty things and heat, Upper midwest with all the snow and insane temps, Florida and all the Humidity and ancient Crocs and snakes….. You get the point. I would hate to live in a boring place like California where the weather is so predictable and bland. I would hate New York with all those shops people love and such. Matheus, people are different and want different things.

  138. Why would you want to live in Texas with all the snakes and bitty things and heat Upper midwest with all the snow and insane temps Florida and all the Humidity and ancient Crocs and snakes…..You get the point. I would hate to live in a boring place like California where the weather is so predictable and bland. I would hate New York with all those shops people love and such.Matheus people are different and want different things.

  139. Good point on the radiators. Heat radiation is covered in their paper, and yes it is a significant issue as we all know. However, I suspect (no I’m not doing the calculations, I’m supposed to be reviewing a spreadsheet on my other screen) that if, as stated, the vast majority of structure and material (i.e. cost) is required to provide a stable, radiation shielded volume, then 1. Use the shielded volume as efficiently as possible (ie. multiple layers) 2. Use unshielded volume to put your radiators in. So, off the top of my head, you get something that looks like a jet turbine fan disk. The inner core, running out to maybe 2/3 of the total radius, is your shielded volume with the outer layers being ~ 1g living spaces and multiple layers on top of that (at lower g, but still fine for plants I guess, and of course fine for humans to go if they don’t live there) being the “outdoorsy” bits. Then, radiating out from there are the “fan blades”. Thin radiators built largely in tension for low mass. The only bit that makes it less than ideally elegant is that the radiators hang “down” so you can’t use natural convection.

  140. Good point on the radiators.Heat radiation is covered in their paper and yes it is a significant issue as we all know.However I suspect (no I’m not doing the calculations I’m supposed to be reviewing a spreadsheet on my other screen) that if as stated the vast majority of structure and material (i.e. cost) is required to provide a stable radiation shielded volume then1. Use the shielded volume as efficiently as possible (ie. multiple layers)2. Use unshielded volume to put your radiators in.So off the top of my head you get something that looks like a jet turbine fan disk. The inner core running out to maybe 2/3 of the total radius is your shielded volume with the outer layers being ~ 1g living spaces and multiple layers on top of that (at lower g but still fine for plants I guess and of course fine for humans to go if they don’t live there) being the outdoorsy”” bits.Then”””” radiating out from there are the “”””fan blades””””. Thin radiators built largely in tension for low mass. The only bit that makes it less than ideally elegant is that the radiators hang “”””down”””” so you can’t use natural convection.”””

  141. Another issue that concerns me is how they are using high strength steel in their calculations. Indeed they keep referring to piano wire. I can’t say this is WRONG per se. But it makes me uneasy. 1. Piano wire is a very… childish? amatuerish? way to talk about high strength steel. It’s very much the sort of thing that you would choose to illustrate the concept to your grandmother. Assuming she didn’t know much about steel. Yes it’s strong, but it’s clearly not what you would make a space station out of. Much better to talk of submarine or ship hulls. But then they aren’t anywhere near as strong. It turns out that the very hard material drawn out into fine wires are very difficult to replicate in thick hulls. Both for engineering reasons and for reasons of basic physics. 2. Surely a much better option would be to look at nickel iron asteroids, and use that material as a guide. Neither of these are showstoppers, but it looks like the kind of thing a 2nd year engineering student would come up with and plug into some equations without a broader understanding. Like I said, not wrong as such, but the wrong flavour.

  142. Another issue that concerns me is how they are using high strength steel in their calculations. Indeed they keep referring to piano wire.I can’t say this is WRONG per se. But it makes me uneasy.1. Piano wire is a very… childish? amatuerish? way to talk about high strength steel. It’s very much the sort of thing that you would choose to illustrate the concept to your grandmother. Assuming she didn’t know much about steel. Yes it’s strong but it’s clearly not what you would make a space station out of. Much better to talk of submarine or ship hulls. But then they aren’t anywhere near as strong. It turns out that the very hard material drawn out into fine wires are very difficult to replicate in thick hulls. Both for engineering reasons and for reasons of basic physics.2. Surely a much better option would be to look at nickel iron asteroids and use that material as a guide.Neither of these are showstoppers but it looks like the kind of thing a 2nd year engineering student would come up with and plug into some equations without a broader understanding.Like I said not wrong as such but the wrong flavour.

  143. Nah, I don’t think in feet. I’d actually have trouble visualising what a 50 foot tree looks like. (About 15 meters tall I’d guess.) My point isn’t that you’ll have all these trees hitting the ceiling (though I would prefer if my luxury gardens DID have some Mountain ash or something) but that you’ll have a ceiling that is clearly THERE. You’ll get echoes from it. Birds couldn’t fly at normal heights. The trees will be distorted (remember the light is coming from the side and being reflected down.) And more generally that you’ve spent astronomical resources to create this volume of radiation free, supported space, and then you are only using the surface of it.

  144. Nah I don’t think in feet. I’d actually have trouble visualising what a 50 foot tree looks like. (About 15 meters tall I’d guess.)My point isn’t that you’ll have all these trees hitting the ceiling (though I would prefer if my luxury gardens DID have some Mountain ash or something) but that you’ll have a ceiling that is clearly THERE. You’ll get echoes from it. Birds couldn’t fly at normal heights. The trees will be distorted (remember the light is coming from the side and being reflected down.)And more generally that you’ve spent astronomical resources to create this volume of radiation free supported space and then you are only using the surface of it.

  145. If you read the paper there was no swapping. The clear intent is a vast, enormous internal area and the minimum outside required to easily grow enough food for the population. And they did the calculations of each, so there was no accidental switching. The internal area is achieved by having multiple floors, which lets you stack much, much more floorspace into a given volume. One wonders why they didn’t try stacking the plant growing region into multiple floors. That would have given them much more area for a given about of outside wall (which is the vast majority of the structure and hence cost).

  146. If you read the paper there was no swapping. The clear intent is a vast enormous internal area and the minimum outside required to easily grow enough food for the population. And they did the calculations of each so there was no accidental switching.The internal area is achieved by having multiple floors which lets you stack much much more floorspace into a given volume.One wonders why they didn’t try stacking the plant growing region into multiple floors. That would have given them much more area for a given about of outside wall (which is the vast majority of the structure and hence cost).

  147. It’s not that nobody wants to live in Antarctica. The great powers couldn’t decide how to split it up, so they agreed nobody would get it.

    If you try to colonize Antarctica, somebody will show up with guns and remove you.

  148. I really do not like this design. The basic concept of a cylindrical habitat with an atmosphere constrained to be shallow to conserve gases is fine. Sizing it so that the required structural mass serves the shielding purpose is fine.

    But the biggest problem in colony design after holding in the air, is getting rid of waste heat, and that fancy light plenum they’ve wrapped around the colony is like putting it in a giant thermos bottle! It greatly complicates the problem of moving heat out of the colony.

  149. Add the periods back in:space nss org/media/NSS-JOURNAL-Natural-Illumination-for-Rotating-Space-Settlements.pdf

  150. If you’re looking to maximize interior space per kg of structure (and shielding) and minimize unneeded atmosphere (at areas say, of less than .5G), then a torus becomes the most efficient structure. Having a lot of blobs, I guess circling a common axle, might be good for self-sufficiency and redundancy, but it wouldn’t be the most cost-effective approach. Might as well connect the blobs together and have yourself a torus.

  151. If you’re looking to maximize interior space per kg of structure (and shielding) and minimize unneeded atmosphere (at areas say of less than .5G) then a torus becomes the most efficient structure. Having a lot of blobs I guess circling a common axle might be good for self-sufficiency and redundancy but it wouldn’t be the most cost-effective approach. Might as well connect the blobs together and have yourself a torus.

  152. Right. Maybe the doctor was thinking 50 feet instead of meters. Trees growing above 160 feet are actually pretty rare.

  153. Follow-up to my previous post below – I followed the link to the PDF by Pekka Janhunen, the numbers are intentional. space nss org/media/NSS-JOURNAL-Natural-Illumination-for-Rotating-Space-Settlements.pdf

  154. Follow-up to my previous post below – I followed the link to the PDF by Pekka Janhunen the numbers are intentional.space nss org/media/NSS-JOURNAL-Natural-Illumination-for-Rotating-Space-Settlements.pdf

  155. I agree it’s doable if by “rural space” you mean “intensive agricultural space”. But then you look at the other half, and 25,000 square meters per person in a urban area? 40 people per square kilometer is normally considered to be a rural population density! But 2000 square meters per person? 500 people per square kilometer? That’s normally regarded as a comfortable or even spacious suburb. And, if you look at the illustration, most of the space in the habitat is labeled “rural”. I think the most likely scenario is that the numbers just got accidentally swapped.

  156. I agree it’s doable if by rural space”” you mean “”””intensive agricultural space””””. But then you look at the other half”” and 25000 square meters per person in a urban area? 40 people per square kilometer is normally considered to be a rural population density! But 2000 square meters per person? 500 people per square kilometer? That’s normally regarded as a comfortable or even spacious suburb.And if you look at the illustration”” most of the space in the habitat is labeled “”””rural””””. I think the most likely scenario is that the numbers just got accidentally swapped.”””

  157. I saw that too, but chalked it up to his ideas that we apparently need to live like royalty to live in space, despite every sci fi movie or book, and despite real-world experience of people flocking to the cities to live in small apartments. Many people in urban areas like to stay within a few blocks radius for most of their experience. Add in VR, you certainly don’t need “enough space so that … the settlement exceed a person’s lifetime-integrated capacity to explore”. Having a (very) high ceiling at the surface level, and occasionally long sight lines would alleviate any feelings of claustrophobia. I’ve done a little research to show with intensive agriculture (and don’t need to worry about seasons), you would need maybe .1 or .2 hectares per person for decent food production. So 2000 sq. meters is indeed doable for what he calls rural space.

  158. I saw that too but chalked it up to his ideas that we apparently need to live like royalty to live in space despite every sci fi movie or book and despite real-world experience of people flocking to the cities to live in small apartments. Many people in urban areas like to stay within a few blocks radius for most of their experience. Add in VR you certainly don’t need enough space so that … the settlement exceed a person’s lifetime-integrated capacity to explore””. Having a (very) high ceiling at the surface level”” and occasionally long sight lines would alleviate any feelings of claustrophobia.I’ve done a little research to show with intensive agriculture (and don’t need to worry about seasons)”” you would need maybe .1 or .2 hectares per person for decent food production. So 2000 sq. meters is indeed doable for what he calls rural space.”””””””

  159. My understanding from research I’ve read, is that it is a non-issue for metals and ceramics, (Including silica fibers.) somewhat of an issue for plastics, (Varies from one to another.) and a real killer for elastomers.

  160. My understanding from research I’ve read is that it is a non-issue for metals and ceramics (Including silica fibers.) somewhat of an issue for plastics (Varies from one to another.) and a real killer for elastomers.

  161. Seems like multiple repeating layers of silica sand with the tops fused into thin glass sheets would distribute stress well and over the area involved tolerate a good deal of bending as well. With leakage retrieval pumps hoovering between layers, net losses would be very small over large areas.

  162. Seems like multiple repeating layers of silica sand with the tops fused into thin glass sheets would distribute stress well and over the area involved tolerate a good deal of bending as well. With leakage retrieval pumps hoovering between layers net losses would be very small over large areas.

  163. And if GoatGuy’s math is correct to with in an order of magnitude, it’s a total non-issue, as my impression from read about the topic had been.

  164. And if GoatGuy’s math is correct to with in an order of magnitude it’s a total non-issue as my impression from read about the topic had been.

  165. Here is the link to the 13 page paperhttp://space.nss.org/media/NSS-JOURNAL-Natural-Illumination-for-Rotating-Space-Settlements.pdf

  166. I solved the problem of finding a chapter of the L-5 society at Michigan Tech by founding one. It was tense problem, but I got past it. The near Earth diurnal light cycle was, explicitly. achieved by putting Venetian blinds on a 24 hour timer… The colony is pointed towards the Sun so that the light doesn’t vary with its rotation. Personally, I prefer LED lighting, it can be tuned to optimize photosynthetic efficiency, and reduce waste heat, the bane of all space colonies, and you don’t need large transparent panels, also a bit of a problem. Mind, you could filter the light at a mirror to the same end, and focus it in vacuum into some pretty narrow light pipes, so maybe LEDs aren’t the way to go. But a colony with a circumference of 31km and a roof that’s only 50-100 meters up can just rotate the mirror to move “day” around the colony on a schedule that is unconnected to the main rotation rate. If your atmosphere is only 50-100 meters thick, and maintained by a roof that’s structurally connected to the floor, it’s comparatively easy to partition the colony space into lots and lots of individual bubbles all resting on the tension hoop base, if this is seen as necessary.

  167. I solved the problem of finding a chapter of the L-5 society at Michigan Tech by founding one. It was tense problem but I got past it.The near Earth diurnal light cycle was explicitly. achieved by putting Venetian blinds on a 24 hour timer… The colony is pointed towards the Sun so that the light doesn’t vary with its rotation. Personally I prefer LED lighting it can be tuned to optimize photosynthetic efficiency and reduce waste heat the bane of all space colonies and you don’t need large transparent panels also a bit of a problem.Mind you could filter the light at a mirror to the same end and focus it in vacuum into some pretty narrow light pipes so maybe LEDs aren’t the way to go. But a colony with a circumference of 31km and a roof that’s only 50-100 meters up can just rotate the mirror to move day”” around the colony on a schedule that is unconnected to the main rotation rate.If your atmosphere is only 50-100 meters thick”” and maintained by a roof that’s structurally connected to the floor it’s comparatively easy to partition the colony space into lots and lots of individual bubbles all resting on the tension hoop base”” if this is seen as necessary.”””

  168. I failed to “socially connect” (can engineer-types socially connect?) with UCBerkeley’s L–5 society chapter. Then again, its not clear that it had one in the mid 1970s. We were still trying to avoid the brontosaurs that infested the campus. One very old idea I’ve fostered — and remain attached to — is the idea of a non-cylinder design. Cylinders penalize all kinds of ordinary happens chance. They’re integral — and sure, they’re going to have hermetic isolation doors aplenty — but leaks are leaks for the (w)hole section. Mass movement isn’t such a penalty as the things get larger: proportionately the structure is growing in total terapascal budget, and relatively each moving mass is smaller compared to the whole. By cylinders also penalize non-uniformity: by definition they’re masses concentrated around a hub as a torus. And not any-old torus, but one that at least in part is semi-circular in cross section. To deal with air pressure. Over a LARGE area. The non-cylinder / torus idea I’ve had is to utilize tethers-and-blobs at the end of them. Visualize a really big condom quarter filled with 20 kg of mercury. What’s it going to look like, suspended from the ceiling? Blob at the bottom, teardrop shaped, suspended by a long, thin strand of condom rubber. If it holds. LOL. Yet, taken as the unit-of-fabrication of a space station, around a central hub of most any length, one could “string out” blobs-on-tethers co-rotating on the axis, in tension. There are a lot of cocktail napkin issues to address: they really cannot be untethered from each other because even small changes in inertial mass distribution would result in their rotational rate changing, then bumping into each other. And “bumping is bad”, so to say. But “tethers are cheap” too. So establishing a fixed inter-blob distance around the perimeter doesn’t sound all that hard in practice. Moreover, having them isolated like little seed pods of a dandelion also divides-and-conquors the w

  169. I failed to socially connect”” (can engineer-types socially connect?) with UCBerkeley’s L–5 society chapter. Then again”” its not clear that it had one in the mid 1970s. We were still trying to avoid the brontosaurs that infested the campus. One very old idea I’ve fostered — and remain attached to — is the idea of a non-cylinder design. Cylinders penalize all kinds of ordinary happens chance. They’re integral — and sure they’re going to have hermetic isolation doors aplenty — but leaks are leaks for the (w)hole section. Mass movement isn’t such a penalty as the things get larger: proportionately the structure is growing in total terapascal budget and relatively each moving mass is smaller compared to the whole. By cylinders also penalize non-uniformity: by definition they’re masses concentrated around a hub as a torus. And not any-old torus but one that at least in part is semi-circular in cross section. To deal with air pressure. Over a LARGE area. The non-cylinder / torus idea I’ve had is to utilize tethers-and-blobs at the end of them. Visualize a really big condom quarter filled with 20 kg of mercury. What’s it going to look like suspended from the ceiling? Blob at the bottom teardrop shaped suspended by a long thin strand of condom rubber. If it holds. LOL. Yet taken as the unit-of-fabrication of a space station around a central hub of most any length”” one could “”””string out”””” blobs-on-tethers co-rotating on the axis”” in tension. There are a lot of cocktail napkin issues to address: they really cannot be untethered from each other because even small changes in inertial mass distribution would result in their rotational rate changing”” then bumping into each other. And “”””bumping is bad”””””””” so to say. But “”””tethers are cheap”””” too. So establishing a fixed inter-blob distance around the perimeter doesn’t sound all that hard in practice. Moreover”” having them isolated like little seed pods of a dandelion also”

  170. I really shouldn’t have said that, now I can’t stop thinking about how to do just that. One of the downsides of being an engineer, I guess.

  171. I really shouldn’t have said that now I can’t stop thinking about how to do just that. One of the downsides of being an engineer I guess.

  172. The numbers look good for steel and ceramics, but you wouldn’t want to use polymers for your O’Neil colony hull. And, of course, you have to consider the tensile loading, it’s going to aggravate the damage.

  173. The numbers look good for steel and ceramics but you wouldn’t want to use polymers for your O’Neil colony hull. And of course you have to consider the tensile loading it’s going to aggravate the damage.

  174. This is why I say the colonization of space on any significant scale demands that we develop Von Neumann machines. The per capita infrastructure requirements are just crazy. But if you get your factories self-reproducing, and you don’t have enough factories, you just give them a few more generations to double.

  175. This is why I say the colonization of space on any significant scale demands that we develop Von Neumann machines. The per capita infrastructure requirements are just crazy.But if you get your factories self-reproducing and you don’t have enough factories you just give them a few more generations to double.

  176. Who says unmaintained? There’s a big difference between maintaining systems, and maintaining a hull that’s in tension. You build a building, you expect to reshingle the roof periodically, but the foundation better be good for the life of the building. For an O’Neil colony, the structural component of the hull is the foundation, it’s very difficult to design one where you can replace that bit by bit.

  177. Who says unmaintained? There’s a big difference between maintaining systems and maintaining a hull that’s in tension. You build a building you expect to reshingle the roof periodically but the foundation better be good for the life of the building.For an O’Neil colony the structural component of the hull is the foundation it’s very difficult to design one where you can replace that bit by bit.

  178. It’s been a while since I ran any structural calculations on a O’Neil colony design, (Used to be a member of the L-5 society in college.) but, just off hand, a 5 km radius doesn’t sound crazy. Just running a quick calculation, if the structure were a silica fiber hoop 2m thick, you’d be looking at a 106MPa load. Not running the numbers for the air and everything, just the hoop. Since E glass has a tensile strength about thirty times that, the whole thing looks very feasible, just needs a lot of silica.

  179. It’s been a while since I ran any structural calculations on a O’Neil colony design (Used to be a member of the L-5 society in college.) but just off hand a 5 km radius doesn’t sound crazy.Just running a quick calculation if the structure were a silica fiber hoop 2m thick you’d be looking at a 106MPa load. Not running the numbers for the air and everything just the hoop. Since E glass has a tensile strength about thirty times that the whole thing looks very feasible just needs a lot of silica.

  180. As Jean Baptiste opines, its just too bad it’d cost so much. Per person. Living in a giant city sized cylinder (hey… if you think of an amount of land of just a flat patch of dirt 10 km in diameter… πr² = 3.14 × 5,000² → 78,000,000 m² or 7800 hectarea … per “level”. San Francisco is about 12,000 hectares. New York City about 75,000 hectares. So yah, these things as imagined are huge. But given that they’re not built on dirt just sitting there, on rivers not passing by, with air encircling the globe “for free”, and contained by gravity “for free” instead of drifting into deep space, the technological hurdles to overcome for a small city-in-space construction that needs to be nearly-perfectly-leak-free … Is HUGE. And “huge” near-always means “hugely expensive”. And that’s the problem. Time to reactivate that file — the Science Fiction file. This falls squarely into it. Just saying, GoatGuy

  181. As Jean Baptiste opines its just too bad it’d cost so much. Per person. Living in a giant city sized cylinder (hey… if you think of an amount of land of just a flat patch of dirt 10 km in diameter… πr² = 3.14 × 5000² → 78000000 m² or 7800 hectarea … per level””. San Francisco is about 12″”000 hectares. New York City about 75000 hectares. So yah these things as imagined are huge. But given that they’re not built on dirt just sitting there on rivers not passing by”” with air encircling the globe “”””for free”””””””” and contained by gravity “”””for free”””” instead of drifting into deep space”””” the technological hurdles to overcome for a small city-in-space construction that needs to be nearly-perfectly-leak-free … Is HUGE.And “”””huge”””” near-always means “”””hugely expensive””””. And that’s the problem.Time to reactivate that file — the Science Fiction file. This falls squarely into it.Just saying””””GoatGuy”””””””

  182. I think the sentiment “it is much slower in space than a nuclear reactor” is actually the right factual answer. Humans do poorly at more than 1 REM per year, total absorbed radiation. What’s that, https:\en.[i]Wikipedia[/i].orgwikiSievert well, the Wikipedia (change backslashes to slashes) sez [i]NASA[/i] limits astronauts to 1 Sv over their entire career. By comparison, the neutron / gamma environment of a LPR reactor, at the containment wall, in operation, at 3 GW thermal is about 1 Sv per µs. And in interplanetary space, cosmic radiation flux is about 1 Sv/year. So… 60 sec × 60 min × 24 hr × 365.25 day / (1 ÷ 1,000,000) sec → 31 TRILLION times less radiation. Just saying. If enbrittlement happens in reactor-years, 31 trillion of them is quite a bit longer. Than I intend to live. LOL GoatGuy ( I could be off by a factor of a million … or ten … and it’d still be usefully instructive.)

  183. I think the sentiment it is much slower in space than a nuclear reactor”” is actually the right factual answer. Humans do poorly at more than 1 REM per year”” total absorbed radiation. What’s that https:\\en.[i]Wikipedia[/i].org\wiki\Sievert well the Wikipedia (change backslashes to slashes) sez [i]NASA[/i] limits astronauts to 1 Sv over their entire career. By comparison the neutron / gamma environment of a LPR reactor at the containment wall in operation at 3 GW thermal is about 1 Sv per µs. And in interplanetary space cosmic radiation flux is about 1 Sv/year. So…60 sec × 60 min × 24 hr × 365.25 day / (1 ÷ 10000) sec → 31 TRILLION times less radiation. Just saying.If enbrittlement happens in reactor-years”” 31 trillion of them is quite a bit longer.Than I intend to live. LOLGoatGuy( I could be off by a factor of a million … or ten … and it’d still be usefully instructive.)”””””””

  184. Generally we’re on the same page. 5 km radius to deliver 8 m/s² (N/kg) AT the rim of centripetal force rotates at 0.38 RPM → 23 revolutions per hour. Modeled (my design option) as a centripetal ring delivering ±10% of that 8 m/s² force, the radial range is 4,000 to 6,000 m; this of course just memorializes that F = ω²r or rotational rate squared times radius. Radius is linear related to centripetal force for fixed omega; I have a pretty detailed model for this (physics / structurally), but I have to say… in the end to me it seemed like 5 km radius is quite a bit larger than might reasonably be practical — even with nearly magical super strong low mass materials. For instance, figuring 150 MPa “section tether” tensile strength, with both radial and axial tension methods to handle the centripetal force of the whole contraption, at 1,250 m radius, the 150 radial spokes would each have diameters of 8 m² per. At 5,000 m radius, the 600 spokes would each need 120 m² area. The centripetal forces are prodigious: 1.1×10¹³ N … just of the outer rim attempting to fly away. Now granted, “my design” for a 10 km diameter job has an outer ring twice as “wide” as it is thick. 4000 m wide, 2000 m thick. 5,000 m radius. 23 RPH. 7.2 to 8.8 m/s² centripetal force. 10 kg/m³ mean density. 125,000,000,000 m³ total volume in ring. 1.2 billion tons. Room for 6,000,000 people, each having about 5,000 m³ of “volume share”. All in … Then you sit back with a nice Extra Special Bitter and watch the pipe smoke swirl about, and think, “Dâhmn! This is ridiculous!” Just saying, GoatGuy

  185. Generally we’re on the same page.5 km radius to deliver 8 m/s² (N/kg) AT the rim of centripetal force rotates at 0.38 RPM → 23 revolutions per hour. Modeled (my design option) as a centripetal ring delivering ±10{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12} of that 8 m/s² force the radial range is 4000 to 6000 m; this of course just memorializes that F = ω²r or rotational rate squared times radius. Radius is linear related to centripetal force for fixed omega; I have a pretty detailed model for this (physics / structurally) but I have to say… in the end to me it seemed like 5 km radius is quite a bit larger than might reasonably be practical — even with nearly magical super strong low mass materials. For instance figuring 150 MPa section tether”” tensile strength”” with both radial and axial tension methods to handle the centripetal force of the whole contraption at 1250 m radius the 150 radial spokes would each have diameters of 8 m² per. At 5000 m radius the 600 spokes would each need 120 m² area. The centripetal forces are prodigious: 1.1×10¹³ N … just of the outer rim attempting to fly away. Now granted”” “”””my design”””” for a 10 km diameter job has an outer ring twice as “”””wide”””” as it is thick. 4000 m wide”” 2000 m thick. 5000 m radius. 23 RPH. 7.2 to 8.8 m/s² centripetal force. 10 kg/m³ mean density. 12500000 m³ total volume in ring. 1.2 billion tons. Room for 60000 people each having about 5″”000 m³ of “”””volume share””””. All in … Then you sit back with a nice Extra Special Bitter and watch the pipe smoke swirl about”” and think”” “”””Dâhmn! This is ridiculous!”””” Just saying”””” GoatGuy”””””””

  186. Why would you want to live in Texas with all the snakes and bitty things and heat, Upper midwest with all the snow and insane temps, Florida and all the Humidity and ancient Crocs and snakes…..

    You get the point. I would hate to live in a boring place like California where the weather is so predictable and bland. I would hate New York with all those shops people love and such.
    Matheus, people are different and want different things.

  187. I did a quick search, and apparently metals and ceramics are fairly safe for long term use, centuries, in normal space radiation environments. Silica fiber is particularly good. OTOH, polymers don’t handle it so well. You’d probably want to avoid the use of polymers on the outside of the habitat, though they’d likely be ok for use inside.

  188. I did a quick search and apparently metals and ceramics are fairly safe for long term use centuries in normal space radiation environments. Silica fiber is particularly good. OTOH polymers don’t handle it so well. You’d probably want to avoid the use of polymers on the outside of the habitat though they’d likely be ok for use inside.

  189. You’d have trouble fitting a Sequoia under a 50 meter roof. But a Sequoia would concentrate enough weight in one place to cause structural concerns anyway. A bit of quick research suggests at 250m of ceiling height would be serious overkill, 120 meters would do fine, it would only be needed if you were deliberately choosing unusually tall tree species.

  190. You’d have trouble fitting a Sequoia under a 50 meter roof. But a Sequoia would concentrate enough weight in one place to cause structural concerns anyway. A bit of quick research suggests at 250m of ceiling height would be serious overkill 120 meters would do fine it would only be needed if you were deliberately choosing unusually tall tree species.

  191. Ok, looking at it further, this does NOT look like a natural shape for a pressurized compartment. You could, of course, maintain a pressurized volume in this shape with enough internal stays. Approximately one 18mm Spectra rope per square meter would do the trick, but they wouldn’t have to be one to a square meter, you could space them at wider intervals if they were thicker, and distribute the load towards the end. But they don’t seem to envision living in a forest of ropes, and a quick scan didn’t turn up any mention of internal stays. However, the talk of reducing structural requirements by a shallow atmosphere only makes sense if the load from the roof is transferred to the floor. Further, the stays would contribute about 200 grams of mass per cubic meter of interior. OK, the air would be 6 times that, so you might indeed save weight by doing it this way. Structurally it looks like a feasible design, just with key details omitted. I really don’t like the lighting scheme, though.

  192. Ok looking at it further this does NOT look like a natural shape for a pressurized compartment. You could of course maintain a pressurized volume in this shape with enough internal stays. Approximately one 18mm Spectra rope per square meter would do the trick but they wouldn’t have to be one to a square meter you could space them at wider intervals if they were thicker and distribute the load towards the end.But they don’t seem to envision living in a forest of ropes and a quick scan didn’t turn up any mention of internal stays. However the talk of reducing structural requirements by a shallow atmosphere only makes sense if the load from the roof is transferred to the floor.Further the stays would contribute about 200 grams of mass per cubic meter of interior. OK the air would be 6 times that so you might indeed save weight by doing it this way.Structurally it looks like a feasible design just with key details omitted. I really don’t like the lighting scheme though.

  193. Good point on the radiators.

    Heat radiation is covered in their paper, and yes it is a significant issue as we all know.

    However, I suspect (no I’m not doing the calculations, I’m supposed to be reviewing a spreadsheet on my other screen) that if, as stated, the vast majority of structure and material (i.e. cost) is required to provide a stable, radiation shielded volume, then
    1. Use the shielded volume as efficiently as possible (ie. multiple layers)
    2. Use unshielded volume to put your radiators in.

    So, off the top of my head, you get something that looks like a jet turbine fan disk. The inner core, running out to maybe 2/3 of the total radius, is your shielded volume with the outer layers being ~ 1g living spaces and multiple layers on top of that (at lower g, but still fine for plants I guess, and of course fine for humans to go if they don’t live there) being the “outdoorsy” bits.

    Then, radiating out from there are the “fan blades”. Thin radiators built largely in tension for low mass. The only bit that makes it less than ideally elegant is that the radiators hang “down” so you can’t use natural convection.

  194. That just means it happens slower. Tensile structural materials are inherently vulnerable to radiation damage, and you’d want a habitat’s structure to last for centuries. How long is Spectra loaded to maybe 20% of it’s yield strength good for under typical radiation levels in space?

  195. up to 25,000 m2 of urban living area and 2000 m2 of rural area per inhabitant ” Are you sure you didn’t get those numbers swapped? Because I used to live in the country, and 2000 square meters would have fit in my front yard with room to spare, it’s a tiny space by rural standards,

  196. up to 25″000 m2 of urban living area and 2000 m2 of rural area per inhabitant “”Are you sure you didn’t get those numbers swapped? Because I used to live in the country”” and 2000 square meters would have fit in my front yard with room to spare it’s a tiny space by rural standards”

  197. Another issue that concerns me is how they are using high strength steel in their calculations. Indeed they keep referring to piano wire.

    I can’t say this is WRONG per se. But it makes me uneasy.

    1. Piano wire is a very… childish? amatuerish? way to talk about high strength steel. It’s very much the sort of thing that you would choose to illustrate the concept to your grandmother. Assuming she didn’t know much about steel. Yes it’s strong, but it’s clearly not what you would make a space station out of. Much better to talk of submarine or ship hulls. But then they aren’t anywhere near as strong. It turns out that the very hard material drawn out into fine wires are very difficult to replicate in thick hulls. Both for engineering reasons and for reasons of basic physics.

    2. Surely a much better option would be to look at nickel iron asteroids, and use that material as a guide.

    Neither of these are showstoppers, but it looks like the kind of thing a 2nd year engineering student would come up with and plug into some equations without a broader understanding.

    Like I said, not wrong as such, but the wrong flavour.

  198. Nah, I don’t think in feet. I’d actually have trouble visualising what a 50 foot tree looks like. (About 15 meters tall I’d guess.)

    My point isn’t that you’ll have all these trees hitting the ceiling (though I would prefer if my luxury gardens DID have some Mountain ash or something) but that you’ll have a ceiling that is clearly THERE. You’ll get echoes from it. Birds couldn’t fly at normal heights. The trees will be distorted (remember the light is coming from the side and being reflected down.)

    And more generally that you’ve spent astronomical resources to create this volume of radiation free, supported space, and then you are only using the surface of it.

  199. If you read the paper there was no swapping. The clear intent is a vast, enormous internal area and the minimum outside required to easily grow enough food for the population. And they did the calculations of each, so there was no accidental switching.

    The internal area is achieved by having multiple floors, which lets you stack much, much more floorspace into a given volume.

    One wonders why they didn’t try stacking the plant growing region into multiple floors. That would have given them much more area for a given about of outside wall (which is the vast majority of the structure and hence cost).

  200. Space exploration is for robots not for humans Why a man should be interested in go live in a moon of Jupiter?

  201. Why noh really , why on Earth should someone be interested to live on the Moon? There are quite a few interesting places on Earth. Space “exploration” is for robots not for hmans

  202. Why noh really why on Earth should someone be interested to live on the Moon? There are quite a few interesting places on Earth. Space exploration”” is for robots not for hmans”””

  203. If you’re looking to maximize interior space per kg of structure (and shielding) and minimize unneeded atmosphere (at areas say, of less than .5G), then a torus becomes the most efficient structure. Having a lot of blobs, I guess circling a common axle, might be good for self-sufficiency and redundancy, but it wouldn’t be the most cost-effective approach. Might as well connect the blobs together and have yourself a torus.

  204. Follow-up to my previous post below – I followed the link to the PDF by Pekka Janhunen, the numbers are intentional.

    space nss org/media/NSS-JOURNAL-Natural-Illumination-for-Rotating-Space-Settlements.pdf

  205. I agree it’s doable if by “rural space” you mean “intensive agricultural space”. But then you look at the other half, and 25,000 square meters per person in a urban area? 40 people per square kilometer is normally considered to be a rural population density!

    But 2000 square meters per person? 500 people per square kilometer? That’s normally regarded as a comfortable or even spacious suburb.

    And, if you look at the illustration, most of the space in the habitat is labeled “rural”. I think the most likely scenario is that the numbers just got accidentally swapped.

  206. I saw that too, but chalked it up to his ideas that we apparently need to live like royalty to live in space, despite every sci fi movie or book, and despite real-world experience of people flocking to the cities to live in small apartments. Many people in urban areas like to stay within a few blocks radius for most of their experience. Add in VR, you certainly don’t need “enough space so that … the settlement exceed a person’s lifetime-integrated capacity to explore”. Having a (very) high ceiling at the surface level, and occasionally long sight lines would alleviate any feelings of claustrophobia.

    I’ve done a little research to show with intensive agriculture (and don’t need to worry about seasons), you would need maybe .1 or .2 hectares per person for decent food production. So 2000 sq. meters is indeed doable for what he calls rural space.

  207. My understanding from research I’ve read, is that it is a non-issue for metals and ceramics, (Including silica fibers.) somewhat of an issue for plastics, (Varies from one to another.) and a real killer for elastomers.

  208. Seems like multiple repeating layers of silica sand with the tops fused into thin glass sheets would distribute stress well and over the area involved tolerate a good deal of bending as well. With leakage retrieval pumps hoovering between layers, net losses would be very small over large areas.

  209. I don’t like how the roof is only 50 m from the floor. That is shorter than a lot of normal trees. I mean it would be fine and liveable, but if we want luxury living “Standard of living reminiscent to contemporary royal families on Earth, quantified by up to 25,000 m2 of urban living area and 2000 m2 of rural area per inhabitant ” then a low ceiling and no big trees seems to be starting off on the wrong foot. Especially if you want birds and things living there. Now cranking it up to say 250 m of ceiling height only requires another (2000 sq.m x 200 m x 1.3 equals 520 tonnes of air/capita). Whereas the walls (errr.. floor) are supposed to be 10 tonnes/sq.m x 2000 sq.m equals 20 000 tonnes. So the extra air is trivial. I suspect they haven’t seen the work on atmospheric scoops that means that getting oxygen and nitrogen to earth orbit might be even easier and cheaper than asteroid material.

  210. I don’t like how the roof is only 50 m from the floor. That is shorter than a lot of normal trees.I mean it would be fine and liveable but if we want luxury living Standard of living reminiscent to contemporary royal families on Earth” quantified by up to 25″000 m2 of urban living area and 2000 m2 of rural area per inhabitant “” then a low ceiling and no big trees seems to be starting off on the wrong foot. Especially if you want birds and things living there.Now cranking it up to say 250 m of ceiling height only requires another (2000 sq.m x 200 m x 1.3 equals 520 tonnes of air/capita).Whereas the walls (errr.. floor) are supposed to be 10 tonnes/sq.m x 2000 sq.m equals 20 000 tonnes. So the extra air is trivial.I suspect they haven’t seen the work on atmospheric scoops that means that getting oxygen and nitrogen to earth orbit might be even easier and cheaper than asteroid material.”””

  211. Maybe our nuclear scientists can leap in here, but if you are relying on the structural mass of your construction to provide radiation shielding, then will the material properties of your structure be weakened by radiation, the way it happens in reactors?

  212. Maybe our nuclear scientists can leap in here but if you are relying on the structural mass of your construction to provide radiation shielding then will the material properties of your structure be weakened by radiation the way it happens in reactors?

  213. Nice revisiting of the High Frontier, with slightly less ambitious objectives (no full O’Neill cylinder, but close) and probably far more updated requirement calculations. Nevertheless, this still suffers from the same problem: who’t gonna pay for this in the beginning? My hope is that we can make a viable case for space settlement in orbit with far less ambitious plans. Like some labs and commercial facilities using rotational gravity in LEO, protected from radiation by Earth’s magnetosphere, for showing it can be done profitably. Having access to both gravity and weightlessness in a same factory/building ought to have some commercial value. If does for human habitation, so probably some orbital enterprise requiring human presence for some long periods will be the first one of giving a healthier environment to its employees. Or a space hotel, catering to tourists looking for a exotic getaway but without relinquishing all the comforts of Earthly life. But from that to this, there is a long road.

  214. Nice revisiting of the High Frontier with slightly less ambitious objectives (no full O’Neill cylinder but close) and probably far more updated requirement calculations.Nevertheless this still suffers from the same problem: who’t gonna pay for this in the beginning?My hope is that we can make a viable case for space settlement in orbit with far less ambitious plans. Like some labs and commercial facilities using rotational gravity in LEO protected from radiation by Earth’s magnetosphere for showing it can be done profitably. Having access to both gravity and weightlessness in a same factory/building ought to have some commercial value.If does for human habitation so probably some orbital enterprise requiring human presence for some long periods will be the first one of giving a healthier environment to its employees. Or a space hotel catering to tourists looking for a exotic getaway but without relinquishing all the comforts of Earthly life.But from that to this there is a long road.

  215. I solved the problem of finding a chapter of the L-5 society at Michigan Tech by founding one. It was tense problem, but I got past it.

    The near Earth diurnal light cycle was, explicitly. achieved by putting Venetian blinds on a 24 hour timer… The colony is pointed towards the Sun so that the light doesn’t vary with its rotation. Personally, I prefer LED lighting, it can be tuned to optimize photosynthetic efficiency, and reduce waste heat, the bane of all space colonies, and you don’t need large transparent panels, also a bit of a problem.

    Mind, you could filter the light at a mirror to the same end, and focus it in vacuum into some pretty narrow light pipes, so maybe LEDs aren’t the way to go. But a colony with a circumference of 31km and a roof that’s only 50-100 meters up can just rotate the mirror to move “day” around the colony on a schedule that is unconnected to the main rotation rate.

    If your atmosphere is only 50-100 meters thick, and maintained by a roof that’s structurally connected to the floor, it’s comparatively easy to partition the colony space into lots and lots of individual bubbles all resting on the tension hoop base, if this is seen as necessary.

  216. I love the thinking behind this. What primarily drove European colonization of the Americas wasn’t a desire to explore but the opportunity to have a much higher standard of living than could be expected in Europe. Being able to offer that in off-world settlements will be key to driving migration. We too often get caught up in what would be the minimum viable option to enable settlements, but who wants to live at a minimal standard of living?

  217. I love the thinking behind this. What primarily drove European colonization of the Americas wasn’t a desire to explore but the opportunity to have a much higher standard of living than could be expected in Europe. Being able to offer that in off-world settlements will be key to driving migration. We too often get caught up in what would be the minimum viable option to enable settlements but who wants to live at a minimal standard of living?

  218. I failed to “socially connect” (can engineer-types socially connect?) with UCBerkeley’s L–5 society chapter. Then again, its not clear that it had one in the mid 1970s. We were still trying to avoid the brontosaurs that infested the campus.

    One very old idea I’ve fostered — and remain attached to — is the idea of a non-cylinder design. Cylinders penalize all kinds of ordinary happens chance.

    They’re integral — and sure, they’re going to have hermetic isolation doors aplenty — but leaks are leaks for the (w)hole section. Mass movement isn’t such a penalty as the things get larger: proportionately the structure is growing in total terapascal budget, and relatively each moving mass is smaller compared to the whole. By cylinders also penalize non-uniformity: by definition they’re masses concentrated around a hub as a torus. And not any-old torus, but one that at least in part is semi-circular in cross section. To deal with air pressure. Over a LARGE area.

    The non-cylinder / torus idea I’ve had is to utilize tethers-and-blobs at the end of them. Visualize a really big condom quarter filled with 20 kg of mercury. What’s it going to look like, suspended from the ceiling? Blob at the bottom, teardrop shaped, suspended by a long, thin strand of condom rubber. If it holds. LOL.

    Yet, taken as the unit-of-fabrication of a space station, around a central hub of most any length, one could “string out” blobs-on-tethers co-rotating on the axis, in tension. There are a lot of cocktail napkin issues to address: they really cannot be untethered from each other because even small changes in inertial mass distribution would result in their rotational rate changing, then bumping into each other.

    And “bumping is bad”, so to say. But “tethers are cheap” too. So establishing a fixed inter-blob distance around the perimeter doesn’t sound all that hard in practice. Moreover, having them isolated like little seed pods of a dandelion also divides-and-conquors the whole-system-leakage problem. Each can be its own self-sustaining environment.

    Given that the rotational rate tho’ varies from 70 RPH to 23 RPH (1,000 to 10,000 m diameter), I personally don’t see how this author’s claim of having near-Earth like diurnal light cycles is possible. I frankly think that whatever lighting the Humans will need will be artificially provided. Any light that the agricultural side needs will be flipping with the rotational rate. And the plants really don’t care. At least most of them.

    Moreover, if we remember that this is “the future”, there is a LONG time ‘twixt now and then to genetically engineer all food-source plants to deal with rapidly changing light cycles.

    Just Saying,
    GoatGuy

  219. The numbers look good for steel and ceramics, but you wouldn’t want to use polymers for your O’Neil colony hull. And, of course, you have to consider the tensile loading, it’s going to aggravate the damage.

  220. This is why I say the colonization of space on any significant scale demands that we develop Von Neumann machines. The per capita infrastructure requirements are just crazy.

    But if you get your factories self-reproducing, and you don’t have enough factories, you just give them a few more generations to double.

  221. Who says unmaintained? There’s a big difference between maintaining systems, and maintaining a hull that’s in tension. You build a building, you expect to reshingle the roof periodically, but the foundation better be good for the life of the building.

    For an O’Neil colony, the structural component of the hull is the foundation, it’s very difficult to design one where you can replace that bit by bit.

  222. It’s been a while since I ran any structural calculations on a O’Neil colony design, (Used to be a member of the L-5 society in college.) but, just off hand, a 5 km radius doesn’t sound crazy.

    Just running a quick calculation, if the structure were a silica fiber hoop 2m thick, you’d be looking at a 106MPa load. Not running the numbers for the air and everything, just the hoop. Since E glass has a tensile strength about thirty times that, the whole thing looks very feasible, just needs a lot of silica.

  223. As Jean Baptiste opines, its just too bad it’d cost so much. Per person. Living in a giant city sized cylinder (hey… if you think of an amount of land of just a flat patch of dirt 10 km in diameter… πr² = 3.14 × 5,000² → 78,000,000 m² or 7800 hectarea … per “level”. San Francisco is about 12,000 hectares. New York City about 75,000 hectares.

    So yah, these things as imagined are huge.

    But given that they’re not built on dirt just sitting there, on rivers not passing by, with air encircling the globe “for free”, and contained by gravity “for free” instead of drifting into deep space, the technological hurdles to overcome for a small city-in-space construction that needs to be nearly-perfectly-leak-free …

    Is HUGE.

    And “huge” near-always means “hugely expensive”.
    And that’s the problem.

    Time to reactivate that file — the Science Fiction file.
    This falls squarely into it.

    Just saying,
    GoatGuy

  224. I think the sentiment “it is much slower in space than a nuclear reactor” is actually the right factual answer.

    Humans do poorly at more than 1 REM per year, total absorbed radiation. What’s that, https:\\en.[i]Wikipedia[/i].org\wiki\Sievert well, the Wikipedia (change backslashes to slashes) sez [i]NASA[/i] limits astronauts to 1 Sv over their entire career. By comparison, the neutron / gamma environment of a LPR reactor, at the containment wall, in operation, at 3 GW thermal is about 1 Sv per µs. And in interplanetary space, cosmic radiation flux is about 1 Sv/year. So…

    60 sec × 60 min × 24 hr × 365.25 day / (1 ÷ 1,000,000) sec → 31 TRILLION times less radiation.

    Just saying.
    If enbrittlement happens in reactor-years, 31 trillion of them is quite a bit longer.
    Than I intend to live.

    LOL
    GoatGuy

    ( I could be off by a factor of a million … or ten … and it’d still be usefully instructive.)

  225. Generally we’re on the same page.

    5 km radius to deliver 8 m/s² (N/kg) AT the rim of centripetal force rotates at 0.38 RPM → 23 revolutions per hour. Modeled (my design option) as a centripetal ring delivering ±10% of that 8 m/s² force, the radial range is 4,000 to 6,000 m; this of course just memorializes that F = ω²r or rotational rate squared times radius. Radius is linear related to centripetal force for fixed omega;

    I have a pretty detailed model for this (physics / structurally), but I have to say… in the end to me it seemed like 5 km radius is quite a bit larger than might reasonably be practical — even with nearly magical super strong low mass materials.

    For instance, figuring 150 MPa “section tether” tensile strength, with both radial and axial tension methods to handle the centripetal force of the whole contraption, at 1,250 m radius, the 150 radial spokes would each have diameters of 8 m² per. At 5,000 m radius, the 600 spokes would each need 120 m² area. The centripetal forces are prodigious: 1.1×10¹³ N … just of the outer rim attempting to fly away.

    Now granted, “my design” for a 10 km diameter job has an outer ring twice as “wide” as it is thick. 4000 m wide, 2000 m thick. 5,000 m radius. 23 RPH. 7.2 to 8.8 m/s² centripetal force. 10 kg/m³ mean density. 125,000,000,000 m³ total volume in ring. 1.2 billion tons. Room for 6,000,000 people, each having about 5,000 m³ of “volume share”. All in …

    Then you sit back with a nice Extra Special Bitter and watch the pipe smoke swirl about, and think, “Dâhmn! This is ridiculous!”

    Just saying,
    GoatGuy

  226. ” That just means it happens slower. ” <-- And I cannot see us designing to live in 100yo unmaintained, unmaintainable space colonies anymore than we live in 100yo, unmaintained and unmaintainable ships.

  227. I did a quick search, and apparently metals and ceramics are fairly safe for long term use, centuries, in normal space radiation environments. Silica fiber is particularly good.

    OTOH, polymers don’t handle it so well.

    You’d probably want to avoid the use of polymers on the outside of the habitat, though they’d likely be ok for use inside.

  228. You’d have trouble fitting a Sequoia under a 50 meter roof. But a Sequoia would concentrate enough weight in one place to cause structural concerns anyway. A bit of quick research suggests at 250m of ceiling height would be serious overkill, 120 meters would do fine, it would only be needed if you were deliberately choosing unusually tall tree species.

  229. Ok, looking at it further, this does NOT look like a natural shape for a pressurized compartment. You could, of course, maintain a pressurized volume in this shape with enough internal stays. Approximately one 18mm Spectra rope per square meter would do the trick, but they wouldn’t have to be one to a square meter, you could space them at wider intervals if they were thicker, and distribute the load towards the end.

    But they don’t seem to envision living in a forest of ropes, and a quick scan didn’t turn up any mention of internal stays. However, the talk of reducing structural requirements by a shallow atmosphere only makes sense if the load from the roof is transferred to the floor.

    Further, the stays would contribute about 200 grams of mass per cubic meter of interior. OK, the air would be 6 times that, so you might indeed save weight by doing it this way.

    Structurally it looks like a feasible design, just with key details omitted. I really don’t like the lighting scheme, though.

  230. That just means it happens slower. Tensile structural materials are inherently vulnerable to radiation damage, and you’d want a habitat’s structure to last for centuries. How long is Spectra loaded to maybe 20% of it’s yield strength good for under typical radiation levels in space?

  231. ” up to 25,000 m2 of urban living area and 2000 m2 of rural area per inhabitant ”

    Are you sure you didn’t get those numbers swapped? Because I used to live in the country, and 2000 square meters would have fit in my front yard with room to spare, it’s a tiny space by rural standards,

  232. I don’t like how the roof is only 50 m from the floor. That is shorter than a lot of normal trees.
    I mean it would be fine and liveable, but if we want luxury living “Standard of living reminiscent to contemporary royal families on Earth, quantified by up to 25,000 m2 of urban living area and 2000 m2 of rural area per inhabitant ” then a low ceiling and no big trees seems to be starting off on the wrong foot. Especially if you want birds and things living there.

    Now cranking it up to say 250 m of ceiling height only requires another (2000 sq.m x 200 m x 1.3 equals 520 tonnes of air/capita).

    Whereas the walls (errr.. floor) are supposed to be 10 tonnes/sq.m x 2000 sq.m equals 20 000 tonnes. So the extra air is trivial.

    I suspect they haven’t seen the work on atmospheric scoops that means that getting oxygen and nitrogen to earth orbit might be even easier and cheaper than asteroid material.

  233. Maybe our nuclear scientists can leap in here, but if you are relying on the structural mass of your construction to provide radiation shielding, then will the material properties of your structure be weakened by radiation, the way it happens in reactors?

  234. Nice revisiting of the High Frontier, with slightly less ambitious objectives (no full O’Neill cylinder, but close) and probably far more updated requirement calculations.

    Nevertheless, this still suffers from the same problem: who’t gonna pay for this in the beginning?

    My hope is that we can make a viable case for space settlement in orbit with far less ambitious plans.

    Like some labs and commercial facilities using rotational gravity in LEO, protected from radiation by Earth’s magnetosphere, for showing it can be done profitably. Having access to both gravity and weightlessness in a same factory/building ought to have some commercial value.

    If does for human habitation, so probably some orbital enterprise requiring human presence for some long periods will be the first one of giving a healthier environment to its employees. Or a space hotel, catering to tourists looking for a exotic getaway but without relinquishing all the comforts of Earthly life.

    But from that to this, there is a long road.

  235. I love the thinking behind this. What primarily drove European colonization of the Americas wasn’t a desire to explore but the opportunity to have a much higher standard of living than could be expected in Europe. Being able to offer that in off-world settlements will be key to driving migration. We too often get caught up in what would be the minimum viable option to enable settlements, but who wants to live at a minimal standard of living?

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