Lighting up a megacity at night will lead to night solar farm lighting

Chengdu plans to launch in 2020 a mirror satellite to create dusk lighting at night. The satellite will appear to be 8 times a full moon. They believe this will remove the need for most street lighting which will save power and reduce air pollution. They dusk level of lighting may not disturb animals or plants.

I believe lighting up a megacity at night is only step one. China has the most solar farms in the world. Large 5-gigawatt solar farms have the area of a megacity. China is preparing to triple the capital value of its solar farms. A constellation of $37 billion of solar mirror satellites will boost several large solar farms and would twice the power and efficiency of the Three Gorges Dam.

This would clear a path to China having 70-80% baseload energy from solar. This would mean significant chunks of China perhaps a few hundred massive solar farms would have constant light. People could then wring their hands about the nocturnal animals. But full realization of this plan would enable China to phase out coal power with zero emission power.

So will environmentalists get behind this plan? Has the panic over the IPCC climate report been real or not? Do they really want to have massive reduction of fossil fuel or not? The affordable and scalable paths to massive fossil fuel reduction involve converting solar to constant power production with huge mirror satellite constellations and factory mass produced nuclear power.

Do people think this is not where China is going with this? Although lighting up a megacity at night is a big and bold move. It does not move the big energy or environment needle for China (or the world). I think it is pretty clear the end game is lighting up the big solar farms. China has the most and biggest solar farms and the most solar power in the world. China has to get rid of the coal.

Upward of 70 percent of China’s utility-scale wind and solar farms have been built in the country’s sparsely populated northern provinces.

By 2020, China is planning to build 16 new ultra-high-voltage DC lines, on top of eight already in operation, connecting these provinces to coastal load centers, according to BNEF analysts. Less than half of these lines are designated to transmit renewable electricity. Lighting solar power at night would require more ultra-high-voltage DC lines, but China does not have any issues with more large construction.

More about the Chengdu fake full moon satellite

The Chengdu night light mirror satellite will be able to illuminate an area with a diameter between 10 and 80 km, while the precise lighting beam can be controlled in a few tens of meters.

Satellite tests started years ago and now the technology is ready to be put into practice.

Kang Weimin – director of the Institute of Optics, School of Aerospace, Harbin Institute of Technology – tries to calm the concerned animalists and explained that the satellite light will be like a twilight glow; therefore it should not affect the routine of the animals.

Chengdu is the capital of southwestern China’s Sichuan province and it has about 14-15 million people.

Where is China’s solar power now?

China’s solar deployment is concentrated overwhelmingly in a handful of provinces, many of them in rural areas located far from population centers that need electricity and in areas where transmission development has not kept pace with renewables deployment and there is little storage capacity. Some of those provinces, solar-curtailment rates have approached 30%.

Solar curtailment is the rejection by China’s grid operators of a portion of the electricity that China’s solar projects generate.

The grid operators cannot take the extra power from spikes in the solar power generation. Mirror satellites can smooth out the power and make it more predictable.

Solar power remains a negligible energy source globally, contributing only about 1-2% to worldwide electricity production.

It is no forgone conclusion that solar will become cost-competitive at a scale necessary to meaningfully curb carbon emissions.

The Three Gorges Dam’s output amounted to one-third of the 253 million megawatt-hours of electricity produced in 2015 by all of the solar installations on the planet combined.

In 2016, China produced 71% of the world’s solar modules, IHS Markit estimates. China installs the majority of them within its borders—mainly in large solar farms in a handful of Chinese provinces.

Precursor to perpetual lighting for big solar farms

Mirror satellites can be used to provide constant light for large solar farms. This could remove the need for battery storage.

This city scale lighting looks step two on a roadmap to lighting of 5 Gigawatt solar farms at night.

Lightweight mirrors in a Dawn-Dusk Orbit beam sunlight to earth PV stations providing solar electricity in evening winter for 14 hours per day increasing solar power station capacity factor to 60% and reducing solar electricity cost to under 6 cents / kWh.

JX Crystals proposed satellite mirrors to boost solar power on earth.

Assumptions – 2025 – Revenue
1.) 18 satellites in dawn/dusk orbit 1000 km above earth.
2.) The sun’s disc diameter viewed from earth is 10 mrad. This implies solar spot size on earth from a mirror up 1000 km equal 1000 tan(10 mrad) = 10 km.
3.) Assume each mirror satellite array has diameter of 10 km.
4.) Now assume that in the year 2022 there are 40 ground stations distributed around
the world that the 18 satellite constellation will serve and that the constellation gives 1 hr x 0.7 kW/m2 of sunlight to each station in both the morning and in the evening for a total of 2 hr x 0.7 kW/m2 of sunlight per day per station.
5.) Combined, the 40 earth stations will produce 5.5 x 40 = 220 GW. Assume that the
price for electricity is $0.1 / kWh, annual revenue = $3×10^10 / yr = $16 billion per yr.

Mirror Satellite Constellation Cost
It all depends on launch cost for LEO orbit.
The ISC SPS study (4) assume $400 per kg. SpaceX Falcon Heavy (7) = $1,100 per kg.
MiraSolar sat (4) cost $0.6 B; constellation (4) $11 B.
MiraSolar sat (7) cost $1.8 B; constellation (7) $32 B.

Payback time range:
Assuming 40 ground stations and $400 per kg launch cost: 0.7 years.
Assuming 40 ground stations and $1100 per kg launch cost: 2 years.

163 thoughts on “Lighting up a megacity at night will lead to night solar farm lighting”

  1. You can BET it will disrupt the sleeping habits of insects, animals, plants and anything else that has a circadian rhythm.

  2. I wonder if 8x brightness is an achievement or what is appropriate for the application. If you could make it 1000x brightness it would only take a few hundred satellites to make the region a 24/7 growing operation. A hundred might let you tame the winters and seriously extend the grow seasons for the region.

  3. You can BET it will disrupt the sleeping habits of insects animals plants and anything else thathas a circadian rhythm.

  4. I wonder if 8x brightness is an achievement or what is appropriate for the application. If you could make it 1000x brightness it would only take a few hundred satellites to make the region a 24/7 growing operation. A hundred might let you tame the winters and seriously extend the grow seasons for the region.

  5. Another drawback: If these satellites are in 1,000km orbits and 18 are needed to keep a city in “dusk” (over 12 hours or 24?), then they will need to change orientation before and after each pass over the city to avoid lighting up a path around the world. That means a fair amount of propulsion/power to reorient a 10km(? Is that even technically feasible today?) dish twice a day. The last thing you want to do is add light to already sun lit areas. I suppose the same 18 sats could service other cities on the same latitude, right? Sorry, just having a hard time imagining how 18-10km wide satellites will work… And another thing: Isn’t it “bad” to be adding all that energy/heat through the atmosphere?

  6. If you put the mirror in a low orbit, you can illuminate just a city, but not for long, because your mirror will be sweeping across the sky, and will end up in the Earth’s shadow quick enough. If you put the mirror in a high orbit, ideally geosynchronous, you can illuminate the same point as long as you want, but your minimum spot size will be over 300 km in diameter. So, this isn’t aimed at just a city. It’s going to light up the area of a mid sized state.

  7. I was going to comment the exact same thing, but then I thought: They’re going to be illuminating megalopolitan areas, and it’s not like the neon, LED, mercury and low-pressure sodium lighting (not to mention the godawful noise) isn’t ALREADY throwing off the circadiam rhythm of everything in the area. If they happen to illuminate some rural area with this, then I agree it’s probably ill-advised. Heck, it might be ill-advised anyway because of something else we haven’t thought of. File this under “needs more consideration”.

  8. Didn’t we already run the numbers on this? (In comments that Brian threw away, of course…) If you’re up in geosynchronous orbit, which is kind of necessary if you mean to illuminate the same area all night, you’re about 36,000 km up. At the equator, it gets a bit worse away from it. Sunlight is about 400,000 times brighter than Moonlight. So they’re aiming for 0.00002 suns illumination. Assuming a perfect mirror, you’re going to get a spot size of about 334 km wide, from geosynch. To achieve the targeted brightness… a 1.5km diameter mirror. OK, guess it’s feasible, but they’re not going to be illuminating a city, they’re illuminating an entire region.

  9. Can it be focussed more tightly like in Die Another Day? That’s the real question, because if you can concentrate a 10km area of light down to 10m, you’ve got yourself a death ray. The Sun is ~4E5 times brighter than the Moon, the reflector 8 times. That makes the sun 5E4 times brighter than the reflector. A 10m circle is 1E6 times smaller than a 10km circle, 1E6 / 5E4 gives us ~20 times brighter than the sun. Okay so maybe not a death ray, but it’ll be really bright out!

  10. Another drawback: If these satellites are in 1000km orbits and 18 are needed to keep a city in dusk”” (over 12 hours or 24?)”” then they will need to change orientation before and after each pass over the city to avoid lighting up a path around the world. That means a fair amount of propulsion/power to reorient a 10km(? Is that even technically feasible today?) dish twice a day. The last thing you want to do is add light to already sun lit areas. I suppose the same 18 sats could service other cities on the same latitude right? Sorry”” just having a hard time imagining how 18-10km wide satellites will work…And another thing: Isn’t it “”””bad”””” to be adding all that energy/heat through the atmosphere?”””

  11. If you put the mirror in a low orbit you can illuminate just a city but not for long because your mirror will be sweeping across the sky and will end up in the Earth’s shadow quick enough.If you put the mirror in a high orbit ideally geosynchronous you can illuminate the same point as long as you want but your minimum spot size will be over 300 km in diameter.So this isn’t aimed at just a city. It’s going to light up the area of a mid sized state.

  12. I was going to comment the exact same thing but then I thought: They’re going to be illuminating megalopolitan areas and it’s not like the neon LED mercury and low-pressure sodium lighting (not to mention the godawful noise) isn’t ALREADY throwing off the circadiam rhythm of everything in the area.If they happen to illuminate some rural area with this then I agree it’s probably ill-advised. Heck it might be ill-advised anyway because of something else we haven’t thought of. File this under eeds more consideration””.”””

  13. Didn’t we already run the numbers on this? (In comments that Brian threw away of course…)If you’re up in geosynchronous orbit which is kind of necessary if you mean to illuminate the same area all night you’re about 36000 km up. At the equator it gets a bit worse away from it.Sunlight is about 400000 times brighter than Moonlight. So they’re aiming for 0.00002 suns illumination.Assuming a perfect mirror you’re going to get a spot size of about 334 km wide from geosynch.To achieve the targeted brightness… a 1.5km diameter mirror. OK guess it’s feasible but they’re not going to be illuminating a city they’re illuminating an entire region.

  14. Can it be focussed more tightly like in Die Another Day? That’s the real question because if you can concentrate a 10km area of light down to 10m you’ve got yourself a death ray.The Sun is ~4E5 times brighter than the Moon the reflector 8 times. That makes the sun 5E4 times brighter than the reflector. A 10m circle is 1E6 times smaller than a 10km circle 1E6 / 5E4 gives us ~20 times brighter than the sun. Okay so maybe not a death ray but it’ll be really bright out!

  15. Another of your gratuitous attacks on environmentalists. It’s clear from the comments here that this plan has many more uncertainties than just building more conventional solar farms, but you are already attacking them for not getting behind it.

  16. I must express my doubt that those old comments are ever coming back in any meaningful form. They had both html formatting and links, and often were long. Your new commenting system forbids all html, and places a strict limit on comment length. Even if you did bring them back, they’d be a mess. It would be different if you’d switched to a new commenting system that had equivalent functionality, rather than this bare bones system. Then automated translation of the comments into the new system would have been fairly straightforward. But you didn’t, you switched to Vuulke, which is, remarkably, less feature laden than IRC. Furthermore, this isn’t the first time you’ve changed comment systems, asserting that the old comments would be preserved. How did it work out last time?

  17. It also makes them more violent and accident prone. This thing ought to have a measurable body count just due to car accidents and distracted people run over by cars. Albeit criminality may be reduced, given the correlation of crime and poor lightning.

  18. Pretty easy to defeat with any non hollywood ASAT weapon. Just lob carbon pellets at it and hit the reflector with 10,000 hypersonic pellets on a ballsitic orbit (so the pellets don’t go in to orbit and make a large mess). Seriously Hollywood films will make you dumber, stop watching them.

  19. They won’t use that many satellites. The cost will be prohibitive and it will mess up everyone’s sleep. If China wants more power 24/7 then just build another nuke plant. PPT design by central committee.

  20. Another of your gratuitous attacks on environmentalists. It’s clear from the comments here that this plan has many more uncertainties than just building more conventional solar farms but you are already attacking them for not getting behind it.

  21. I must express my doubt that those old comments are ever coming back in any meaningful form. They had both html formatting and links and often were long. Your new commenting system forbids all html and places a strict limit on comment length.Even if you did bring them back they’d be a mess.It would be different if you’d switched to a new commenting system that had equivalent functionality rather than this bare bones system. Then automated translation of the comments into the new system would have been fairly straightforward. But you didn’t you switched to Vuulke which is remarkably less feature laden than IRC.Furthermore this isn’t the first time you’ve changed comment systems asserting that the old comments would be preserved. How did it work out last time?

  22. It also makes them more violent and accident prone. This thing ought to have a measurable body count just due to car accidents and distracted people run over by cars.Albeit criminality may be reduced given the correlation of crime and poor lightning.

  23. Pretty easy to defeat with any non hollywood ASAT weapon. Just lob carbon pellets at it and hit the reflector with 10000 hypersonic pellets on a ballsitic orbit (so the pellets don’t go in to orbit and make a large mess).Seriously Hollywood films will make you dumber stop watching them.

  24. They won’t use that many satellites. The cost will be prohibitive and it will mess up everyone’s sleep.If China wants more power 24/7 then just build another nuke plant.PPT design by central committee.

  25. An idea that can arise and supported only by a Chines communist mind. The fanatic adoration of mega projects blind to the consequences. People in the cities are suffering from light pollution already which causes stress and sleep deprivation. If anything we need to redesign street lighting and other sources of light at night in order to reclaim the natural stary night sky.

  26. It can’t be focused any more than 10km because the sun is a certain diameter in arch of the visible sky. So the fact that it would be in such a low orbit helps keep it down to 10km but you can’t make it any tighter unless you come up with some sort of funky meta-material with unheard of optics for your mirrors. You can, however, increase the power going to that 10km area by adding more area to your mirrors.

  27. The solution to street lighting is just don’t do it. People can see in the dark well enough. And the few times they can’t and the few people who can’t they can use a flashlight. Too much light while sleeping is bad for your health. Let the night return. There are stars in the sky, wonderful stars.

  28. Incredible giant step forward ! Hopefully there will be an environmental impact study esp regarding nocturnal animals.

  29. I know it is, no they won’t, and no. Grow up and let people enjoy things. Also in this case, they’d better impart quite a bit of energy, or the lightweight reflector will just have 10,000 tiny holes in it, barely affecting it.

  30. The solution to street lighting is just don’t do it. People can see in the dark well enough. And the few times they can’t and the few people who can’t they can use a flashlight. Too much light while sleeping is bad for your health. Let the night return. There are stars in the sky wonderful stars.

  31. Incredible giant step forward ! Hopefully there will be an environmental impact study esp regarding nocturnal animals.

  32. I know it is no they won’t and no. Grow up and let people enjoy things.Also in this case they’d better impart quite a bit of energy or the lightweight reflector will just have 10000 tiny holes in it barely affecting it.

  33. You’d have trouble finding enough customers for your sunlight in the southern hemisphere, and when the atlantic, and pacific were simultaneously under the sats.

  34. The satellites won’t go into the Earth’s shadow because it would be in a sun-synchronous polar orbit so the ring of satellites would always be flying above the divide between the night and day, above the boarder between the lit part of the Earth and the dark part all year long. In the city to be lit by these you would see a series of these satellites passing overhead from north to south or visa versa, shining light over from the twilight sun from over the horizon. As one passes your city the next one would redirect its mirrors to shine on you. This would only work for about an hour after sunset and also before dawn, that’s it. But that is a big help and saves energy and could with big enough mirrors power solar arrays during the peak power demand in the evening when solar normally quits.

  35. One of the — at least to me — coolest things about “pinhole cameras” is that the resolution on the image plane is no smaller than the hole (or the bit-of-mirror) used. For instance, if you use a tiny ¼ cm mirror and are standing 100 ft (30 m) away from a shaded white screen, and are reflecting the sun at that screen, ⇒ spot = dist × 0.0094 … spot = 30 × 0.0094 … spot = 0.282 m → 28 cm. And the resolution of the sun’s face is still… ¼ cm or 2.5 mm: ⇒ spot = 282 mm ⇒ pixels across = 282 mm ÷ 2.5 mm → 112 px ∴ pixels area = π • (¹¹²⁄₂)² … pixels area = 10,000 Want higher res? Make the chip of mirror smaller. Is there a limit? Yep… sure is. Its called diffraction, and it is a weird quantum mess. In the end, it remains bound by {res = 1.22λ/diameter}. So, while we might LIKE our solar pinhole image to have 10,000 pixels over its face, the 1.22λ/D thing limits it to only 950 pixels. If you do the math. Making the chip-of-mirror smaller only goes to lower resolution. The crossover point (where theoretical resolution of a pinhole, less diffraction and the diffraction mirror-diameter limit) is — for this 30 meter system — is empirically determined to be ⇒ optimal pinhole diameter = 0.86 √( distance ); … = 0.86 √( 30 ); … = 4.7 mm And the resolved solar image would be 1,500 pixels across face. Pixels is the WRONG word, but it best fits what people these days expect. Fizzy disk is more like it, but who knows what that is any more? At 1,000 km, the same math works, and the diffraction optimazation calls for a 86 centimeter diameter mirror. Nearly 3 feet across. Wouldn’t be terribly bright of course. About 1,000 radiative watts, or ¹⁄₁₀₀₀ the brightness of the above calculation. And you’d still have the same 9.3 km solar image circle. 50 megapixels. Math is fun. Just saying, GoatGuy

  36. That… and of course the more obvious: if you look “kind of straight down” at a city, it is MOSTLY rooftop. The streets, the walkways are nestled at the bottom. Moreover, since a satellite — of the non-geosynchronous type, at 1,000 km altitude — is going to rise from a horizon and then go dark around ⅓ the way across the sky (of course changing all night long, this relation), the angle of illumination is terrible. For streets. In cities. In short, it is just a Brain Fâhrt. Lovely to contemplate for a few minutes. Nothing more. Just saying, GoatGuy

  37. Wait… weren’t we somewhat concerned about … ahem … global warming … as it is? Diurnal cooling is an important part of how Big Cities get rid of their absorbed solar heating from the daytime. Just saying… it seems wrong. GoatGuy

  38. What you say is true. ⇒ spot = Satellite Altitude • Sol Diam / Sol Dist ⇒ Sol Diam ≈ 1.391×10⁶ km ⇒ Sol Dist ≈ 149.5×10⁶ km ⇒ Satellite Altitude ≈ (1000 km MEO, 35,400 km GSO, …) ∴ spot = 9.3 km diameter Basic trig. Anyway, its close enough to 10 km diameter that I’m not really putting up a complaint. 9.3, 10, its all essentially rounding error differences. My question was, “I wonder how big the reflector needs to be ‘up there’?” My initial guess is that its size would follow some sort of square-of-altitude sizing. Then there is the “transit time” for which the artificial city-candle rises from one of the horizons, and whizzes overhead, ultimately to be cast into Earth’s shadow. Well, its tough to be a satellite. If… ⇒ Satellite Altitude = 1,000 km (then doing a bunch of math…) ⇒ Satellite Gravity = 7.33 N/kg ⇒ Satellite Velocity = 7,347 m/s ⇒ Satellite Period = 6,300 s → 105 min → 1.75 hr → 13.7 orb/day ⇒ Satellite SpotDia = 9300 m And… ⇒ Satellite SpotArea = 68,000,000 m² → 680,000 hectares With… ⇒ Desired Illumination = 8× Luna (peak) ⇒ … which is = 8 × 0.0019 W/m² → 0.0152 W/m² at Earth ⇒ Total reflected power = 1,000,000 W ⇒ Satellite reflectance = 90% ⇒ Satellite Sol illum = 1363 W/m² &theref; Satellite area = 841 m² &theref; Satellite diameter = 32 m Well, how about that. Something plausibly launchable! The surface of the mirror doesn’t need to be ultra-flat (or especially curved). From Earth, it’d look just like a wee dot. Nothing at all Moon sized. A really, really bright star. In fact, if it were exactly flat, it would act as the ultimate pinhole camera of the Sun. With an image size of 9.3 kilometers on the average in diameter. That’d be cool. Without being curved, the image would have a spatial resolution of about: ⇒ Apparent angular size = 0.0000327 rad ⇒ Sol’s min feature = 4,900 km ⇒ Sol pixellation = 63,500 over face And each virtual pixel would be 33 m in diameter of that huge solar image. LOL! Just saying, GoatGuy

  39. You’d have trouble finding enough customers for your sunlight in the southern hemisphere and when the atlantic and pacific were simultaneously under the sats.

  40. The satellites won’t go into the Earth’s shadow because it would be in a sun-synchronous polar orbit so the ring of satellites would always be flying above the divide between the night and day above the boarder between the lit part of the Earth and the dark part all year long. In the city to be lit by these you would see a series of these satellites passing overhead from north to south or visa versa shining light over from the twilight sun from over the horizon. As one passes your city the next one would redirect its mirrors to shine on you. This would only work for about an hour after sunset and also before dawn that’s it. But that is a big help and saves energy and could with big enough mirrors power solar arrays during the peak power demand in the evening when solar normally quits.

  41. One of the — at least to me — coolest things about “pinhole cameras” is that the resolution on the image plane is no smaller than the hole (or the bit-of-mirror) used. For instance if you use a tiny ¼ cm mirror and are standing 100 ft (30 m) away from a shaded white screen and are reflecting the sun at that screen ⇒ spot = dist × 0.0094… spot = 30 × 0.0094… spot = 0.282 m → 28 cm.And the resolution of the sun’s face is still… ¼ cm or 2.5 mm:⇒ spot = 282 mm⇒ pixels across = 282 mm ÷ 2.5 mm → 112 px∴ pixels area = π • (¹¹²⁄₂)²… pixels area = 10000Want higher res? Make the chip of mirror smaller. Is there a limit? Yep… sure is. Its called diffraction and it is a weird quantum mess. In the end it remains bound by {res = 1.22λ/diameter}. So while we might LIKE our solar pinhole image to have 10000 pixels over its face the 1.22λ/D thing limits it to only 950 pixels. If you do the math. Making the chip-of-mirror smaller only goes to lower resolution. The crossover point (where theoretical resolution of a pinhole less diffraction and the diffraction mirror-diameter limit) is — for this 30 meter system — is empirically determined to be ⇒ optimal pinhole diameter = 0.86 √( distance );… = 0.86 √( 30 );… = 4.7 mmAnd the resolved solar image would be 1500 pixels across face. Pixels is the WRONG word but it best fits what people these days expect. Fizzy disk is more like it but who knows what that is any more?At 1000 km the same math works and the diffraction optimazation calls for a 86 centimeter diameter mirror. Nearly 3 feet across. Wouldn’t be terribly bright of course. About 1000 radiative watts or ¹⁄₁₀₀₀ the brightness of the above calculation. And you’d still have the same 9.3 km solar image circle. 50 megapixels. Math is fun.Just sayingGoatGuy”

  42. That… and of course the more obvious: if you look kind of straight down”” at a city”” it is MOSTLY rooftop. The streets the walkways are nestled at the bottom. Moreover since a satellite — of the non-geosynchronous type at 1000 km altitude — is going to rise from a horizon and then go dark around ⅓ the way across the sky (of course changing all night long this relation) the angle of illumination is terrible. For streets. In cities. In short it is just a Brain Fâhrt. Lovely to contemplate for a few minutes.Nothing more. Just saying””GoatGuy”””””””

  43. Wait… weren’t we somewhat concerned about … ahem … global warming … as it is? Diurnal cooling is an important part of how Big Cities get rid of their absorbed solar heating from the daytime. Just saying… it seems wrong. GoatGuy

  44. What you say is true.⇒ spot = Satellite Altitude • Sol Diam / Sol Dist⇒ Sol Diam ≈ 1.391×10⁶ km⇒ Sol Dist ≈ 149.5×10⁶ km⇒ Satellite Altitude ≈ (1000 km MEO 35400 km GSO …)∴ spot = 9.3 km diameterBasic trig. Anyway its close enough to 10 km diameter that I’m not really putting up a complaint. 9.3 10 its all essentially rounding error differences. My question was “I wonder how big the reflector needs to be ‘up there’?” My initial guess is that its size would follow some sort of square-of-altitude sizing. Then there is the “transit time” for which the artificial city-candle rises from one of the horizons and whizzes overhead ultimately to be cast into Earth’s shadow. Well its tough to be a satellite. If…⇒ Satellite Altitude = 1000 km (then doing a bunch of math…)⇒ Satellite Gravity = 7.33 N/kg⇒ Satellite Velocity = 7347 m/s⇒ Satellite Period = 6300 s → 105 min → 1.75 hr → 13.7 orb/day⇒ Satellite SpotDia = 9300 mAnd…⇒ Satellite SpotArea = 68000000 m² → 680000 hectaresWith…⇒ Desired Illumination = 8× Luna (peak)⇒ … which is = 8 × 0.0019 W/m² → 0.0152 W/m² at Earth⇒ Total reflected power = 1000000 W⇒ Satellite reflectance = 90{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12}⇒ Satellite Sol illum = 1363 W/m²&theref; Satellite area = 841 m²&theref; Satellite diameter = 32 mWell how about that. Something plausibly launchable! The surface of the mirror doesn’t need to be ultra-flat (or especially curved). From Earth it’d look just like a wee dot. Nothing at all Moon sized. A really really bright star.In fact if it were exactly flat it would act as the ultimate pinhole camera of the Sun. With an image size of 9.3 kilometers on the average in diameter. That’d be cool. Without being curved the image would have a spatial resolution of about:⇒ Apparent angular size = 0.0000327 rad⇒ Sol’s min feature = 4900 km⇒ Sol pixellation = 63500 over faceAnd each v

  45. Actually that’s not true. Human eyes aren’t optimized for night vision. We can see ok-ish once the eyes adapt, but we still miss a whole bunch of details, and any flash of light would make us nearly blind until our eyes re-adapt. If the street was empty and flat, that may be ok, but as it is, that’s an opening for accidents and injuries. It’s even worse for older people. And it’s been shown that crime rates are higher in poor lighting. Flashlights count as “flash of light”, and adaptation can take around a minute or so, so are you going to stop for a minute because you can’t see anything everytime someone flashes a flashlight at you (even unintentionally)? That’s going to happen pretty often, since nobody wants to stop like that. Everyone’s going to be carrying flashlights, and it’ll just end up an uncomfortable mess. Unlit streets may work out in the country, where there aren’t many people, but not in a city. No, city streets need to be lit up. I’d say they need to be lit up even better than they are now, at least during the active hours of early evening and morning. But the lights need to be much more directional to stay out of people’s windows and minimize light pollution. That would also make the lighting more efficient, since light that goes where it’s not needed is wasted energy. The lights can be turned down during sleep hours, and switched to more red lighting, which doesn’t interfere with eye adaptation as much.

  46. It’ll be just as buggy/slow/etc as any commenting startup. Making and polishing a good commenting system takes a lot of effort and time. Just go back to Disqus and be done with it.

  47. Actually that’s not true. Human eyes aren’t optimized for night vision. We can see ok-ish once the eyes adapt but we still miss a whole bunch of details and any flash of light would make us nearly blind until our eyes re-adapt. If the street was empty and flat that may be ok but as it is that’s an opening for accidents and injuries. It’s even worse for older people. And it’s been shown that crime rates are higher in poor lighting.Flashlights count as flash of light””” and adaptation can take around a minute or so so are you going to stop for a minute because you can’t see anything everytime someone flashes a flashlight at you (even unintentionally)? That’s going to happen pretty often since nobody wants to stop like that. Everyone’s going to be carrying flashlights and it’ll just end up an uncomfortable mess. Unlit streets may work out in the country where there aren’t many people but not in a city.No city streets need to be lit up. I’d say they need to be lit up even better than they are now at least during the active hours of early evening and morning. But the lights need to be much more directional to stay out of people’s windows and minimize light pollution. That would also make the lighting more efficient since light that goes where it’s not needed is wasted energy. The lights can be turned down during sleep hours and switched to more red lighting”” which doesn’t interfere with eye adaptation as much.”””

  48. It’ll be just as buggy/slow/etc as any commenting startup. Making and polishing a good commenting system takes a lot of effort and time. Just go back to Disqus and be done with it.

  49. Ok, I’ll call the BS on this one. Anyone been to Chengdu? me has. Smog. And what do you do when it’s cloudy? So in any case you still need base power. The Sichuan solution for this is natural gas. If anyone has followed Chinese energy investments you’ll see the money being plowed into natgas, refineries and pipes in Sichuan is multiples of anything like a “artificial sun/moon”. The whole idea of reflectors is ludicrous when the Chinese themselves are putting their money on something else – good old reliable power plants and upstream production. Never mind the technical idiocy. Just need to look at PV efficacy to see this is beyond stupid. Full moonlight on a cloudless night without discernible air pollution is 1/345th the power of sunlight under the same conditions. It’s meaningless to try and convert this into useable PV power even at twice the brightness (during the few hours it can be used). Nah. I call the reflector thingy a hoax no matter what China Daily says. There is no “Wu Chunfeng” There is no “Chengdu Aerospace Science and Technology Microelectronics System” There is no “Tian Fu New Area Science Society” No media outlet has been able to reach these organizations for a comment, because they don’t exist. Yet somehow, media still prints this obvious fake news. You can ask why? Let you draw your on conclusions.

  50. Ok I’ll call the BS on this one. Anyone been to Chengdu? me has. Smog. And what do you do when it’s cloudy? So in any case you still need base power. The Sichuan solution for this is natural gas. If anyone has followed Chinese energy investments you’ll see the money being plowed into natgas refineries and pipes in Sichuan is multiples of anything like a artificial sun/moon””. The whole idea of reflectors is ludicrous when the Chinese themselves are putting their money on something else – good old reliable power plants and upstream production. Never mind the technical idiocy. Just need to look at PV efficacy to see this is beyond stupid. Full moonlight on a cloudless night without discernible air pollution is 1/345th the power of sunlight under the same conditions. It’s meaningless to try and convert this into useable PV power even at twice the brightness (during the few hours it can be used).Nah. I call the reflector thingy a hoax no matter what China Daily says.There is no “”””Wu Chunfeng””””There is no “”””Chengdu Aerospace Science and Technology Microelectronics System””””There is no “”””Tian Fu New Area Science Society””””No media outlet has been able to reach these organizations for a comment”” because they don’t exist. Yet somehow”” media still prints this obvious fake news. You can ask why? Let you draw your on conclusions.”””

  51. Ok, I’ll call the BS on this one. Anyone been to Chengdu? me has. Smog. And what do you do when it’s cloudy? So in any case you still need base power. The Sichuan solution for this is natural gas. If anyone has followed Chinese energy investments you’ll see the money being plowed into natgas, refineries and pipes in Sichuan is multiples of anything like a “artificial sun/moon”. The whole idea of reflectors is ludicrous when the Chinese themselves are putting their money on something else – good old reliable power plants and upstream production. Never mind the technical idiocy. Just need to look at PV efficacy to see this is beyond stupid. Full moonlight on a cloudless night without discernible air pollution is 1/345th the power of sunlight under the same conditions. It’s meaningless to try and convert this into useable PV power even at twice the brightness (during the few hours it can be used). Nah. I call the reflector thingy a hoax no matter what China Daily says. There is no “Wu Chunfeng” There is no “Chengdu Aerospace Science and Technology Microelectronics System” There is no “Tian Fu New Area Science Society” No media outlet has been able to reach these organizations for a comment, because they don’t exist. Yet somehow, media still prints this obvious fake news. You can ask why? Let you draw your on conclusions.

  52. Ok I’ll call the BS on this one. Anyone been to Chengdu? me has. Smog. And what do you do when it’s cloudy? So in any case you still need base power. The Sichuan solution for this is natural gas. If anyone has followed Chinese energy investments you’ll see the money being plowed into natgas refineries and pipes in Sichuan is multiples of anything like a artificial sun/moon””. The whole idea of reflectors is ludicrous when the Chinese themselves are putting their money on something else – good old reliable power plants and upstream production. Never mind the technical idiocy. Just need to look at PV efficacy to see this is beyond stupid. Full moonlight on a cloudless night without discernible air pollution is 1/345th the power of sunlight under the same conditions. It’s meaningless to try and convert this into useable PV power even at twice the brightness (during the few hours it can be used).Nah. I call the reflector thingy a hoax no matter what China Daily says.There is no “”””Wu Chunfeng””””There is no “”””Chengdu Aerospace Science and Technology Microelectronics System””””There is no “”””Tian Fu New Area Science Society””””No media outlet has been able to reach these organizations for a comment”” because they don’t exist. Yet somehow”” media still prints this obvious fake news. You can ask why? Let you draw your on conclusions.”””

  53. Actually that’s not true. Human eyes aren’t optimized for night vision. We can see ok-ish once the eyes adapt, but we still miss a whole bunch of details, and any flash of light would make us nearly blind until our eyes re-adapt. If the street was empty and flat, that may be ok, but as it is, that’s an opening for accidents and injuries. It’s even worse for older people. And it’s been shown that crime rates are higher in poor lighting. Flashlights count as “flash of light”, and adaptation can take around a minute or so, so are you going to stop for a minute because you can’t see anything everytime someone flashes a flashlight at you (even unintentionally)? That’s going to happen pretty often, since nobody wants to stop like that. Everyone’s going to be carrying flashlights, and it’ll just end up an uncomfortable mess. Unlit streets may work out in the country, where there aren’t many people, but not in a city. No, city streets need to be lit up. I’d say they need to be lit up even better than they are now, at least during the active hours of early evening and morning. But the lights need to be much more directional to stay out of people’s windows and minimize light pollution. That would also make the lighting more efficient, since light that goes where it’s not needed is wasted energy. The lights can be turned down during sleep hours, and switched to more red lighting, which doesn’t interfere with eye adaptation as much.

  54. Actually that’s not true. Human eyes aren’t optimized for night vision. We can see ok-ish once the eyes adapt but we still miss a whole bunch of details and any flash of light would make us nearly blind until our eyes re-adapt. If the street was empty and flat that may be ok but as it is that’s an opening for accidents and injuries. It’s even worse for older people. And it’s been shown that crime rates are higher in poor lighting.Flashlights count as flash of light””” and adaptation can take around a minute or so so are you going to stop for a minute because you can’t see anything everytime someone flashes a flashlight at you (even unintentionally)? That’s going to happen pretty often since nobody wants to stop like that. Everyone’s going to be carrying flashlights and it’ll just end up an uncomfortable mess. Unlit streets may work out in the country where there aren’t many people but not in a city.No city streets need to be lit up. I’d say they need to be lit up even better than they are now at least during the active hours of early evening and morning. But the lights need to be much more directional to stay out of people’s windows and minimize light pollution. That would also make the lighting more efficient since light that goes where it’s not needed is wasted energy. The lights can be turned down during sleep hours and switched to more red lighting”” which doesn’t interfere with eye adaptation as much.”””

  55. It’ll be just as buggy/slow/etc as any commenting startup. Making and polishing a good commenting system takes a lot of effort and time. Just go back to Disqus and be done with it.

  56. It’ll be just as buggy/slow/etc as any commenting startup. Making and polishing a good commenting system takes a lot of effort and time. Just go back to Disqus and be done with it.

  57. Ok, I’ll call the BS on this one. Anyone been to Chengdu? me has. Smog. And what do you do when it’s cloudy? So in any case you still need base power. The Sichuan solution for this is natural gas. If anyone has followed Chinese energy investments you’ll see the money being plowed into natgas, refineries and pipes in Sichuan is multiples of anything like a “artificial sun/moon”. The whole idea of reflectors is ludicrous when the Chinese themselves are putting their money on something else – good old reliable power plants and upstream production. Never mind the technical idiocy. Just need to look at PV efficacy to see this is beyond stupid. Full moonlight on a cloudless night without discernible air pollution is 1/345th the power of sunlight under the same conditions. It’s meaningless to try and convert this into useable PV power even at twice the brightness (during the few hours it can be used).

    Nah. I call the reflector thingy a hoax no matter what China Daily says.
    There is no “Wu Chunfeng”
    There is no “Chengdu Aerospace Science and Technology Microelectronics System”
    There is no “Tian Fu New Area Science Society”

    No media outlet has been able to reach these organizations for a comment, because they don’t exist. Yet somehow, media still prints this obvious fake news.

    You can ask why? Let you draw your on conclusions.

  58. Actually that’s not true. Human eyes aren’t optimized for night vision. We can see ok-ish once the eyes adapt, but we still miss a whole bunch of details, and any flash of light would make us nearly blind until our eyes re-adapt. If the street was empty and flat, that may be ok, but as it is, that’s an opening for accidents and injuries. It’s even worse for older people. And it’s been shown that crime rates are higher in poor lighting.

    Flashlights count as “flash of light”, and adaptation can take around a minute or so, so are you going to stop for a minute because you can’t see anything everytime someone flashes a flashlight at you (even unintentionally)? That’s going to happen pretty often, since nobody wants to stop like that. Everyone’s going to be carrying flashlights, and it’ll just end up an uncomfortable mess. Unlit streets may work out in the country, where there aren’t many people, but not in a city.

    No, city streets need to be lit up. I’d say they need to be lit up even better than they are now, at least during the active hours of early evening and morning. But the lights need to be much more directional to stay out of people’s windows and minimize light pollution. That would also make the lighting more efficient, since light that goes where it’s not needed is wasted energy. The lights can be turned down during sleep hours, and switched to more red lighting, which doesn’t interfere with eye adaptation as much.

  59. It’ll be just as buggy/slow/etc as any commenting startup. Making and polishing a good commenting system takes a lot of effort and time. Just go back to Disqus and be done with it.

  60. You’d have trouble finding enough customers for your sunlight in the southern hemisphere, and when the atlantic, and pacific were simultaneously under the sats.

  61. You’d have trouble finding enough customers for your sunlight in the southern hemisphere and when the atlantic and pacific were simultaneously under the sats.

  62. The satellites won’t go into the Earth’s shadow because it would be in a sun-synchronous polar orbit so the ring of satellites would always be flying above the divide between the night and day, above the boarder between the lit part of the Earth and the dark part all year long. In the city to be lit by these you would see a series of these satellites passing overhead from north to south or visa versa, shining light over from the twilight sun from over the horizon. As one passes your city the next one would redirect its mirrors to shine on you. This would only work for about an hour after sunset and also before dawn, that’s it. But that is a big help and saves energy and could with big enough mirrors power solar arrays during the peak power demand in the evening when solar normally quits.

  63. The satellites won’t go into the Earth’s shadow because it would be in a sun-synchronous polar orbit so the ring of satellites would always be flying above the divide between the night and day above the boarder between the lit part of the Earth and the dark part all year long. In the city to be lit by these you would see a series of these satellites passing overhead from north to south or visa versa shining light over from the twilight sun from over the horizon. As one passes your city the next one would redirect its mirrors to shine on you. This would only work for about an hour after sunset and also before dawn that’s it. But that is a big help and saves energy and could with big enough mirrors power solar arrays during the peak power demand in the evening when solar normally quits.

  64. One of the — at least to me — coolest things about “pinhole cameras” is that the resolution on the image plane is no smaller than the hole (or the bit-of-mirror) used. For instance, if you use a tiny ¼ cm mirror and are standing 100 ft (30 m) away from a shaded white screen, and are reflecting the sun at that screen, ⇒ spot = dist × 0.0094 … spot = 30 × 0.0094 … spot = 0.282 m → 28 cm. And the resolution of the sun’s face is still… ¼ cm or 2.5 mm: ⇒ spot = 282 mm ⇒ pixels across = 282 mm ÷ 2.5 mm → 112 px ∴ pixels area = π • (¹¹²⁄₂)² … pixels area = 10,000 Want higher res? Make the chip of mirror smaller. Is there a limit? Yep… sure is. Its called diffraction, and it is a weird quantum mess. In the end, it remains bound by {res = 1.22λ/diameter}. So, while we might LIKE our solar pinhole image to have 10,000 pixels over its face, the 1.22λ/D thing limits it to only 950 pixels. If you do the math. Making the chip-of-mirror smaller only goes to lower resolution. The crossover point (where theoretical resolution of a pinhole, less diffraction and the diffraction mirror-diameter limit) is — for this 30 meter system — is empirically determined to be ⇒ optimal pinhole diameter = 0.86 √( distance ); … = 0.86 √( 30 ); … = 4.7 mm And the resolved solar image would be 1,500 pixels across face. Pixels is the WRONG word, but it best fits what people these days expect. Fizzy disk is more like it, but who knows what that is any more? At 1,000 km, the same math works, and the diffraction optimazation calls for a 86 centimeter diameter mirror. Nearly 3 feet across. Wouldn’t be terribly bright of course. About 1,000 radiative watts, or ¹⁄₁₀₀₀ the brightness of the above calculation. And you’d still have the same 9.3 km solar image circle. 50 megapixels. Math is fun. Just saying, GoatGuy

  65. One of the — at least to me — coolest things about “pinhole cameras” is that the resolution on the image plane is no smaller than the hole (or the bit-of-mirror) used. For instance if you use a tiny ¼ cm mirror and are standing 100 ft (30 m) away from a shaded white screen and are reflecting the sun at that screen ⇒ spot = dist × 0.0094… spot = 30 × 0.0094… spot = 0.282 m → 28 cm.And the resolution of the sun’s face is still… ¼ cm or 2.5 mm:⇒ spot = 282 mm⇒ pixels across = 282 mm ÷ 2.5 mm → 112 px∴ pixels area = π • (¹¹²⁄₂)²… pixels area = 10000Want higher res? Make the chip of mirror smaller. Is there a limit? Yep… sure is. Its called diffraction and it is a weird quantum mess. In the end it remains bound by {res = 1.22λ/diameter}. So while we might LIKE our solar pinhole image to have 10000 pixels over its face the 1.22λ/D thing limits it to only 950 pixels. If you do the math. Making the chip-of-mirror smaller only goes to lower resolution. The crossover point (where theoretical resolution of a pinhole less diffraction and the diffraction mirror-diameter limit) is — for this 30 meter system — is empirically determined to be ⇒ optimal pinhole diameter = 0.86 √( distance );… = 0.86 √( 30 );… = 4.7 mmAnd the resolved solar image would be 1500 pixels across face. Pixels is the WRONG word but it best fits what people these days expect. Fizzy disk is more like it but who knows what that is any more?At 1000 km the same math works and the diffraction optimazation calls for a 86 centimeter diameter mirror. Nearly 3 feet across. Wouldn’t be terribly bright of course. About 1000 radiative watts or ¹⁄₁₀₀₀ the brightness of the above calculation. And you’d still have the same 9.3 km solar image circle. 50 megapixels. Math is fun.Just sayingGoatGuy”

  66. That… and of course the more obvious: if you look “kind of straight down” at a city, it is MOSTLY rooftop. The streets, the walkways are nestled at the bottom. Moreover, since a satellite — of the non-geosynchronous type, at 1,000 km altitude — is going to rise from a horizon and then go dark around ⅓ the way across the sky (of course changing all night long, this relation), the angle of illumination is terrible. For streets. In cities. In short, it is just a Brain Fâhrt. Lovely to contemplate for a few minutes. Nothing more. Just saying, GoatGuy

  67. That… and of course the more obvious: if you look kind of straight down”” at a city”” it is MOSTLY rooftop. The streets the walkways are nestled at the bottom. Moreover since a satellite — of the non-geosynchronous type at 1000 km altitude — is going to rise from a horizon and then go dark around ⅓ the way across the sky (of course changing all night long this relation) the angle of illumination is terrible. For streets. In cities. In short it is just a Brain Fâhrt. Lovely to contemplate for a few minutes.Nothing more. Just saying””GoatGuy”””””””

  68. Wait… weren’t we somewhat concerned about … ahem … global warming … as it is? Diurnal cooling is an important part of how Big Cities get rid of their absorbed solar heating from the daytime. Just saying… it seems wrong. GoatGuy

  69. Wait… weren’t we somewhat concerned about … ahem … global warming … as it is? Diurnal cooling is an important part of how Big Cities get rid of their absorbed solar heating from the daytime. Just saying… it seems wrong. GoatGuy

  70. What you say is true. ⇒ spot = Satellite Altitude • Sol Diam / Sol Dist ⇒ Sol Diam ≈ 1.391×10⁶ km ⇒ Sol Dist ≈ 149.5×10⁶ km ⇒ Satellite Altitude ≈ (1000 km MEO, 35,400 km GSO, …) ∴ spot = 9.3 km diameter Basic trig. Anyway, its close enough to 10 km diameter that I’m not really putting up a complaint. 9.3, 10, its all essentially rounding error differences. My question was, “I wonder how big the reflector needs to be ‘up there’?” My initial guess is that its size would follow some sort of square-of-altitude sizing. Then there is the “transit time” for which the artificial city-candle rises from one of the horizons, and whizzes overhead, ultimately to be cast into Earth’s shadow. Well, its tough to be a satellite. If… ⇒ Satellite Altitude = 1,000 km (then doing a bunch of math…) ⇒ Satellite Gravity = 7.33 N/kg ⇒ Satellite Velocity = 7,347 m/s ⇒ Satellite Period = 6,300 s → 105 min → 1.75 hr → 13.7 orb/day ⇒ Satellite SpotDia = 9300 m And… ⇒ Satellite SpotArea = 68,000,000 m² → 680,000 hectares With… ⇒ Desired Illumination = 8× Luna (peak) ⇒ … which is = 8 × 0.0019 W/m² → 0.0152 W/m² at Earth ⇒ Total reflected power = 1,000,000 W ⇒ Satellite reflectance = 90% ⇒ Satellite Sol illum = 1363 W/m² &theref; Satellite area = 841 m² &theref; Satellite diameter = 32 m Well, how about that. Something plausibly launchable! The surface of the mirror doesn’t need to be ultra-flat (or especially curved). From Earth, it’d look just like a wee dot. Nothing at all Moon sized. A really, really bright star. In fact, if it were exactly flat, it would act as the ultimate pinhole camera of the Sun. With an image size of 9.3 kilometers on the average in diameter. That’d be cool. Without being curved, the image would have a spatial resolution of about: ⇒ Apparent angular size = 0.0000327 rad ⇒ Sol’s min feature = 4,900 km ⇒ Sol pixellation = 63,500 over face And each virtual pixel would be 33 m in diameter of that huge solar image. LOL! Just saying, GoatGuy

  71. What you say is true.⇒ spot = Satellite Altitude • Sol Diam / Sol Dist⇒ Sol Diam ≈ 1.391×10⁶ km⇒ Sol Dist ≈ 149.5×10⁶ km⇒ Satellite Altitude ≈ (1000 km MEO 35400 km GSO …)∴ spot = 9.3 km diameterBasic trig. Anyway its close enough to 10 km diameter that I’m not really putting up a complaint. 9.3 10 its all essentially rounding error differences. My question was “I wonder how big the reflector needs to be ‘up there’?” My initial guess is that its size would follow some sort of square-of-altitude sizing. Then there is the “transit time” for which the artificial city-candle rises from one of the horizons and whizzes overhead ultimately to be cast into Earth’s shadow. Well its tough to be a satellite. If…⇒ Satellite Altitude = 1000 km (then doing a bunch of math…)⇒ Satellite Gravity = 7.33 N/kg⇒ Satellite Velocity = 7347 m/s⇒ Satellite Period = 6300 s → 105 min → 1.75 hr → 13.7 orb/day⇒ Satellite SpotDia = 9300 mAnd…⇒ Satellite SpotArea = 68000000 m² → 680000 hectaresWith…⇒ Desired Illumination = 8× Luna (peak)⇒ … which is = 8 × 0.0019 W/m² → 0.0152 W/m² at Earth⇒ Total reflected power = 1000000 W⇒ Satellite reflectance = 90{22800fc54956079738b58e74e4dcd846757aa319aad70fcf90c97a58f3119a12}⇒ Satellite Sol illum = 1363 W/m²&theref; Satellite area = 841 m²&theref; Satellite diameter = 32 mWell how about that. Something plausibly launchable! The surface of the mirror doesn’t need to be ultra-flat (or especially curved). From Earth it’d look just like a wee dot. Nothing at all Moon sized. A really really bright star.In fact if it were exactly flat it would act as the ultimate pinhole camera of the Sun. With an image size of 9.3 kilometers on the average in diameter. That’d be cool. Without being curved the image would have a spatial resolution of about:⇒ Apparent angular size = 0.0000327 rad⇒ Sol’s min feature = 4900 km⇒ Sol pixellation = 63500 over faceAnd each v

  72. The solution to street lighting is just don’t do it. People can see in the dark well enough. And the few times they can’t and the few people who can’t they can use a flashlight. Too much light while sleeping is bad for your health. Let the night return. There are stars in the sky, wonderful stars.

  73. The solution to street lighting is just don’t do it. People can see in the dark well enough. And the few times they can’t and the few people who can’t they can use a flashlight. Too much light while sleeping is bad for your health. Let the night return. There are stars in the sky wonderful stars.

  74. Incredible giant step forward ! Hopefully there will be an environmental impact study esp regarding nocturnal animals.

  75. Incredible giant step forward ! Hopefully there will be an environmental impact study esp regarding nocturnal animals.

  76. I know it is, no they won’t, and no. Grow up and let people enjoy things. Also in this case, they’d better impart quite a bit of energy, or the lightweight reflector will just have 10,000 tiny holes in it, barely affecting it.

  77. I know it is no they won’t and no. Grow up and let people enjoy things.Also in this case they’d better impart quite a bit of energy or the lightweight reflector will just have 10000 tiny holes in it barely affecting it.

  78. The satellites won’t go into the Earth’s shadow because it would be in a sun-synchronous polar orbit so the ring of satellites would always be flying above the divide between the night and day, above the boarder between the lit part of the Earth and the dark part all year long. In the city to be lit by these you would see a series of these satellites passing overhead from north to south or visa versa, shining light over from the twilight sun from over the horizon. As one passes your city the next one would redirect its mirrors to shine on you. This would only work for about an hour after sunset and also before dawn, that’s it. But that is a big help and saves energy and could with big enough mirrors power solar arrays during the peak power demand in the evening when solar normally quits.

  79. One of the — at least to me — coolest things about “pinhole cameras” is that the resolution on the image plane is no smaller than the hole (or the bit-of-mirror) used.

    For instance, if you use a tiny ¼ cm mirror and are standing 100 ft (30 m) away from a shaded white screen, and are reflecting the sun at that screen,

    ⇒ spot = dist × 0.0094
    … spot = 30 × 0.0094
    … spot = 0.282 m → 28 cm.

    And the resolution of the sun’s face is still… ¼ cm or 2.5 mm:

    ⇒ spot = 282 mm
    ⇒ pixels across = 282 mm ÷ 2.5 mm → 112 px
    ∴ pixels area = π • (¹¹²⁄₂)²
    … pixels area = 10,000

    Want higher res? Make the chip of mirror smaller. Is there a limit? Yep… sure is. Its called diffraction, and it is a weird quantum mess. In the end, it remains bound by {res = 1.22λ/diameter}. So, while we might LIKE our solar pinhole image to have 10,000 pixels over its face, the 1.22λ/D thing limits it to only 950 pixels. If you do the math.

    Making the chip-of-mirror smaller only goes to lower resolution. The crossover point (where theoretical resolution of a pinhole, less diffraction and the diffraction mirror-diameter limit) is — for this 30 meter system — is empirically determined to be

    ⇒ optimal pinhole diameter = 0.86 √( distance );
    … = 0.86 √( 30 );
    … = 4.7 mm

    And the resolved solar image would be 1,500 pixels across face. Pixels is the WRONG word, but it best fits what people these days expect. Fizzy disk is more like it, but who knows what that is any more?

    At 1,000 km, the same math works, and the diffraction optimazation calls for a 86 centimeter diameter mirror. Nearly 3 feet across. Wouldn’t be terribly bright of course. About 1,000 radiative watts, or ¹⁄₁₀₀₀ the brightness of the above calculation. And you’d still have the same 9.3 km solar image circle. 50 megapixels.

    Math is fun.

    Just saying,
    GoatGuy

  80. That… and of course the more obvious: if you look “kind of straight down” at a city, it is MOSTLY rooftop. The streets, the walkways are nestled at the bottom. Moreover, since a satellite — of the non-geosynchronous type, at 1,000 km altitude — is going to rise from a horizon and then go dark around ⅓ the way across the sky (of course changing all night long, this relation), the angle of illumination is terrible. For streets. In cities.

    In short, it is just a Brain Fâhrt.
    Lovely to contemplate for a few minutes.
    Nothing more.

    Just saying,
    GoatGuy

  81. Wait… weren’t we somewhat concerned about … ahem … global warming … as it is? Diurnal cooling is an important part of how Big Cities get rid of their absorbed solar heating from the daytime. Just saying… it seems wrong. GoatGuy

  82. What you say is true.

    ⇒ spot = Satellite Altitude • Sol Diam / Sol Dist

    ⇒ Sol Diam ≈ 1.391×10⁶ km
    ⇒ Sol Dist ≈ 149.5×10⁶ km
    ⇒ Satellite Altitude ≈ (1000 km MEO, 35,400 km GSO, …)

    ∴ spot = 9.3 km diameter

    Basic trig. Anyway, its close enough to 10 km diameter that I’m not really putting up a complaint. 9.3, 10, its all essentially rounding error differences.

    My question was, “I wonder how big the reflector needs to be ‘up there’?” My initial guess is that its size would follow some sort of square-of-altitude sizing. Then there is the “transit time” for which the artificial city-candle rises from one of the horizons, and whizzes overhead, ultimately to be cast into Earth’s shadow. Well, its tough to be a satellite.

    If…

    ⇒ Satellite Altitude = 1,000 km (then doing a bunch of math…)
    ⇒ Satellite Gravity = 7.33 N/kg
    ⇒ Satellite Velocity = 7,347 m/s
    ⇒ Satellite Period = 6,300 s → 105 min → 1.75 hr → 13.7 orb/day
    ⇒ Satellite SpotDia = 9300 m

    And…

    ⇒ Satellite SpotArea = 68,000,000 m² → 680,000 hectares

    With…

    ⇒ Desired Illumination = 8× Luna (peak)
    ⇒ … which is = 8 × 0.0019 W/m² → 0.0152 W/m² at Earth
    ⇒ Total reflected power = 1,000,000 W
    ⇒ Satellite reflectance = 90%
    ⇒ Satellite Sol illum = 1363 W/m²

    &theref; Satellite area = 841 m²
    &theref; Satellite diameter = 32 m

    Well, how about that. Something plausibly launchable! The surface of the mirror doesn’t need to be ultra-flat (or especially curved). From Earth, it’d look just like a wee dot. Nothing at all Moon sized. A really, really bright star.

    In fact, if it were exactly flat, it would act as the ultimate pinhole camera of the Sun. With an image size of 9.3 kilometers on the average in diameter. That’d be cool. Without being curved, the image would have a spatial resolution of about:

    ⇒ Apparent angular size = 0.0000327 rad
    ⇒ Sol’s min feature = 4,900 km
    ⇒ Sol pixellation = 63,500 over face

    And each virtual pixel would be 33 m in diameter of that huge solar image. LOL!
    Just saying,
    GoatGuy

  83. It can’t be focused any more than 10km because the sun is a certain diameter in arch of the visible sky. So the fact that it would be in such a low orbit helps keep it down to 10km but you can’t make it any tighter unless you come up with some sort of funky meta-material with unheard of optics for your mirrors. You can, however, increase the power going to that 10km area by adding more area to your mirrors.

  84. It can’t be focused any more than 10km because the sun is a certain diameter in arch of the visible sky. So the fact that it would be in such a low orbit helps keep it down to 10km but you can’t make it any tighter unless you come up with some sort of funky meta-material with unheard of optics for your mirrors. You can however increase the power going to that 10km area by adding more area to your mirrors.

  85. The solution to street lighting is just don’t do it. People can see in the dark well enough. And the few times they can’t and the few people who can’t they can use a flashlight. Too much light while sleeping is bad for your health. Let the night return. There are stars in the sky, wonderful stars.

  86. An idea that can arise and supported only by a Chines communist mind. The fanatic adoration of mega projects blind to the consequences. People in the cities are suffering from light pollution already which causes stress and sleep deprivation. If anything we need to redesign street lighting and other sources of light at night in order to reclaim the natural stary night sky.

  87. An idea that can arise and supported only by a Chines communist mind. The fanatic adoration of mega projects blind to the consequences. People in the cities are suffering from light pollution already which causes stress and sleep deprivation. If anything we need to redesign street lighting and other sources of light at night in order to reclaim the natural stary night sky.

  88. I am working with another company for a more full featured comment system. My apologies for the long delay.

  89. I am working with another company for a more full featured comment system. My apologies for the long delay.

  90. Another of your gratuitous attacks on environmentalists. It’s clear from the comments here that this plan has many more uncertainties than just building more conventional solar farms, but you are already attacking them for not getting behind it.

  91. Another of your gratuitous attacks on environmentalists. It’s clear from the comments here that this plan has many more uncertainties than just building more conventional solar farms but you are already attacking them for not getting behind it.

  92. I know it is, no they won’t, and no. Grow up and let people enjoy things.

    Also in this case, they’d better impart quite a bit of energy, or the lightweight reflector will just have 10,000 tiny holes in it, barely affecting it.

  93. I must express my doubt that those old comments are ever coming back in any meaningful form. They had both html formatting and links, and often were long. Your new commenting system forbids all html, and places a strict limit on comment length. Even if you did bring them back, they’d be a mess. It would be different if you’d switched to a new commenting system that had equivalent functionality, rather than this bare bones system. Then automated translation of the comments into the new system would have been fairly straightforward. But you didn’t, you switched to Vuulke, which is, remarkably, less feature laden than IRC. Furthermore, this isn’t the first time you’ve changed comment systems, asserting that the old comments would be preserved. How did it work out last time?

  94. I must express my doubt that those old comments are ever coming back in any meaningful form. They had both html formatting and links and often were long. Your new commenting system forbids all html and places a strict limit on comment length.Even if you did bring them back they’d be a mess.It would be different if you’d switched to a new commenting system that had equivalent functionality rather than this bare bones system. Then automated translation of the comments into the new system would have been fairly straightforward. But you didn’t you switched to Vuulke which is remarkably less feature laden than IRC.Furthermore this isn’t the first time you’ve changed comment systems asserting that the old comments would be preserved. How did it work out last time?

  95. It also makes them more violent and accident prone. This thing ought to have a measurable body count just due to car accidents and distracted people run over by cars. Albeit criminality may be reduced, given the correlation of crime and poor lightning.

  96. It also makes them more violent and accident prone. This thing ought to have a measurable body count just due to car accidents and distracted people run over by cars.Albeit criminality may be reduced given the correlation of crime and poor lightning.

  97. Pretty easy to defeat with any non hollywood ASAT weapon. Just lob carbon pellets at it and hit the reflector with 10,000 hypersonic pellets on a ballsitic orbit (so the pellets don’t go in to orbit and make a large mess). Seriously Hollywood films will make you dumber, stop watching them.

  98. Pretty easy to defeat with any non hollywood ASAT weapon. Just lob carbon pellets at it and hit the reflector with 10000 hypersonic pellets on a ballsitic orbit (so the pellets don’t go in to orbit and make a large mess).Seriously Hollywood films will make you dumber stop watching them.

  99. They won’t use that many satellites. The cost will be prohibitive and it will mess up everyone’s sleep. If China wants more power 24/7 then just build another nuke plant. PPT design by central committee.

  100. They won’t use that many satellites. The cost will be prohibitive and it will mess up everyone’s sleep.If China wants more power 24/7 then just build another nuke plant.PPT design by central committee.

  101. Another drawback: If these satellites are in 1,000km orbits and 18 are needed to keep a city in “dusk” (over 12 hours or 24?), then they will need to change orientation before and after each pass over the city to avoid lighting up a path around the world. That means a fair amount of propulsion/power to reorient a 10km(? Is that even technically feasible today?) dish twice a day. The last thing you want to do is add light to already sun lit areas. I suppose the same 18 sats could service other cities on the same latitude, right? Sorry, just having a hard time imagining how 18-10km wide satellites will work… And another thing: Isn’t it “bad” to be adding all that energy/heat through the atmosphere?

  102. Another drawback: If these satellites are in 1000km orbits and 18 are needed to keep a city in dusk”” (over 12 hours or 24?)”” then they will need to change orientation before and after each pass over the city to avoid lighting up a path around the world. That means a fair amount of propulsion/power to reorient a 10km(? Is that even technically feasible today?) dish twice a day. The last thing you want to do is add light to already sun lit areas. I suppose the same 18 sats could service other cities on the same latitude right? Sorry”” just having a hard time imagining how 18-10km wide satellites will work…And another thing: Isn’t it “”””bad”””” to be adding all that energy/heat through the atmosphere?”””

  103. I am still working to bring back old comments. They are not geosynch, they are lower.

  104. If you put the mirror in a low orbit, you can illuminate just a city, but not for long, because your mirror will be sweeping across the sky, and will end up in the Earth’s shadow quick enough. If you put the mirror in a high orbit, ideally geosynchronous, you can illuminate the same point as long as you want, but your minimum spot size will be over 300 km in diameter. So, this isn’t aimed at just a city. It’s going to light up the area of a mid sized state.

  105. If you put the mirror in a low orbit you can illuminate just a city but not for long because your mirror will be sweeping across the sky and will end up in the Earth’s shadow quick enough.If you put the mirror in a high orbit ideally geosynchronous you can illuminate the same point as long as you want but your minimum spot size will be over 300 km in diameter.So this isn’t aimed at just a city. It’s going to light up the area of a mid sized state.

  106. I was going to comment the exact same thing, but then I thought: They’re going to be illuminating megalopolitan areas, and it’s not like the neon, LED, mercury and low-pressure sodium lighting (not to mention the godawful noise) isn’t ALREADY throwing off the circadiam rhythm of everything in the area. If they happen to illuminate some rural area with this, then I agree it’s probably ill-advised. Heck, it might be ill-advised anyway because of something else we haven’t thought of. File this under “needs more consideration”.

  107. I was going to comment the exact same thing but then I thought: They’re going to be illuminating megalopolitan areas and it’s not like the neon LED mercury and low-pressure sodium lighting (not to mention the godawful noise) isn’t ALREADY throwing off the circadiam rhythm of everything in the area.If they happen to illuminate some rural area with this then I agree it’s probably ill-advised. Heck it might be ill-advised anyway because of something else we haven’t thought of. File this under eeds more consideration””.”””

  108. Didn’t we already run the numbers on this? (In comments that Brian threw away, of course…) If you’re up in geosynchronous orbit, which is kind of necessary if you mean to illuminate the same area all night, you’re about 36,000 km up. At the equator, it gets a bit worse away from it. Sunlight is about 400,000 times brighter than Moonlight. So they’re aiming for 0.00002 suns illumination. Assuming a perfect mirror, you’re going to get a spot size of about 334 km wide, from geosynch. To achieve the targeted brightness… a 1.5km diameter mirror. OK, guess it’s feasible, but they’re not going to be illuminating a city, they’re illuminating an entire region.

  109. Didn’t we already run the numbers on this? (In comments that Brian threw away of course…)If you’re up in geosynchronous orbit which is kind of necessary if you mean to illuminate the same area all night you’re about 36000 km up. At the equator it gets a bit worse away from it.Sunlight is about 400000 times brighter than Moonlight. So they’re aiming for 0.00002 suns illumination.Assuming a perfect mirror you’re going to get a spot size of about 334 km wide from geosynch.To achieve the targeted brightness… a 1.5km diameter mirror. OK guess it’s feasible but they’re not going to be illuminating a city they’re illuminating an entire region.

  110. Can it be focussed more tightly like in Die Another Day? That’s the real question, because if you can concentrate a 10km area of light down to 10m, you’ve got yourself a death ray. The Sun is ~4E5 times brighter than the Moon, the reflector 8 times. That makes the sun 5E4 times brighter than the reflector. A 10m circle is 1E6 times smaller than a 10km circle, 1E6 / 5E4 gives us ~20 times brighter than the sun. Okay so maybe not a death ray, but it’ll be really bright out!

  111. Can it be focussed more tightly like in Die Another Day? That’s the real question because if you can concentrate a 10km area of light down to 10m you’ve got yourself a death ray.The Sun is ~4E5 times brighter than the Moon the reflector 8 times. That makes the sun 5E4 times brighter than the reflector. A 10m circle is 1E6 times smaller than a 10km circle 1E6 / 5E4 gives us ~20 times brighter than the sun. Okay so maybe not a death ray but it’ll be really bright out!

  112. You can BET it will disrupt the sleeping habits of insects, animals, plants and anything else that has a circadian rhythm.

  113. You can BET it will disrupt the sleeping habits of insects animals plants and anything else thathas a circadian rhythm.

  114. I wonder if 8x brightness is an achievement or what is appropriate for the application. If you could make it 1000x brightness it would only take a few hundred satellites to make the region a 24/7 growing operation. A hundred might let you tame the winters and seriously extend the grow seasons for the region.

  115. I wonder if 8x brightness is an achievement or what is appropriate for the application. If you could make it 1000x brightness it would only take a few hundred satellites to make the region a 24/7 growing operation. A hundred might let you tame the winters and seriously extend the grow seasons for the region.

  116. It can’t be focused any more than 10km because the sun is a certain diameter in arch of the visible sky. So the fact that it would be in such a low orbit helps keep it down to 10km but you can’t make it any tighter unless you come up with some sort of funky meta-material with unheard of optics for your mirrors. You can, however, increase the power going to that 10km area by adding more area to your mirrors.

  117. If it is at 1000km and orbiting in a dusk-dawn orbit then they are almost certainly talking about Sun-synchronous orbit (although sun-synch is generally lower orbit than that). This is perfect for giving more hours of light to both cities and solar power stations especially in the winter months but not for all night. But this is when solar power is most needed because the highest demand is in the twilight hours when solar has already faded. Thus it does have its advantages. Google “Duck Curve”

  118. An idea that can arise and supported only by a Chines communist mind. The fanatic adoration of mega projects blind to the consequences. People in the cities are suffering from light pollution already which causes stress and sleep deprivation. If anything we need to redesign street lighting and other sources of light at night in order to reclaim the natural stary night sky.

  119. Another of your gratuitous attacks on environmentalists. It’s clear from the comments here that this plan has many more uncertainties than just building more conventional solar farms, but you are already attacking them for not getting behind it.

  120. I must express my doubt that those old comments are ever coming back in any meaningful form. They had both html formatting and links, and often were long. Your new commenting system forbids all html, and places a strict limit on comment length.

    Even if you did bring them back, they’d be a mess.

    It would be different if you’d switched to a new commenting system that had equivalent functionality, rather than this bare bones system. Then automated translation of the comments into the new system would have been fairly straightforward. But you didn’t, you switched to Vuulke, which is, remarkably, less feature laden than IRC.

    Furthermore, this isn’t the first time you’ve changed comment systems, asserting that the old comments would be preserved. How did it work out last time?

  121. It also makes them more violent and accident prone. This thing ought to have a measurable body count just due to car accidents and distracted people run over by cars.

    Albeit criminality may be reduced, given the correlation of crime and poor lightning.

  122. Pretty easy to defeat with any non hollywood ASAT weapon. Just lob carbon pellets at it and hit the reflector with 10,000 hypersonic pellets on a ballsitic orbit (so the pellets don’t go in to orbit and make a large mess).

    Seriously Hollywood films will make you dumber, stop watching them.

  123. They won’t use that many satellites. The cost will be prohibitive and it will mess up everyone’s sleep.

    If China wants more power 24/7 then just build another nuke plant.

    PPT design by central committee.

  124. Another drawback: If these satellites are in 1,000km orbits and 18 are needed to keep a city in “dusk” (over 12 hours or 24?), then they will need to change orientation before and after each pass over the city to avoid lighting up a path around the world. That means a fair amount of propulsion/power to reorient a 10km(? Is that even technically feasible today?) dish twice a day. The last thing you want to do is add light to already sun lit areas. I suppose the same 18 sats could service other cities on the same latitude, right? Sorry, just having a hard time imagining how 18-10km wide satellites will work…

    And another thing: Isn’t it “bad” to be adding all that energy/heat through the atmosphere?

  125. If you put the mirror in a low orbit, you can illuminate just a city, but not for long, because your mirror will be sweeping across the sky, and will end up in the Earth’s shadow quick enough.

    If you put the mirror in a high orbit, ideally geosynchronous, you can illuminate the same point as long as you want, but your minimum spot size will be over 300 km in diameter.

    So, this isn’t aimed at just a city. It’s going to light up the area of a mid sized state.

  126. I was going to comment the exact same thing, but then I thought: They’re going to be illuminating megalopolitan areas, and it’s not like the neon, LED, mercury and low-pressure sodium lighting (not to mention the godawful noise) isn’t ALREADY throwing off the circadiam rhythm of everything in the area.

    If they happen to illuminate some rural area with this, then I agree it’s probably ill-advised. Heck, it might be ill-advised anyway because of something else we haven’t thought of. File this under “needs more consideration”.

  127. Didn’t we already run the numbers on this? (In comments that Brian threw away, of course…)

    If you’re up in geosynchronous orbit, which is kind of necessary if you mean to illuminate the same area all night, you’re about 36,000 km up. At the equator, it gets a bit worse away from it.

    Sunlight is about 400,000 times brighter than Moonlight. So they’re aiming for 0.00002 suns illumination.

    Assuming a perfect mirror, you’re going to get a spot size of about 334 km wide, from geosynch.

    To achieve the targeted brightness… a 1.5km diameter mirror. OK, guess it’s feasible, but they’re not going to be illuminating a city, they’re illuminating an entire region.

  128. Can it be focussed more tightly like in Die Another Day? That’s the real question, because if you can concentrate a 10km area of light down to 10m, you’ve got yourself a death ray.

    The Sun is ~4E5 times brighter than the Moon, the reflector 8 times. That makes the sun 5E4 times brighter than the reflector. A 10m circle is 1E6 times smaller than a 10km circle, 1E6 / 5E4 gives us ~20 times brighter than the sun. Okay so maybe not a death ray, but it’ll be really bright out!

  129. I wonder if 8x brightness is an achievement or what is appropriate for the application. If you could make it 1000x brightness it would only take a few hundred satellites to make the region a 24/7 growing operation. A hundred might let you tame the winters and seriously extend the grow seasons for the region.

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