Gigawatt Scale Moon Base

SpaceX had published a picture of a moonbase with multiple Starships and a solar farm.

On earth, a photovoltaic solar plant producing about one 1 GWh per year, will require around 2.8 acres of land. The moon has no atmosphere, so a 300-watt panel on Earth would produce 400 watts on the moon.

A GWh could be produced using 2 acres of land on the moon. An acre is 43,560 square feet (180 feet X 242 feet). In the SpaceX picture, it looks like they have solar panels on 200 acres. This would be about 100 GWh per year.

A rule of thumb on earth is 1kW per 100 square feet. On the moon with higher efficiency panels and better sunlight it could be 2 kW per 100 square feet. 200 acres would be about 170 megawatts. This could be 200 GWh per year. If the moon base solar power was six times bigger then it would be over 1 gigawatt of power. This would be 1200 acres or just under two square miles.

The system could weight 1 kilogram per kilowatt. In 2015, space-based solar power was 6.7 kilograms per kilowatt. The weight efficiency is being improved and simple lunar materials could be used to make some of the structures. This would mean transporting 1000 tons of material for a gigawatt of solar power on the moon. This would be ten refueled Starship landings for the main solar power systems and another five for construction machinery and other systems. There could another five Starship landings to provide batteries.

If construction of the moon-based started in 2023, then it could be completed and scaled to a gigawatt base by about 2026.

The base would support a few thousand people and would enable the seed for major lunar factories and lunar mining.

Twenty-SpaceX Starships to the moon would need several launches to orbit to refuel them. If the launches and the materials were about $500 million per lunar Starship mission, then it would be about $10 billion for a major lunar base.

Written by Brian Wang,

81 thoughts on “Gigawatt Scale Moon Base”

  1. Then you need some sort of conductor grid, or your checkerboard cells need to be small (on the scale of the thermal gradient width). The regolith alone won’t give you much conduction.

    So basically you end up with a solar-cell/radiator checkerboard instead. You may as well arrange it in narrow stripes, and coat the radiators with a reflective coating so it would absorb as little as possible of the sunlight. While you’re at it, may as well point the useful frequencies at the solar cells, to get more power. Just need to make sure everything else and especially the heat radiation still goes mostly to space.

    This is starting to sound a lot like GoatGuy’s V-shaped dichroic panels (and somewhat similar to Brett’s chevrons).

  2. Please see Criswell. The diffraction problem is gone once the radars have to be *that* big anyway, to handle the load. Thus, there are 7 such radars, not just one.
    Please consider cost etc of 20-200TWe “launch subassemblies for RF-beamed solar power from GEO.”

  3. You’re inviting an anti-SLS rant here, and I’m happy to provide it. Even under the most optimistic assumptions made for SLS costs, an SLS/Orion-based Artemis mission is roughly nine times the cost of a similar mission using a lunar Starship-based HLS, staged from LEO, with crew loaded and off-loaded via an F9/D2. And when (if) Starship matures to the point where it can launch crews directly and recover them through EDL, SLS/Orion costs more like sixty times as much.

    That’s an awful lot of extra money to develop surface payload packages and send them to the Moon. You don’t need a new tax; you just need the political courage to cancel SLS and Orion.

  4. Not from the Moon. You’re diffraction-limited, unless you solve a whole bunch of problems with cooling high-energy optical systems, and have a reliable way of receiving the beam above any cloud cover.

    The better play is to fabricate and launch subassemblies for RF-beamed solar power from GEO.

  5. If you have a checkerboard of lit and unlit areas, you actually want conduction, because emittance falls off so quickly as the average temperature drops.

  6. If you can make cheap ISRU PV, then storing energy as hydrolox makes more sense than either batteries or nukes. But any kind of ISRU-driven manufacturing is out there a ways.

  7. You got my point about making PV. When you figure in storage what is the W/kg of the power supply brought to the moon, I would be surprised if that doesn’t work out much better for the reactor. If *some* of what you are doing can be turned off at night then once you have ISRU PV manufacturing on the moon, you have reactors for baseload & PV for stuff you run only during lunar day. Also there might be mineable concentrations of U or Th on the moon, so ISRU nuclear on the moon isn’t impossible.

  8. Once you have water mining, you may want to go with hydrolox for backup power. It’s easier to make on the Moon, and liquid hydrogen has 2-3 times the energy density of liquid methane (though not sure if that still holds after adjusting for hydrolox vs methalox – including the oxygen – and for practical system inefficiencies).
    edit: Though for ISRU, the energy density doesn’t really matter much.

    Also, you missed the bit about “If we are making PV on the moon”. Maybe I interpret that wrong, but it sounds like trying to make PV from ISRU? In that case, we won’t be making the latest and greatest triple junction stuff any time soon (but then again, we also won’t be making kilopower off ISRU).

  9. Conduction should be minimal, because regolith is a good insulator. It’s a mix of ceramics with high porosity “filled” with vacuum. At equilibrium, you’d likely find a narrow temperature gradient between the lit and shadowed areas, with the rest at constant temp. So conduction effects can probably be neglected if you’re fine with a close approximation.

  10. Even if he said what you said he said, that just means he was writing loosely. Obviously he could not possibly have meant that stuff in vacuum instantly equilibriates to the surrounding temperature or however you are interpreting it. (I’m not sure exactly how you are interpreting it).

    Also, on the original question, you were wrong and Dan Lantz’s criticism of your view is correct, though it depends on the scale.

    Rocks are a pretty decent insulator. And the insulation provided by an insulating layer depends on its thickness. If you have a heat generating surface placed on a larger solid, the effective thickness of the insulating later provided by the solid is something comparable to the radius of the heat generating surface – which in a lunar solar installation would likely be very large. Which means a super thick insulating layer, and thus near-perfect insulation.

    Of course, if the rocks start cold, then you can dump heat into them until they equilibriate, but this is a temporary situation.

    Vacuum behaves completely differently. Any size of flat surface facing empty space can dump heat to space at the same rate per surface area.

    Thus, by putting the heat generating surface on rocks, you effectively cut heat dissipation in half (since it’s effectively zero heat dissipation through the rocks).

  11. See my “chevrons” proposal: Once you get away from the equator, you might as well have gaps between the panels, and you can reflect the IR from the back of the panels up between the gaps.

  12. Hmm. This is literally one of those “calculate the flux from a flat plate” problems.

    As Daniel pointed out, if you want to track the sun without occulting your neighbors, there has to be space between them, so some of the ground surrounding the panels will be emitting. But it’s also conducting heat from the lit areas to the ones shadowed by the panels themselves, which reduces the temperature. And, since emittance is proportional to temperature to the fourth power, modest reductions in ground temperature can have a big impact on flux.

    It’s a really freakin’ complicated model. That said, my famously fallible intuition says that this is likely less of a problem than you think.

    One suggestion: putting an angled mylar “skirt” around the outside of your array could keep the outer edges cool by reflecting EM flux away, since the elements there don’t have neighbors shading the nearby ground.

  13. Space-grade triple-junction solar panels have a specific power that’s now close 200 W/kg. The 10 kWe version of Kilopower is expected to have a mass of 1500 kg, so specific power is 6.7 W/kg. Which of those would you rather transport to the lunar surface, at a specific cost of somewhere between $1500-$3000/kg?

    As for Megapower, it barely exists on the drawing board. At least Kilopower has gone through the KRUSTY testing, albeit at only 1 kWe scale.

    Update: Missed your storage reference up above. Yes, if you have a 50/50 light/dark cycle and you need as much power in the dark as you do during the day, then a gang of 10 kWe Kilopowers does substantially better than solar and batteries. But you can be clever:

    If you site at a PONQUEL, the worst-case light/dark is 75/25, and the average case is about 99/1. Since you’re hardly ever in darkness, you can power down almost everything for the one week a year of darkness, and rely on a methalox APU for peaking during the power down.

    Batteries have specific energy of about 250 Wh/kg
    Methalox has a specific energy of about 1.08 kWh/kg from an APU

    100 kW base @ 200 W/kg = 0.5t solar panels. Let’s make it 1.0t with supports.
    10 kW during darkness lasting 7 days @ 250 Wh/kg = 6.7t batteries
    10 kWh of peaking energy @ 1.08 kWh/kg = 9.3t of methalox.
    Total: 17t

    That’s pretty much even with 10 Kilopowers. Admittedly, the methalox is non-renewable, but it’s basically free from FPR taken from cargo Starships.

  14. The best you get are PONQUELs (Peaks of Not-Quite Eternal Light). The best of those still has a week of darkness at some point during the year. Since your storage requirements are proportional to the worst-case period of darkness, this isn’t nearly as advantageous as you think.

    While the PONQUEL certainly helps your worst case, unless you’re willing to develop the technology to put solar “curtains” on masts hundreds of meters high, this real estate isn’t as prime as you think. And if you have the mast technology, you have a much wider range of places near the poles to site your base.

  15. Sorry to mis-state that, but I was referring to when he first asked the question, 1969 I believe. Shuttle started 1972, about time of Physics Today, so few price figures had been released. Nixon had not yet had time to mess with it yet. I only mentioned Shuttle to lead to: “I try to point out that this idea is independent of launch cost, not to say cheap launch does not help, but to say that cheap launch means cheap ISRU, not *NO* ISRU!” I agree everything is easier now. But if we could send Viking and rovers to Mars, why are we only now, 2020, about to launch to see directly the water on the Moon? I agree that “So all those big space projects got shelved.”, but I, starting ’77, and many others have been objecting specifically to *no Moon. No. No. No Moon*, even tho in my case I feigned interest in Mars until a few years ago, to say that Mars requires Moon first. Perhaps by another ? years we will do the simple conveyor processor that heats, collects O, glass and slag, proposed as first step. That is what I mean by O’Neill, ISRU , not only full blown projects. Those who supported Mars Only/First/Direct were the problem, not tech.

  16. The answer to “which came first, the chicken or the egg” is feathered therapod dinosaurs. They were egg-laying long before chickens, and their descendants are all the modern birds who survived when most dinosaurs died out.

  17. Dude, I met O’Neill and Bill Snow, the guy who was working in the lab on mass drivers, in the late 70’s when I was still a student at Columbia. I took a trip down to Princeton to meet them. The promise of the Space Shuttle, which hadn’t flown yet, and a Shuttle-derived HLLV (all cargo, no orbiter), was most certainly on their minds. Computers and automation were nothing like they are today – the IBM PC still hadn’t come out yet. So a colony with 10,000 people was required to do the SPS construction, farming, etc. Getting that bootstrapped at a reasonable cost would take multiple launches of both vehicles – Shuttle for the humans, HLLV for cargo. We also didn’t yet have electric propulsion, so getting stuff to the lunar neighborhood had a large multiplier on what you can get to low orbit.

    The 1980 Advanced Automation for Space Missions study hypothesized a 100 ton automated “seed factory” landed on the Moon, but the computing power to run the factory was far beyond what was available. So that idea got put aside. It wasn’t until 2010 or so that suitable computers were available. If you couldn’t use computers, you had to have people, and people means a lot of tonnage to keep them alive, even for a small number just setting up a base.

    Now we have tested laser links from the Moon. That vastly increases the bandwidth, so you don’t even need a powerful computer, you can use VR and remote control things from Earth. So boostrapping has gotten much easier.

  18. O’Neill was thinking independently of the Shuttle promises. In fact, his second most important point after where to live was ISRU, as a way to avoid launch costs. His “bootstrapping” is same sort of idea as “seed factory”. I try to point out that this idea is independent of launch cost, not to say cheap launch does not help, but to say that cheap launch means cheap ISRU, not *NO* ISRU! People just assume cheap launch means we can do their project without bothering with ISRU, so get on with it. A bad outlook, long term.
    We still need to find more NEOs, as the ones we see are too big!

  19. Yes, but the lack of atmos also makes cells on the suface more efficient, so less reason to make sats. Just power beam Moon to Moon with reflector screens, redirectors, if not in the right place. Still a trade off, so the answer is probably that lunar surface will get power like the Earth, from sats or Lunar Solar Power whichever is done large scale.

  20. Certainly a worrisome point! My *hope*, not that what I hope matters in this case, is that the *dust* kicked up by mining will not “blow around” like it does on Earth, but just fall back down. Orbital *dust* from rockets everybody sees as a big, quick problem, and will take steps to prevent. Curiously, both of the Space Solar guys would know about this particular topic, as Glaser was studying the retro-reflectors and Criswell was studying the electrostatic lifted sprays when they were each struck by the strong sunlight on the Moon, or Space in general. Strong sunlight -> get some. Criswell may have been the leading expert at one time on this topic, but he designs flat panels, which would seem the worst for this. It could be that the charge builds up on higher surfaces and helps keep them clean by spewing mostly from them. Would have been nice to check around on the Moon a little over the last 40+ years, at least with some rovers, to see what actually goes on there!

  21. Harking back to dust on the lunar retro-reflectors, there’ll probably be orders of magnitude more dust generated if hundreds of rockets are taking off and landing, plus a mining industry. One of the Apollo astronauts broke the ‘mudguard’ on their rover, and the resulting spray of dust was endangering the cooling of the batteries. Houston had to design a make-do out of duct tape and check sheets to solve the problem. – Haynes Lunar Rover Manual: 1971-1972 (Apollo 15-17; LRV1-3 & 1G Trainer)

  22. If we could properly monetize the IP developed through living on the moon, I’m sure you could generate a positive return. Plus it would allow the completion of infrastructure projects like a giant telescope that can accelerate astronomy research. There’s quite possibly a military benefit at some point.

  23. A lunar base would almost certainly be on a Peak of Eternal Light, near shadowed craters with water ice, not most other places with a 2 week night. One good argument to do it ASAP is to do it on the very limited prime real estate before somebody else does.

  24. 1999 was a great show for children. The nerdy ones would
    tell the others the most obvious science mistakes, and then
    they would all go to enjoy the wondrous special effects, and
    spaceship models, on a par with ‘2001’ and inferior only to
    Star Wars’. First half of episodes was financed for half of
    the budget by the Italian Television, in the hope of replicating
    Star Trek’s success. When said success didn’t fully materialize,
    they retired their financial support, and it shows.

  25. Could you build a solar power satellite to beam down power to a lunar base? There’s no atmosphere to absorb the energy.

  26. The work that O’Neill and others did on space colonies and solar power satellites was based on the Space Shuttle costing as advertised, and a follow-on heavy booster being even cheaper (by replacing the orbiter with a bigger payload. We all know that didn’t happen, it ended up costing around 25 times more than projected. So all those big space projects got shelved.

    Assuming the SpaceX Starship works the way it is intended, then all those old studies can be pulled off the shelf, updated to account for science and technology since the mid-1970’s, and proposed anew. For example, back then we only knew of about 60 near-earth asteroids, so they were ignored. Today we know of 23,000 and rising fast, and have even visited some with sample return probes.

    As far as the chicken & egg problem, that is addressed by the “seed factory” concept. It is a set of starter machines which are used to make more machines, until you have what you need. By combining metallic and carbonaceous asteroid rock, we get a decent iron-nickel-cobalt steel. That’s suitable feedstock to standard machine tools.The second generation machines are then designed to work with other materials and processes, scaling up in size and range of products.

  27. NASA has been developing a “Kilopower” reactor, which can produce 1-10 kW electric, and about 3 times that in thermal heat. For a small lunar outpost, you would then include multiple units to reach whatever power level you need. You can’t bury a reactor. You need to radiate waste heat to space, or run a heat pipe to somewhere else if you need process heat. Any large boulder or small crater is sufficient for radiation protection.
    Nobody is working on megawatt-class reactors yet, because the people with money aren’t thinking that far ahead.

  28. Re: 1 – 30% is the quoted efficiency for Spectrolab space-type cells with cerium-doped cover glass to reduce radiation damage. These are commonly used on communications satellites, and I assume would work on the Moon.

    Re: 4 – I agree that the installation would be location-dependent, like it is on Earth. The semicircular layout in the illustration above is silly. What you really want is rows oriented N-S with a sun-tracker drive.

  29. If we are making PV on the moon we probably won’t get high efficiency soon. We will want whatever can be made *cheaply* on the moon. We will probably want a kilopower or Megapower reactor for bases that aren’t near the poles to allow continuous solar power. Much easier than storage.

  30. Apparently you think heat and EM radiation are different in this context? That was the purpose of the edit, to make it easier for you to find black body concepts.

  31. Please don’t lie about my edit. Especially by saying I removed a true statement, that being “vacuum is no insulator at all for heat”. Other than that, feel free to continue humiliating yourself.

  32. There was a plan (don’t blame me) to thermally *sink* (melt into) the lunar surface a sphere of (Titanium?) with *waste* Plutonium in it, creating a flow of molten stuff ready to process. Failure would result in the eventual diluting to solid of the contents, no prob!

  33. No. 4 can be solved as Criswell does, by building pairs of simple/cheap collectors, and power beaming the energy anywhere needed, Moon to Moon being even easier than Earth to Earth, and a good start for larger plans. The trade off is between no. 4 tech and building ~3 times the area as simple collectors. That is 2x for day/nite and another sqrt(2) because not pointable. I think of power beaming as an attractive feature, for balance of load and source, and it is already mentioned as a possible way into the crater for even this small plan. These are very important issues right now!

  34. I see you’ve edited your previous post in order to remove your ridiculous ~’vacuum is no insulator at all for heat’ assertion, Dan Lantz.
    Next time, try to bring to the table less word salad, and at least some understanding of the subject under discussion.
    Your diploma is meaningless without said understanding.

  35. You are preaching to a member of the choir that has been singing the ISRU song for over 40 years. Time to get to work, no? How about some numbers that will help others see this need! BTW, the egg came first. The actual question concerns the chicken or the chicken egg. In that case, the two things that made the first egg were not chickens, or they would have come from chicken eggs.

  36. Yah, its all good.
    Except not in practice. 

    The “chief problem” is that before one can plan for using the abundant lunar (or geosynchronous) power, one has to have a pretty substantial manufacturing infrastructure in situ, a priori (or coëval).  

    Was it the chicken or the egg that came first?

    ⋅-⋅-⋅ Just saying, ⋅-⋅-⋅
    ⋅-=≡ GoatGuy ✓ ≡=-⋅

  37. Because a “small reactor” requires a small reactor! Replete with nuclear fuel, coolants, radiators, safety cladding, heat-to-electricity generating doodads, sensors, controls, reservoirs, you name it. And a small reactor. Did I mention that? LOL

  38. Assumes efficient dichroic mirror tech., I guess. only reflect the spectral parts the PV can absorb? Makes sense.  

    However, on that line, wouldn’t V shaped PV (maybe only centimeter scale!) really also be the answer? Same dichroic business, but (conceptually) the ‘left’ and ‘right’ PV cells are at a 90° angle to each other. The left dichroic reflects all-but what it needs toward the right. The right, vice versa, toward the left.  in net, all light not needed is reflected back, directly at Sol.  

    PV isn’t a single spike passband. It is somewhat wider. Still … dichroic mirrors are rather good at passbands of fairly well defined skirt-reflectivity. 

    Who knows. Maybe this is an answer for Planet Dirt located PV as well.  Especially for ‘concentrated solar’ PV.  Might eliminate most of the thermal load problem. Or some.

    ⋅-=≡ GoatGuy ✓ ≡=-⋅

  39. Hmm… ⊕1.  However, a number of things you said also don’t quite click.  

    № 1 — 30% multilayer PV cells. Yep, but ‘simplex’ style … only to use the abundant IR and UV that Earth’s atmosphere normally absorbs from Sol. Simplex or molecular epiaxially deposited bi-layer is doable, without much complication.

    № 2 — Using all 1363 insolation watts. Not really. There is a LOT of the solar spectrum that won’t be used. Even if 30% conversion is achieved, 70% of 1360 watts, is almost 1,000 watts of heat. Sadly. 

    № 3 — Mitigating waste heat. Actually it’d be useful. Heat pipe tech works find on Luna. Use the thermals to bulk-heat 10 million m³ of regolith. Call it ‘home sweet home’. Warm regolith is NOT a problem.

    № 4 — Conversion area. If polar positioned, the real problem is trying to face Sol. For smaller installations, a pole-and-a-giant-panel more-or-less is the paradigm. But larger than that? I don’t suppose thinking Eiffel Tower scale is a problem. ⅙ the weight per mass. REALLY big pole, and REALLY big panel. No wind! Hmmm…

    Until now, I felt that a huge circular rail system would be best. Mount the enormous panel between the rails, let it rotate every 28 days. Always facing Sol. The big pole might be better. Less to get out of alignment.

    But yes … power storage.

    If we assume regolith distillation, then making batteries ain’t a problem. 

    ⋅-⋅-⋅ Just saying, ⋅-⋅-⋅
    ⋅-=≡ GoatGuy ✓ ≡=-⋅

  40. One answer, I majored in Physics at Michigan in the early 70s, when it was a better school than after the first oil embargo. Another, more proper, is that vacuum is not a convective heat removing medium, so is not as good a cooler as we are used to on Earth, even tho it is not an insulator. You are welcome!

  41. Really, Dan Lantz?
    You think vacuum is no insulator at all for heat?
    Then why do you think getting rid of heat is so difficult in space? Why do you think large radiators are needed in order to remove heat via EM radiation?

  42. To continue:
    Dust-retroreflector question has been pondered, but not answered(for me!). A good one!
    Duty cycle. This is because the panels and radars are on the surface of the Moon, which has some imperfections as a Solar Power Sat, which, Criswell points out, it IS. At least you did not simply state that the Moon has a day/nite cycle and declare LSP hopeless! This duty cycle and the distances are the two main differences between LSP and GEO SPS. The transmitting distance issue goes away as the relevant load (20TWe minimum)requires such large radar anyway that the size required for Moon(to focus) is still too small, and multiple *stations* are needed to balance down the cell to radar distances. In other words, when in the sun, the radars are already big enuf to cover the 10x distance, no extra charge. In a related issue, the GEO cells are 100x as bright as they would be at L5, and cells on Moon contribute exactly 0 to this or Space junk. Now, the radars are still down half the time, and even worse, the cells are not illuminated straight on even when the sun is up, so their duty cycle is only about 1/3, not the 1/2 of the radars.This extra equipment cost has to balanced by all of the other advantages of LSP. No station keeping. No sat structure to build. No Space junk concerns. No light pollution concerns. Plenty of other projects on Moon to cooperate with(A biggie!) or even grow from, such as the subject of this article.

  43. Several issues, but it seems to me you are dismissing Criswell’s pp 10 and 13, power beaming Moon-Earth and esp Earth-Earth. Moon-Moon is a just as easy “extra infrastructure to redirect the power around “(Moon). No advantage to GEO here as multiple balanced targeting of loads is *better* than fixed links to variable loads! (altho GEO is still 10x closer.) Solving variable load is as important as solving variable source(intermittancy). Redirecting power beam screens allow both Space and Earth based power to be distributed and balanced. Not a bad solution! In fact, a good place to start.
    And “The Moon would probably work quite well for high voltage transmission lines” is a puzzling statement, as the only place this is mentioned is short lines to cover ~100 km for exact new Moon condition.
    And “It has to go all the way around the Moon before anybody will buy the power” sounds like you are referring to the Shimizu plan, an equatorial belt requiring circumlunar superconductor(avoided altogether by that clever Criswell), not Criswell station pairs, which are good to start full time immediately.

  44. I preferred the moon base in UFO; The chicks with purple hair were cool. And, of course the plot of Space: 1999 was insane.

    Based on what they did with the Enterprise, I’m guessing that NASA will deliberately use “Moonbase Alpha” for the name of a disposable shack on the Moon just to make sure no permanent base gets called that.

  45. I’ll give you this: The Moon would probably work quite well for high voltage transmission lines, given the lack of atmosphere and weather.

    My chief objection to Criswell is that I can’t see the Moon from where I live half the time, which is another way of saying you’d need extra infrastructure to redirect the power around the Earth. And, of course, low duty cycle for the equipment. In theory dust could actually be an issue, too; The Moon actually has a slight atmosphere of electrostatically levitated dust, which *might* eventually accumulate on panels and have to be cleaned. And it’s abrasive, so you don’t want to just wipe it off. Hm, there’s that retroreflector they left on the Moon during Apollo, does somebody have numbers on how fast it’s getting dusty?

    That’s why I’d rather go with SPS in geosynch, where you have a fixed relationship with the ground receiver, and near 100% duty cycle. I like schemes that can work starting small, and then be scaled up by feeding some of the profit back into them. Criswell has to be large scale to work at all; It has to go all the way around the Moon before anybody will buy the power, because nobody wants power that cuts out for weeks at a time, you need the complete redirection system to consistently serve any particular customer, and the transmitting antenna has to be large to get a decent spot size from that distance.

    I think the advantages of SPS more than make up for the need to loft the materials.

  46. Like I said, it’s possible to deal with the heat sinking issue.

    1) Use the mass of the ground as a heat sink. The issue here is that the day is two weeks long! That means you need to use a LOT of mass per square meter of surface, so you can’t just use the top, you need to penetrate it with heat pipes so that you can use it to a substantial depth. Then you need to exhaust that heat during the night using the heat pipes. (Fortunately, in that direction convection helps, not hinders.) Workable, but needs extra equipment beyond the panels, moderately massive equipment.

    2) Space out the active panels, above the ground, with IR reflective chevrons underneath, and cover the ground between them with inverted chevrons. The non-diffuse sunlight hitting between the panels can be reflected away, and the thermal emissions from the backs of the panels will “see” the dark sky even during the day. The equipment here is quite simple and light, but you can only use half or less of the available area for panels. This should work quite well anyway away from the equator of the Moon, because you’re limited in that regard anyway!

    3) Go thermal: Dig a deep bore hole, and focus the sunlight down it during the day, to turn a column of regolith into a thermal reservoir. Surround that column with heat engines exhausting the heat back at the surface in the shadow of your concentrator. The nice thing about this is that if the thermal reservoir is sized right, it runs right through the night!

  47. I supported a visitable Moonbase rather than ISS, but must admit LEO presence is very useful too. My objection to ISS is focus on 0 g studies, only needed for Mars, instead of gateway to Moon and spin g from lunar materials, the obvious next step even at this late date.

  48. Yes, Elon once mentioned that he’d watched the TV show Mooonbase Alpha as a kid (he was obviously referring to Space 1999 by Gerry Anderson), and felt that a moonbase was long overdue. He said this back when NASA first announced Artemis.

  49. Vacuum is a good insulator compared to convection at pressure under g (Thermos on Earth). It is no insulator at all for EM radiation, thus the “dark of space* reference. Moon rocks are low surface area per mass, so can moderate temp by absorbing/releasing heat day/nite, for acceptable operating temp. All clever ideas welcome!

  50. Maybe just evacuate and mothball at night.

    I mean, the low G is unhealthy anyway. So get your high power industrial activities done in a two week shift during the day, then rocket up to an orbiting wheel station for two weeks of exercise and R&R before returning for another day shift.

  51. I agree. It is also easier than trying to process the material on the Moon, as varous comments about that very difficulty show. The Moon is also a planet, for this discussion. Use ONLY as needed.

  52. Or put the panels in permanent -150C shadowed areas and use mirrors to illuminate them.
    Some PV cells use the IR though so there is a tradeoff

  53. I understand your rage. Moon solar is most viable at polar mountaintops for constant radiation. No atmosphere = no problem with low sun.

  54. The next article discusses the Metzger study which proposes that there would be a near term market for $2.4 billion per year for lunar produced fuel and water.

  55. mining the moon and constructing a huge emag “slingshot” (aka, Gerard K. O’Neill) would be very useful for getting non-refined materials up into one of the Lagrangian points between earth and moon (L5?) and refining it there to build space colonies… -much cheaper to launch tonnage into orbit from the moon than earth (once infra has been built for that purpose :-))…

  56. Few people will live on the Moon, rather in Space. It is the fact that the Moon already exists that gives it an advantage, even tho not perfect, for solar panels.

  57. Seems like building the stuff on the Moon in pairs would be a well understood solution to the day/nite prob on the Moon. Criswell has it right up front, and EVERYBODY on this site has heard of Criswell!

  58. Not convinced that putting delicate, surface-clean-sensitive, and high-maintenance panels/ dishes/ optics on the moon surface will be a efficient, serviceable, and financially-prudent project. Colonies with below ground presence and rough surface resilience is the LunArchitecture of choice.

  59. “two-week lunar night” As on Earth, relay screens will distribute power, if you build a small rectenna, and assume more than one field. The distances are small, so the antennae are too.

  60. Not here on NBF, but another site with another SpaceX moonbase article referred to it as ‘moon base alpha’. Elon perhaps was a fan of 1999? He’s the right age.

  61. There’s a substantial difference, in that space solar panels face the Sun on one side, and the dark of space, (Several degrees Kelvin!) on the other. This nets out at a reasonable temperature, -23C.

    Heat sinking on the Moon during the day is possible, but takes substantial work. Either using the ground as a heat sink, or spacing the panels out so that they can radiate heat to the part of the sky that isn’t the Sun.

  62. We will need a new tax to pay for that base, unless some money can be diverted from one of these curated budget line items.

    NASA $22.6 billion
    Base-Defense-budget total: $554.1 billion
    War-budget total: $173.8 billion
    Nuclear-budget total: $24.8 billion
    Defense-related-activities total: $9 billion
    Veterans Affairs total: $216 billion
    Homeland Security total: $69.2 billion
    International-affairs total: $51 billion
    Intelligence-budget total: $80 billion
    Defense share of national debt total: $156.3 billion
    ~$68 billion on food stamps every year.
    SLS cost ~$18 billion since 2010.

  63. It gets just as hot for space solar panels in Earth orbit, as they are the same distance from the Sun. This is basically a solved problem. You may want to cover the ground under the panels with a low emissivity material to cut down ground-side heating.

  64. So many errors in the calculations, and mixing metric and english units, shame on you.

    Terrestrial panels are about 20% efficient, and therefore produce 200W/m^2 against the standard 1 kw/m^2 at sea-level noon. Average location gets 1600 hours of equivalent output/year. The panel output varies with weather and sun elevation, but that’s the integrated hour equivalent. Thus 320 kWh/m^2/year. To get 1 GWh then requires 3125 square meters of panels. The ground area depends what kind of mounting you use.

    On the Moon we would use triple-layer cells which are 30% efficient state-of-art against 1361 W/m^2 solar flux, or 400W/m^2. Due to lunar night and inter-row shadowing, you would operate about 40% of the time, or 3500 hours/year. So each square meter produces 1400 kWh. Ti get 1 GWh then requires 714 m^2. Again, ground area depends on how it is installed.

    Your mass estimate entirely ignores the two-week lunar night. If there are people there, you need power all the time. Two week batteries will be heavy. Solar-thermal storage is an option. You have nearly unlimited loose rock down to dust. Take an empty rocket tank and fill it with suitable size rocks. Use solar concentrators to heat a working fluid and flow it through the rock medium during the day. At night you extract the heat to run a turbine. Cover the tank with multi-layer insulation to minimize thermal loss. The ground it sits on is a natural insulator due to vacuum between particles.

  65. There is a bit of an issue that it gets rather hot during the day on the Moon. Over 120 degrees C. Heat isn’t good for photovoltaics.

    This could be coped with, of course, but the easiest way to do so involves spacing the panels out so that you can’t use 100% of the surface area.

    I wonder if it would be possible to come up with a thin film that would transmit only IR and a good frequency for the solar panel, and reflect the rest of the light? This sort of selective film could substantially reduce the temperature of the panels.

    Alternatively, you could take advantage of the fact that the illumination on the Moon isn’t at all diffuse, and use solar concentrators and thermionics; 120C is still a decently low temperature for thermionics to be rejecting heat at.

  66. Useful for mass drivers.

    But they will need to have some backup too, in form of nuclear reactors keeping the light on during the 2 weeks of night.


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