Space-Based Solar Power

a public discussion sponsored by the Space Frontier Foundation

Google Lunar X-Prize and Space-Based Solar Power

Posted by Coyote on November 22, 2007


One of our regular contributors, Dan Lantz, provided us with a link to an incredibly well done Internet video that explains the Google Lunar X-Prizes for Lunar Exploration in a production called “Moon 2.0.” Space-Based Solar Power makes a cameo appearance!

Personally, I think it steals the scene, like Sean Connery arriving triumphantly in the last scene of Keven Costner’s movie “Robin Hood, Prince of Thieves.” Oops, did I spoil it? Sorry.

The long term plan is to eventually produce such satellites on the Moon and boost them back to Earth orbit to provide clean energy! That way we take advantage of the Moon’s lower gravity that makes launching them back to Earth an much easier energy proposition. Naturally we will have to construct considerable infrastructure on the Moon first to make it happen. I’d like to point out that we may also need solar power satellites in Lunar orbit and eventually Martian orbit as well.

The short term plan, of course is to produce solar power satellites on the Earth and boost them into our orbit until the Moon is developed sufficiently to begin production and launch from there.

Please take a look at the video. Think about it. What type of incentives do you think are appropriate and effective stimuli to promote private sector investment in space-based solar power and its supporting infrastructure? Who might offer such prizes?

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16 Responses to “Google Lunar X-Prize and Space-Based Solar Power”

  1. Rocky said

    Instead of a prize, why not a contract to provide 1MW at 10cents/kW anywhere in the world for the first company to demonstrate the capacity to deliver? Get the DOD to guarantee a minimum contract of $100 million.

  2. Dan Lantz said


    Thanx for promoting scene stealer! (Yes, you did-I have not seen the movie). Those who have read Gerard K. O’Neill’s “The High Frontier” (1977) can snicker NOW!
    I still, still, still question the assumption (which opposes what Dr. David R. Criswell sez) that the Moon is NOT Earth’s natural primary Solar Power Satellite! (This would be a rare exception to O’Neill’s genius insights).
    Seems that there is a “backwardsness” to the popular overall concept that people should live on plantary bodies (Mars, Moon, other stars’ planets, etc.), yet collect energy in orbit (Solar Power Satellites). We should primarily live, work, mine, manufacture, farm etc. in Free Space, where we choose the conditions such as gravity, temperature, etc. But collect solar energy on the MOON, where there is an EXISTING surface area, with free station keeping, free basic structure, free space junk prevention, free materials for radiation (thermal, solar and cosmic) shielding, not to mention free construction material. (Altho it may sometimes be better to send raw lunar material to orbit for manufacture, then return product to Moon).
    On a more specific topic, it seems that we need “relay” satellites no matter what the eventual “best” collection plan is. Geosync Solar Power Satellites (SPSs) need relays to get energy to “polar” latitudes. Lunar Solar Power (LSP) system needs relays for both polar destinations and non-polar, when the Moon is “down”, altho these would be the same relays in different parts of their orbits, perhaps for no additional cost!
    Also, relays may perhaps be initially placed between Moon and Earth, so that lunar transmitters can start out smaller. Basic idea is that size of transmitter is square of distance, so putting relay halfway will lead to lunar transmitter being one-fourth the size, then relay being also that size, for one-fourth plus one-fourth being one-half initial total, with the relay being re-usable once lunar transmitter is full size, based upon power load rather than diffraction limit. A small but perhaps important difference.
    ALSO, I am more and more in favor of putting relay in orbit FIRST! This would allow demonstration of “hard” stuff, by transmitting energy from Earth, to relay, back to Earth, that is, twice thru atmoshpere. This would solve initial military requirement, which is so great that source of energy is not important-delivery is. Getting solution to initial driving problem perhaps years ahead of other plans is BIG advantage! Pretty easy to then convince people that you should collect the energy in Space.

  3. AK said

    Hi Coyote…

    I’m a little concerned about your statement:

    The short term plan, of course is to produce solar power satellites on the Earth and boost them into our orbit until the Moon is developed sufficiently to begin production and launch from there.

    I’m going to neglect laser based systems, since they will be too small and expensive to compete except in specialized arenas (e.g. military).

    I would like to propose, or rather pass along a proposal by Martin Vermeer, an alternative track to large-scale microwave SBSP. The idea is to put up a reflector or phased-array re-transmitting antenna in GEO and use it to retransmit earth-based power from where it’s generated to where it’s needed. I estimated 8,000-10,000 tons for a 5-Km sphere (at 100 grams/square meter), which would be 800-1000 launches for an Ariane 5 ECA. At 10Kw/square meter, it would have a total “re-beaming” capacity of perhaps 200 gigawatts.

    Martin’s thinking in terms of a passive mirror (like chicken wire), I’m pushing more for a “smart” phased array, but not much heavier.

    A system like this is doable (barely), and energy could be generated using (semi-)mature Concentrating Solar Power technology while the technology to create space-based power satellites is developed and matured. IMO the re-beamer would pay for itself in flexibility of transmission and removing the need for power lines (especially over ocean or hostile polities), while once it’s up every solar power satellite put in orbit could use it to send power to Earth without needing a similar sized antenna. (Assuming it’s in GEO close to the re-beamer.)

    I also need to mention Martin’s and my efforts (not very successful) to convince the people with climate concerns at RealClimate that SBSP is the only good long-term solution to the earth’s power needs. This is a very dismissive and somewhat hostile audience, some of whom have technical expertise with space, and none of whom seems to think SBSP will have an impact this century. See my first post on the subject here, and subsequent posts with objections and answers. We could use some help with this sort of audience, including some simple, easily found, explanations of the proposed technology, without the gee-whiz pictures and lack of hard numbers I’ve seen in the discussions I’ve found.

  4. Neil Cox said

    Hi AK: With the phased array sphere at GEO altitude only about 25% of the sphere’s surface area would be used to receive and send back energy to and from Earth. Why not a segment of a sphere, which would require about 1/4 the mass. The pitch and yaw would be critical, but I think such station keeping is practical with present technology. Neil

  5. AK said

    Hi Neil…

    I was thinking of making it possible to beam power in every direction. Still, I suppose that could wait. Ideally you’d want at least six of them, so power could be transferred from anywhere on the globe to anywhere else.

    In a spherical configuration, that would use 5/6 of a sphere, although you could probably get the same effect with an ellipse twice as long as it was high.

    The most important thing about this idea is that it allows leveraging existing power technology, while getting our feet wet in space. Details could be worked out once there was a decision to pursue the general approach.


  6. Chris said

    Dan and Coyote,

    The planned moon base provides an ideal opportunity to develop a small scale SSP. Either pole for the moon has extended night periods where moon based solar systems will not be collecting power during these extended night periods. Innovative projects for the moon bases will have a much better chance of being funded. Delivering a baseline load to the base is appealing. Further, many countries or groups of countries are planning moon bases. A single SSP could support the needs of all of them, and it provides an opportunity to build global support and global funding.

    Also, it seems like a viable business opportunity for to jump start the international company to run SSP. This is one of the recommendations within your report. I imagine that any of the moon base projects ESA, NASA, ect. would be willing to pay $1 to $2 for reliable baseline energy especially if the launch cost was paid for by the company.

    A SSP that services the moon probably could be placed in High Lunar orbit with relays to ensure continuous delivery for all parties. This should simplify the logistics. The project would require robotic assembly, space tugs for long-term boosting, the relays, the SSP, and multiple receiving locations. Sounds like a great testing ground for all of the components of the system.

  7. Dan Lantz said

    Chris #6:

    Initial location of lunar base is probably near or on top of crater rim very near South Pole of Moon. Place selected will be where high areas near base have sunlight on various sides of “peaks” at all times. Thus ~half of collectors will be lit at any time. Mirrors, towers, or rotating parts could improve on this, especially on certain ridges where Sun never sets. (Moon has no seasons, is smaller than Earth, so get such places!)
    Also MAY have water on low points nearby. Would be nice but that may have been over-emphasized in past, as most of the mass of water is Oxygen, same with H based rocket fuel, and O is pretty much waste product of many processes of metal extraction, etc. Will be able to crash (small!) comet into cold, plastic covered crater someday to get water on Moon if none now.
    Compare two costs:
    1) Cost of the cell/cable/electronics (stuff you actually need to collect and cable energy to the nearby base, when built near the base on the Moon).
    -Ideally using lunar resource for as many parts as possible, in which case those parts can be simple and heavy, thus cheap.
    -Include extra for lunar night, and landing on Moon of parts not made from lunar materials.
    2) Cost of Solar Power Satellite (in lunar orbit in this case).
    -Needs to be light, launchable (or some parts made in orbit from launched lunar materials).
    -Must have basic structure.
    -Any radiation shielding must be supplied (free on Moon).
    -Must have life-of-satellite station-keeping mechanism and fuel.
    -Must have transmitter, and receiver on Moon, not to mention relay(s).
    -”Junk” in lunar orbit worse than junk in Earth orbit-NO atmosphere!
    If 1 is less than 2, lunar base should go with 1.
    This may seem to contradict in spirit the initial reason to use SSP, that Earth based solar is not as good. But the (non polar mountain) Moon has ~half the light avail in Free Space (and, you could orbit mirrors), with no greatly variable clouds, etc. It has the SURFACE AREA needed for things that need large surface areas, such as collecting solar power or transmitting electricity, already there.
    After collecting the energy on the lunar surface, relay sats start to come into play. Things in Earth or lunar orbit have an annoying habit of not wanting to stay over the poles! Any relay sats used to serve high latitudes will spend much of their time over low latitudes, and are thus “free” for those low latitudes. Until the energy is sent thru the atmosphere, frequency can be picked for best results.
    Live in Free Space, collect sunlight on the Moon!

  8. Edawg said

    B.P Launch services is looking for angel investors for seed money to get this boat off the dock.

  9. Dan Lantz said

    Coyote, All:;_ylt=AkPP7pZQkH1bRpv5bTeGjN1vieAA
    Is AP story very interesting!

  10. John Routledge said

    The 500-Prize:
    Ten billion US dollars for the first company that builds a working vehicle capable of delivering cargo into LEO for $500/kg; and which is safe and reliable enough for FAA or equivalent certification. At that cost, SSP is very competitive against fossil fuels. And some air-freight too come to think of it. Plus there’s the minor savings from NASA’s $300B jaunt to Mars. All of the major american aerospace companies have said this can be done, as have many european ones.

    Simply give them the opportunity to prove it.

    Who might put the money up:
    Aside from the obvious choice of the US government… The UK as a whole spends $37B a year on fuel for its power stations. That means it pays the total cost for building an SSP replacement for its entire power grid every 11 years. (~$400B, including 500-Prize.) And UK power needs are pretty typical. Plug a $37B a year bleeding sore in your economy, reduce electricity CO2 to zero, and enjoy a few other minor fringe benefits. If the economics could be explained in these terms, *ANY* western government might be willing to put up the money. Just need to get past the middle men and nay-sayers first…

  11. Dan Lantz said

    John # 10:

    I like your perspective! People often think of SSP as a “Space” program, when in fact it is an “energy” program, and MUST work to “pay for itself” after initial seed effort. SSP is simply too big to run as space programs have been.
    One caution: do not set yourself up to rely upon cheap launch from Earth surface. O’Neill (Space Studies Institute) and Criswell (Lunar Solar Power) have well thought out plans that AVOID launch as much as possible, making 95-99% of the product from lunar material (In Space Resource Use). Not that cheap launch wouldn’t be terrific! It would speed up ISRU plans even more!

  12. Dan # 11

    Using lunar materials does make sense in the long run, but in the short run it’s very difficult to put a cost value on such material. For a small nation (like Britain) it also doesn’t make as much sense as it does for a large nation like America. Finally, the 500-Prize is about minimizing government risk:

    The competition can end up with no entries, no successful entries, or one or more successful entries. The money only gets paid out in the last eventuality, at which point the problem of cheap space flight is not a problem any more. With cheap space flight most of the risk of SSP also disappears, because we know it can be done with cheap space flight. It might not be the absolute level best way to do it, but we know it can be done that way.

    By contrast relying on lunar materials is a much higher risk, as it requires a government or company to invest sums of money closer to $100B before it can even start to build SSP. In the long run this woudl of course pay for itself, but such an initial outlay will be off putting to many government officials and electorates.

  13. Dan Lantz said

    John #12:

    I’m all in favor of cheap Space flight!
    Also, Criswell’s plan is to have international cooperation for R&D, then national and/or private ownership of collection fields constructed. He estimates $500B before income supported build out starts, at ~100 GWe.
    One thing to remember is that ISRU is not an “absolute” in that at first only simple products will be possible. Radiation shielding, Oxygen, glass/metals for basic structures, solar panel structure, cable… Cheap launch of the factories to make these would be ideal!
    There are three areas of concern that lead to thoughts of ISRU:
    (1) Zero g problems
    (2) Radiation exposure dangers
    (3) Scale up of SSP to globally meaningful size
    ISS/Mir experience has been that zero g is a bummer. Living on Moon probably as bad. Question is whether it is POSSIBLE to deal with zero g, and best way if it is.
    Radiation exposure danger seems to have created a state of denial.
    ISRU allows both of these problems to be bypassed! Supply artificial g and shielding without spending a lot of time doing studies that may indicate that you MUST supply artificial g and/or shielding!
    Scale of SSP needs to be ~20-200 TWe for global energy solution. Other than demonstration (which Criswell opposes as waste of time), there is no real point in starting with a plan that cannot scale up as needed. The “long run” only gets longer the longer you wait to start! I’ve been promoting ISRU for 30+ years. I have supported ISRU for (now known as) ISS structure, and Mars transfer ship, as well as SSP.
    When you launch form Earth, you have a linear return on investment, followed by an exponential decay of value as things wear out. ISRU starts a process of exponential growth from initial investment, as the factories can continue working to produce things that do not have to be launched, eventually cheaper than they can be produced on Earth!

  14. Neil Cox said

    Hi Dan: Are you thinking of building giant merry go rounds = centrifuges on the moon to provide perhaps 0.9g on the outer rim? Radius one kilometer perhaps turning at 1/4 RPM? I suppose this is possible in 1/6g, but surely requires, things stronger than melted regloth extruded into meter size I beams of a combined length of 1000 kilometers. Has anyone designed a machine that will excrude such an I beam at one kilometer per hour? How many gigawatts would be needed to heat the regloth to excrusion temperature at perhaps 500 tons per hour, in a vacuum at 100 degrees c ambient temperature? Can we build it on Earth to make a continous one meter I beam from low quality quartz sand = SiO2 = silicon dioxide? It appears to me the strength of materials problems are somewhat less in free fall = zero g. Also in free fall we have the option of two space stations tethered by 2 kilometers of very strong cable(spining about 1/4 RPM to produce about 0.9 g. Faster turning with a shorter radius will make 0.9g, but we don’t know if humans will tolerate the corriellus forces long term.
    Does a Mars transfer ship travel between low Earth orbit and low Mars orbit? Neil

  15. Dan Lantz said

    Neil #14:

    I’m more in line with O’Neill, don’t want to live on Moon, just put solar panels and “mines” there, using telebots run from Earth to do most of the work.
    O’Neill talks about diameter/RPM options for free space artificial g. Large habitat design hits “sweet spot” when structure requirement matches thickness needed for shielding. Smaller Bernal Sphere has (slow) counter-rotating outer shell for shield. Start small with cables, as you suggest.
    Mars tranfer ship(s) would stay in solar orbit, be shifted to go near Earth or Mars, but not stop and start, from plans I have seen. Similar to elongated Earth orbits that go by Moon every few times around Earth.

  16. B.P Launch services is looking for angel investors for seed money to get this boat off the dock.

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