Space-Based Solar Power

a public discussion sponsored by the Space Frontier Foundation

Space Solar Power: Much More Than Clean Energy

Posted by Coyote on July 16, 2007

In a recent posting to, author Steven Mufson pessimistically asserts in “Climate Change Debate Hinges on Economics:”


I tend to agree with Mufson.

We must not kid ourselves; nothing is a more farther-reaching climate proposal than space-based solar power. If pursued for that reason alone–especially as a big government program–I believe nothing would come of it. Not to despair. There are many more reasons to develop space-based solar power, and another way of going about it.

We must always keep in mind that space-based solar power systems confer additional independence from foreign energy sources and the entanglements they so often engender. Also, as traditional energy resources become scarcer and competition for them increase, energy provided by space-based solar power systems help reduce the incentives for energy wars.  In addition, eventually we will be able to broadcast power from space to places in dire need of energy such as sites of natural or manmade disasters, war zones, and areas of the world without much infrastructure

Space critics will point out that developing clean energy alternatives such as ground-based solar, wind, and nuclear power can be completed sooner using off-the-shelf technology, and probably deliver energy at a cheaper cost to the consumer.  I’m not going to argue with that.  I hope all nations seriously and aggressively pursue such alternatives!   But another really good reason for pursuing space-based solar power is because doing so advances the art of spacefaring.  The infrastructure required to make space-based solar power a reality–cheaper, reliable, reusable spacelift, on-orbit assembly, operating enormous space structures, etc–are capabilities in the critical technology paths to exploration and the full commercialization of space. Alternatives such as ground-based solar power, wind, and nuclear power are good and necessary, but leave us trapped on Earth.  There is a universe of untapped resources beyond.

We’ve all heard it…”Why go to space when all of our problems are right here on Earth?”  For starters, we want to go to space because the solutions to many of our problems can be found in space; energy, raw resources, and other places to live.  Tapping into the abundant solar energy that is ceaslessly blowing past Earth represents the easiest way to begin solving our problems here on Earth from space…and leaves in place educational, industrial, and commercial infrastructures that will make all future endeavors in space easier.

Our goal is to make space-based solar power affordable by the customer and profitable for the company who trades it.  The National Security Space Office is working with our friends in the Office of Space Commercialization in the Department of Commerce to develop space-based solar power in the commercial sector. We seek to incentivize the pathway for the commercial sector to develop space-based solar power–tapping into an industry of potentially trillions of dollars annually.

We want to leverage off of other space programs already in the pipeline to develop the infrastrucutre we require, and make prudent investments in niche technologies to help close the business case for space-based solar power.  The last thing we want is a large government program that will invariably become a political hot potato(e)! 

Your comments are most welcomed!

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17 Responses to “Space Solar Power: Much More Than Clean Energy”

  1. Moniz said

    You want to capture solar photons that would normally miss Earth and pump the energy down here? This is going to help global warming how?
    You might orbit mirrored balloons to equalize the energy budget. Then we get global dimming. Also, you could orbit them in fleets and use them for weather control.
    I want to be your lawyer!

  2. dradler said

    It turns out that solar energy makes it relatively unscathed through our atmosphere to the surface. How about we develop a terawatt-scale solar energy collection capability on the ground at several orders of magnitude less cost and less time than it would take to do it in space? Has anyone come up with an idea dumber than space-based solar power to solve our energy problems? (Ok, I bet they have, but this one is up there.)

    As a professional space explorer, I would say that the only benefit, if partially successful, of space-based solar power is to take advantage of the money available for Earth energy needs, in a remarkably wasteful way, in order to construct a vastly cheaper infrastructure for space access than we have today. But still nowhere cheap enough to compete with ground solar power. All I can figure is that this is some sort of ruse to advance other evangelical space objectives.

    Space-based solar power simply doesn’t make any sense as any part of a solution to our energy and environmental problems.

  3. whomd said

    OK, first of all I am a scientist and not at all prone to conspiracy theories, but this technology could easily be used as a weapon and not just for energy production. Think about it.

    Just as Dradler mentioned above, why not construct a vastly cheaper array here on the ground that could be producing energy in a matter of years not decades? How exactly do they plan to direct the energy to the ground? Among other physical/technical hurdles, this thing would have to be targetable, right? Just how much energy would be in this beam? Enough to fry a potato I would imagine. Why is the pentagon so interested?

    Again, I spend most of my time debunking conspiracy nuts, but if I’m the only one who can see how this “space-based directed energy device” can easily be used as a weapon (if built that is), then I guess I’ve become a conspiracy nut myself. I mean, after all, Iran’s nuclear program is only for energy production as well, right?


  4. Dradler – actually the economics aren’t nearly as clear-cut as you suggest, because of the significantly differing characteristics of ground and space solar.

    You assert “solar energy makes it relatively unscathed through our atmosphere” but in fact that’s not true at all in the sense you are implying. First of all, about 40% of incoming sunlight never reaches the surface of Earth at all. And 50% of the time solar energy doesn’t make it to the ground where you are because the body of the Earth is in the way (i.e. night)! In space you can point your solar panel at the Sun all day long without any (substantial) hardware required to move it around. On the surface, if you want to make full use of the incoming sunlight you need to orient it carefully and differently every minute of every day. Then there’s the weather, meaning only a very limited number of locations on Earth’s surface come close to the limit of maximum incoming sunlight.

    In practice that means that a space platform with a given quantity of solar PV material is guaranteed to capture at least 3.3 times as much solar energy as the same quantity on the ground, and in practice the ratio is usually between 5 and 10 times as much, for typical ground installations. Now there are losses in wireless transmission, but if quantity of solar panel is the limiting factor in costs, space power wins handily.

    If solar panel costs are able to drop dramatically, that would be wonderful (both for Earth and space) – but that so far hasn’t been happening: prices (in current dollars) are almost the same in 2007 as they were in 1987 at $3-5/peak watt.

    Obviously this has been discussed extensively in other forums – you can find one of my articles on the subject via Google for instance.

  5. Coyote said


    If I was designing a weapon I wouldn’t be doing it online in front of the international community and certainly wouldn’t be giving media interviews about it!

    That said, I totally understand your concern and I am working hard to disabuse people of that notion. Keep in mind that the goal is to hand off this effort to the commercial sector–probably a consortia or multi-national corporation–at the earliest possible time. The DoD’s interest in space-based solar power is purely to be a customer of the energy it provides.

    Why is the Pentagon so interested? First, a huge percentage of U.S. casualties in the Iraq and Afghanistan occur during petroleum convoys. Moving petroleum through cities is the riskiest mission the DoD performs. The white markered fields of Arlington are growing and we need to do what we can to prevent this sprawl.

    Second, after we extract the crude from the gulf region, we use our Navy to guard its convoy to the U.S. where it is refined. Then we use our Navy again to convoy it back to the Middle East where we load it into heavily armed convoys and drive it through the streets of cities to deliver it to the electric plant. After we pay the death benefits incidental to losses, one of our analysts estimates that our delivered cost is between $300-$800 per gallon!

    Third, the prime target for the terrorists is the power generation plants and the fuel storage areas. These come under regular attack…but this is true in most every war situation we’ve faced for nearly a century. We’d like a method to circumvent this vulnerability–space-based solar power gives the DoD more options

    Third, 70% of all logistics movements into the region are petroleum. If I didn’t need to move that much petroleum I could keep my logistics footprint and expenses much, much lower.

    Fourth, we assess that the greatest stimulus of major warfare between the great powers in the 21st century will be energy competition. Energy production will pique around 2015 to 2017. After that the demand will exceed production as not only the population continues to grow, but as China and India become fully industrialized.

    Fifth, whenever the DoD (or anyone else) is called to perform disaster relief or other humanitarian missions there is always a demand for energy that the local infrastructure can’t seem to provide. Space-based solar power systems will give us the opportunity to put power exactly where we need it, when we need it. Think of what happened in the aftermath of Katrina. Practically all energy production ceased in the New Orleans region in the wake of the storm. Among the more frustrating factors that rescue and recovery personnel had to deal with was the lack of power. Think about how much easier UN missions will be in some of the remote areas their peacekeeping forces engage in if they have power broadcast to them.

    The primary reason why General Armor directed this study be undertaken by the National Security Space Office is because space-based solar power falls between the organizational cracks. NASA doesn’t do energy. The Department of Energy doesn’t do space. The DoD is a customer with a huge need for safe, clean energy that can be delivered wherever operations are underway–preferably at a savings of lives and dollars over the petroleum method.

    I am working with Ed Morris, the Director of the Office of Space Commercialization, to find ways that we can transition this effort to the commercial sector as soon as possible–with the DoD being an obvious early customer. NASA is also interested in these same systems providing power in orbit around the Moon, and eventually Mars, but they are also working other related projects.

    We strongly encourage the development of all forms of clean energy. We do not want to put all of our eggs in any one basket. No doubt ground-based, wind, and even nuclear energy sources have benefits over space-based solar power. But they are susceptible to night/day, seasons, weather, natural disasters, and lawsuits. Space-based solar power avoids most of the terrestrial threats, and although the space environment presents hazards of its own, only space-based solar power allows me to simply redirect the very low density microwave broadcast anywhere in a hemisphere to provide power.

    Thanks for your comment.

  6. Daniel said

    I’m not a scientist or anyone important like that, but I had a thought. For the ground-based Solar arrays, where would you put them? It’s my understanding that a large percentage of the U.S. is already occupied land, either farming, forested, or populated. You would need huge arrays to provide the kind of power that is necessary to offset what we’re already getting through power plants. Once you put the arrays in, you cant farm the land underneath it, I doubt anyone will want to live perpetually in the shade. And the arrays would have to be protected from terrorists. You really can’t use that land for anything else I don’t believe. If we dont curb global warming, the oceans are going to rise and those people in coastal cities are going to need a place to go. We’re going to crowd ourselves enough as it is.

    With a Space-based system, all of the infrastructure will be in orbit, you could replace some of the smaller power plants with a receiver station and use in-place wiring to deliver power to communities. And if built with some forsight, the arrays in orbit can be built in quick-disconnect panels, so if one is struck by a piece of debris, pop it out swap in a new one. This would also give us the ability to simply add on panels if we need more power from one part of the constellation than we do from others. The possibility for growth is not limited by space up there (excuse the pun, couldn’t resist).

    One more thought from my imagination, If we ever do get the opportunity to consume some materials from asteroids, a manufacturing plant could theoretically be set up in orbit, which is honestly where I think we should be heading as a parallel to space-based power. Once we can create all materials we need right there in orbit, we wont have to rely on nasa’s taxi service as much, reducing costs, yeah?

    We’re going to have to spend money to save money and the world. And with most of the worlds wealth tied up in the top 1% or 2% of our population… I don’t see a problem with that.

  7. Hu Davis said

    Coyote has it right! We are paying an incredible price for gasoline and diesel fuel — not only in Iraq, but here at home, if the costs of protecting the suppliers and transportion of the goods and other “indirect costs” such as safe and clean waste disposal are considered.

    Mark Shenk of Bloomberg was reported in my paper today as predicting $100/bbl oil “only months away”. That means $5.00/gal. gasoline here and who-knows-what delivered to our troops.

    Perhaps, just perhaps, the DoD interest will finally break the myth that launch costs will always remain prohibitively high. Not so, if we will only apply what we have known for many years. But, it will take effort — and funding — to break this false barricade to power from space, for the benefit of all mankind. Funding? Large — about the same as any other major weaponry program, but with far greater permanent and broad-based benefits.

    Hey, folks, let’s just go do it while we still have the financial ability to do so.

  8. John Lee said


    A comment about your post. It will indeed require very large areas of solar arrays to supply the grid to any great extent. But I don’t think it’s going to play out the way most people imagine. The whole structure of power distribution will change over the next 20 years as printed thin film photovoltaics become available. We will go from centralized distribution to a decentralized system as the hundreds of millions of businesses and homeowners in the US realize that they can generate enough power on their own roofs to meet their needs and have excess to sell to the grid as well. SO, Land Based Solar Power is coming and it will be done without using any more large areas of new land.

    Even though, LBSP will come, it is a mute point here. What we should be discussing here is: Do we need SBSP and if so, can we do it. I think Coyote’s previous post quite nicely made the case for our need for a SBSP system. That just leaves just one point of discussion:Can we do it; If so, how do we go about it?

    We don’t have to choose between SBSP or LBSP, because neither is best in all situations. LBSP will have it’s day, I’m sure; but there will be times when we will need a SBSP system or wish we had one.


  9. A couple of things from a business perspective -

    1) SBSP needs to demonstrated on a *small* scale (because that is all we will likely get funding for, even with a consortium of public and private partners as I discussed on the panel at the conference in DC a week ago) before we start looking at the possibility of doing a REAL SBSP system by 2050 that can generate even 1% of the base energy demand in the US.

    2) A totally new launch architecture will have to be invested in and developed. Even assuming we could figure out how to do on-orbit assembly at GEO (using robotics, one would assume) and could get said mass to orbit using big dumb boosters (ELVs), and assuming the cost of such is NOT prohibitively expensive (which I would argue it is – especially in the current budgetary environment), how the heck would we fix such a thing if we couldn’t access it regularly? Building an autonomous power station at GEO with no way to easily service it is just not a viable option – not from an investor perspective.

    3) Discussions of weaponisation are red herrings. Virtually anything can be turned into a weapon – and Coyote’s right, if we wanted to develop this as a weapon, doing it a in an open forum is hardly subtle :-)

    4) while we *do* need to inestigate if SBSP energy beamed down affects the atmosphere in a “global warming” way, common sense says to me that burning a fossil fuel will create more problems than the relatively cleaner energy being beamed. Don’t spend too much time debating this point – we’ll know more once we have a demosat in orbit. Until then, this is largely academic, and we have smart people who can argue either side of this as effectively, to no end result….

    Just my $0.02 on an early monday morning here in Sydney…

  10. James Kielland said

    Hu Davis wrote:

    “Hey, folks, let’s just go do it while we still have the financial ability to do so.”

    An important point. While many will point to the future with the hope that things will be more affordable then due to technology improvements, it very well could end up being less affordable if we are facing an energy shortage related economic contraction.

    Energy = the capacity to do work. Building an elaborate space based solar system will clearly require a tremendous investment in energy. If we wait until energy is too expensive things couild become increasingly prohibitive.

  11. James Kielland said

    Daniel wrote:


    There are vast, vast untapped areas. To start with, every bit of roofing in the country. If that’s not enough, create more roofing. Many major highways going through cities could be covered with an inexpensive and lightweight roofing. You’d need to let some light through for visibility, but you could still harvest substantial amounts. Covering freeways could have other benefits as well: reducing accidents due to weather, noise reduction, and so forth. With a white interior to such roofs you could cut down on the amount of nighttime light needed to illuminate the road surface. Covering all the freeways running through a city like Los Angeles is certainly not cheap, nor the best near-term solution. But it’s an example of available space, could have secondary benefits, and would provide electricity extremely close to its consumption point.

    An additional possibility is the ocean. There’s plenty of ocean space available. Developing floating platforms to hold vast arrays couldn’t be that difficult at all: panels are not that heavy. Certainly nowhere near the challenge of putting arrays in orbit. Very small and efficient motors, using locally harvested energy, could move the platforms away from clouds/storms and to the best light. Transmission to land could be very long cables or bouncing off an orbital repeater and down to a terrestial station.

    In fact, that last suggestion, while certainly not particularly efficient, might be something we should be considering BEFORE trying to build the collectors in orbit. The critical thing that the Pentagon needs IS NOT SPACE BASED SOLAR, if we take the aims of the proposal seriously. The critical goal is to precisely deliver power to remote locations. Perhaps our first goal should be accomplishing relaying terrestially generated power up and then down to where we want. Having proven the ability to do that AND observing the atmospheric effects and other unforeseens, we could then worry about how to lift the collectors. Worrying about lifting the collectors before these other issues have been addressed seems to be putting the cart before the horse.

  12. mmdray said

    I understand that this blog is about space based solar power, which is clean and green but seems to lack the power to do much of anything. I am curious as to why there are no feasibility studies underway to placing liquid metal cooled fast reactors in space. The Russians have been using exceptionally small 150 MWe ones in their Alpha class subs for over 2 decasdes.

    It seems to come down to a risk vs. reward argument. On one hand they were prone to mechanical problems early on in their development. (Whether the issues have been fixed or how much they have progressed in technology I do not know.) But it seems to me that being able to put 150 – 200 MWe into space on a scalable level would provide tremendous electrical resources that no other country would be close to being able to provide.

    The amount of power available to conduct experiments would be far greater than anything else ever put into space. Aside from that, the availability for military applications would be of extreme strategic importance to the US military. Much greater power would be available to transmit to troops on the ground, whether it be in the form of x-rays or microwaves. In addition the old “Rods from God” concept could become closer to reality as alot of the physics problems with rail guns exerienced due to the atmosphere and cooling issues could be overcome with much greater ease.

    I am not a hawk in favor of militarizing space, however from a strategic perspective, the ability to fire a 5-6 ton tungsten rod anywhere from 35,000 to 50,000 feet per second at a target anywhere on earth at a moments notice would be an advantage that no one else could concievably have in place for 20-30 years.
    Military targets could be taken out in seconds as opposed to minutes or hours with conventional systems. The only thing that limits this is the amount of available power for these types of systems. I find it hard to believe that there could be a solar powered system that is comparable in power generation and cost effective.

  13. live2scan said

    I’m back with more uses for a Dark Sky Station. I was reluctant to include active military ones, but since Mmdray opened the bag. A DSS would make a fine missle or RFG/laser platform. A DSS would have a huge upper surface area that could be all thin film PV or mirror for a dynamic system. Since any of these systems would likely need non-continous power even if the considerable output possible with this system wasn’t sufficient for continous operation, a charged ultra-capacitor is probably much lighter than a reactor. Need to light an entire battlefield ? A DSS either with a onboard laser system or just with a passive mirror hung beneath reflecting a beam from elsewhere.
    In addition, even if a space elevator is ever built, it may not be desirable to build it with a single cable. Due to the problems that might arise with a cable passing through our active atmosphere (lightning, high winds,etc.) a multi part system might be needed with a DSS as an isolatable transfer point. Eventually a DSS might be even supported all or in part by the elevator cable from GEO.

  14. Gary Oleson said

    The terrestrial solar vs space solar either/or debate is even more pointless than the man vs robot in space either/or debate. Humanity’s growing economies will eat everything that both terrestrial and space solar can provide and squack for more. The energy problem is so big that you could throw in a dozen more new energy sources and still not solve it. The most meaningful question remains how to get the cost low enough to get started.

  15. Coyote said

    Mmdray and Live2scan,

    We’ve got no interest whatsoever in putting weapons in space or on floating platforms. There is no military imperative to do so, but there is an enormous political imperative NOT to do so…consistent with our National Space Policy which has remained consistent for 50 years.

    Our goal is to turn this entire venture over to the commercial sector at the earliest possible time. We’d be delighted if a multinational corporation became the space-based solar power supplier. The DoD would almost certainly sign up to be the first customer.

  16. live2scan said

    Glad to hear there is no push to futher militarize near earth space. I’m still pushing the DSS, though. If you wanted a fully functional SSPS testbed in operation very soon after financing was available a DSS might be a simple way to accomplish that. A dynamic sterling system (see )on the upper surface of a DSS would take minimal development time and scale up very easily since the reflector could be part of the bouancy system and be built to arbitrarily large size with minimal difficulty-inflated. To me it seems like the multi megawatt system that is being sold to the SoCal power producers might actually be cheaper to build and operate as a DSS. Sun tracking would be much easier (rotate entire DSS), no weather problems, no need to purchase massive tracts of land for collector siting(site over Pacific)low cost of upkeep(no sand storms up there)and you could move the enire system anywhere it was needed(salable) can’t move a site stuck on the ground in AZ to FL, but ‘cha can move a DSS.

  17. James Kielland said

    Coyote wrote:


    Also, under ABOUT THE STUDY ( ) this is listed under the assumptions:

    “2. Space-Based Solar Power must be moved to the commercial sector at the earliest possible time during the research and development phase–government merely wants to be an energy customer.”

    While generally being highly sympathetic to free-market ideology, I find these statements to be curious. Why the #2 assumption? Why is this even an assumption? I don’t find this to be in any way a self-evidently wise. By listing it as assumption you’re essentially saying that it’s beyond debate or discussion.

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