Space-Based Solar Power

a public discussion sponsored by the Space Frontier Foundation

A Skeptical Engineer Has His Say…

Posted by Coyote on June 24, 2007

Click here to view briefing:  A Skeptical Analysis

A very good friend of mine who is a respected engineer constantly reminds me of how formidable a task space-based solar power really is. He quite literally thinks it is a ludicrous idea. He provided me with his first order assessment of the proposition to provide 100% of current US base load energy from space given today’s industry and infrastructure. It is filled with statements like:

“At 100% efficiency and effective array thickness of 0.001 m (1 mm) mass on-orbit would be down by factor of ten – so it would only take ~ 1000 years to deploy at one EELV Heavy launch a day”

That doesn’t do it for me. Personally, I’d be delighted if space-based solar power could produce say, 10% of the US energy requirement by 2050, as part of a comprehensive clean energy program that includes, wind, ground-based solar power, nuclear, hydrogen, bio fuels, and other things we haven’t imagined yet. Moreover, I’d like to think that we will no longer be stuck with hugely expensive expendable rockets like EELV, and proper conservation initiatives will actually decrease our overall energy requirements by then.

Take a look at the briefing linked above. Give some thought, and share your comments.

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65 Responses to “A Skeptical Engineer Has His Say…”

  1. shubber said

    Coyote -

    you and your friend are both right.

    Given today’s architecture for launch, with the big expensive “good for one use” rockets, SBSP doesn’t make economic or practical sense.

    But if we assume for the moment that we can actually develop a CRATS-based architecture for space access, then SBSP becomes a basic engineering problem that requires a business case to finance, not a flight of fancy.

    I would argue that the response to your friend is “you’re right, given what we have today – the question is, what steps do we need to take to *make* it viable in XX years?”

    Granted, you’ve answered with a question, but the conversation is then moving in the correct direction.

  2. He’s right – one EELV heavy a year won’t do the job – but think thousands of reusable vehicle flights per year. SpaceX has this vision already, among other comp[anies – they just need customers – market – that would be SSP.
    By the way, Atlanta and Chicago each do a million jet flights per year for comparision – similar amount of fuel per flight.
    Beyond that Electromagnetic launch of the first stage from a mountain near the equator can do even better – below $100/kg to GSO.
    Thin Film photovoltaics are far thinner than 1 mm, Ovonics demonstrated this on Mir with reannealing amorphous silicon for 19 months.
    2000 Watts/Kg thin film photovoltaics are available now. Just need somebody with deep pockets and a AA credit rating to write some big checks, to create production lines for RLV’s, thin-film PV and assorted other shopping items. This is not something we don’t understand, we have been improving this stuff for 50 years. CIGS thin film looks like the next big thing for even higher Watts/Kg.
    The proper pathway is a Congressionally chartered public/private corporation, like Comsat was chartered in 1962. Comsat built communications satellites into a $100+ Billion industry, Sunsat would build power satellites into a Trillion dollar per year industry. The draft legislation is at
    Unless you know some folks with $40 Billion and true grit…

  3. Edward Wright said

    The proper pathway is a Congressionally chartered public/private corporation, like Comsat was chartered in 1962. Comsat built communications satellites into a $100+ Billion industry

    Comsat (and its international sister, Intelsat) actually retarded the growth of satellite communications. The big boom didn’t come until the 1980′s when a few companies started to find ways of making end-runs around the Intelsat monopoly.

    Comsat was last sold for $790 million — a far cry from $100+ billion.

    It’s also possible Comsat retarded the development of space transportation by 40 years. When Convair and Rocketdyne were studying the Reusable Atlas, they had two customers in mind. One was the Air Force, the other was AT&T (which was then working on Telstar). They lost the Air Force when Kennedy decided manned space would be done by NASA astronauts riding on guided missiles, then they lost AT&T when he decided to nationalize the satellite communications industry.

  4. Sam Dinkin said

    100 years ago we would have been quite surprised to find that internal combustion trucks would have hauled so much cargo today. That airplanes would haul the daily mail and that stamps would be less expensive after inflation.

    But we should be careful what we wish for. Getting the price of orbital transportation down to within a factor of 10 of a jet flight to New Zealand would open up space to common people and create a new frontier.

    The US has 1000 GW of capacity. We’ll probably need about 3 times that by 2050 so let’s say your goal is 300 GW by 2050. Let’s say you can get 150W/kg (about 4 times what we get on ultra expensive arrays now). To hit your goal, we would need to loft 2 billion kilograms of payload. We would also need to do that to be competitive with coal and carbon sequestration or whatever the current best terrestrial technology at (I predict) less than $2/watt in 2007 dollars. That means we need to get launch costs down to $300/kg even if manufacturing is free. Maybe half that.

    But at $300/kg, you might find that you have many other more pressing uses of the launch capacity. How about a $30,000 space fare to orbit with half the planet making more than that per year in salary? How about $150,000 to emigrate to the Moon? How about a movie studio to produce $1 billion movies with on location space scenes? Every use that is more valuable than $300/kg will need to be satisfied before supply will be sufficient to drive the price down to $300/kg.

    To loft 2 billion kg in 43 years, we would need 45 million kg launch capacity a year just for the solar power. We’d need a factor of 25 decrease in launch cost from the Falcon IX heavy and about 10 launches per day. There is a virtuous cycle that starts if we can make rockets into a mass produced item with a high utilization rate, we can get the price lower. If the price is lower, demand will become higher spurring more innovation, utilization, and economy of high quantity.

    The trouble is, we can’t just buy 4000 Falcon IX heavies at current prices and jump start the revolution because that would cost $7500/kg at $360 billion. Research a little, buy a little, I guess is what you need to do.

    Don’t expect Moon mass drivers to help. With your time line, it’s probably unwise to wait for Lunar mining to get up to speed. Maybe it will help after 2050 with the next 10% of US power consumption.

    I think it’s reasonable to set out to satiate the world’s appetite for energy via space solar power, but what I think you’ll end up with is hotels, condos, casinos, sports facilities, utilities, parks, restaurants and commercial facilities and all the kinds of things you find in the highest rent districts of the highest cost of living locales on Earth like Tokyo or Martha’s Vineyard.

    The space solar will come once the technology and demand is there to cut the launch costs. But only after the manufacturing capacity is there for the launchers and the solar panels. And launch capacity for everything else that’s worth more than that. At $300/kg, the cost to deliver skylab to orbit would be $7 million. I’d buy in to a time share to spend a couple of weeks a year in a space station time share for $250,000 + $30,000 per trip. That’s less than I spent on I’m not even in the top 1% of earners. There will be tens of millions of millionaire families by 2050. If only 1% want what I do, that would be another 8000 cargo flights (175 million kilograms) to set up the infrastructure and 29,000 7-person transportation flights (20 million kilograms) a year ahead of your solar panels. So if you want to solve solar at 10% capacity, plan on a launch industry that can support 15% or 20% of the capacity of the US electricity grid.

    Then there’s security. If a ballistic missile ticket becomes as cheap as a Concorde ticket, then spaceline security will need to be as tight as airline security. If we create high value, high profile assets in space, we need to defend them against bad actors. And not just the movie studios.

    You need to find and promote the high value uses of launch services to get onto the virtuous mass production/mass market curve. Otherwise, the gap is going to be very expensive to bridge in your time frame. I’m not saying it would be a bad investment to spend $360 billion to jump start the New Space Economy, just that it’s probably not politically feasible and it would be hard to prove it would be self-supporting after that.

  5. Sam Dinkin said

    [P]roper conservation initiatives will actually decrease our overall energy requirements by then

    No, a tax on carbon and waste heat will help us figure out how to balance the Earth’s heat budget cheaply. My guess is on the order of $20/ton of carbon. India and China will use about what we use per capita now with China north of $30,000/year per capita in today’s dollars by 2050. We’ll probably use twice that per capita. Energy Intensity or the number of dollars of GDP per unit of energy is going up, but not as fast as GDP. Plan on a rich country and a rich world demanding lots of air and space flights, lots of energy for their large houses, their big TVs, their big computers, their hybrid SUVs and all their other gadgets. And why not? If the planet is saved, let’s focus on getting ready so that everyone can command enough energy to emigrate to the Moon or Mars.

  6. Ed Wright states, “Comsat was last sold for $790 million — a far cry from $100+ billion.”
    The VALUE of the space communications industry today is what was claimed, which far exceeds 100+ Billion, as stated. Comsat did it’s job – blazing a trail to create the industry and then fading as they were overtaken by a growing multitude of other players – DirectTV, PANAMSAT, XM radio, QualComm, Boeing, building a wide variety of communications satellites, such as GPS satellites… Comsat also provided consulting expertise to numerous players such as the military for navigation satellites (NAVSATS) which evolved in our current GPS system. The communications industry in 1962 then was far different than today’s power industry. AT&T WAS then American communications industry. Congress was actually worried when AT&T offered to move into space so Congress used the charter to also start diversifying communications ownership, eventually breaking AT&T up. (AT&T was allowed to buy 29% of Comsat.)

  7. Christine said

    Sam, I think it’s more likely that we would be using much larger vehicles. Something like Boeing’s proposal from the 70′s, except scaled up almost an order of magnitude.

  8. Christine said

    Sam, I think it’s more likely that we would be using much larger vehicles. Something like Boeing’s VTVL TSTO proposal from the 70′s, except scaled up almost an order of magnitude.

    ps. screwed up tags, the blog needs a preview button.

  9. Christine said

    Darel, despite the $3B market cap I have strong doubts that the valuation of XM radio is a whole lot greater than Iridium. The company is still taking $700M per annum losses and has -$550M in net equity. I’m surprised that their creditors have let them go this long. Sirius radio is doing even worse.

  10. Edward Wright said

    “Comsat was last sold for $790 million — a far cry from $100+ billion.” The VALUE of the space communications industry today is what was claimed, which far exceeds 100+ Billion, as stated.

    The Satellite Industry Association’s last report stated industy revenues at $88 billion, but the way they define “satellite industry” is somewhat misleading. Building and launching satellites is only $10.8 billion. Operating them adds a little more revenue, but most of that $88 billion is really the value of services and content delivered by satellites, not the satellite systems themselves.

    Direct-to-home television content is more than $41 billion, for example. Without satellites, that programming would not go away. Programmers would simply find another way to distribute it. You can’t measure the value of the satellites by the total value of progamming they carry, any more than you can measure the value of a road by the amount of gold in armored cars that drive across it.

    To put these numbers into perspective, analysts expect Apple and AT&T to sell $200 million worth of iPhones on Friday. That’s one-quarter of Comsat’s selling price or 2% of what’s spent every year to build and launch satellites. Merril Lynch predicts Apple will sell $6.5 billion worth of iPhones in 2008. That’s about 2/3 of the satellite manufacturing/launch industry, and that’s just one model of phone. Nor does it include monthly service fees or the value of Internet content that might be transmitting across iPhones (the equivalent of direct tv programming carried across satellites).

  11. Edward Wright said

    I think it’s more likely that we would be using much larger vehicles. Something like Boeing’s VTVL TSTO proposal from the 70’s, except scaled up almost an order of magnitude

    Then you’ll have a hangar queen that’s about as economical as the Shuttle, except scaled up almost an order of magnitude.

  12. Raymond Neil Cox said

    I think we can be more optimistic. We don’t need a plan to produce a trillion gigawatt hours at $50 per megawatt hour, before we build somthing that will likely make one gigawatt hour at a cost of one billion dollars. Admittedly a billion dollars is a lot of money, unless we have reasonable hope that the cost may fall to a million dollars per gigawatt hour, before we finish spending the second billion dollars.
    We can put two hundred magnetrons in semipolar low Earth orbit, plus enough photovoltaic panels to power the magnetrons about ten hours per day. An antenna that will produce a spot on Earth which averages one watt per square meter = 1/10 miliwatt per square centimeter, may be the most expensive part of the orbiting equpment. If the spot is uniformly illuminated by the signal it has an area of 100,000 square meters if the magnetrons with the help of the transmitting antenna average 500 watts each, delivered to the spot on Earth’s surface. We have built almost a billion of these magnetrons for microwave ovens, so the technology is very mature. We likely want to build one rectenna almost that large, but we can demonstrate the technology with much smaller rectennas widely scattered over Earth. Each rectenna can have a microwave beacon. The orbiting antenna will home in on the strongest signal it receives, and point into space when no signal is received. Please comment, embellish and/or refute. Neil

  13. Raymond Neil Cox said

    Alternately we can charge capacitors from the solar panels and transmit to rectennas even in the dark as long as the charge lasts. These capacitors will shortly be mass produced to power electric automobiles. Neil

  14. Raymond Neil Cox said

    A perhaps less costly approach is free flying one kilometer hot air balloons with photovoltaic panels on the top 10% and a stearable mirror hanging perhaps 100 meters below. This will swing like a very slow pendulum, so the mirror will be illuminated by sunlight part of each swing even when the sun is directly over head. The beam from the mirror will shine through a hole in the clouds, illuminating a solar site on the surface of Earth, thus supplimenting the solar energy being received directly. The illuminated area will be much larger than most existing solar sites at present, but we can build larger solar sites. The balloon would circle the globe a few times and be recovered near the Arctic circle each fall of the year. This is likely impractical for the Southern Hemisphere, as it would be too costly to recover the balloons in Antarctica. The balloons would also provide valuable weather data and could serve as cell phone towers 40 kilometers tall, thus providing service occasionally to remote areas not presently served. Tightly focused microwaves may be beyond even a one kilometer balloon, but one watt per square meter should be achivable with current technology. Neil

  15. Lasers also need to be considered for the transmission of power down to Earth. The high-power (MW), solid-state pumped thin film lasers now beginning to come on-line have efficiency, would be much lighter than MW transmitters and can easily be used with small collecting areas on the ground (Vetrovec at Boeing). The current issue is lifetime of the diode but that is rapidly improving as well.

  16. Brian Wang said

    Starting off small and cheap. Trying to address the easier to invest and start

    $10 million for Dnepr rocket. 4500kg to LEO. $2222/kg.

    thin film solar cells on Kapton 1250+ W/kg

    Record power density 4300 W/kg AMO (1367 W/m²) Gossamer Thin Film CP1 Polyimide/Amorphous Silicon (CP1/a-Si:H)

    Or using the thin film reflectors onto the 40% efficient spectrolab cells.

    Magnetic inflating cables to deploy.

    4-15MW systems could be deployed.

    Use power for solar ion tugs or send power to other satellites.
    Supply power to the ISS. It only has a few hundred KW.
    Supply power to Bigelow’s hotels.

    Might be able keep the overall first system project to under $100 million.

    Tethers for boosting from LEO and/or Ion drive tugs.

  17. Brian Wang said

    the 4300w/kg thin film is quite expensive at $250/w.
    which would keep a 2.4MW system at $600 million.

    10,000w/kg seems possible in futrue.

    Getting the per watt cost down for the thin film system is key.

    Kapton/aluminum reflectors seem like the cheaper way to go .
    11 grams/ square meter.
    Reflect onto the spectrolab cells. (40% efficiency).

    how much do the new 105 meter tri-beam truss systems weigh ?
    what is their cost?

    Rough estimate of 900kg / MW for the magnetically inflated cable inflation system.


    20kg deployment boom for 400 square meters.
    4.4 kg for reflector material.
    8 kg for the spectrolab concentrator cells and
    218 KW from 400 square meters onto 40% efficient cells.
    If a lightweight station keeping method could be produced. then you could have 100 of those systems launched with each Dnepr rocket. 21 MW.

  18. Alex Gimarc said

    Coyote et all -

    The mass issue is why those of us who played with SPS 25-30 years ago soon migrated to the use of extraterrestrial materials to construct them. What has changed in the interum? We have found a population of Near Earth Asteroids (NEAs), Comets, and other bodies that have orbits that cross earth’s orbit. There are a number of these bodies that are as close or closer than the surface of the moon in terms of delta-v. Trip times are a bit long (compared with the moon), but required energy to get from here to there is not outrageous. John Lewis of LPL and Joe Carrol of Tether Applications have been looking at these for a while and believe it is doable.

    Should the business model start turning toward the use of extraterrestrial materials for construction / operation / movement of SPS, I expect the NEAs and similar bodies would do very well as resource options if for no other reason that they are rich in volatiles – which will also have to be lifted. The old business models had requirements for millions of tons of propellents. Why lift them if you can reach out and grab them?

    Additionally, should DoD start thinking about moving NEAs around for supply and logistics purposes (sources of volitales), it is not a large step to start actively moving inbound objects that pose an impact threat and standing up a planetary defense capability.

    There is more, but this is enough to start with. Cheers -

    – AG

  19. Coyote said


    It appears that the the success of space-based solar power hinges on putting the right infrastructure in place so eventually the business case makes itself. This will be true if we intend to build the systems from Earth materials or extraterrestrial materials. I think you are right that mass/scale issue makes it highly desirable to use extraterrestrial materials. However, doing so would require the development of significantly more and radically different technologies and infrastructure.

    Here’s what I suspect; We will develop space-based solar power from Earth materials, then eventually we will transition to use extraterrestrial materials.


  20. Alex Gimarc said

    Coyote -

    I think if you run the numbers on propellent required to move to a future with significant contribution by SPS-based energy to the surface, you will identify a rather large amount of volitales (propellent and oxygen which can be provided by decompostion of water ice) needed to move things around and support manned missions.

    The old studies concentrated on the actual use of lunar regolith for manufacturing and construction of SPS – which goes after one of the “long poles” for SPS construction and operation. The other “long pole” is propellent / volitales needed to support construction and operations – things which can pretty easily be obtained from properly selected NEAs. Run those numbers and see what you come up with. I think the break point for choosing extraterrestrial materials for your volitales will kick in long before you pass the 100 megawatt energy production level – even with a fleet of RLVs and current technology power stations. Once you get into the business of lifting your tools and producing your volitales off planet, it is a short step to permanent residence and actual military capabilities in CisLunar space. Cheers -

    – AG

  21. Coyote said


    You really raise an interesting question…There are two business cases that really need to be assessed. The first has to do with SBSP from terrestrial materials and the second is a transition to extraterrestrial materials.

    I’ve given this all of 10 to 15 minutes worth of thought, but it seems to me that the second business case must justify the additional infrastructure required to do SBSP from space resources.

    Is that the central line of reasoning, or am I missing something?



  22. Lee Valentine said

    So far as I know, no one has assembled enough good data to make the case for the breakpoint for superiority of the terrestrial option over the non terrestrial. There are many independent(and dependent) variables. In the absence of well costed alternative technologies and power satellite designs, there will be a (large) element of faith in anyone’s opinion.

    The case for any given system must be an economic one. The design of a power satellite optimized for construction from lunar materials is likely quite different from one optimized for construction from terrestrial materials. It would be very useful to have some well characterized technologies for the production of engineering materials from non terrestrial sources.

    Keep in mind that cheap launch may benefit the non terrestrial option more than it does the terrestrial one, since it would allow cheap transportation of heavy equipment to the Moon or asteroids, and full time human tended operations. That implies cheap development and set up of non terrestrial materials manufacturing facilities, too.

    There are many, many options for system and subsystem designs and one hopes they will not be prematurely optimized.

    There is a particular risk in an SSP program run by a government bureaucracy of premature optimization. The current generation of light water power reactors provides an example. That is not to say that premature optimization cannot occur in a commercial program, but the incentives are against it; whereas incentives almost demand premature optimization in a politically controlled program.
    (“What do you mean you need more study? Don’t you know what you’re doing? My administration promised the American people XYZ by 20xx, you’ve got to deliver it now.” Et c. Or similar words from across the aisle.)

  23. Lee Valentine said

    It is hard to know where to begin when the engineer in question has his units wrong and makes assumptions so conservative that they are silly.

  24. Alex Gimarc said

    Coyote & Lee -
    I am going in a bit of a different direction with this, and waving off (for the time being) the notion of actual construction of SPS from lunar or other extraterrestrial materials.
    As a thought experiment, say your new approach to SPS is economically viable regardless of who does it – that of directly launching light, highly flexible SPS from the earth into orbit via a fleet of RLVs and putting them together in orbit. Once you get those things into orbit, you still have to get them into GEO – and that will take bunch of fuel. What I propose is the use of NEAs as a supply for those propellents so you don’t also have to lift it.
    Water ice is incredibly valuable to anything you want to do in space, as you can drink it as water, break it down and use it as propellent, and breathe it. You get the water ice from the NEAs and use it for orbital transfer / operations and life support. The only specialized new technology necessary ought to be equipment that will mine and separate ices from dust and other regolith – which is not all that technically challenging.
    All I am saying is that it is worth looking at while you guys construct your various scenarios / business cases. Cheers -

  25. Coyote said


    I like thought experiments as they come at the right price.

    Concluding space-based solar power seems to hinge on developing sufficient infrastructure on the government’s dime, so the business case makes itself and some commercial enterprise steps in and closes the deal. They’ll need to leverage off other programs and projects underway now that leave in place sufficient infrastructure. The trick then, if to promote those efforts underway and on the books that advances the art of spacefaring that will grow the requisite infrastrucutre. It is a very indirect approach.

    We know we need to develop cheap, reliable, spacelift. I’ve got folks working on that. Solar array efficiencies need to improve. I’ve got my eye on people who are woring that. Our ability to fabricate large lightweight materials, such as ultra-thin arrays, and support structures needs dramatic improvement. Yes, I’ve got my eye on some folks who really want to manufacture SUVs that weigh less than 100 lbs. But we also need Space tugs…space refuelers…a mix of manned and robotic assembly and repair…initial deployment to LEO with transition to GEO, etc. That will require a lot of terrestrial infrastructure to before I field the space infrastructure!

    It seems that harvesting space resources and establishing production factories in space is exponentially harder than doing space-based solar power from terrestrial materials. While there may be savings on the back end by doing that, I can’t hide the development of space-based solar power infrastructure in other people’s work…and budget. In other words, I would have to establish large programs dedicated to developing space resource harvesting and factories in space before I can field space-based solar power systems.

    I suspect the natural flow will be from developing SBSP from terrestrial resources and then industry will independently migrate their production to space.

    Is that right?


  26. Sam Dinkin said

    Regarding Lunar materials and NEO materials, they have a lower Earth propellant cost, but have a lower capital utilization. If it takes months or years to get to a NEO object to set up shop and cart the material back locally, that’s a big handicap. With the Moon, there’s a huge startup hit at the beginning because tools to gather and transport materials from the Moon need to be hauled up from Earth.

    The minimum scale on the Moon or NEO for breakeven might be much bigger.

    Lunar solar should be developed to support Lunar exploration and development, but there needs to be a business case that includes the cost of capital that shows that Lunar is better. Even then, the Moon is days away instead of hours which may provide a big reduction in launcher utilization. Exotic techniques like mass drivers have not been successfully demonstrating at required commercial masses on Earth yet, much less in space.

    To grow launch service by a factor of 100 from 40 launches to 4000 (or fewer super heavies or more little guys) and raise the launch industry from single digit billions to three digit billions is a gargantuan task, but fundamentally a mass production and production and design optimization problem of existing hardware. If we only have 43 years to install the hardware, we don’t want to eat up 10 of them waiting for researchers to get to the Moon and another 10 researching and proving techniques of Lunar resource gathering.

    In short, one should focus on traffic control, launch capacity, launch economics, property rights, beaming technology and co-produced items. E.g., market development for human spaceflight, cheap add-ins to the solar satellites that may make other fleets of satellites redundant.

    Also one should invest in figuring out if we’ll need space solar. If methane hydrates, terrestrial solar, geothermal, nuclear, biomass, wind and water power can handle energy needs cheaper and we figure out cheap ways to sequester greenhouse gases and otherwise cheaply reign in our planet’s heat budget, then the money can go toward other items. Such as beaming Earth power to the Moon to bootstrap its industry.

  27. The Moon does not have to be that difficult to bootstrap up in production. Interestingly, the key to lunar industrialization today is not materials but energy. Klauss Heiss has a good idea in deploying large quantities of solar power systems on the Moon. As we begin to produce metals as well as oxygen (Ed McCullough’s magma electrosys is a good start or Steurer’s vapor phase pyrolsys) then the metals can be shaped into the heavy parts of vehicles. As the boostrapping process gets going the goods transported from the Earth shifts, from complete systems to subsystem components that can then be integrated into locally produced vehicle frames.

    We still know so little about the overall resource potential of the Moon, relying on incomplete Apollo data and a paucity of missions since. We need much more than a map in order to accurately design and cost ISRU systems.

    The same mass production techniques for launch vehicles is far easier for space systems themselves.

  28. Brian Wang said

    I was hoping to get some feedback on the near term plans that I had proposed.
    I had some feedback from some of those in the “space business” putting up a plan that could be invested in.

    I have put up what I think is the best next step for space and something that has the key elements of an investable plan.

    1. Dnepr rocket $10 million per launch (pretty the cheapest launch)
    2. the thin film solar or the solar concentrators. Again cheapest and most effective by weight solar for space
    3. Sell power to those willing to pay the most money. Other space satellites. High payers on earth.

    Low cost and a profitable market. Able to launch systems that are 10 to 100 times cheaper than current solar that goes with satellites or is installed on the ISS. 10 to 100 times the power levels into the megawatts. Scale this up and refine various aspects of the technology for another 10 times drop in costs and move towards the gigawatt level.

    Improve step by step and then worry about space mining etc…

    The multi-megawatts and then gigawatt can be used to power movement from LEO to GEO and on the moon but those are later steps. Once we prove out the first steps then we can justify scaling up but making the multi-megawatt level work should be the first priority.

  29. Christine said

    Then you’ll have a hangar queen that’s about as economical as the Shuttle, except scaled up almost an order of magnitude.

    Oh, so you mean that there will be no payloads then. I agree completely agree with you because space based solar power is stupid. Just build three times as many ground based panels and use pumped storage and nuclear to supply base load.

  30. Coyote said


    Thanks for joining the discussion. I probably need to be clearer about our intentions regarding space-based solar power to prevent confusion and misdirection in the study. We do NOT want space-based solar power to provide our total baseload of energy. We merely want to develop it as one more clean energy alternative among several. We surely do NOT want to put all of our eggs in one energy basket. Any number of natural or manmade disasters can cripple significant pieces of energy production and delivery. We think more sources of clean energy with the ability to pick up slack if one or more systems are adversely affected is prudent.

    If we could generate, say 10% of the U.S. national electrical baseload by 2050, I’d be happy with that. If the business case suggests more, then so be it. If it suggests less, then that’s what will likely happen. In addition, we do NOT want to make this a large government program. We really would like to identify all the infrastructure pieces that make SBSP more economically viable with confidence that if we develop that infrastructure incidental to other space efforts that commercial ventures will step up and field SBSP systems when the business case becomes obvious.

  31. Jim Fiske said


    For more than 40 years now, “Rocket Scientists” have been claiming cheap access to space is just around the corner. In fact, rocket launch costs are no lower now than they were 40 years ago. Nor is there any robust evidence they will improve to an adequate degree, ever.

    There are, however, several non-rocket launch technologies that could slash launch costs. They have largely been ignored by NASA. The Air Force is funding work on a couple of them. If successful, these systems could achieve launch costs in the vicinity of $100/kg, at a development and constuction cost of a few hundred million dollars. So far, this prospect has not seemed very interesting to many space advocates.

    I’m not yet convinced that space solar power makes economic sense, but I do think the launch-cost part of the equation will be solved — and soon.

    This implies that non-terrestrial resources are unlikely to play a significant role. When the time-value of money is considered, it will be extremely difficult for lunar or asteroid materials to compete with industrial-grade materials delivered to LEO at ~$100/kg over their purchase price.

  32. There are, however, several non-rocket launch technologies that could slash launch costs. They have largely been ignored by NASA. The Air Force is funding work on a couple of them. If successful, these systems could achieve launch costs in the vicinity of $100/kg, at a development and constuction cost of a few hundred million dollars. So far, this prospect has not seemed very interesting to many space advocates.

    Just curious, Jim – which technologies are you referring to..?

  33. Jim Fiske said

    RE: non-rocket launch technologies.

    Ram accelerators have potential, but I’m biased in favor of the Launch Ring, currently funded by the Air Force Office of Scientific Research. A paper on an early version was published in the AIAA Space 2006 conference proceedings. The Launch Ring is only useful for G-hardened payloads, but it may enable low-cost construction of EDOX (, which could provide passenger transport to LEO at close to airline ticket prices (if some design issues can be resolved). Detailed analysis, modeling and experiments to verify their feasibility will cost a few million dollars. If the results are as positive as appears likely right now, the total capital investment cost of these two systems will be roughly equivalent to the cost of a single shuttle flight. NASA doesn’t have the will to pursue projects like this (they recently killed all NIAC funding). The Air Force might.

  34. shubber said

    The Launch Ring is only useful for G-hardened payloads, but it may enable low-cost construction of EDOX (, which could provide passenger transport to LEO at close to airline ticket prices (if some design issues can be resolved).

    I’m sorry – i thought we were seriously looking at ways to do this SBSP assignment without resorting to unobtanium and star trek.

    Apparently not.

  35. Jim Fiske said


    This illustrates the difficulty of debating a highly technical subject in a public forum. Uneducated bystanders are always ready to spend 20 seconds studying a proposal before announcing to the world that “Unconventional transportation system X (steamship, locomotive, motor car, airplane, launch system, etc.) is clearly impossible”. This makes it difficult for serious participants to separate the wheat from the chaff.

    In this case, the facts are:
    1. A team of engineers with degrees from M.I.T., Caltech and Stanford (among others) spent several years developing a detailed launch system design, with funding from the Air Force. If successful, the system offers the potential to reduce the cost of launch to LEO by nearly a factor of 100 within ten years.
    2. An Air Force advanced concepts team rated this launch system design in the top 5 (and the only launch system selected) out of nearly 400 advanced space system concepts they evaluated. It is currently undergoing more detailed Air Force analysis.

    Now, if there are well-founded reasons for rejecting this launch approach, I would dearly like to hear them so I can stop wasting my time. But a lot of very smart people have been looking for such reasons for years, and have not found any.

    One thing is clear — without radical reductions in launch costs, Space Solar Power will never be more than an interesting concept. Such reductions will not come from business-as-usual rocket launch.

  36. Coyote said


    Thanks for your comment! I can assure you that the “skeptical engineer” who prepared the estimate you are responding to is top notch and routinely eats MIT, Caltech, and Stanford engineers for breakfast! Okay, I’m kidding, but my friend is totally top notch and he has studied space-based solar power on and off for years.

    His estimates are based on the state of the spacefaring art today–using comfortable confidence levels. This illustrates the enormity of the task at hand!

    The spacelift problem is the most fundamental. While the business case requires cheap lift to LEO and out to GEO, the technical feasibility seems to require a fleet of reliable, rapidly reusable lifters that can make several trips each week, if not a couple of times a day. There may be other approaches and I am anxious to hear about them.

    I’m curious about the launch system you are alluding to. If it is the system I am thinking of, our very own “skeptical engineer” is leading the Air Force analysis on it. Now THAT would be ironic!


  37. Des Emery said

    Hi, Coyote — It seems everybody nowadays is in an immutable rush to get somewhere and can’t wait another second to get there. Space based solar power must be prepared to hold its horses until a fairly cheap method of getting materials AND personnel up to orbit is developed. I say developed but perhaps it will take a new ‘invention’ instead. It would be awful if you worked so hard to get a system into development and then found out that someone else would do it more cheaply. At the same time, delivery of equipment is only one part of the whole project. Perhaps a slow but steady stream of items ascending the ribbon of a space elevator would be inexpensive enough to allow progress of the other parts of the equation.

  38. John Lee said


    I have been trying to read all the postings in the various areas of concern as they relate to SBSP. It seems that there are a couple of issues that continue to spark differences of opinion. If any productive recommendations are to come out of these discussions then we will need to reach some kind of agreement or accommodation on these issues.

    1. The first issue is: Do we really need SBSP at all; wouldn’t LBSP(Land Based Solar Power) be much more economical. The DOE just recently announced over 200 million in grant money to Universities, Research Institutes, and Companies involved in production of solar energy; with the stated aim of bringing the cost of LBSP down to a level on par with the Grid in 5 to 10 years. So, will we need SBSP to supply the Grid? Probably not; but only the future can answer that question for sure. Now, that is only one side of the coin; there are many other applications where only SBSP can supply power when and where needed. In emergency situations, natural disasters, brown outs, black outs, and of course Military uses, a SBSP system could provide uninterrupted power, where Land Based Sources can’t. The greatest potential for SBSP appears to be the transmission of power from point to point in space itself. Whether to a habitat, a satellite, to the Moon, to Mars, or to places we haven’t even considered yet, only SBSP makes sense in such cases. Can we then, all agree that the development of a SBSP system is desirable, even though we don’t know with 100% confidence all the areas in which it might be useful?

    2. The other area of disagreement is the Lift question. How are we going to get a massive SBSP array into the desired orbit. On the one hand there are those who believe that we have heavy lift rockets now that work; why not use them? A second group believes that we will need some type of unobtanium, star trek, ubertube, or other form of mass transit system to lift the mega tonnage required for a full scale SBSP system. We have all agreed that the access to space problem is the only potential “show stopper” for this project. If we don’t want to spend hundreds of millions proving that SBSP will work, only to discover that the project must be abandoned because we can’t afford to deploy it; then maybe a more balanced approach should be considered. During the research and development stage of the SBSP project; let’s also spend a few hundred million to research a few of the non classical methods of reaching space, in the hope that one will become our mass transit access to space. We can still do our Proof of Concept and Pilot SBSP mission using heavy lift rockets; but we all know that before we can build a large scale power system, we will need some other means of putting it there. Perhaps there is a way to share research cost with other space projects, since all would benefit from cheap access to space.

    Just a short summary of my thinking Coyote; what do you think?


  39. oldfart53 said

    The flaw in launch vehicles was to think big. Cost analysis shows us that the smaller the launch vehicle, the less it costs to develop. Ground personnel costs are also reduced by using smaller vehicles. To meet payload needs requires multiple flights, so operations become more efficient. Reusability and lower vehicle costs per flight become practical at high flight rates. Working against us is orbital dynamics which limits us to one flight a day from the US to a particular location in orbit. We can have a single launch site support multiple space stations or multiple launch sites support a single large space station or a combination of the two. The decisions that shaped our launch vehicles were made behind closed doors but we are still influenced by them even if we do not understand the basis of the decision.

  40. Coyote said


    I’m one of those guys who hates to put all of his eggs in one basket. I want several launch and recovery sites–coastal, interior, at sea, and in allied territories. This ensures that any reasonable combination of disasters won’t deny me access to space by knocking out my spaceports. This also allows me to launch/recover more assets in a single day during surge operations.

    I need a fleet of diverse, reliable, rapidly reusable spacelifters. When something goes wrong with one of the vehicles–as it invariably does–all vehicles of that design series will be grounded until the problem is resolved over the course of several months. By fielding a fleet of diverse vehicles I can keep part of my fleet flying.

    (Reading back on my reply it is apparent that I am becoming very posessive…”I want,” “I need”…”my fleet.” Hope you don’t mind.)


  41. Oldfart53 said

    In looking at the problem of a launch vehicle I’ve realized that the engine is the biggest cost factor so my approach to development calls on focusing on reducing the cost of the engine and then using multiple engines in the final design. I’ve also realized that the more expensive the project the less likely it is to be funded. The key to space development is a proof of concept demonstration. I believe that a 500 lb payload class vehicle can be built to be fully re-usable and operate on a daily basis at a cost of two to four times of its fuel cost. Once such a vehicle is in operation it is difficult to argue that a larger vehicles cannot be built in the same manner.

  42. Des Emery said

    Hey Coyote – I’m really happy to see you taking ‘possession ‘ of this topic and the program it is trying to describe. Only a personal interest will eventually see the opening of the way. I’m sure Columbus, while happily taking Queen Isabella’s crown jewels to finance the trip overseas, visualized the exploration as ‘his own.’ He didn’t throw all bets on just one ship, either. Until the right way comes along, no possibility should be prematurely discarded.

  43. Harvey said

    Has anyone done serious study of the effect of laser or highly focused microwave energy on the atmosphere, day after day, year after year?

    What is the effect of importing terawatts of energy, effectively making the earth a much larger solar absorber? Is global warming not happening fast enough for us?

    Technical questions aside, SHOULD mankind attempt such a thing? It would impact every human, every species for geologic timeframes.

    An effort better spent would be to make every building and vehicle on the planet zero-net-energy consumers. In fact it would probably be cheaper.

  44. Mike said

    With respect to building the solar array in space, I believe a significant (but often overlooked) component of the process should be developing a viable youth-culture around the push for a space-based solar array. This might include running a number of these forums (perhaps even a forum where engineers/physics majors, etc can show drafts of proposed parts, equipment, etc.), and developing a serious marketing strategy that will energize young minds and inspire their hearts toward the “final frontier” (tv ads, local “roundtable” discussions). Just as the push for the first man on the moon took a president (JFK) who declared a vision that inspired hearts and minds, I think this type of endeavour will take nothing short of a clear and carefully defined vision that is communicated to the current and forthcoming generations in a potent manner.

  45. robinsoncrusoe said

    Scanned the briefing provided by your skeptic and some of the comments. It’s a good discussion- the author points out some of the shortcomings of a direct launch system using representative current technology, the kind of reasoning that led to studies on utilization of extraterrestrial materials, improved launch systems and better conversion technologies, some of which the commentators have discussed. At this point, the economic and logistic concerns still seem (at first glance at least) to make a large scale space-based system less practical near-term than a somewhat less conversion-efficient (i.e., even larger) ground-based system. Bringing this idea under the realm of this discussion on space-based power, just to throw out a thought: how about using an array of space-based reflectors to enhance the efficiency of a ground-based system and provide partial functioning at night? Say aluminized mylar on a frame? As it would be an auxiliary system there would be no real minimum size & it could be added to at will. Could be added to augment ground-based system(s) at any time. Low tech except for the pointing and and orbital figuring (keeping these solar sails from perturbing their orbits too badly). Could be made up of multiple small arrays to keep from monopolizing sections of the GEO orbit that might be needed for some other satellites.

  46. Paul Larry said

    Novice here.
    Very interesting. I guess it is quite a chore to get material out of Earth’s atmosphere. Curious if the Space Elevator will pan out? I understand it is very close to production. If it does, wouldn’t that significantly reduce the costs in getting material up in orbit for far less than using rockets?

  47. Ian Woollard said

    I think most of the replies are thinking too high tech- by the time you’ve developed a huge new reusable vehicle you start off multiple billions in the hole. Negative cash flow is bad, even for governments.

    Instead notice that the Germans launched more than 10 liquid fuelled rockets per *day* in WWII (the V2 was about the same size as a Falcon I). And they were being shot at as well.

    So tricks like launching from a rocket erector truck are enablers for large launch rates.

    I calculate that if you take an existing vehicle and cost engineer and mass produce it, you can get the price per kg of payload down by about an order of magnitude, which is about what you need here; and this is even with expendables.

  48. Brian Wang said

    To Harvey (comment 43)

    One of many studies on microwaves through the atmosphere

    Search on google with
    “space based solar power” “environmental impact” microwaves atmosphere

    NASA and others have done a few thousand studies on space based solar power on the various issues involved.

    re: environmental impact. Even if there is some impact from space based solar and beaming of power, remember to calculate what is being offset. If you offset coal energy usage then that is big benefit to offset any negatives.

  49. Steve Mickler said

    I’d just like to point out that there are already a couple million pounds of dead comsats in Clarke orbit that contain considerable aluminum. This could be formed into concentrator mirrors once on-orbit telerobotic capability is finally obtained.
    In addition, the development of NEO regolith collection and return to Clarke orbit combined with the 4 frames a second telepresence via telerobotics for manufacture will shift the paradigm.
    I have to laugh a little at all you guys for your primitive Earth centric thinking. ISRU and telerobotic manufacturing in Clake orbit are key enabling technologies whose benefits go far beyond mere solar power sats.
    For sending power to Earth, oil production from NEO material using solar power in Clake orbit would have greater value although platinum for cheaper fuel cells is also available from NEO,s.

    Steve Mickler
    Solar Thermal/Electric Propulsion enthusiast.

  50. Coyote said

    Des Emery: Thanks, brother. I appreciate your comments.

    Harvey: Wonderful questions! That line of inquiry is certainly part of this study and has probably gotten short shrift to date. There are two forms of power beaming; microwave and laser. We have lots of experience with microwaves and consider them to be quit safe, but they require large antennas (kilometers across!) Lasers are of much smaller size and need a relatively small receive antenna…but are far more succeptable to atmospheric effects. Both methods will be kept in the trade space for the next couple of decades until we can figure out which is best.

    Mike: I totally agree. Our overall national space efforts need to be communicated broadly to the public…especially to kids…who seem predisposed to think that space and dinosaurs are cool! (Note to self…play “dinosaurs in space” with 8-yr-old son tonight)

    robinsoncrusoe: There is no doubt that space-based solar power is technically and economically impossible with today’s technology. Tomorrow’s technology will help close the business case. i suspect the technology from the day after tomorrow will close the business case for space-based soalr power quite nicely. Now we need to lay plans to make short cuts, so perhaps we can close the business case tomorrow.

    Brian Wang: Nicely said!

  51. Coyote said

    Steve Mickler: You’re right, this is Earth-centric thinking. If I can actually get the commercial sector to do space-based solar power, I believe we will open the heavens broadly for much wider commerical activity.

  52. Finley Shapiro said

    To consider using space satellites to provide power to the terrestrial electrical grid, you should do a side-by-side comparison to alternatives. I published such a comparison in Refocus, Volume 3, Issue 6, November-December 2002, Pages 54-57. The abstract is available for free at, but it seems that you have to pay for the whole article. I’ll post it if there’s enough interest.

    In the paper I considered some of the proposals that had recently been published for satellites beaming microwaves down to earth. I compared just the terrestrial parts of these systems (not considering the space technology) with a land-based PV system of the same size using technology already available, and I concluded that the land-based system was better.

    We also need to consider the time and money involved. We can spend large amounts of money for the next 20 years trying to develop space-based solar power, while global warming continues and possibly accelerates, or we can spend the same money putting PV and wind power on the grid, with gradual improvements in the technology as we go.

    Here are some solid numbers. For each $1 billion we spend developing space-based solar power, we could do a project putting 100 to 200 peak megawatts of PV on the grid, maximally available on sunny summer days when the power is needed the most. Generation can begin as each part of the project is completed, even if the whole project is not completed for several years. Depending on size and location, the $1 billion project would generate 100 to 500 gigawatt-hours of electricity yearly once completed. This is entirely based on available off-the-shelf technology. We know we can do it today, we know it will work, and we know it won’t cost much more than we say. It can start reducing greenhouse gas emissions as soon as part of it is up and running, even while the rest is under construction. It does not require launching systems that we do not know how to build, or ideas we do not yet have. Space-based solar power cannot make the same claim.

  53. John Lee said


    We keep coming back to the same two questions I tried to address in Post #38.

    1. Space Based or Land Based Solar Power

    2. The access to space problem

    To continue the either or debate does not seem to be very productive; the more balanced approach could put us all on the same path.

    What do you think?


  54. Coyote said


    It is not a question of either ground-based or space-based solar power…I need both. Each has its own niche.

    When it comes to solving the spacelift problem, space-based solar power is just one more reason the national and commercial labs need to get serious about this.

  55. Steve Mickler said

    As long as space operations are conducted without ISRU the economics of space solar power are unlikely to be favorable vs. land based solar power. Untill on-orbit telerobotics is developed space manufacturing and construction will also likely remain prohibitively expensive.
    With these technologies along with solar thermal power for refining, power and propulsion the economics of ANY space endevour completely change. Possibilities shunned now or unimagined now can flourish in such an environment. The future could easily see thousands of workers telecommuting to Clarke orbit to do a work day via telepresence. The tech has already been demonstrated by the Nextsat – Astro operations recently and telesurgery is advancing all the time. Obviously there are no major technical hurdles that must be overcome just old fashioned thinking.
    Steve Mickler
    Solar Thermal/Electric Propulsion enthusiast
    First STEP

  56. another mike said

    As a layman, i wonder what the cost and technicalities of putting a ‘web’ in L1 (between the earth and sun) are. This would have a 2 fold affect. It would cut down on the radiant energy collected by earth, and would be able to transmit energy collected from the center (or from different points on the web, i guess it doesn’t matter) back to home base, where it could be more easily turned into electricity. From my understanding, the transmission and conversion of microwaves to electrical energy is much easier than visible light. The mass of the web need not be too huge, the aim being to capture maybe 0.0001%. This is still, in my understanding, a significant amount of energy and, over the long term (2 – 300 years) will result in a significant impact on our climate.

  57. there are already a couple million pounds of dead comsats in Clarke orbit that contain considerable aluminum.

    Just a little nitpick (sorry, should focus on the bigger glaring issues being raised in this discussion, but i hate sloppy math)

    If the average dead comsat had a mass of, say, 4000 lbs, you are claiming that there are 500 such dead comsats sitting out there in GEO.

    That’s just wrong on so many levels. Go do a count of the global comsats launched to date to GEO and then take out all the C, Ku, and Ka band sats still in operation and I think you’ll find the number is MUCH MUCH lower.

    Now back to the regularly scheduled programming….

  58. Steve Mickler said

    Shubber Ali
    The figure does sound way to high doesn’t it. That’s exactly why I mentioned it. Conventional “wisdom” on this matter is just plain wrong. The number of active comsats at present is estimated by the AIAA to be between 519 and 529. It is very difficult to find out the number of dead ones. Ten years or so ago I ran across a listing in “Air & Space” mag that listed all payloads to GEO and I stopped counting at 700. The individual mass of these payloads is increasing as well and 4000lb. avg. is probably lowball. Suffice to say that there are unquestionably millions of pounds of material in Clarke orbit.
    The fact that not all of these has yet died is sort of irrelevant since any SPS would be built a few years from now anyway. I appreciate that you were just “nitpicking” but its really unfair of you not to nail down your facts first especially when “nitpicking”.
    That said I think it important to inventory what you have first before making detailed plans and we already have quite a lot up there.
    Steve Mickler
    Solar Thermal/Electric Propulsion enthusiast
    First STEP

  59. Steve Mickler,

    Apologies for the nitpick – i’d be interested in your source links from AIAA if you have them. I do question the numbers still for two reasons, first – there are many active comsats which are NOT in GEO (Iridium and Globalstar but two examples which by themselves count for well over 100) so do you know if that number you cited was in fact GEO or otherwise? Second, the mass of the earlier comsats was considerably less than the latest generation of satellites, which is why i picked an arbitrary average of 4000 (the Hughes 376 for example was anywhere from under 1200 kg to above 1700 kg).

    But i think we are in agreement on a number of issues, including that there are a LOT of existing assets at GEO which will need to be taken into account if we are planning to park a massive SBSP satellite there in 50 years (or longer)….

  60. Steve Mickler said

    Here’s my source: – 20k

    You make some good points and when I have time I’m gonna try to find out more.


  61. Steve Mickler said

    Just want to add a thought…
    One possible use for all this mass already in Clarke orbit would be as a counterweight for a diamond film tech based tether. Such a tether would only need a 3 to 1 taper to suppot its own weight according to a recent study. A counterweight would greatly reduce the required mass to be lofted to Clarke orbit and thereby reduce the number of required launches.
    Once the tether is in place additional tethers can be added untill the tether can then lift signifigant payloads. A solar power system could be attached to the tether and send its power down the tether itself perhaps using nanotubes or graphene as the conductor. A elevator “car” could use the associated electromagnetic feild of the current to haul itself up the tether at a high speed perhaps.
    Such a scenario will be aided by solar thermal/electric tranfer vehicles which can haul the first tether up from LEO saving costs and then be used thereafter to transport refined NEO regolith to teleoperated factories in Clarke orbit. I’d guess the cost of this project at under a billion dollars and maybe way under. It would lead to an exponential expansion of space based industry and world GDP as more tethers are added by other countries.
    Hey it would just change the world economy and politics radically and quickly for the better, but after all we want to keep using rockets to get up there don’t we? Tethers after all are a sci-fi kind of idea and rocketry is the conventional, cautious way to go isn’t it?
    Steve Mickler
    Solar Thermal/Electric Propulsion enthusiast
    First STEP

  62. John S. Wolter said

    This Skeptical Analysis thread is most useful. I want to ask for an separate and identified ongoing discussion of the business case on this web site. That section would need to include an evolving market and financial analysis models. It would be a kind of progress chart towards actually doing the deed.

    The models would be real numbers and analysis of just the business side of the SPS’s needs to fullfill. I can imagine that information being used to suggest how to redesign and re-target markets of SPS’s.

    An example is the cost of transportation of materials. Would it better to bring items from Earth or materials from the Moon or both? What impact will the cost of money and insurance have on SPS design? Would a better market for SPS power be base, mid-day, peak power, remote or emergency loads? What are the overall elements of cost analysis?

    If a common understanding can be developed of markets and the economics then that will drive the engineering effort to find the needed solutions.

  63. Neil Cox said

    Sure premature optimization adds to the cost, But it may occur anyway, if we talk for ten more years before we start building. We may not have ten more years. Let’s get going in several parallel areas. We can put two ladies in an asteroid with a sperm bank and embryo bank and lots of essential supplies. We could have done this 20 years ago, if we had seen this as a high priority. I’m still not sure what the ladies and their born in space children can do that is useful near term, other than learn how to live in solar orbit. If we start soon, we can have 100 humans who have lived in space their entire lives by 2050. Surely these hundred can help us build a megawatt or gigawatt SBSP in 2050, but most of them won’t be old enough in 2050, if we talk for ten more years. These asteroid dwellers can start the process of extracting useful materials from asteroids. My guess is it will take 30 years to learn enough to be competitive with materials lifted from Earth’s surface.
    Of course we should launch the demonstration SBSP, and several modest scale ups before 2017. We don’t have to wait until most of the details are optimised. When we set the date and start cutting the metal, we get a lot more people thinking efficiently about how it can be done better, but many of our best people will give little thought to SBSP, until it is clear that we will launch an SBSP soon. Neil

  64. Neil Cox said

    Hi John #62 There is a slight possibility that solar pumped diode lasers will be space ready for the demonstration SBSP, which needs to optimised to demonstrate; which likely means semipolar LEO = low Earth orbit. Perhaps we can work many separate designs in parallel. Solar pumped laser diodes. Low voltage dc pumped laser diodes. Millimeter wave microwave. Balloon supported in Earth’s upper atmosphere and LEO.
    The lasers are likely essential for narrow beam, small receiver applications that DOD needs for emergency electric power, so these designs should be prefered, if a 2012 launch date for the demonstration is realistic for the laser diodes or some other kind of laser, hopefully to slip to no later than 2017.
    Later, we can, perhaps, move to solar synchronous orbit or GEO orbit, which are presently impractical in my opinion. The space elevator would make GEO more accessable than LEO, but we should not count on space elevator until the first 20 ton model is operating satisfactorally, which could be never.
    Laser energy can be delivered to the larger solar sites already, operational and a few built dedicated to the laser wave length. The millimeter waves can possibly be received by existing radio telescopes, with some modification, but the rectennas for millimeter waves are largely untested, so there could be some unpleasent surprises when we build the first one, a square kilometer or larger.
    The solar synchronous orbit is ideal to supply the energy during the peak demand period, while GEO is best for baseline. LEO will supply energy predicably sporatic when a SBSP satelite is near overhead for perhaps 20 minutes, several or many times per day. Neil

  65. Neil Cox said

    Thank you Finley #52: As you guessed, I like numbers. Without subsidies, the peak watts are about right for 1 pm in June and early July. While we get much less in December, we have a shot at exceeding 500 gigawatt hours for the year = 500 million kilowatt hours = 50 million dollars per year at 10 cents per kilowatt hour = pay back 20 years. 20 years is too long to attract venture capital without both guarantees and subsidies. I agree, even bigger subsidies and guarantees are needed to get SBSP rolling, but SBSP is unproven and ground solar is approaching mature technology, which typically is much less costly than new technology. Someone needs to invest in new technology at considerable risk, or we won’t get new technology with as big a price tag as SBSP. For both ground PV = photovoltaic and SBSP someone needs to assure a market for the PV to get lots of new PV plants manufacturing the panels. With sufficient incentives, we can likely double the production of the newer and better types of PV needed for SBSP. We need to do this until 2050 to have panels ready to fly with the SBSP at each step of our SBSP goal. Ground PV can get the lots of leftovers even if SBSP is faster than our goals. This will drive down the price of PV improving the business picture for both.
    Ground PV tends to overlook trees and shrubs, which are rare in Southwes, USA, but a sizable cost most everywhere else. Are we goung to mount the PV panels on scafolding 20 meters tall? Even that will require cutting the top out of an occasional tree which will infuriate the global warming people. Let’s go with SBSP. Neil

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