Space-Based Solar Power

a public discussion sponsored by the Space Frontier Foundation

Crawl, Walk, Run: A Path To Space-Based Solar Power

Posted by Coyote on June 15, 2007

Our space-based solar power effort is like a newborn that has not yet learned to crawl–but this study puts us on the verge of crawling!

I’m speaking specifically about our ability to feed space-based solar power into electrical power grids on Earth or use it to drive the production of clean liquid fuels. With a desired end state of handing this entire enterprise over to the commercial sector it is clear that we have to create a supportive geopolitical environment and deliver capabilities that will ultimately enable companies to make a healthy profit by delivering energy to consumers at a competitive fair market price. I’m going out on a limb here, but I don’t think this can happen if we strap those companies with the entire research & development cost before they produce their first unit of energy. Please take a chainsaw to the limb if I am off base!

I’ll assert for argument’s sake that governments must accept the investment costs until the time comes that all the requisite technologies and industrial infrastructure is in place to make space-based solar power profitable. My opinion, based on working with governments and industry, is that a direct approach will not work. In other words, making a single large budget item called “space-based solar power” that tries to solve all the problems along the way will not work. An indirect approach is necessary that leverages off of other people’s budget and work in related areas. This keeps the budget much smaller, but keeps the program moving forward. Governments will only accept the cost if there is a long list of spin-off benefits, especially jobs. How am I doing so far?

I suggest a three-phase approach to space-based solar power. First we crawl. We stand up a small but active office to sustain the effort over the long haul. During this phase we continue to study the problem, but formalize and fund the research, leveraging heavily off of related work being done among other programs (an indirect approach). We conduct full-blown architecture and environmental impact studies, seek appropriate partnerships, build political support, but most important of all, we identify all the pieces of technology and other infrastructure elements that must be developed to make this a viable concept, and use our little office to track and propel their progress. We must also review space law, treaties, and customs to determine what changes must be made to normalize human commercial enterprises in space and on the heavenly bodies to facilitate the prudent use of space resources.

Next, we walk. In this phase we stimulate investment in the related technical and infrastructure items (such as lift, photovoltaics, rectenna technology, etc) and advance our spacefaring prowess in those areas. We conduct on-orbit experiments to validate our work and incrementally retire risks. All the while, the office we established in the crawl-phase is working with the think tanks, internationals, private industry, legislative liaisons, and the laboratories to keep everything greased and on track. In this phase we must work aggressively with the global community to establish a favorable legal regime for this and future human commercial activities in space.

Then we run. Well, we start with a jog actually. While jogging we conclude contracts and set up industry for production and operation of the system(s). We’ll need to square away the method of handing this over to the commercial sector. The running starts when we commence launch and on-orbit assembly through checkout, and hand over the keys to this bad boy to some dude or dudette in appropriate business attire.

Viola–space-based solar power becomes reality. Then it’s time for tea and medals.

Coyote

34 Responses to “Crawl, Walk, Run: A Path To Space-Based Solar Power”

  1. Adam said

    Why is it that I always see powersats quoted as being in the 5-10 GW range when conventional power plants are typically 1/10th that? Surely a 100 MW demonstrator powersat makes more sense than trying to sell people on 5 GW colossii?

  2. thebonobo said

    in an interview with RU Sirius, Scientology victim and L5 Society founder Keith Henson talks about the possibility of Solar Power Satellites and Space Elevators.

  3. spacepolicy said

    Coyote,

    You do know that one of the Foundation’s older mottos is “Crawl, Walk, Orbit” … right?

    I even have an old t-shirt with this phrase.

    I agree with your general approach.

    – Charles

  4. Coyote said

    Charles,

    Dude! That is too cool of a slogan.

    The approach seems obvious now, but I really needed to learn a great deal before I could frame it in simple terms. I am wide open to suggestions on how to set up the phases.

    Coyote

  5. Des Emery said

    Hi, Coyote — Alan Boyle of MSNBC has your site on his news blog, which is how I got here. I can only hope you are in no ways related to the infamous Wile E Coyote. He always advocated weird and wonderful ways to snare his victim, obtaining the necessary tools from the Acme Corp. He never succeeded. But I hope you do. I have my doubts, but I can see you have a well-thought-out ‘business plan’ for reaching your goal, and that bodes well for its ultimate success. If you are going to rely on private business interests to bring your work to fruition, I have only one comment left for you: Watch Your Back.

  6. Sam Dinkin said

    Coyote,

    You are on the right track. The trick is to figure out how to advance the ball as far as possible with the political capital you can bring to bear. Rectenna technology holds some promise for terrestrial spinoffs. Using existing tower infrastructure, power can be beamed to:

    1) Cut down on copper needs of the grid
    2) Provide competition to existing power providers to the benefit of the economy
    3) Cut down on the cost of backup generators by centralizing them
    4) Increase the loitering time for UAVs and opening up other new defense applications that could increase capabilities and save defense money
    5) Eventually increase the energy efficiency of the air transportation grid
    6) Provide a US technology that will be very competitive for rural electrification in developing countries

    High quality, low cost terrestrial solar can have Earth applications
    1) Reducing electronics costs
    2) Reducing subsidies for terrestrial solar
    3) Reducing solar’s environmental footprint in terms of land and waste heat

    The advantages of low cost launch are direct to the taxpayer and consumer and will enable more communication, navigation and observation equipment and more tourists (about 5000 to 1 of the former vs. the latter at current demand levels) to go into space.

    I would encourage you to let the private sector own the intellectual property that results from the research. The R&D costs won’t be significantly lower, but the prospect of their actually being D will be higher and the government gets more taxes if GDP is higher.

  7. Coyote said

    Des Emery,

    After carefully reviewing tapes of my cousins antics with the Road Runner and comparing them to past approaches to space-based solar power, I realize that both efforts failed because of the direct approach. Too many moving parts…too complicated…and way too expensive to be done in one fell swoop.

    Both require an incremental and indirect approach that will take more time, but yields far greater chances of success. The indirect method first solves all the problems around the edges before going to the goal.

    Regarding Acme, there is a lawsuit pending and the family is under counsel to make no statements but to refer you to Mr Ian Frazier, Coyote V. Acme (New York: Frarrar, Straus, and Giroux, 1996), 40-46. You may also obtain a copy at the following link: http://www.rvc.cc.il.us/faclink/pruckman/humor/acme.htm

    Oh, yes, my friend, someday Wile E. will catch the Road Runner. And when he does I hope he grills him over an electric range powered by space-based solar power!

    Coyote
    P.S. I’ll keep your comment in mind and will think about it often.

  8. Coyote said

    Sam,

    Thanks for starting the discussion of spin-offs technologies. These will be important as we consider where to invest in the technologies that must be developed. We also need to find our what the current state of the art is, and who is actually making rectannas today.

    I’m a bit leery about giving the intellectual property straight to the private sector. Our early aviation industry was crippled by the lock on various intellectual properties owned by either the Wright Brothers or Glenn Curtis. We were unable to field descent aircraft in WWI as a result, and watched Europe far surpass us. There will be some intellectual properties given to the private sector, but we need to do so wisely.

    Coyote

  9. Jaycubed said

    I think we would do far better to use space generated electricity in space, say in “L5” based factories, or microwaves beamed out to receivers into the asteroid belt, an even better location for space factories & refineries.

    The idea of intentionally adding even more solar energy into the Earth’s ecosystem seems foolish until we make some serious impact on global warming trends. The idea of intentionally adding billions of watts more electromagnetic radiation into the environment is also troublesome, especially considering we have been in an runaway, uncontrolled & poorly monitored experiment in EM’s effects on biology for a century.

  10. Coyote said

    Jaycubed,

    Environmental concerns are a major driver of this study.

    Environmental studies will be conducted in the “crawl phase” in concert with the full blown architecture studies.

    Coyote

  11. spacepolicy said

    Jaycubed,

    Some argue that global warming is one of the strongest arguments FOR investing in space solar power (SSP).

    Think of it this way — if we actually had *economical* space solar power in hand, and if we had hydrogen technology (for cars, trucks, planes) to transport energy — then we would be in a position to eliminate almost all uses of CO2-generating fossil fuels.

    It can be definitively demonstrated that the warming effect from increased C02 (and other greenhouse gasses) in the Earth’s atmosphere far outweighs the warming effect of beaming power to Earth from orbit.

    Of course, I don’t expect you to take my word for it. This statement can and should be scientifically demonstrated — to the satisfaction of scientists of all positions.

    The HARD part is making SSP economical.

    – Charles

  12. J said

    Hold the phone! The first priority is to price todays energy properly. (Would adding $100 to the price of a barrel of oil today be too high or to low when considering the value to future generations?)

    Once we get that number correct, the second priority is to put solar panel systems (and later next generation solar panel systems) on the homes and offices of America.

    With those two priorities out of the way, then lets see who wants to pay for space-based solar power. If someone wants to great! But, me sitting in my home grid-tied home breaking-even with the electric company means I have zero interest in the space-based variety.

    Now, if I am a shareholder in a company that is selling energy from a space-based solar energy company that is a whole different story. But, my taxes should never ever go to such an endeavor until I am breaking even with the electric company.

  13. Des Emery said

    Well, Coyote, I commend your family loyalty in anticipating a drumstick barbecued to a turn by
    wile E., himself. I, a born Westerner, have always felt partial to the members of the Coyote family, and I applaud your own efforts to bring down Power from the Heavens. I hope that your project can share in the proceeds of the lawsuit by Wile E. against Acme. Your product does not seem to share Acme’s propensity to casually ‘invent’ anything and everything explosive. Does it?

    I return to the problem of financing the endeavour. Private capital is the best way to obtain funding, without a doubt. But private capital is, in its present condition, only interested in ‘return on the dollar,’ ‘the bottom line,’ ‘the interests of the shareholders,’ and not in the intrinsic value of ‘cheap’ power or your ultimate aim, ‘space exploration.’ Consider Big Oil, the current Cock of the Walk, and its nominee for successor, Big Agriculture. Neither would hesitate for a moment in cutting the ground from under your feet, so to speak, in their general opposition to Solar Power, especially from Space, especially broadcast power freely available. As long as terrestrial-based solar panels are low productivity except in ultra-massive installations Big Oil is not worried, and Big Ag is busily acquiring ‘land’ for ethanol additive from corn, and quickly jacking up the prices of both real estate and food as a result. You are starting with a viable business plan, but again I have to say — Watch Your Back.

  14. Sam Dinkin said

    Coyote,

    If the government owns the IP, will it license it broadly? If so, there may not be sufficient incentive to develop the technologies. Unsuccessful development would be borne by the developer, while successful development would be shared with other licensees. You would see lack of investment which would perpetuate your mission, but not further it. If not, then the government would be participating in the “lock”. Is DoD really better placed to pick winners and losers than the private sector?

    On our way to space solar, very little IP in the crawl phase may end up on commercial plants. The commercial plants might not appear until the patents have run. IP published will end up being invented around. The trick is to get the private sector both excited about space solar and give them the maximum incentive you can to participate in the research given your political capital. What does the trade off for keeping the ip look like? If you can keep it on the books as an asset at the price of the research, maybe you can make the deficit look smaller. But how many patents do you need for that? One per project? The rest may be able to go to the private sector. Perhaps with a provision that they must give a free license to y’all or license one or two other unaffiliated parties selected by an open auction.

    Ironically, one thing that might improve the prospects of space solar is auctioning a 20-year concession forbidding down broadcasting of power except by one party. The odds of getting a diplomatic effort together to have that be broader than US would be unlikely. But telling all US entities that they may not down broadcast might be easier. That would give one entity a kind of super patent with a strong incentive to develop space solar during their concession. The auction money could go for more research into launch costs and other indirect multipliers.

    Another policy idea would be to directly subsidize power delivered from space. If you committed to buy space solar at twice the going rate for terrestrial solar electricity up to a certain quantity, you might get more. That’s not for the crawl phase, but if you post the prize/contract early, the crawl phase might be really short.

    Think about how Thomas Jefferson settled the West. He had a land office where settlers could buy land. They encouraged settlement by companies and by citizens. They provided surveying, forts, governance and the occasional canal, railroad or road. But the companies and the people improved the properties and settled the frontier. If you don’t give out the deeds and concessions, you might not get as much development unless you micromanage it through direct subsidies.

    The West visited Alaska in 1741 and after the US bought it 136 years later, is now heavily developed for $27B/year GDP.

    Antarctica was visited 80 years later in 1821.

    80 years ago Alaska had about 60,000 residents. Today, Antarctica has about 4000 summer residents and 1000 winter ones none of whom are permanent.

    In 120 years, which do you want for space? The difference? US Law, property rights, cheap transportation, energy infrastructure, telecom infrastructure, law enforcement, ports, roads, hotels, etc. But in 1867, all we had was Seward’s dream. Anatartica is a park, a commons, with no sovereignty allowed. A 1960 treaty keeps it that way. Sound familiar? Part of the crawl phase should include space property rights with an emphasis on geographic solar concessions.

  15. shubber said

    The West visited Alaska in 1741 and after the US bought it 136 years later, is now heavily developed for $27B/year GDP.

    Antarctica was visited 80 years later in 1821.

    80 years ago Alaska had about 60,000 residents. Today, Antarctica has about 4000 summer residents and 1000 winter ones none of whom are permanent.

    In 120 years, which do you want for space? The difference? US Law, property rights, cheap transportation, energy infrastructure, telecom infrastructure, law enforcement, ports, roads, hotels, etc. But in 1867, all we had was Seward’s dream. Anatartica is a park, a commons, with no sovereignty allowed. A 1960 treaty keeps it that way. Sound familiar? Part of the crawl phase should include space property rights with an emphasis on geographic solar concessions.

    Oh, God, not again.

    Enough with the bad analogies already!

    1) Alaska is PHYSICALLY CONNECTED to the rest of North America. This means that all sorts of things can walk, fly, or crawl to it. Antarctica is, um, a big island surrounded by a freezing ocean.

    2) Because of (1) above, there were already people living there when we “found” Alaska. We, of course, eventually wiped most of them out (nasty habit that we had back in the “frontier” days). Remind me again who was already living in Antarctica when we arrived?

    3) Yes, it is a commons, but that is not the only reason that it wasn’t developed. The world’s oceans are a commons – and they are regularly “mined” for resources by fishing fleets, oil explorers, you name it. Antarctica was made off limits and turned into a park – that’s a far cry from a commons.

    4) The reason “space” wasn’t developed after the moon race of the 60s is because it is too damned expensive, not because you can’t own anything up there. The only major commercial “development” of space since then has been in the Comsat (and, more recently, imaging) sector, because the cost of launch was recovered through the course of their regular business operations (telephony, IP traffic, etc).

  16. Coyote said

    Sam and Shubber,

    In a round-about way you guys reminded me of how absolutely essential making a supportive legal regime will be. We will need to study this closely and act early to create the requisite set of laws, treaties, or customary practices. I suspect this may drive the internationalization of this project sooner rather than later.

    Thanks!

    Coyote

  17. Des Emery said

    Hey, Coyote — Among ‘first things first’ you might consider getting a licence yourself and making sure it is recognized by other governments. Remember, the original ‘space race’ was a real race, and the Russians won in a wide open but secretive endeavour. The USA won in getting a man on the moon. Government gloating was very evident in both cases. But the Space Station now is (very luckily) an international effort, benefitting all humanity. Do not allow yourself only the narrow path of old-fashioned jingoism, but keep all the entrances to space wide open for any and all who can and desire to participate. The wild coyote wanders where he will, not recognizing national signposts as deterrents to his voyages.

  18. shubber said

    I suspect this may drive the internationalization of this project sooner rather than later.

    Coyote – be careful. Internationalisation, or “cooperation”, is often the kiss of death in both the public and private sector.

    Competition is the single biggest driver of innovation. It’s true in nature: look at how hyper-evolved species become when they have to compete for resources.*

    Same goes for business – innovation and product development thrives in a competitive environment. Just recall Soviet era department stores (does anyone even remember G.U.M. anymore?) vs the standard US department store. Same goes for investment banking product development in the US vs. Europe (I did a paper on this at business school, on the effects of Glass Steagall Act and investment banking innovation vs. the staid Euro-model where stocks were more like bonds… by I digress). Pick your industry, it doesn’t really matter.

    Competition drives Innovation.

    Memorize that statement.

    Do not fall for the politically expedient trap that the space sector got sucked into with ISS.

    Just my $0.02

    * note – for those who frequent this discussion board that believe the Earth is only 6,000 years old and that evolution is a myth, please ignore this paragraph – the rest is still valid.

  19. Des Emery said

    Shubber extolls the benefits of competition over co-operation, and rightly so, in certain cases — IF, and that’s a very important qualification, if the competitors start from a comparatively equal footing. You don’t send the high-school football team into the fray against any of the NFL teams and expect them to win. 9/11 proved that the competition between the FBI and the CIA focussed more on the competition than on results, and that co-operation between the agencies could have prevented the disaster. There is a time and a place for everything under the sun; don’t waste the opportunity to succeed in fruitless struggle for supremacy. The wild coyote seeks his opportunity carefully, and does not antagonize the wolf. Consequently, there are more coyotes than wolves.

  20. Sam Dinkin said

    Shubber,

    If you couldn’t own your GEO slot and your spectrum band, there would be a big mess in orbit.

    Good point about Antarctica not being connected. Transportation cost is another reason it hasn’t been developed and LEO hasn’t been developed.

    If space is a big park like Antarctica, inaccessible like Antarctica, then it will be less developed than places that aren’t big parks that are accessible.

    I like your oceans analogy. Fisheries would be far more productive at less cost if they were owned fee simple.

    Commons get developed. But I’m sure you’ve heard of the tragedy of the commons. They get developed badly and slowly.

  21. Sam Dinkin said

    I suspect this may drive the internationalization of this project sooner rather than later.

    If by internationalization you mean getting someone to talk to the handful of space law people that care about space property rights, then yes. That’s about as much intergovernmental international cooperation as our H-1B visa program gets; i.e., none because we can do almost everything unilaterally. There’s no need to get international technology coordination, buy in or anything else. There just needs to be a tiny investment in making sure that the space law is ready when the banks and venture capitalists are ready. Since we are years from the latter and space law is doing pretty well for satellites, there is a huge amount of room to go it alone.

  22. shubber said

    But I’m sure you’ve heard of the tragedy of the commons. They get developed badly and slowly.

    Heard about it and taught it in my strategy class at Georgetown, actually. Unfortunately, you actually missed the point of the “tragedy of the commons”. The tragedy of the commons, simply put, refers to the OVER exploitation of a piece of property or resource when it does not have a specific owner – and NOT it’s underdevelopment or slow development.

    The actual example: A commons in traditional terms was a field in the English countryside that was of “common” use by all the local farmers. The economic description of what would happen is as follows: imagine there are 10 farmers who graze their small flocks on the commons – each of the farmers has 10 sheep and each sheep can sell on the open market for $100, when fully fed/nourished. The commons supports 100 sheep at it’s normal productive capacity.

    Each farmer has $1000 worth of sheep.

    Now the tragedy kicks in – each farmer also has the individual incentive to add an additional sheep to the flock, because they can extract another $100 of value from the commons. But the problem is that the commons does not sustain 101 sheep as well as 100, so they are all *slightly* less healthy than at 100. So let’s say each one sells for $99 instead.

    Well, farmer A (with 11 sheep) is making $1089 instead of $1000, so he’s better off. However, farmers B, C, etc. are all now getting $990 instead of $1000. Each one has the same perverse incentive to add additional sheep, and each sheep provides a further marginal degradation to the overall commons, and thus the sales price of each sheep. In the long run, you could end up with more sheep than the sustainable level but lower return to all the individual farmers than if they had just done the “right” thing.

    THAT is the tragedy of the commons.

    Your comment on fisheries is actually more in tune than you realise I think: fisheries in many cases are considered commons and are in fact proven to be drastically overfished by fishermen who look at the individual return of a “bumper” harvest and don’t take into account the long term survivability of the commons. Private ownership does not necessarily improve the lot if an individual owner is only interested in the short term extractive value of an area. Government support programs for fishing industries only exacerbates the situation by keeping marginal players in the game rather than letting economics force them into other industries/jobs.

  23. Phil Chapman said

    SBSP in GEO

    For background: I was a scientist-astronaut during Apollo, but left NASA and worked for Peter Glaser in the 70s/80s, becoming deeply involved in the original DOE study of the SPS. I have maintained a strong interest in the subject ever since.

    If the SPS is to be a competitive source of baseload power, we cannot afford to spend more than about $1500 for launch to LEO of the equipment needed to deliver 1 kW from the rectenna to the grid. (Amortized over 30 years @ 5% interest, that will contribute about 1.4 cents/kWh to the cost of delivered energy). For example, we can afford a launch cost to LEO of $375/kg, if we can build a gossamer SPS with a mass of 4 kg/kW. These are challenging but not impossible numbers.

    My currently preferred design uses thermionic conversion with cathodes made from thin films of doped artificial diamond. There are many advantages:

    (1) The conversion efficiency is high ( >60% with a room temperature sink, but probably c. 40% with space radiators as sinks).
    (2) The manufacturing cost is low (less than $100/kW).
    (3) The radiation resistance is high, giving a long life in GEO.
    (4) The high radiation resistance also means that the SPS can be assembled in LEO and use its own power output to drive itself through the radiation belts to GEO.
    (5) Maintaining the required cathode temperature requires a concentration ratio of c. 100. This means that 99% of the collector area can be light-weight reflectors.

    The high concentration requires tracking the Sun in declination as well as right ascension. The best way to do this is to use a conical array. It is easy to show that a uniform conical shell is isoinertial if the vertex semi-angle is 25.2 deg. There are no first-order gravity gradient torques on such a structure, so it doesn’t need much control authority to keep the vertex pointed at the Sun. The only movement wrt inertial space is an annual rotation about the normal to the ecliptic.

    I gave a preliminary paper about this at the 55th IAC in Vancouver in 2004, and would be happy to send a .pdf to anybody interested in more details. This system needs much more serious study.

  24. Hu said

    “Crawl, Walk, Orbit” — Love it!

    The vital demonstrations need to be funded by whichever group directly benefits from their results, perhaps just enhancing future business opportunities. A lot of these will belong to DoD!

    Phil’s SBPS suggestions deserve careful assessment by Mankin;s group

  25. The high concentration requires tracking the Sun in declination as well as right ascension. The best way to do this is to use a conical array. It is easy to show that a uniform conical shell is isoinertial if the vertex semi-angle is 25.2 deg. There are no first-order gravity gradient torques on such a structure, so it doesn’t need much control authority to keep the vertex pointed at the Sun. The only movement wrt inertial space is an annual rotation about the normal to the ecliptic.

    Even if there is no net forces from the control of the structure there is still the 43 meters/second delta v to consider in North South/East West station keeping. There is still the solar pressure as well on such a structure. Do you have a rendering of this design, it does sound interesting.

  26. GuessWho said

    A couple of observations based on past experience with solar power systems. I have my doubts about thermionics. Chapman quates some performance numbers for the thermionics that are significantly higher than I have ever seen or measured. These may be theoretical numbers based on a given set of emitter and collector temperatures (he doesn’t provide details, but even low temperature thermionics need an emitter temp in the range of 1400K) but having tested a high temperature diode (Te ~ 2000K, Tc ~1000K) the best I was able to demonstrate was 10% for a single diode. Life is defiitely an issue but we can probably crawl our way into that one. An alternative option would be TPV if you were looking for a high temperature static approach. Otherwise, I would look seriously at solar dynamic (brayton or stirling). Brayton will scale better at the high powers. Given where high efficiency solar cells are today, any dynamic system will face an uphill challenge to show competitiveness unless there are other mitigating issues (e.g., radiation tolerance). I also have to question the use of thin-film solar concentrators. Yes, large inflatible mirrors have been developed for other military applications, but the demands of a solar concentrator with high concentration ratios are far beyond what inflatible can deliver given SOA. And high concentration rations are absolutely required to keep mass/areas down to a manageable size.

    As for others, just my $0.02.

  27. Everett Williams said

    Inflatables can be rigidized at zero pressure by the use of appropriate aerogels, reducing final mass of concentrators for whatever purpose.

  28. Neil Cox said

    #6 Sam Dinkin Says:
    Rectenna technology holds some promise for terrestrial spinoffs. Using existing tower infrastructure, power can be beamed to:

    1) Cut down on copper needs of the grid
    me: For an early demonstration: I suggest three tall mountains about 200 km apart in a triangle. Assuming Dan Lantz is correct, and one phased array antenna can be designed to transmit, redirect and serve as an rectenna simultaneously; wind and terrestrial solar can be produced and shared at each of the three sites. The sites will be space ready when a beam from space becomes available. Is there a practical way to use the power beaming over flat terrain (over more than a few kilometers) other than sending the energy up and back with an orbiting or balloon supported redirect?
    2) Provide competition to existing power providers to the benefit of the economy.
    me: Cheap dependable baseline power from GEO will put some of the local competition out of business. From Sun snychronous or LEO = low Earth orbit, should however allow all, but the most inefficient power providers a nitch.
    3) Cut down on the cost of backup generators by centralizing them
    4) Increase the loitering time for UAVs and opening up other new defense applications that could increase capabilities and save defense money
    me: This should be practical for LEO and balloon supported, but the small spot size may not be practical from longer distances.
    5) Eventually increase the energy efficiency of the air transportation grid
    6) Provide a US technology that will be very competitive for rural electrification in developing countries

    High quality, low cost terrestrial solar can have Earth applications
    1) Reducing electronics costs
    2) Reducing subsidies for terrestrial solar
    3) Reducing solar’s environmental footprint in terms of land and waste heat
    me: Installing terrestrial solar in locals that only receive half as much solar energy does double the foot print. Beaming may mean we can concentrate on the best locations. Can you give us more details on “waste heat” reduction by beaming?
    The advantages of low cost launch are direct to the taxpayer and consumer and will enable more communication, navigation and observation equipment and more tourists (about 5000 to 1 of the former vs. the latter at current demand levels) to go into space.

    I would encourage you to let the private sector own the intellectual property that results from the research. The R&D costs won’t be significantly lower, but the prospect of their actually being D = domestic will be higher and the government gets more taxes if GDP = gross domestic product is higher.

  29. Dan Lantz said

    Neil #28:

    Altho you could use transmitter as receiver, it is probably tricky and may not be possible at each instant, having to switch back and forth rapidly. Biggest problem is that you will usually want rectennae facing different direction than transmitters, and each different than solar collectors.
    I think the general idea is to use one transmitter to multiple rectennae, whether source of energy is local solar collector or local rectenna getting energy form some other transmitter, perhaps at a “better” frequency than that used to go thru atmosphere.
    A question: Can phased array transmitters designed to be “full” at a certain frequency, that is, such as to avoid “sparse array curse”, send lower frequencies just as effectively? Is “too full” an issue? Does the lower frequency have to be power of two times lower?

  30. Neil Cox said

    Hi Dan: What you typed seems correct. I’m unsure of the answers you seek. As the wavelength decreases, the phased array elements get proportionately smaller, so the number of elements needed per square kilometer (to avoid the sparce array curse)likely increases as the square of the frequency. The material needed for a square kilometer may not increase much as each element is smaller and lighter, but manufacturing and station keeping for one hundred million millimeter elements may be much more costly than one million centimeter elements, unless the process can be highly automated, even if no more material is needed. I’m assuming the array needs slightly more square meters than the area of the spot size of the beam. The spot size can decrease proportionately to the wave length, unless we reach the maximum safe watts per square meter. Likely there are some other factors that determine beam spreading, so the illuminated spot size area may not decrease much more than proportional to the wave length. Sorry about switching from wave lenght to frequency repeatedly. I did this to avoid typing about inversely proportional and inverse square.
    Much of the spectrum needs to be avoided, due to high path loss, but low loss windows occur up to the frequency of green visable light and perhaps higher. Neil

  31. Neil Cox said

    Since about 95% of Earth’s population lives closer to the Equator than 55 degrees latitude, and the torrid zone is typically too poor to pay for the electricity, SSP is likely to favor middle latitudes. Closer to the poles rectennas are thus best located on steep South facing slopes in the Northern hemisphere.
    While some experts think carbon dioxide from human activities is warming Earth significantly, scarcely any experts think the waste heat from human activities is significant compared to the kilowatt per square meter of sunlight not reflected back into space. That could change if humans become more numerous and keep increasing our energy needs and wants.
    Considering the heat produced by mining, trasporting and processing fossil fuel, only about 15% of the total warming does useful work. Terrestrial solar and wind power are only slightly better, but Earth gets nearly all this heat whether we use it or not.
    If most of the materials for SSP come from off Earth locations more than half of the waste heat is disapated off planet, making SSP better than any other energy source that I can think of including bio and nuclear. Not producing the energy is better, but that is improbable for the rest of this century, if not longer.
    Near term we urgently need to get the first SSPs operational, so we should temporararily put our environmental concerns aside, in my opinion. Neil

  32. Dan Lantz said

    #30 Neil:

    Question in #29 was to see if same antenna could send higher frequency thru space, esp. a longer distance, and also (at same time?) be used to send needed lower frequency thru atmosphere, with a shorter distance.
    What I “want” is to take advantage of higher frequency needing smaller overall aperture (for given distance), and then use this same aperture to send lower frequency shorter distance. Would the “extra” elements be in the way at lower frequency? If not, could the elements’ length be switched electronically? Could they be switched to become rectenna elements? Could all the elements be used, or only those at wavelength spacing?

  33. Neil Cox said

    I’m not up to speed on phased arrays, but other types of high gain antennas other than a big dish are quite narrow in frequency. It may be practical to disassemble some of the surplus short wavelength elements and splice them to make longer elements for twice the wave length.
    Likely you hope to use the same phased array for two or more widely separated frequencies simultaniously. Apparently, both the element length and the element spacing is critical, perhaps very critical, to get minimum spot size and minimum energy scattered in other directions.
    On the other hand, I think it is practical to use diodes to remove a portion of the energy from a redirect phased array for local use with only small increase in minimum spot size. Neil

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