Space-Based Solar Power

a public discussion sponsored by the Space Frontier Foundation

Space-Based Solar Power Interim Assessment (Release 0.1) is Published!

Posted by Coyote on October 10, 2007

Hello Everyone!

Click here for the “Interim Assessment!”

From the Foreword of the report itself:

Preventing resource conflicts in the face of increasing global populations and demands in the 21st century is a high priority for the Department of Defense. All solution options to these challenges should be explored, including opportunities from space.

In March 2007, the National Security Space Office’s Advanced Concepts Office presented the idea of space‐based solar power (SBSP) as a potential grand opportunity to address not only energy security, but environmental, economic, intellectual, and space security as well. First proposed in the late 1960’s, the concept was last explored in the NASA’s 1997 “Fresh Look” Study. In the decade since this last study, advances in technology and new challenges to security have warranted a current exploration of the strategic implications of SBSP. For these reasons, my office sponsored a no‐cost Phase 0 Architecture Feasibility Study of SBSP during the Spring and Summer of 2007.

Unlike traditional contracted architecture studies, the attached report was compiled through an innovative and collaborative approach that relied heavily upon voluntary internet discussions by more than 170 academic, scientific, technical, legal, and business experts around the world. I applaud the high quality of work accomplished by the team leaders and all participants who contributed in the last six months. I encourage them to continue their work in earnest as they move beyond this interim report and seek to answer the question of whether SBSP can be developed and deployed within the first half of this century to provide affordable, clean, safe, reliable, sustainable and expandable energy for mankind.

This interim assessment contains significant initial findings and recommendations that should provide pause and consideration for national and international policy makers, business leaders, and citizens alike. It appears that technological challenges are closing rapidly and the business case for creating SBSP is improving with each passing year. Still absent, however, is an appropriate catalyst to stimulate the various interested parties toward actually developing a SBSP capability. I encourage all to read this report and consider the opportunities that SBSP presents as part of a national and international debate for action on how best to preserve security for all.

//signed 9 Oct 07//
Acting Director, National Security Space Office


74 Responses to “Space-Based Solar Power Interim Assessment (Release 0.1) is Published!”

  1. […] Space-Based Solar Power Interim Assessment (Release 0.1) is Published! […]

  2. […] final report issued concludes many things, but the most important point is that the effort will go no where fast […]

  3. brian wang said

    I think the plan should include the laser transmission of power option and not just the microwave transmission.

  4. Coyote said


    That’s probably an oops on our part for not making it clear that laser transmission of power is something we need to assess more closely as well. It is well within the trade-space and is very relevant to smaller satellites that may be used for testing, and for larger applications that need to limit the size of the transmitter/receiver.

    Thank you–good catch!

  5. Harnessing solar power should be the top priority in whatevr way.

  6. Robert Braunstein said

    This may be a dumb question since I haven’t looked at the web site or interim report in detail yet, but did it consider the use of space elevators to bring the power back down to Earth via cable instead of electromagnetic radiation of one sort or another?

  7. Dan Lantz said

    “Tastes Great!…Can’t Wait!”
    A-2: “(requiring a transmitter 100 times the area as a similar system in geostationary Earth orbit)”
    I’m pretty sure that receiving rectennae must be “solid”(to microwaves) to gather all the energy, thus as small as possible to save on costs. To get the small receiving rectennae, large sending antennae are needed. They, however, do not need to be “solid”, as they are sending energy. Thus the very same sending elements that are used in geosync Solar Power Satellite can be spread out on the lunar surface by a factor matching the greater distance to the Moon, and supply the same receiving rectennae. Or, spread them out even further and get even smaller rectennae on Earth. The Moon is very large. It is thus an advantage, rather than a disadvantge, to be sending from the Moon, even tho the antennae “covers” 100 times or greater the area, it is not inherently more massive. Throw in the free station keeping, radiation shielding, and basic structure and it ends up lighter.

  8. Graham Madarasz said

    Excellent work gentlement. I’m extremely pleased to see that someone is
    paying attention to the advancements in solar and the impending break-even
    point with conventional, dirty energy.

    I was suprised to see that all solutions proposed involved collection in earth orbits.

    Every time I’ve envisioned this program, it involved collecting much closer to the sun
    (1/r^2 being what it is) and using a Penning trap to contain anti-matter generated
    with a huge cap charged with the incoming solar flux for storage for the trip home.

    I also figured this would need to be converted to something more safely distributable
    before re-entry so I’m very excited by the analysis of beamed distribution.

  9. […] More […]

  10. See feasible earthbound projects. They can be monitored, maintained and are feasible. 300 takeoff of shuttles to transport 3,000 MT to space which are necessary to built one solar power satellite are out of question. USA has the deserts which may deliver all energy to get hydrogen enough to feed all cars of the nation, without emission. Get the whole story at
    A global strategy suggested as a follower of the Kyoto-Protocol at the Climate Conference at Bali in December is presented there.
    Best regards

  11. pemomasek said

    This is a wasted effort. In his book Entering Space, Robert Zubrin takes a few paragraphs to show that the only advantage of space-based solar power is that it is more expensive than ground-based solar power. … Wait! That’s a disadvantage!

  12. Coyote said

    Robert Braunstein: We looked as space elevators briefly. The engineering and assembly challenges are quite formidable, so we did not assess them.

    Dan Lantz: There is no doubt that Moon-Based Solar power has its merits, but this was a space-based solar power study. We did chat with several MBSP advocates and we all agreed that the Moon moves in position relative to the Earth and most of its surface experiences considerable time in the shade. The work arounds to these problems added infrastructure that would drive up the start-up and operating costs. I support MBSP, but I think we need to cut our teeth on SBSP first.

    Graham Madarasz: We thought about solar-related orbits beyond the cislunar system, and even the Lagrange points, but that adds more infrastructure to the system. Suddenly you need power relay systems and have to put up with greater path loss. So, we decided to keep it as simple as possible to see what happens to the business case. We went with satellites beaming power from relatively fixed GEO orbits to fixed ground-based receivers and feeding the power into existing power grids. Even the infrastructure required to do that is huge! In later phases of this study when we start experimenting and collect real empirical data, perhaps something will convince us to shift orbits outward.

    Karl Heinz Wilm: I totally support your efforts and hope you succeed, however, I still need power that I can broadcast into places where the infrastructure to flow liquid fuels is either absent or disrupted due to natural or man made causes. Good luck…we need all the sources of clean, abundant energy that we can develop!

    Pemomasek: I haven’t discussed it directly with Bob, but he should take heart that we are already thinking about sending space-based solar power satellites along with the ships carrying humans to Mars as a way of providing an off-board power supply en route. Then the SBSP satellites will be placed in Martian orbits to provide power to the settlers. And the same holds true for the development of the Moon, too. You see, if I develop such systems for use on Earth…then missions to other worlds can capitalize on the the work done previously. Becoming truly spacefaring is about developing useful infrastructure that can be used over-and-over. Is space-based solar power more expensive than ground-based? It depends on the situation of the customer.

  13. Fuzz said

    Space junk… Not really but read on. Sorry, I have not had time to read the interim report, will do so on shift tomorrow. Is there a possibility of using this potential energy source as a means of refueling assets built to accept such energy uploads? Reducing the potential for space junk with our current limited life components that we send up now by having an orbiting “refueling station” is very tantalizing and has long range implications in both the areas of space asset enhancement as well as space control.

  14. Mark Sonter said

    Hi Coyote:

    Thanks for a good report: I think it has killed the ‘giggle factor’.

    You asked for comments on ‘trade factors’: here are mine on GEO versus LEO.

    Equatorial Low Earth Orbit (ca 1000 km altitude) whilst not geostationary, DOES provide flyover every 90 minutes. It is energetically less demanding to access, and close enough for manned assist in assembly, and geometrically much less demanding with regard to beam spread AND minimum transmit antenna size, AND… with something like 6 to 8 satellites equally spaced, you can still have power delivery continuity (during daytime), without need for storage.

    You talk of niche markets being military forward bases, and disaster relief bases. Here is another, potentially very big, and politically productive:

    Niche markets in a band of (say) 2000 km north and south of the equator include lots of underdeveloped regions where electricity is generated from diesel gensets and the fuel has to be trucked in, over (sometimes) hundreds of km of rough roads, thus the people pay very high rates for power. Think most of Africa, South America, Indonesia, southern India.

    There is a ‘soft power’ opportunity here….

    And the technical and economic cases BOTH become easier to close.

    I have lots more on this, Coyote, including comments on the necessary *equatorial* launch site, please contact me off-line.

  15. Dan Lantz said

    Coyote #12:
    “There is no doubt that Moon-Based Solar power has its merits, but this was a space-based solar power study.”
    That reminds me of a story: Abe used to ask “If you call a tail a leg, how many legs does a dog have?” His answer: “Four. Calling a tail a leg does not make it one.”
    Vote on whether collecting solar power on the Moon and beaming it to Earth is to be called “space based solar power”. Does the result of the vote matter?
    A-2: “Furthermore, power from the Moon must be beamed ten times the distance (requiring a transmitter 100 times the area as a similar system in geostationary Earth orbit) and because the Moon is not geostationary, would require reflectors or retransmitters in Earth orbit, or a global power distribution grid to enable continuous power to be delivered to markets on the Earth.”
    How about: The Moon is much larger than any proposed geosync transmitter, so much so that it can send a more precise beam to the Earth, even tho 10 times the distance. This is one of the advantages of Lunar Solar Power. The first part of the A-2 statement is not wrong in “scale”, but, even worse, wrong in “sign”.
    Also: By rotating under the Moon, most of the Earth’s surface can be “empowered” every day for ~6-8 hours, from one pre-existing satellite. This allows such things as fuel generation, heating and cooling, and other heavy energy use activities that do not need to be continuously powered to be directly beamed during that time. The “reflectors or retransmitters in Earth orbit” needed to supply far North/South locations whether starting with geosync SPS or LPS will, of course, have orbits that cross the rest of the Earth most of the time, so can be used to “fill in” when the Moon is down, for far less in orbit than SPS. Add to them as needed, and/or put big ones at L 4-5. Fuel cells that make general purpose fuel when Moon is up can convert it back to electricity with little added cost when Moon is down.
    “…most of its surface experiences considerable time in the shade.”
    Worst case problem with lunar night is double size of installation. Getting basic structure, larger transmitter(smaller rectennae on Earth), permanent station keeping, radiation shielding and “junk” prevention for free are balancing factors, even if you don’t use lunar material for raw manufacturing source. Mirrors in lunar orbit may help too, especially if mirrors are to be used anyway for light concentration.
    Don’t make the same mistake the “Fresh Look” study did! By excluding lunar resource use, and probably having never heard of LSP, they excluded a proposed solution to launch costs, then found that launch costs were too high! Study starting with (needed under any plan) retransmitters, powered from Earth at first, then get estimate of scale at which LSP is better than SPS. You may find it starts out that way. You will certainly find that lunar resource use/LSP looks good at any scale that would be considered global.

  16. Neil Cox said

    Since I recomended laser diodes, I decided to learn about them. It was not encouraging as most suppliers give few specs, but I did learn from that ultra violet lasers are available with cw output up to 100 milliwatts = 1/10 th watt. 1.5 watts at longer wavelengths. Apparently most laser diodes require elaborate protective circuitry to operate safely near their max rated output which some claimed (without details) to be as high as 5 watts. My guess is considerable R & D would be needed to operate 100,000 laser diodes in series, even at half their optimistic rating, with rare failures. This is especially true, over the wide temperature range in space and in our upper atmosphere. At least one was recomended for 10 to 40 degrees c without details, such as automatic reduced power at 40 degees c.
    I think these lasers came with optics to produce a 1/4 mm beam with with 4 milliradians = plus and minus 2 milliradians of divergence of the beam. Apparently the beam diverges several degrees without optics. I think we need less than a nanoradian for 10 kilowatts per square meter, even at 100 kilometers beam length, but that is likely possible with more elaborate optics.
    In pulsed mode 15,000 hertz is apparently standard, but much faster is likely possible. Hopefully someone with hands on laser experience can provide more details. Neil

  17. Neil Cox said

    We will want backup power for our SBSP. An ultracapacitor can supply a megawatt briefly. Here is a paste from an MIT forum
    How do you deliver 15KWH into an energy storage unit in a vehicle at home in 10 minutes?
    Me: Your utilty has several thousand volts, single phase, on a pole about one hundred feet from your house. They will run this into your house for about $1000, and they will charge you a higher rate if you use 90 kw a few minutes per day. This is called use of demand. They will also charge you extra because your charger will distort their sine wave significantly. If you want even faster charging they will likely charge you more than $1000 for the hookup. If you use a second ultra capacitor to limit the charge rate they may give you a reduced rate as you will be doing power factor correction, and less sine wave distortion. With good luck you won’t need a transformer. You may also get a reduced rate if you charge slower after midnight.
    y: You need a peak energy capacity of 90KW to achieve a 10 minute charge.

  18. Neil Cox said

    y: Even if the owner installed a 3 phase hookup, the device would, with 100% efficiency in conversion from AC to DC, consume 187.5 amps of current for 10 minutes.
    Me: That is high for average, I think. Perhaps somewhat more when you first start charging the discharged ultra capacitor, unless you add a costly constant current device. The electric utility will likely charge you $10,000 for a three phase hookup in a typical residential neigborhood.

    y: That seems a bit impractical to me even ignoring how one would achieve 100% efficiency.
    Me: 98% efficiency is possible if you can avoid using a transformer. If the power company voltage is a bit low, you can cool the ultra capacitor perhaps as cold as minus 20 f until the charge is complete. The capacitor voltage will rise as the ultra capacitor warms, assuming the ultra capacitor has a negative temperature coefficient of capacitance.

    y: Perhaps they are going to sell you two ESU’s? One in the vehicle and the other slowly charging up at a more practical charge rate and then use some 3500V DC transfer process to dump 15KWH into the vehicle in 10 minutes? Even that would involve handling a peak current of 26 amps times 6 = 156 amps at 3500V.
    Me: 26 amps is average for a 60 minute transfer time. Perhaps 200 amps the first minute of 6 minutes, unless you add a costly constant current device.
    Things get really difficult if you want to put 100 KWH in your big SUV in ten minutes. The Tesla roadster uses a 53 KWH battery for a 200 mile range, so EE must be thinking a tiny car. Your extra ESU can power your house if the utility is blacked out, but you need 3 or 4 special design inverters with inputs in series for 3500 volts.
    I’m wondering how EEStor will switch 3500 volts to provide a near constant output voltage to the load as the ESU nears discharged? 3500 volt solid state relays are costly even at low current. Neil

  19. Dave Lermit said

    Some out of the World thinking from the old World…
    Once you have a early bird demonstrator Death Ray from Orbital Space Satellite (Station) DROSS (probably a Mk2.0) from ISS or other platform. Hows about this:
    Get Rectenna constructors to prototype 1 -10 metre rectenna ‘umbrellas’ with (O)LED lights or other sort of received power indicator that will work. (Test it first!) THEN and hand em out to interested parties: Articulate Space Nauts/Nuts. Then get said parties to stand out in the wilderness somewhere (central plains to central park!) and start beaming… (O)LED lights up!
    Repeat under orbital track all around the world!

    * proves ‘Death’ rays are in fact harmless
    * proves that system works
    * proves that you can aim the beam
    * demonstrator is personalised… My free space power!
    * internationalises space energy
    * free positive media stunt before you hit them for the 10 billion for the LEO prototype

    Personally I’m amazed you didn’t get started during the last Oil Crunch. But who am I to comment after all we gave our space program away to the French! And then kinda turned our backs on the whole New Frontier thing…
    But the spirit of Dan Dare lives!

  20. pvperf said

    How bright will the light reflecting off the satellite components appear on earth? Will it affect circadian rhythms, plant flowering, or earth based observational astronomy? I heard that some designs may appear as bright as a first quarter moon.
    Keith Emery

  21. Coyote said

    Fuzz: Although we have not studied the concepts you propose in any great detail, we have sat around discussing the possibilities of using SBSP satellites to broadcast power to other satellites. Flywheels and ion drives would love the energy SBSP could provide. We are beginning to study space debris mitigation and even removal as a way of restoring freedom of action in space for all users. SBSP could supply energy to systems that “sweep” away the debris.

    Mark Sonter: Good comments. Even if we base the finished SBSP satellites at GEO well will need to assemble them in LEO and either self-propel or tug them to their GEO station. Discussions of early test satellites will probably be LEO-based so we can do empirical assessments at that time. The key is leave the trade spaces open and let empirical evidence indicate the better decisions. As for soft power…I am totally on board with you!

    Dan Lantz: Interesting! Some questions come to mind: What type of infrastructure will need to be built on the Moon, in space, and on Earth to make Moon-Based Solar Power a reality? What cahnges or reversals in international law will be required to appropriate areas of the lunar surface to such commercial or government exploitation? How will you deal with the dust problem? I certainly think its worth exploring.

    Neil, Neil, and Neil: We’re headed for a deeper study of all technical and design issues…on our way to testing, demos, and on-orbit experimentation. You’ve got a lot of great ideas. A big factor will be the ability to mass produce components. We will likely have to avoid the ultra-high efficiency exotic materials and go for second or third best performers to achieve production rates and costs we will be looking for. This will largely determine the design of the satellites, transmitters, and receivers. This is more of the Russian than the American approach.

    Dave Lermit: Dude, I was concerned with the first “death rays” remark until I read your whole comment. Brilliant! As you read through past threads and my comments you’ll see that I am very, very concerned about confirming and verifying to the global community that space-based solar power systems are safe and are not weapons! This is a 2-way street. I can think of half-a-dozen states that if they operated SBSP satellites I’d be worried about their weapons potential, too! We have a great opportunity here to demonstrate that, not only are the power broadcasts safe, but that the design of such systems precludes their being used as weapons. The security we are seeking is clean energy independence for American, its Allies, and the World.

    Pvperf: Um…hmmm. Quite frankly, I hadn’t thought of that. That is a very good and intelligent question that we need to answer! We will certainly look into that! See, because of the open collaborative environment that we are in, YOU, my friend, have just made a solid contribution to the effort. That said, I can foresee the answer being something simple like, “The satellites will always have their collection surfaces pointing directly at the sun, therefore there will be no direct reflection onto the Earth.” I’ll add this to the list of research questions. Good job!



  22. brian wang said

    Japan’s direct conversion laser again (sunlight into laser 40% efficient)

    100kw solid state laser being assembled

    Northrop Grumman Corporation (NYSE:NOC) has entered the integration and test phase for the Joint High Power Solid State Laser (JHPSSL) Phase 3 program after exceeding all demonstration requirements for the first gain module, or building block, that forms the core of its 100 kW solid-state laser system. This is four months after the 67 kilowatt solid state laser was announced.

    2002 discussion of laser costs

    McKearn predicts the cost will go down from current [2002] levels of $70 to $100 per watt down to $5 per watt during the next several years. [In 1997], he said, “a single 100 kw laser would have used three times the world’s yearly production of diodes.

    Page 21 of this pdf on the laser industry indicates that in 2006 the price of solid state laser diodes is $30/watt So the diodes for the 100KW laser are about $3 million.

    So if price trends continue, then $10-15/watt in 2010 for high power laser diodes.

    For doing anything on the moon. Use low energy orbital transfers. Takes longer but sending robots to the moon should be super cheap.

  23. Marcus said

    You people realize you may actually have saved humanity from collapse by having the raw courage to implement this step? I was close to giving up on the US, […]. But evidently there are some people with brains left in the US military.

    I am not exaggerating one bit. If the US stays […] addicted to an ever more price-sensitive commodity (oil), with a national infrastructure both brittle as well as oil dependent, an economic paradigm completely dependent on more and more and more economic growth, only this route will offer any chance on salvation.

    […] (W)hat if the fossil politicians wake up, in the US, in Europe, in Russia, in China… in Saudi Arabia! If this plan works and remains sustainable, it will change the global political landscape in one axe blow.

    Gerald K O’Neill, we had to wait thirty years but finally there is hope!

  24. AK said

    Hi Coyote…

    Were you in Princeton in ’75? I remember from that conference (which I attended on my own hook) a presentation of a complete plan for extracting materials from Lunar surface and slingshotting them Earthwards. I don’t remember the details but certainly somebody will have kept his/her handouts? Active thought seems to be going on here as well.

    Something that occurred to me a few years ago: both space-based and terrestrial phased array antennas could be “smart”, that is the phasing of individual antennas could be controlled by real-time position sensing so you wouldn’t need precision placement or long term stability.

    I haven’t read the report yet, but just in case this wasn’t considered…

    I saw mention somewhere (I think it was in this report) of long-flying aircraft, but another concept I’ve been thinking of is broadcast powered shuttles, perhaps using MHD shooting ionized nitrogen. With reaction velocities of >50 Km/sec you could get total reaction mass down to an easily manageable fraction. You might even be able to set up a sort of “ramjet” effect ionizing the air on the way in and shooting it out the back with MHD. This would reduce the environmental footprint to heat.

  25. Neil Cox said

    #19 Dave Lermit infers:
    Ten kilowatt, millimeter wave transmitter with a large antenna at ISS produces 10 milliwatt per square meter in an illuminated spot of 500,000 square meters assuming 50% delivery to the spot. 500 meters by 1000 meters. Ten milliwatts is sufficient to light a LED dimly assuming 50% effecieny of the rectenna. 80 square meters lights a bright LED brightly, but this is much too large to pass around even savy spectators. It is large, 33 feet, and either very fragile or heavy enough to cause injuries. Worse the millimeter equipment likely carries a high classification. Using a longer wave length, means the antenna for the ISS won’t fit in the space shuttle cargo bay except folded or disassembled. Input power to the 10 kw transmitter is likely at least 15 kw which the ISS will be reluctant to supply, as they will need to shut down other equipment.The project is marginal at best, unless we make the illuminated spot, much less than 1/2 square kilometer. This requires a larger antenna that can be pointed very precisely at the ISS which may be ok as the antenna can serve other purposes, such as radio telescope. Neil

  26. Neil Cox said

    Hi Coyote: I agree, the photovoltaic panel should face the sun plus or minus one degree, so only at sunset or sunrise will refleted light fall on Earth’s surface. In this case it will be seen though hundreds of kilometers of Earth’s atmosphere, so it will be almost invisable right next to the Sun, even if this is a 1000 square kilometer photovoltaic panel. By carefully selecting the one degree pointing error, I think we can insure that the reflection is not visable anywhere on Earth’s surface.

    On the other hand, if we use concentrating mirrors these will fairly often illuminate Earth, slightly, during twilight hours, except the photovoltaic panel (or boiler) will eclipse the beam from the mirror if the mirror is aimed for maximum energy transfer, or so it seems to me. Neil

  27. […] Law Probe discusses the legal ramifications of solar power satellites, Space Solar Power describes the approach taken to compiling the study, and Astroprof goes into depth describing the […]

  28. Dan Lantz said

    AK #24:

    See You were witness to History!
    Also, making redirect antennae in orbit “smart” to cooperate with each other is great idea!

    Coyote #21:

    In the 90’s there was effort to start a Lunar Port Authority, seems that a “port” has special legal status that matches what is needed on Moon: private property ownership of development without full claim of sovereignty. I’m fortunate to be a law school drop-out, so will leave this one for others!
    Dust and infrastructue questions can get too specific to try to decide in detail now. I like to look at the basic physics of the situation to see if there is A way, then worry about the BEST way as late as practical, so as to not get locked in to old ideas or miss new opportunities. Brainstorming is good, but “iteration” of the whole concept is better than trying to decide everything at the start (“waterfall”). Also, once you are confident a smallish problem CAN be solved, bringing it up only gives distraction to those who are undecided or new to the overall concept.
    Basic physics sez:
    -Avoid Earth launch. However you can. Whenever you can. I agree with Shubber on this!
    -It is ~200 times easier to launch from the Moon than the Earth.
    -It is inherently easier to manufacture/mine in Free Space than on the Earth, once you get there and fully get started, even if Earth launch were free. Call me crazy, but this is clearly true! (Think BIG).
    -There is sometimes benefit by being on a “planetary” (the Moon, in Lunar Solar Power case) surface, if what you want is a large surface (for things such as collecting/transmitting solar energy), but that is an exception to the prior observation.
    -If you don’t have to launch at all, by maufacturing on/for the Moon (LSP), you can ignore mass and packing/unpacking of factory product(solar collectors, cable and energy transmitters), and go for what is cheapest, simplest and most robust. This makes the factory simpler! This same advantage applies to using asteroidal material in free space. Launch of raw lunar material into free space, for use in free space, is almost as good. If there is some special manufacturing advantage to zero g that is used for making things to put back on the Moon, that works too.
    Also, other general considerations:
    -Keep in mind that there are scale related “tipping points” where things such as lunar factories first become similar in cost to Earth launch plans, and that these should be aggressively moved toward, even at initially higher cost. Buy one tomato “plant”, instead of one tomato every day.
    -Try to “crawl” in the right direction. You will learn to walk no matter which way you go, but trying to sell a different system after starting will be difficult. Work to “finish”.

  29. Dan Lantz said

    Pvpref #20, Coyote#21, Neil #26:

    I think the panels will reflect back towards the Sun, as they face it almost squarely. When they are opposite the Sun, as seen from the Earth, that is, in the middle of the night, they will appear brightest, unless EXACTLY in the Earth’s shadow. Even incidental reflection off of such large structures will be visible. Put them on the Moon, and no one will notice! Strange how couterintuitive these things can be, isn’t it!

  30. Dan Lantz said


    This idea of using many redirect antennae as single phased array/synthetic aperture system is true advance! Moon’s size advantage is limited in that, no matter how good the beam is focused, “twinkle” in Earth’s atmosphere spreads it back out, making rectennae’ size grow again. However, redirects are in space, so their receiving rectennae can be small and solid(to microwaves), taking full advantage of being hit precisely from the Moon-sized phased array transmitter scattered there on the Moon. Then the redirectors that are overhead send their “new” beam down, from high overhead, avoiding the sideways trip thru the atmosphere, thus limiting twinkle.
    But the best part is that retransmitter sending antennae need not be individually large, as they are part of an array!
    Incidentally, the phased array transmitter on the Moon should be able to hit deep space power consumers quite nicely, having no twinkle to worry about.

  31. AK said


    I don’t think a rectanna has to be solid, I’m not positive of the math but I seem to recall that if the individual elements are separated by some fraction of the wavelength they will capture virtually all the energy. (Think of the see-through doors of microwave ovens.)

    As for phased array antennas, in space they could be strung out on an open mesh several Km across, perhaps held out by rotation or perhaps by lightly pressurized gas. I would think any orbiting antennas would want to be physically linked, else you’d always be spending reaction mass to keep them close together.

    I’m thinking of thin aluminum wires or coated glass threads for elements, each with a tiny silicon chip at its base, linked together by thin glass fibers and glass insulated aluminum wires. Here there would be tremendous advantage in not having to keep precise alignment.

    In the long run, engineering in zero-g will be easier than even Lunar gravity, IMO.

    Has there been any work on defining property rights re orbits? You need something as space fills up, or you won’t have the confidence in non-collision needed to secure investment capital. (I suppose that’s one argument in favor of using the Lunar surface.)

  32. AK said


    Sorry, I didn’t see your “solid to microwaves” in my first read-through.

  33. Neil Cox said

    #29 Dan Lantz: I think you are correct, but the beam of reflected light spreads about 1 degree, so it illuminates all (or most)of the night side of Earth, and thus will be no brighter than the moon, even for a 1000 square kilometer photovoltaic panel. Perhaps we can make the photovoltaic panel slightly convex, so it spreads the reflected beam even wider than 1 degree, if a small moon occasionally causes any problems of significance. Slightly convex will also be stronger mechanically than flat. I think slightly convex will produce a smaller and dimmer extra moon, but for more hours per month.
    #30 Don’t we need continuous station keeping energy to keep these redirects in the optimum location? Neil

  34. Neil Cox said

    #7 Dan Lantz: Suppose we produce twenty billion watts (average) on the moon, tied to a power line that circles the equator. The transmitter to Earth needs to be close to the center of the side that faces Earth for minimum construction costs. The beam is six billion watts (some of the power is needed for the moon colonies) 4 billion watts falls on a typical large rectenna on Earth. Likely optimistic, if we used two or three redirects.

    400,000 square meters is 10,000 watts per square meter, if we can convince people that is reasonably safe and that the beam will be shut down in 3.7 seconds, if it is pointing wrong. Rectennas more than a square kilometer can be built at higher cost, but some communities will decide not to spend the money for 5 or 6 hours per day. This is especially true for the mid Pacific community which likely does not need 3 billion watts (a typical rectenna puts 75% on the grid?) except when the moon is high in the sky during the peak demand period. Four consecutive days per month? If Hawaii is the Pacific community, we likely need another rectenna, about 6000 kilometers farther to the West or Southwest. We may also have difficulty locating a rectenna in the Mid East or Eastern Africa. I don’t think splitting the beam between two or more communities is practical, but perhaps the last redirect can split the beam efficiently.
    The surface of the moon has about as much dangerous radiation as GEO altitude, which is often protected by Earth’s magnetic field. The moon does have some wobble = liberation and the beam needs to be re-aimed several times per day (will we shut off the beam while it pans 6000 kilometers to the next rectenna?) so the savings in station keeping energy is trivial.

    Why not consider a solar synchronous satellite that beams energy to perhaps a dozen rectennas around the Earth (daily instead of monthly) during the peak demand period? Since it is about 20 times closer, smaller is cost effective and split beam without redirects is likely practical. Neil

  35. Dan Lantz said

    AK#24 (continued from #30):

    More on idea of “smart” (phased array) orbiting redirect (and other) transmitter antennae:
    -Seems that this is quite likely possible, but needs confirmation.
    -If is possible, seems to remove need for redirects to be close to the Earth, similar to situation of Moon where distance is balanced by spacing.
    -Thus redirects could be slightly beyond geosync distance, and in highly inclined orbits, so many would be visible at any one time, nearly overhead. The advantages of being beyond geosync are that they would never block communications from geosync, they are each visible from more of the Earth’s surface, move slower and are not as visible to eye. Don’t want to go too far out, or some will be harder to hit from sunlit limb of the Moon.
    -In place, this swarm of small antennae could send beam far into deep space, given huge dimension, and see approaching asteroids/comets, not to mention being a great radio telescope.
    -So, collect energy on Moon, send precisely to spread-out elements in a much larger volume, and re-organize energy to go anywhere on Earth or Out from this Really Very Large Array.
    sounds like a plan!

  36. Michael Antoniewicz II said

    Okay, who’s going to Wirec 2008 and present the 0.1 release and any updated info by the 2008Mar04-06 conference dates?

  37. Dan Lantz said

    AK#31 (second and third para):

    You have (I hope!) underestimated your own great idea (#24)! The possibility that the phased array elements DO NOT have to be rigidly connected is the key, if it is possible! (I will assume it is possible for the time being, to avoid repetitive qualifiers).
    I’m thinking of completely separate redirect sats forming phased array with “full sky” dimension. Each sat can have own array rather than single emitter, too, to handle power load and help aim.
    The transmitter array does not have to be “solid”, only the receiver does (to microwaves).
    I think that the more spread out the array is, the better, as long as it is held in stable position OR is “smart”, and creates “new” arrays as positions change. This is relevant to Neil#33(comment on #30), as no particular array position has to be maintained. A fairly random set of redirect sats will do the trick. I’m so excited by this I can hardly type! Make such a “smart” array just beyond the geosync “graveyard” of fuel empty (former) communication sats. The limit as to how SMALL the individual redirects can be is now receiving from the Moon: the same as rectennae on the ground, minus effect of “twinkle”.

    AK#31 (para four): I fully agree that “Space is the place” and hope that Lunar Solar Power does not keep people from seeing O’Neill/Asimov basic point. However, I think O’Neill jumped to SPS with notion that it was first/best product of his concept, without seeing that there might be exceptions to the general rule. If you need surface area, the surface area of a planetary body (or the Moon) is not automatically disqualified! Dr. Criswell claims that his plan is 50-100 easier than SPS from lunar resources. These are important questions!

  38. Dan Lantz said

    Neil #33:

    There is a fairly recent “accidental” discovery of etching metal that makes pits that absorb pretty much all of the light that hits the surface, which may cut down on incidental reflection from structure. The light reflecting from the panels themselves will probably be fairly diffuse even without convex shape, but keeping panels flat may actually allow aiming most away from Earth even more effectively. Ideally, they would absorb it all!
    See #37 (middle) for comment on #33 (para two).

  39. Dan Lantz said

    Neil #34:

    (para one): One of Criswell’s main points is that the transmitter be spread out along the limb of the Moon, to take advantage of the great size of the Moon in creating phased array transmitter with large dimension. Individual elements are added “cost” based on total power, not how far apart they are. Can then collect one half on “near” far side (with short transmission lines) for full power even at new Moon.
    (para two): Balance between efficiency of direct beam from Moon and need for contiuous service thru redirects is complex question, but “invisible hand” will give the answer. Also, Criswell talks of thousands of rectennae, making up ~70% of the total cost of the system! These elimiate need for long distance transmission lines, are built/owned locally, and do not have dangerous levels of microwave flux even directly in the beam. Plan is based on build out to 20 TWe for entire Earth needs, which is 20,000 Billion watts (electric, as opposed to thermal). This “fast track/Apollo level” plan is estimated to achieve pay back, profit and complete funding of continued construction at around 100 GWe, or about 1/200th of total. Anything less than this “break even” 100 GWe and we shouldn’t mention climate change, as our proposal will not matter in that regard.
    Multiple rectennae can be powered at same time from same phased array, one of the advantages of phased array system, whether LSP, SPS, redirect, or combination.
    (para 3) Radiation at geosync is probably about same as on lunar surface, even if some protection from van Allen belts, as Moon blocks half when on lunar surface. Main advantage of Moon is how easy it is to provide radiation/thermal shield, by piling on that problematic dust!
    Also, beam is continuously re-aimed as each rectennae sends pilot signal to keep beam from wandering, and request power level, for SPS or LSP system. May have to figure how far things move in 2 seconds (light speed delay), but other than that it is “real time”. I think station keeping may be one of the most important considerations in this whole “contest” between LSP and SPS!
    (para four): I thought solar sync was way out there, where SOHO is, beyond Moon’s orbit. Not a bad place for second SPS, after Moon, as it would shade Earth too!

  40. AK said


    I’m still not sure about this separated antennas deal, I’ve heard about it before (in SF) and I’ve always thought you wouldn’t be able to focus your output on a single spot, you’d be stuck with a regular array of spots depending on the locations of your antennas. I admit I don’t know the math, but has anybody actually tried this with, perhaps, some OTS WiFi phased array antennas? I’m from Missouri: Show Me!

    I don’t know how big your individual antennas are supposed to be, but if they’re in the 1-10 Km range I think you could get major cost savings making the individual elements “smart”, not just the whole antennas.

    If multiple separate antennas are feasible, you could use low-power IR lasers to get distance measurements to within a micron or two, two or three in a row will give you equally accurate relative velocity, timing can be calculated from distance, and you’re withing a few thousandths or better of a microwave wavelength for phase control.

    Oh, and you wouldn’t need rigid links (if you need them at all), since your antennas are smart you just need something to keep them from drifting too far away. Very light cables with “smart” springs, and perhaps a bit of extra spin on the whole structure, would probably be enough.

  41. Dan Lantz said

    AK #40:
    shows that it won’t work!
    It seems to keep the resolution, but not the power. Separate receivers work for seeing image, but elements must be together for sending/receiving power. The big costs are in the many receiving rectennae and the huge area of mirrors/collectors needed. At some point, the amount of power will force the transmitter size beyond the need for focus, so it is more of a start up cost than long range cost. Oh well!

  42. Neil Cox said

    For the redirect; I’m thinking a wave length of 2 millimeters, which makes yaggy antenna elements about one millimeter in length on a boom perhaps 2 centimeters long with perhaps a dozen directors and several reflectors to get the very small spot size we want for the one kilometer rectennas. We need about ten trillion of these yaggys, orbiting just beyond GEO altitude. Ten trillion spaces them a meter apart, for a total area for the redirect of ten million square kilometers. Segments of the redirect can send a beam to a hundred rectennas simultaneously. This may be over optimistic for several reasons: ten million square kilometers may be much too little area for the redirect. Apparently, phase allignment and station keeping is critical within each group. One meter spacing likely is too much for millimeter waves. Less than perfect conditions may only redirect a small portion of the beam and/or make the beams wider than the rectennas.
    A possible solution is: A trillion balloons in the stratosphere, covering a million square kilometers total redirect area. An added bonus is this many balloons would cool Earth perhaps one degree c, thus offsetting global warming. A longer wavelength may help, but will make the Moon (or other location) transmitting antenna larger.
    These are all wild guesses, so don’t hesitate to refute, correct and embellish. Neil

  43. I am new to the effort and am thrilled that it has come this far. Please forgive me if I ask some rather dumb questions. I have read Wikipedia and the report itself and have some confusion over the specifics of the plan. Is there a website where various hardware proposals are laid out in detail? Power Sat, transmitting antenna, and the receiving antenna configurations in particular?

    How about the construction methods to be employed? What is the extent of infrastructure needed to build the 10MW pilot plant? Does it require a return to the moon?

    The first question on anybodies lips when I bring up your report is about the power beam itself. The report is great but has studies been completed addressing the effect of the beam on our atmosphere? on planes flying through it? on birds? The second most popular question is how big does the ground receiver need to be? Wiki indicates an oval 10×15 km. Is this correct? Is this for a single 5GW station? If I am reading the report correctly, the US will need approximately 69 of these to just replace the current energy demand.

    Oh, and by the way… Thanks for doing this. I have been saying for years that space is the only hope humanity has for long term survival, even wrote a speculative fiction novel about it called Evolution’s Child. This report gives me hope that something will eventually get done along those lines. China launched their first lunar probe and last month it was Japan. We have some work ahead of us but I find it encouraging that the Pentagon sees this as part of our national security.

  44. Dan Lantz said

    Coyote, Neil, AK and Brian:

    I have realized where I led myself astray on the sparse array (thinned array) issue. When Dr. Criswell describes building pairs of transmitters, this is for lunar day/night, not to create longer baseline (altho the Moon still provides the platform size for this, if you want to make dense array transmitter larger). Pairs work for receiving if you want to see position clearly, and were making news at the time with pairs of optical telescopes seeing one sharp image.
    Thinned array curse means(if I understand it this time!):
    -that small demo will probably not work, as at least half the elements must be in place before ANY tightly aimed beam is formed.
    -elements must exist one wavelength apart in “both” directions, but may not need to be exactly flat. This may preclude forming phased array from visible light diode lasers, unless they can be made that small(?). I do remember seeing story of tiny laser “wells” that may be small enuf.
    -there is an “optimally small” or minimum “full transmitter use” starting wattage of each SPS or lunar “farm” that is determined by how small the transmitter can be (many factors go into this!) and how much power each element can deliver. There may be some play in this if lower power-rated elements are much cheaper: The first transmitter could use these and get started, then make later ones to handle more load.
    -it is better to have a minimum size required than a maximum possible, as most proposed Earth based systems do!

  45. Alienthe said

    @AK post #40

    I’m still not sure about this separated antennas deal, I’ve heard about it before (in SF) and I’ve always thought you wouldn’t be able to focus your output on a single spot, you’d be stuck with a regular array of spots depending on the locations of your antennas. I admit I don’t know the math, but has anybody actually tried this with, perhaps, some OTS WiFi phased array antennas? I’m from Missouri: Show Me!
    Easy. This is the same principle as used in electronic beam steering on radars, has been in use for decades. I am not sure if any are in Missouri but I know you will find a few cold war era systems such as Pave PAWS in places like Alaska:

    Featuring a 27 m diameter face I would say DOD already has proven technology at its disposal.

  46. Edawg said

    I was wondering if a gun launched space system existed .Could it be used for regional planetary defense? Think about launching a nuke at 8kms at an incoming asteroid fragment thats already hitting the atmoshphere!!!?? I wonder how the physics would work out? I would be willing to bet that it would make a good study.Talk about star wars heritage

  47. Coyote said

    Chuck Lesher: We have not progressed to the design phase yet, so we do not have websites that lay out the particulars in any greater detail than you see written here. What we’ve done is a Phase Zero architecture study that does nothing more than survey the issue of space-based solar power and answers one basic question; “Is there sufficient merit to the space-based solar power concept to merit further study?” During the study we observed that there are clear trends over the last 35 years that indicate that related technologies are rapidly advancing in ways making the business case for space-based solar power more viable over time. From this we concluded that yes, every aspect of space-based solar power deserves a deeper look.

    Chuck Lesher (Continued): So, you see, we do not have design or construction methods worked out. Those will be part of later studies…and most likely will be predicated on empirical data collected during experimentation or concept demos that will point the way ahead. You are to be commended for your environmental concern regarding beam safety. I share this concern fully. Let’s keep in mind that SECURITY DEMANDS CLEAN ENERGY because developing the ultimate energy source (whatever that might be) is worthless if it ultimately destroys our food supply, floods the coasts, or causes real physical injuries–as most people now believe carbon-based fuel consumption is doing. Yes, this needs to be a very key part of future studies on this issue. There is cause for optimism…we are already awash in microwaves since this is the medium that carries most cellular phone signals and many (if not most) point-to-point broadcasts here on Earth. The risk appears very small, but as I said…environmental safety is a central issue for SBSP. I do not want to be dependent on any single source of clean energy, so we’ve strongly advocated that SBSP be part of a mix of other sources. Economics will likely drive the balance between sources, but we must hedge all bets by developing as many clean energy sources as possible. The Moon always comes up in these discussions, and Moon-Based Solar Power has some very aggressive advocates. I am very confident that we will also develop the Moon for solar energy (first for use on the Moon, then for broadcast to Earth), but developing the infrastructure on the Moon to do that is far more formidable than building and fielding SBSP systems from Earth–at least initially. In the later part of this century or the next I believe most of humanity’s spacefaring activities will be conducted from the Moon simply to take advantage of the very preferable low gravity situation that makes access to orbital space very easy by comparison. Lastly, you should write a novel about SBSP. Start in the future with SBSP already on line and doing great things for humanity. Then back up and tell the story about how it came to be. Throw in some international intrigue and a love story and you’re done! Best seller for sure!

    Dan Lantz: Thanks for explaining how your thoughts have evolved regarding the thin arrays. I find this very helpful in my education and I’m sure others do as well.

    Edawg: Preventing asteroids from causing extinction events on Earth is of special interest to me (and I hope to all of you out there). Setting aside faith-based explanations of the end of the world, I can say with complete mathematical certainty that over time many asteroids will hit the Earth. Some will be big enough to cause damage, and some will be big enough to destroy the biosphere beyond human habitation. Of great concern is that we have only rudimentary systems to detect such threats and no capability to deflect them whatsoever. I find Apollo astronaut Rusty Schweickart of the B612 Foundation to be brilliant and convincing on this point. He has done considerable work to advance awareness of this issue and proposes a few solutions that I personally think should be looked at very seriously. You can learn a great deal about this on the Spaceworks Engineering Incorporated website that is dedicated to planetary defense. There are no gun launch systems in existence, although there are many who advocate for such systems principally as a means of cheap access to space. As for your idea of “launching a nuke at 8kms at an incoming asteroid fragment that (is) already hitting the atmosphere” By then it would be too late, and you’d be setting nukes off inside the atmosphere. We’ve got to find better ways.

  48. Kevin Reed said


    Laser +PV could be included as a “Grid” connected type WPT (Wireless Power Transmission)but it is not a money maker for start-up SBSP. A start-up commercial SBSP enterprise requires the return on investment (ROI) found in current communications satellites and Satellite TV. As it is total worldwide manufacturing of all solar cells, everywhere, is 1.29 GW Gigawatt per year and solar cell manufacturing for GW scale space solar arrays to make laser + PV or microwave “Grid Connected” space solar arrays at energy generation cost parity does not exist.

    This means that commercial SBSP start-up also requires something that can succeed commercially at the Megawatt Space Solar Array level. This narrows the field to WPT end user device recharge from SBSP in the MW scale. This is not bad as 1 MW beam down of a uniform,low level ambient microwave field in a metropolitan area can use WPT to charge 1,000,000 cell phones in the beam down area.

    This is 1 million cell phones at 1 Watt hour each recharge with a likely $50 monthly service contract attached if WPT phone service contracts were priced at the same level as normal plug-in recharge cell phones. 1M WPT cell phones should then earn $50M gross income monthly. $600 M per year from a 1.2 MW Space Solar Array for Early Commercial Demonstration of SPS and this SPS will last at least 50 years using consecutive deployment arrays. Lots-o-cash there at $600M per year from an investment only a few times larger than a current SOA communications satellite and space launch.

    You can’t recharge end user products with laser + PV so that leave Laser out of the picture for commercial star-up SBSP. Laser + PV will of course be demonstrated with the microwave technologies as demonstration of future GW “Grid Connected” power generation systems and specialized use of laser + PV at the MW level for Lunar or in space missions.

  49. Dan Lantz said

    Chuck Lesher #43:

    I have said in the past that the biggest problem is the (physics-ignorant-irrational) fear of microwaves. I still find this to be true. People will believe in the non-supported claim far before the proven claim because they are CRAZY!

    #45 Alienthe:

    Thanx for confirming how easy it is to assume the impossible!

    Coyote #47 (yos):

    Thin/Sparse arrays: This whole topic is only important to microwave system starting/testing. Full system (Solar Power Satellite/SPS or Lunar Solar Power/LSP) will need many transmitters, so minimum size will not matter. However(?), it may mean that visible/ultraviolet light phased arrays are off in the future.

    Coyote (Chuck Lesher):

    “The Moon always comes up in these discussions, and Moon-Based Solar Power has some very aggressive advocates. I am very confident that we will also develop the Moon for solar energy (first for use on the Moon, then for broadcast to Earth), but developing the infrastructure on the Moon to do that is far more formidable than building and fielding SBSP systems from Earth–at least initially. In the later part of this century or the next I believe most of humanity’s spacefaring activities will be conducted from the Moon simply to take advantage of the very preferable low gravity situation that makes access to orbital space very easy by comparison.”
    Instead of re-inventing, as they say: How about starting two new lines of blog: One in which only those who have read at least one edition of G. K. O’Neill’s “The High Frontier” can contribute, and an even more esoteric one in which only those familiar with Dr. David R. Criswell’s specifically exceptional correction to O’Neill’s basic concept (that “Space is the Place”), that is, UNLESS YOU NEED SURFACE AREA, can contribute. Claiming to be familiar will focus the mind!
    “developing the infrastructure on the Moon to do that is far more formidable than building and fielding SBSP systems from Earth–at least initially.”
    Assumptions like ‘”fielding SBSP systems from Earth” is obviously the way to start’ are EXACTLY what I have been trying to QUESTION for over 30 years now! When I tried to talk to the “Mars First/Mars Society” people about this (starting in the late 70″s), they tried to exclude me from the meetings, or “patted me on the head” as impossibly naive. Now, they are wishing we were already on the Moon, so their artificial gravity/radiation shielded Mars express craft could be almost ready to go!
    When I tried to talk to the Space Station (now aka ISS) people in the early 80’s, they said that building the basic structure from lunar metals was way too far out to consider. $100,000,000 later, they are still launching structural metallic components from Earth!
    Now, as I talk (again) to Solar Power Satellite (SPS) people, they don’t want to wait for lunar resources to be developed, and certainly don’t want to hear that the Moon IS the best SPS!
    Get the picture?

    Coyote (Edawg):

    Interesting work reported in recent NYT Science Times: Look at washes along coasts, then triangulate into ocean to find source of waves: Deep sea crater! New estimate of big asteroid impact: every 5,000 to 10,000 years, as opposed to every 500,000 to 1,000,000 years based upon possible candidates observed. They must be coming in from deep space directly! Get on it now! The very same tech needed to deflect large asteroid/comet can be used to capture small asteroid/comet for O’Neill style L-5 etc use. Time to do it!

    Neil #42:

    Perhaps putting rectennae on balloons is great idea! Rectennae need not accurately “see” source of power, so need not be stable/large as transmitters do. Especially in North/South locations, they would avoid “twinkle” from atmosphere.

  50. Alienthe said

    @Coyote Post #47

    Preventing asteroids from causing extinction events on Earth is of special interest to me (and I hope to all of you out there).

    Have you considered dual use of SBSP? A microwave power downlink could also work as part of a solar system scaled radar system and given the power of it I am sure we should be able to map out the planetary part of the solar system (not sure if we could get anything meaningful as far out as the Oort cloud or the Kuiper belt, would be an interesting question in itself).

    Should an uppety rock be found it might contain enough ice for us to literally boil it in a microwave beam or an optical beam. With less ice it might still be enough that the matter jet from the object will deflect it from crossing Earth’s orbit.

    This too could be a means for funding.

  51. Hubert Davis said


    I really like your comments of Oct. 27, item 47.

    Certainly we do not yet have a design, certainly we will need every source of clean energy we can acquire. Certainly we need to begin modestly and grow as we learn more. Thank you for including some TBD use of our Moon in your report.

    What is important is that your study found no “show stoppers” and you added greatly to the credibility of the concept.

    Now, what we need most is a project plan for the next ten to twelve years — concentrating upon answering the basic questions identified in your report and reducing the granularity of vital data.

    Additionally, we need to demonstrate key aspects to enlarge the population that is clamoring for a (or rather this) solution to the truly desperate energy situation we now face.

    Congratulations to you and your helpers on a great job of assembling a coherent report.

  52. Edawg said

    ~Coyote thanks for the link,I know Rusty is heavily in the anti-nukes encampment.And i think that any planetery defense system should have several back up stages.BTW i was wondering if this really happened the day of closest approach a metorite hit a mountain in the middle of Norway and another one hit the moon(not to mention we had a FEMA tsunami exercise around then.But i cant find the websites anymore :(…

  53. Neil Cox said

    Hi coyote: I sort of disagree with what you told Chuck Lesher. We need to get into the details to be sure SBSP is feasable, otherwise we may not discover a show stopper until it is half built. I suggest a thread on testing the thin film photovoltaic panels at the ISS, which can make good use of a few extra watts. Likely the thin film manufactures need a gaurentee that DOD will buy a megawatt of their panels before 2009, and a bonus if the panels function in spec for a year on the ISS. Likely DOD has already provided insentives to the laser diode manufactuers to increase production of space rated laser diodes.
    We can have several threads on various hardwear options for the SBSP and the vehicles that take the components to LEO = low earth orbit. Likely more distant orbits can be discused later, but we can have threads for Earth’s upper atmosphere, in case LEO proves too costly. The rectenna and the laser receiver also need discussion, plus how we get the energy onto the local grid at 2000 volts 60 hertz ac or more voltage. As far as I know, this is largely untested, except small scale.
    I agree, we don’t need to get into construction of SBSP on the moon until we have demostrated that it sort of works from LEO and/or supported by very high flying balloons.
    My guess is the first rectennas need to be about one square kilometer and the laser receiving sites almost that large as we may have to go back to the drawing boards to get the beam as narrow as is desirable for your military applications. If narrow beams prove elusive from LEO orbit, this needs to be corrected before, we make hundred times wider beams from GEO. Increasing the beam power is also likely to widen the beam, at least a little. Stars Wars = Strategic Defence Inititive, likely has this data, but accessing it may be difficult, due to being highly classified.

  54. abecker said

    A couple of general comments to the admins on this group:
    1. Thanks for this! This is a great cause and you are making a great effort!
    2. you should allow people to message you directly and privately
    3. I would ask entrepreneurs to look at components of the SBSP like efficient solar, wireless power transmission, robotic assembly & manufacturing etc. I encourage anyone with an idea for a business that might contribute to clean energy to look at and contact me if you are interested in entering a business plan into the competition! abecker – at –
    4. Keep contacting your representatives!

  55. abecker said

    One more thing you guys should really have a message board!

  56. Neil Cox said

    Alienthe #50: Radar pulses have pinged the planet Mercury about 100 million kilometers away, so with more power from a very large SBSP, smaller targets and/or farther should be possible, but not much farther as radar range decreases as the 4th power of the distance. We can send out coded pulse bursts as the microwave transmitting antenna swings across the solar system for perhaps ten minutes. We can then use many radar receiving sites to look for the echos 24/7. Most will return in a few minutes, but we might be surpriesed to get an echo back from the Oort cloud weeks later after traveling a million times a million kilometers. This way we only interupt delivery of the power perhaps ten minutes per month to repeat the the long string of coded pulses. Likely the SBSP that will transmitt from GEO with the narrowest beam yet produce by humans. Narrow means the transmitting beam has very high gain = the most powerful pulses ever sent long distance. It also means the data has excellent resolution in both direction and distance. Neil

  57. Alienthe said

    @Neil Cox #56
    Oort cloud is about 1 light year out, I would be amazed if we could get a useful reflection of objects there and reflection time would be more than just weeks.
    In the Kuiper belt we find “2005 FY9” which is big (ca. 1500km diameter) and quite a way out (ca. 40 – 50 AU) about 300 – 400 light minutes which would not strain patience too much. It is a while since I worked on microwave equipment, not sure if we can get any readable reflections off such an object.
    “Eris” is nearly the same size but 40-100 AU out.

  58. Neil Cox said

    I would have typed Kuiper belt instead of Oort cloud, but I did not know how to spell (or pronouce) Kuiper. (technology forum) has some gustimates of the specs of the COIL laser mounted in a Herculies cargo aircraft: The laser weighs 6 tons, 20 tons, including auxillary equipment. 100 kilowatts pulsed oxygen-iodine laser, range 20 kilometers in atmosphere. Spot size as small as 4 inches = 10 centimeters. If we scale up 1000 times to 20,000 kilometers = about the solar synchonous altitude, we get minimum spot size, 10,000 centimeters = 100 meters = about 8000 square meters = about 10 kilowatt per square meter, 20% gets scattered = one watt per square centimeter = ten times the maximum allowable leakage from microwave ovens = slightly dangerous to humans. 8000 square meters is too big to power vehicles or for most tactical military applications, but likely we can narrow the beam by the time we build a SSP at solar synchronous altitude. From LEO = low Earth orbit, the spot size will be small enough to propel moving vehicles, except when the satellite is close to the horizon. We still need a laser that can produce 100 kw plus in at least 10 minute pulses for a demonstration SSP. COIL lkely produces pulses much less than one second long, and needs to be rebuilt after about 100 pulses. We can presently do this with laser diodes, but we need about a million diodes. The technology is improving rapidly and will likely prove adequit if DOD promises too buy lots of laser diodes, with great specs. Neil

  59. Andreas said

    On 40, 41, 44, thinned array curse:

    The thinned array curse is indeed a bummer. But perhaps there is a way out in the form of three dimensional phased arrays. I have not found this treated mathematically, but presumably (and I will make this assumption), the transmitters in a phased array do not all have to be in the same plane, but could be distributed as a three-dimensional cloud. The thinned array curse would require the cross-sectional density along the beam axis to be at least one transmitter per square wavelength. This should be easily achievable, with a sufficiently large array.

    I think this is an extremely important opportunity for SSPS, because it would permit building space solar power capacity as a swarm of small, identical spacecraft instead of large, rigid structures. Each craft would essentially consist of one solar power panel coupled to a very simple microwave transmitter. I am thinking around one square meter and a kilowatt, but scale is of course open to adjustment. The transmitters of the swarm would operate in concert as a giant phased array, beaming power with the same efficiency and precision as a very BIG rigid antenna would. The swarm could be kept together with a minimum of propulsion, perhaps achieved by a combination of solar light pressure and “air” resistance on the panels, or by electromagnetic forces between neighboring craft, produced by coils or electrostatic charges.

    The individual craft could weigh in at mere kilograms, in principle. They would be real easy to build and launch, and a small swarm could demonstrate all of the concepts, except tight beam focusing, which is mathematically accessible. An initial demonstration could be ridiculously cheap as space projects go. This is important, given the uphill struggle faced by SSPS proposals.

    The system would be naturally fault tolerant and easy to maintain by launching replacement units regularly. No human presence or space infrastructure would be needed, and any old launch vehicle could be used, although high volume would still be needed to get a minimally useful capacity up.

    The ultimate end-product could be an orbiting ring of billions of solar micro-satellites capable of delivering Gigawatt power beams around the world (and space) on demand, instantly.


  60. Dan Lantz said

    Andreas #59:

    My “gut” feeling is that elements have to be in pretty much a plane, or there will be diffraction edges all thru the volume. I feel your pain! Don’t give up if you see ANY hope!

  61. Andreas said

    Dan #60: Actually, I think I can show quite easily that elements do not have to be in a plane, that swarm arrays work efficiently, and that there is no conflict with the thinned array curse.

    Imagine starting with a conventional array, a square grid of, say, 1000×1000 transmitters. Consider a point far away, in the far field, such as the center of the Earth rectenna. The beam is maintained by phasing each transmitter such that complete constructive interference occurs in the target direction.

    We know this works, and is efficient. Now consider two modifications:

    1) Swarm array: Move each transmitter randomly along the beam, such that they spread out along the beam to form a three-dimensional swarm. Then, adjust the phase of each to regain complete constructive interference in the target direction. This will not reduce the beam power at the target, because the number of transmitters remains the same. If the power at the target is the same, the only way total transmitted power could be reduced is if the beam were narrower. This, however, cannot happen because it would violate the aperture law, the original beam was already the narrowest possible. Thus, no power is lost by spreading transmitters out along the beam axis.

    2) Thinned array: If instead of moving transmitters along the beam, you move them transversally to increase the diameter of the array. Again, the power at the target remains the same, but now the beam becomes narrower, because of the increased aperture. Thus, total beam power is reduced, which is known as the thinned array curse.

    From the above I conclude that 1) a swarm array of the right density will perform just as well as a regular array, and 2) this does not conflict with the thinned array curse.


  62. Dan Lantz said

    Andreas #61:

    To avoid thinned array curse, you must keep all members of swarm in exact position (assuming 1)). Why is this better than plane?
    I still “think” each element must have next door element to capture or redirect side lobes, but you may be right about moving them along single beam axis. However, most designs have many more rectennae than transmitters, so that would only be possible from (nearly flat) plane.
    I hope you are right!

  63. Jim said

    Is it intended or expected that there will be a formal (or informal) response to the Study and its analyses and recommendations by the NSSO or other government organisation?
    Recommendation #1 and other elements of the Study point to the need for further study and analysis, including further business case development – is any entity assuming responsibility for undertaking this further work ?
    These are the immediate next steps and if we are serious about SBSP they are critical.

  64. Edawg said

    there needs to be international business regulations for new space companies.Most of the technology needed has National defense written on it in big giant letters.Without regulation you run the risk of having space pirates.I think there needs to be a new UN Outer space Treaty but the Pentagon may not want that.

  65. Coyote said


    The technical discussion here is outstanding. You are raising excellent issues that testing must resolve.

    Edawg (64): I am speaking only as a private citizen here, so please do not misconstrue my comments as “official” by any stretch of the imagination…please extend to me a degree of academic freedom and do not cite me, please. I speculate that the current administration–and hence the Pentagon–sees great potential in space, but like the Internet, they are hesitant to constrain its natural development with more regulations, laws, and treaties. That said, it is my opinion, based on numerous discussions with various space lawyers and space entrepreneurs, that the commercial sector would benefit greatly by additional international space laws that clarify many questions in current laws and treaties regarding licensing, liability, indemnity, registration, and various on-orbit and lunar property/mineral rights issues. Such clarification would create greater certainty and predictability among the investors, bankers, insurers and customers. That would probably be good. You mentioned piracy. We are already experiencing incidents of satellite signal and bandwidth theft. The Chinese have accused the Falun Gong of such attacks on their satellites, and we tend to believe them. I’m not sure any laws or treaties will prevent such acts.

  66. Edawg said

    I am all for acedemic freedom I just think that disruptive polices regarding National Security and Space Exploration should be changed.The Terrestrial Planet Finder is a good example of this(?) And so is Blackstar.Some International laws would help out alought with space development there is to many variables and uncertainty as you realize,traditional economics does not apply to the current space market in any way shape or form.Calculating your business expenses x+y=z with a timetable goes out the window.I wonder if the wild west model will apply to space colonization?I dont think six-shooters do so well in pressurized environments.

  67. Hybrid said

    I love solar power I think over the next few years it’s going to be exploding even more… as performance of solar panels goes up people are going to be adopting it everywhere they can… after all it’s free energy 🙂

    Some things I’m looking forward to are more effiecient solar panels, about 5 years from now when I buy my house I want to make sure I can power the entire house and my plugin hybrid all on solar power… I’m also hoping that solar paint will finally be in customers hands… having your entire house generate so much electricity and maybe even being able to sell it back to the grid would be amazing…

    BTW here is more great Solar Power information, there is quite a few amazing new solar projects being done right now… it’s really great to see so much focus on alternative energy.

  68. Neil Cox said

    Hi Hybred: Cost per square meter is likely more important than efficiency for the average homeowner considering their own solar power. The power companies need to encourage do it your self co-generating. At present they require an expensive inverter which is poorly adapted to providing emergency power when the power company is blacked out = not providing power. Co-generator means the power company provides your power while your system needs repair or maintenance. Co-generator also means you can start out tiny and expand your own system, later. For much of the USA, a very steep south facing roof improves the output especially in December. SW facing is better for the power company as it puts energy on the grid during the first part of peak demand when the wholesale price of electricity is high. Perhaps we should mandate (in locales favorable to solar power) new house and building contruction with a large area of steep South or SW facing roof, even though this may not be pleasing to the eye = non symmetrical. Vertical walls are too steep for best results in June when the sun is almost straight up at 1 PM daylight time. Roof over hang will shade the panels.
    For SSP we need large production of the type of solar panels we will install in space and watts per kilogram is more important than efficiency. Perhaps price support is the way to pump up production of the type of panels we will need. Neil

  69. It’s nice to approach for the green and infinite solar power ….

  70. mike said

    We need energy !

    We cannot rely on oil forever as it is not renewable. The efficiency of Earth based wind and solar are too low and take up to much land.

    Space-Based Microwave Power seems the most logical.

  71. Space-Based Microwave Power

    If not the US – then I am sure another country will develop it.

  72. Oppopaype said

    I agreed with you

  73. scot4space said

    As a space enthusiast I would like to suggest a slightly different approach to Space Based Power Satellites that would enable it to grow from pilot plant to full scale use and generate income along the way. The basic concept would be a constellation of smaller self contained microwave based SBPS with all the functions of a larger one, ideally they would be launched on a single current launcher such as an Atlas V, or a multiple launch as standard modules and assembled in equatorial orbit using a space tug. The pilot SBPS then could prove out the concept and resolve any teething problems and provide power on an intermittent basis, as more SBPS are launched the gap between satellite passes would be reduced and enable more power to be provided . Ultimately you would use a space tug to place SBPS into GEO orbit, with a constellation of many SBPS focussing onto a single rectennae on earth, you would also have the option of providing power to multiple locations from the same constellation. To drive costs down you need long production runs of launchers as well as satellites, you also need to be able to generate income relatively early on in the process to justify further investment, though being a space enthusiast I’m not conversant on the technical issues. Apoligies in advance if this has already been suggested

  74. It is extremely interesting for me to read that post. Thanks for it. I like such topics and everything that is connected to this matter. I would like to read more soon.

    Bella Swenson

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