Space-Based Solar Power

a public discussion sponsored by the Space Frontier Foundation

Trade Spaces

Posted by Coyote on August 1, 2007

Taking the long view, we don’t need to rush to answer every question immediately.  

 

There are some wide open trade spaces that need to be examined and experimented with much more closely.  Here are some examples:

 

Energy collection:  What method is best; photovoltaic or solar dynamic collection?  Within each method, there are various designs, for example, using the photovoltaic method, which technique of collection is best; large flat arrays or sun towers with concentrator mirrors?

 

Power beaming:  What method should be used to broadcast to the ground; microwave or laser?  Each has pros and cons.  Microwave is certainly safer, but lasers require a relatively small receiver by comparison.  Microwave might be best for permanently supplying a city with power, but laser might be better for broadcasting to a location that needs a rapid set-up time…such as part of a disaster relief effort.

 

What are the other major trade spaces???  

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31 Responses to “Trade Spaces”

  1. Other trade-offs I’m aware of:

    * geosynchronous orbit vs. closer to Earth – geosynch is geometrically easier and assures steady power supply from just one satellite, but the distance is very large; closer orbits work for GPS, why not power?

    * flat photovoltaics vs. concentrator systems: you may get by with lower mass and cost using a mirror or fresnel lenses to focus light onto the electricity-generating elements even if they’re photovoltaic, but this adds system complexity and stricter pointing requirements

    * thin-film photovoltaics: lighter, but may not last as long?

    * rigid structures vs. more flexible: lighter mass if flexible, but can the geometry requirements be met?

    * launch everything from Earth vs. try to make use of space resources (moon, asteroids) – space resources adds a huge additional layer of complexity, but may be worth it if Earth launch costs can’t be significantly reduced.

  2. Louise said

    Hello Coyote, thanks for the talk July 21 at Newspace. (I was the one in a spacesuit.) This is a fun and useful blog. Photovoltaics have the advantage because they are solid state and we have experience at ISS building big arrays. Microwave or laser will probably both be used, depending on whether the end user is a city or unit in the field.

    If science can isolate a micro-black hole, we’ll need just one power satellite with no solar panels at all.

  3. * geosynchronous orbit vs. closer to Earth – geosynch is geometrically easier and assures steady power supply from just one satellite, but the distance is very large; closer orbits work for GPS, why not power?

    Big difference with GPS – it is a broadcast system, not a system that has to maintain a beam to a specific point on the Earth (which is much, MUCH, harder)

    * launch everything from Earth vs. try to make use of space resources (moon, asteroids) – space resources adds a huge additional layer of complexity, but may be worth it if Earth launch costs can’t be significantly reduced.

    If launch costs can’t be reduced by orders of magnitude, how do you propose we are going to even begin the process of mining or extracting resources from space…? Such an infrastructure depends on cheap access to space to begin with.

  4. Edawg said

    can the thin flat photovoltaics take high g acceleration?

  5. James Kielland said

    It would seem as if the critical question in this venture isn’t lift techniques nor the details of the solar collectors. The first critical thing to do would be establishing safe methods for beaming power down, assessing the environmental impact, and developing safety protocols. As I mentioned in another thread, I think this is best done by first trying to send terrestrially generated power up and then direct it back down to particular locations. There would be a world of data to analyze from such research, which could occur concurrently with efforts to reduce lift costs.

    This would also immediately address the Pentagon’s most pressing concern – delivery of power to precise, remote locations – without getting caught up in the rather monstruous technical and economic problems of lift and construction.

    It would also seem that the political viability of this would be based on changing people’s perceptions of terrestrially generated solar power before we could get people excited about space generated power.

    Perhaps the best way we can bring about space based solar is to first build a 100 square mile solar farm in the American Southwest. Once that is done and we’re quite certain that we can safely transmit power up through the atmosphere and then direct it effectively somewhere else, it would seem that popular (and congressional) enthusiasm would increase markedly.

  6. Coyote said

    Edawg: Yes, thin flat photovoltaics can take the G-forces of launch…provided they are stowed properly.

    James Kielland: I am totally there with you regarding the need to ensure safety. There is some good news. Much of the broadcast risk has already been retired with great success. First, we are broadcasting microwaves inside our atmosphere all the time. We are very good at it and have a few decades of experience doing it. For space-based solar power it is really only a matter of picking the best frequencies and signal density from a safety standpoint. Secondly, we have significantly advanced the art of spot-beam communications from geostationary birds in the last ten years. This same technology can readily be adapted for microwave broadcasts…But I completely insist on start-to-finish safety assessments before we proceed and then really shake-out the early systems we field to make absolutely sure that we fully understand the environmental impact of these systems.

  7. allen said

    Photovoltaics. Technological sophistication trumps mechanical complexity.

    It’s obvious that virtually all the work to build power sats is going to be done by autonomous robots. Working in the unforgiving environment of space is a complex and expensive enough activity for a single, highly-trained person, how many thousands of construction workers would have to be employed to build multi-square mile structure of any kind? It’s not just the lift costs that would have to come down several orders of magnitude for power sats to make any kind of sense, virtually everything associated with working in space would also have to come down a great deal.

    Solar thermal is mechanically much more complex then are photovoltaics. Since it’s a heat engine you have to collect the heat, extract power from it and dump what you can’t use. To do all that heat transportation you use a working fluid. To power a “steam” turbine. To spin a generator. Which then has to be cooled and stored so you can do it again.

    Moving the fluid from place to place requires piping which needs fittings of various kinds to attach to various items. You’ll need different types and diameter of piping/fittings for different purposes; condensate doesn’t require large diameter nor strength but high pressure vapor from the solar collector will have to be big and strong.

    Much of the work will be repetitive but complex. That’s not the sort of thing you want people doing here on earth much less space.

    Robotics has come a very long way in a very short time, evidence the DARPA Grand Challenge, but I think it’s asking a lot of the robotics community to produce an autonomous plumber-bot.

    PV, by contrast, would be pig simple to assemble. Designing PV modules that just snap together shouldn’t be that much of a challenge. It ought to be possible to incorporate structural elements into a PV module so that relatively simple robots could autonomously assemble the entire solar array of the power sat.

    So that’s one vote for PV over solar thermal.

    Whew, that was tiring. Where’s the pizza?

  8. Dan Lantz said

    Arthur (1): *#1 (distance) Interferometry is the creation of apparently large antennae from small pieces scattered around. If the signal’s phase is saved or controlled, the resolution (not the power!) of the overall system can be made to look as good as if one large antenna, as big as the pieces are apart from each other, was being used. Several SPS’s could co-operate to send very precicely aimed beams from very far away. This has been done (send and receive) with microwaves for decades, and large telescope pairs are more recently able to receive visible frequencies this way. The Moon is so large that this technique makes the Moon “appear” quite near the Earth, should one have the audacity to put scattered solar cell powered microwave transmitters there!
    *#4 (rigid structure) If you build on the Moon, no large structure is required (other than the one supplied!), only small stands and the like.
    *#5 (exoterrestrial resources) (we don’t have any “extra” here!) If anyone interested in this topic has not read Dr. Gerard K. O’Neill’s “The High Frontier” (1977) (2000 3rd ed.), now would be the earliest you possibly could!
    http://www.ssi.org/
    is his baby. Very big picture analysis. Main oversight is to see SPS as initial project to get things moving, and not realize that the Moon, rather than something constructed from the Moon’s material, IS the SPS. Dr. David R. Criswell figured this out by 1990. Search “Criswell LPS” and also “Criswell LSP” for much of interest.

    Shubbar Ali (3): *#2 (comment) Both all-launched and some-or-more-exoterrestrial derived systems benefit from cheaper launch. It is probably a fairly fixed ratio of advantage no matter what the launch cost is, even if nearly free. Also, not launching at all, ie, leaving the locally manufactured solar cells on the Moon’s surface, removes weight considerations from the process, can focus on cheap, safe and good. Two kinds of launch advantage to exoterrestrial resource use, which may seem the same at first: Direct exoterrestrial resource use, for example radiation shielding (notice: geosynchronous orbit is not protected by the Van Allen belts!), saves launch costs simply. Exoterrestrial raw material use, for manufacturing, is more exciting, as it implies a FACTORY being launched (or itself being built at least partially from exo material), which then produces continuous product, none of which has to be launched. This is O’Neill’s “bootstrap” process.

    Allan (7): Telebots with some control from people over the ‘net will be simpler at first, as long as you don’t go too far away, eg. Mars. Building on Moon largely removes weight (mass, actually) considerations, so allows more options, but I like PV too.

    All: I’ve been talking this up for 30 years now, and the BIGGEST problem is perceived microwave danger. I studied physics and know how impossible such a danger is, but it needs careful public relations handling.

  9. shubber said

    I’ve been talking this up for 30 years now, and the BIGGEST problem is perceived microwave danger. I studied physics and know how impossible such a danger is, but it needs careful public relations handling.

    IMHO, if the conventional wisdom is our biggest problem with getting SBSP going is a PR/perception problem, then conventional wisdom is seriously misguided. We still have major issues that are technical and economic in nature, and many revolving around the fundamental issue of cheap reliable regular access to orbit in order to even build this thing.

  10. Dan Lantz said

    Shubber (9): “the fundamental issue of cheap reliable regular access to orbit”
    O’Neill’s insight was to avoid launch from Earth as much as possible, seeing as clearly as you the problems with launch. My concern is that the current study will repeat the past study in which exoterrestrial resource use is considered too “far out” to consider, and then conclude that launch costs make SPS impractical!

  11. shubber said

    My concern is that the current study will repeat the past study in which exoterrestrial resource use is considered too “far out” to consider, and then conclude that launch costs make SPS impractical!

    IF the study fails to conclude that exoterrestrial resources are too costly, then someone wasn’t being critical enough in their analysis. Just assuming that the launch equation will be solved in such a way that we don’t need to focus on it as the first and most important stumbling block to overcome towards building lasting sustainable infrastructure in space – be it SBSP, L5 Colonies, or a telescope on the far side of the moon, is basically just writing another powerpoint sci-fi chart.

  12. Dan Lantz said

    Shubber (11) : So read the studies and point out the flaws! You will then be adding info to the system!
    Search “Criswell LPS” and also “Criswell LSP” for much of interest.

  13. Charles Miller said

    I am with Shubber on this.

    I don’t need to read the Criswell studies.

    David Criswell himself publicly acknowledges that his LPS will cost at least $500 BILLION.

    Personally, I think Dr. Criswell is off by an order of magnitude, which is typical of the estimates by engineers who are advocating their pet engineering projects. But, let’s assume his cost estimate is accurate. Let’s take him at face value.

    Nobody is going to put up $500 BILLION to develop the LPS system, based a series of risky assumptions (all of which might kill it, or make it much more costly.)

    Congress is clearly willing to fund some clean/renewable energy investments. They are NOT going to pick one particular solution over any other. They are going to fund a portfolio of investments (wind, ground solar, advanced fission, fusion, clean coal/carbon sequestration, energy efficiency, hygrogen (as a transportation medium), fuel cells, various forms of ethanol, etc.)

    SBSP is not going to receive anything that is beyond reason, and out of whack, with what the other alternatives are going to receive.

    Moreover, you need to read your history. Dr. Gerard O’Neill testified to Congress on SPS in the early 1980s. In response to a question from a Member of Congress, Dr. O’Neill answered that SPS would become economical by using lunar materials.

    He was laughed at. Dr. O’Neill is technically brilliant, and he probably deserved to win the Nobel prize in physics, and is one of my personal heros … but his politically naivete killed SPS in the early 1980s.

    The concept of asking this country to commit to financing a $500 BILLION system, that will be build on the Moon, is totally naive in today’s environment. It will be laughed at. If any national leaders looks like they support this idea, they will be the subject of late night talk shows, and the Daily Show.

    Now, maybe — and I mean maybe in the VERY long term — the LPS will eventually come into being. But it will happen as a 3rd or 4th generation version of Space-based Solar Power.

    Alternatively — if you don’t care about politics — try to think of this like a business person.

    We did not get to the Pentium 4 microchip over night.

    We started with the 8080, then the 8086/88, then the 80286, then 80386, then 80486, then the first generation Pentium. Several generations of Pentium later, we had the Pentium 4.

    Proposing to build the LPS now is the equivalent of proposing to build the Pentium 4 in 1972.

    Coyote has said we are going to “Crawl, Walk, Jog, Run”. This is what he is talking about.

    - Charles

  14. Joe Russo said

    First of all, off the top of my head, pick one to start with and design for others too. Use the design process; see my short article on Invention Development at:
    http://blog.360.yahoo.com/blog-llD_u30ib6NeG901eSdXWu2kD2A-?cq=1&p=124

    As for the current subject, I would suggest starting with photovoltaic methods at a geosynchronous orbit with sun towers and mirrors. I say mirrors because it might be less costly to replace mirror(s) that have been damaged by outer space debris rather than other collection devices. A “High Speed,” as they say in the Army, solar cell panel may be costly to keep replacing. Thus it also might help present a way to reduce investor risks.

    I would also consider a microwave technology with a modified beam. There might be a way to create long tubing to help to condense the beam. I will try to look at those design aspects in a month or two; however, I have an ISRU issue and some other projects pending. I would also leave an option to upgrade to laser. Since some people are fearful about what a laser can do, it might be best to reference the use of that technology to beam over to another station which has lost its collection capabilities for one reason or another. Then, the sending station can laser energy to the station that needs to beam the energy down. By the way, I use the word fearful, for I know how extreme people become with fear. That subject alone is a book I am working on. I have 25,000 words left to edit out of the 50,000 on the subject.

    Now, I think we should take this solar subject to a higher level. Building a solar farm on the Moon and lasering the energy to orbiting substations that step the energy down to beam to Earth is attractive. Maybe we could consider a larger distribution system, using the Moon or areas such as L5 (just a suggestion) as the larger initial collection point. This subject MIGHT create an image of more risk, but it may add more to science fiction books. In the meantime, if we have room in the final report, this could be mentioned; however, as pointed out by Charles Miller, let us not become politically naive.

    Also, in the design, we might want to look at a rapid Upgrading Platform with Enhanced Modulation (UPEM). That is present rapid set-up time with attachment models to the main platform. Yes, UPEM since we have a growing acronym vocabulary in this subject.

    I think that a microwave system will present capabilities in terms of operating for a long time to best present the permanent supplying of a city with power, etc. Again, as we know, we need to show big money potential returns too.

    Second, in relation to ISRU, some people appear to not understand that this solar power issue is also part of the ISRU too. In relation to the ISRU of lunar technologies, I do not buy into the utopia that some suggest. I think, to be safe, we need to build the first items on Earth, and then find ways to replace the items with other methods. It might not be to the best interest to put lunar development first, however, based on the people I have not seen commenting in this study, I tend to think that is going to happen. We will see more indications the first or second quarter of next year.(foot note 1) From what I have seen, the ISRU community is at least 10 years behind and it has clashed with the Mars people, sometimes in an unappealing manner which has been heart-breaking for me to watch. ISRU had been around even before the 60s.(2) Additionally, some of the ISRU people have not gained the understanding that less weight can result in no results. At 1/6th the gravitational field on Earth, why do some people think that a really light weight excavator will do the same job that a heavy bulldozer on Earth would do? Also, from my experience in the research, development, and manufacturing of mining equipment, the fabricators use materials that are as light of weight as possible in the first place. Many of the mines have to move equipment in and out of an entry that is five feet by five feet. As confirmed last year at an ISRU meeting, some of the things ISRU people are trying to do might be done with more simplicity and more critical thinking. Do not get me wrong, I am 100% to go on any ISRU as seen in my own work (foot note 2) and I do believe that one day as organizations like Lady Base One becomes alive again as the L5 region will also become prime real estate and a micro-black hole will become the next new weapon or defense. For clarity, I am not disputing making things with the less weight/mass as possible; it is the issue of efficiency and effectiveness too.

    My third point is more related to the business case: I have heard that some people are cautious about our efforts in relation to the disappointing expected growth of current terrestrial solar systems. However, one point to keep in mind is that it might be an unfair analogy because many of the terrestrial systems did not work because not enough trained staff existed to keep the systems going. Maintenance dropped off dramatically. This is another factor to consider in a positive manner to make as a side note to building a case. Since we want to increase education/technology programs in America, this can work hand in hand, for this needed technology is another pragmatic customer to the new work force. I recall reading a book in the late 70s titled Living in Space. It was related to things that we are talking about. The author predicted that the first work force in space would consist of a rush of 200,000 people world wide. I would image that, with the current robotic technology that we have now, that figure could be reduced, and fabrication enhanced. People would work six months at a stretch, and live on Earth for the other six months; as Earth takes its manufacturing to space, nature and forest habitat landscapes would be developed throughout the world.

    Question: Has any percent of the International Space Station been built using ISRU? I do understand this might be an unfair question, however, it does make me wonder how much do we want to present facts and less of a science fiction appearance.

    Using robotics to obtain materials from asteroids is something I have personally been pushing for since the 70′s. As many of us know, even though there is less issues about gravitational pull around asteroids, there are methods that can be implemented for people to mine from them. I do recall that the eyes of a few Congressmen and Congressional staffers sparkled when they became aware of the raw resources waiting for humanity on asteroids. Objections to the passing of the Commercialization to Space Bill started to become non-existent after a listing of the raw materials were provided. It would be nice to see that in relation to this subject too.

    My fourth point is related to military capabilities. Picture a group of military members who cannot finish their missions because of the hazards in the way. A modified system similar to the one used on the front of vehicles to stop bombs from going off can be applied to our platform. Thus, an emergency sweep of the land that is not harmful to life could be conducted, while aiding the military members to safely conduct their business. I have looked into that possibility without the gamming devices being too broad banned across too much land, but my access to the information I am seeking is limited.

    Lastly, related to my offering of assistance, since I have strong CAD and solid modeling skills, let me know if you need any graphical representation in your proposals.

    Foot note

    1 As noted by Arthur Smith “…pace resources adds a huge additional layer of complexity…” Now, on the other side of the coin in relation to ISRU topics, I understand that this area is about to dramatically excel; thus, this might be the time to get on that wave. For some of the people who keep referencing what we should have done in the past, that is the past, and I ask that we look back only to gain what we need to grab onto in reference to what is about to happen. Again, keep your eyes open to ISRU subjects next year; this will help people gauge a relationship of understanding of where the budget is going.

    2. Sine the 1990′s I have work on development of a ISRU excavating unit to use on the Moon, Mars and other bodies in space, development of a bucket drilling head device with multi-mechanical tool excavator, angular cutting tools used to replace bucket ladder technology, etc.

    Works Cited

    1. Invention Development http://blog.360.yahoo.com/blog-llD_u30ib6NeG901eSdXWu2kD2A-?cq=1&p=124.

    2. ISRU/in-situ http://blog.360.yahoo.com/blog-llD_u30ib6NeG901eSdXWu2kD2A-?cq=1&tag=in-situ which also references http://history.nasa.gov/monograph21/Chapter%206.pdf.

  15. Joe Russo said

    yes, that is Since the 1990′ … in the foot note 2. Good night!

  16. Edawg said

    Charles~Proposing to build the LPS now is the equivalent of proposing to build the Pentium 4 in 1972.

    LMAO! thats funny ,not to be offensive or anything..Im 20 my freakin xbox360 is about a million times more powerful than saturn V/Lunar lander/space shuttle/.And those were built in the 60s and 70s.I Learned about space from all those old dusty books in the library =)The question is how committed are we as a nation?

  17. Joe Russo said

    Edawg, thank you for understanding the point about what occurred in the 90’s, 60’s and before that and your question is an interesting one for a nation that is claimed by one group to be allegedly divided on some issues. Now, one can laugh all they want, but as I stated in another posting, many times it is not “whom” or “what group” did, said, or did not, it all matters on who states a case and pushes for it.

    At this point I had planned to all or most subjects like this one, however, COMCAST internet service dropped the ball on me again; this time I had to fix some hardware, and thus my postings might be a little late. Sorry. I am also starting to shop for a better internet provider.

    See you

  18. Dan Lantz said

    I was laughed at for suggesting that the Moon would HELP the manned Mars program in the 70′s, 80′s, 90′s and early 00′s. How they humiliated themselves! Bwaa-aaaa-aaaa (insert maniacal hand rubbing here)!

  19. Joe Russo said

    Dan!!!!!

    Are you talking about the entire group or just some certain members of the group? If it is certain members, please email me specifically so we can talk about this.

    Is your question or concerns really related to a question I have which I posted in another topic:

    What is the proof that the use of lunar resource will reduce the $ per kwh to the point that it competes with current energy production?

  20. Dan Lantz said

    Joe #19
    I’m specifically talking about those who LAUGHED at me, not those who honestly disagreed! I only now saw your other comment, and have already replied.
    Earth launched Mars plan had three main questions: (1) zero g for long periods, (2) radiation load, realizing that small shielding from pressure vessel makes it worse. Avoid the time and expense exploring these questions by starting with lunar supported plan (giving radiation shielding and “artificial” g), and you come out ahead, especially if either is a show stopper. I suspect radiation IS a show stopper, or there would be more howling from the “Mars first” people. Bone density ISS studies are pretty grim, too.
    (3) How much will the second Mars visit cost? The third?… Now the Moon starts looking like a very good place to start.

  21. Dan Lantz said

    Charle #13:
    I know that $500 billion is an absurdly low investment to solve the global energy need, but that is the estimate! I’m ready to kick some in myself!
    Joe #14:
    Altho “ISRU” is the official NASA term, it is so limited that Space Studies Institute people must be shaking their heads in disbelief. Only in very special circumstance, such as using the lunar SURFACE to provide solar panel SURFACE area, is the resource used where it is found. Most of the time, free space is the best place to process/use material, not where it came from.
    Keep up the engineering work!

  22. Joe Russo said

    Dan, thank you for the clarification, I understand the past references now.

  23. Joe Russo said

    Thank you for the clarification, I understand the past references now.

  24. Joe Russo said

    Dan

    Thank you for the clarification. Sorry my confusion. Sorry you were laughed at in the past. No one should be laughed at. Maybe this topic will start to unit more people.

  25. Joe Russo said

    In responce to #8 about sheilding:

    (Plastice Spaceships)

    Another way to address radiation:

    If radiation protection is an issue, please refer to this article by NASA about Plastic Spaceships
    http://science.nasa.gov/headlines/y2005/25aug_plasticspaceships.htm

    As stated in the article “…Most household trash bags are made of a polymer called polyethylene.
    Variants of that molecule turn out to be excellent at shielding the most dangerous forms of space radiation…”

  26. Dan Lantz said

    Joe #22:

    I’m proud to share being laughed at with O’Neill (#13), for saying the same thing essentially.

    #23:
    From plastic spaceships:
    ‘The Bottom Line

    The big question, of course, is the bottom line: Can RXF1 carry humans safely to Mars? At this point, no one knows for sure.

    Some “galactic cosmic rays are so energetic that no reasonable amount of shielding can stop them,” cautions Frank Cucinotta, NASA’s Chief Radiation Health Officer. “All materials have this problem, including polyethylene.” ‘(end quote!)

    By using lunar material, one CAN provide what would obviously be an unreasonable amount of shielding to launch from Earth. This is how you live in space! Approx 3 feet thick solid, very heavy. May want to leave transfer ship(s) in an orbit going near both Earth and Mars. You can even have “gravity” at the same time, but that is proportionally hard until ships get quite large.
    #8 shielding was actually talking about burying cable in lunar “dirt” as shield, instead of having exposure in geosync. Build and place solar collectors on Moon removes most mass considerations, can go for cheap and robust rather than low mass.

  27. Joe Russo said

    Dan

    I do not disagree with you and thank you for the reply. I am a big advocate of lunar material or anything related to new technology/resources to better the human race. My first college paper in the 80′s was on methods such as developing Lunarcreate as I opened a chapter of the L5 society, etc. Example of more recent work titled Excavating on Mars, Moon, etc. what is needed? found at http://blog.360.yahoo.com/blog-llD_u30ib6NeG901eSdXWu2kD2A-?cq=1&tag=bucketwheelexcavator

    I do understand the radiation shielding of lunar material and the thicknesses that are required. I also know that as some lunar material becomes smaller, its magnetic properties increase which could be a plus or minus depending on the processing systems and material handling methods.

    I just caution that we do not add more complexity to the first part of the solar power goal to the point we push off the fist construction of it way past 2040.

    Also, I would like to see the speculations of use of lunar material become more hard facts. If there is anything I can do to help that happen, let me know. If so, please email me directly for I will be off line for a little while.

    Thank you

  28. tqft said

    I hope someone is still reading this.

    Why only PV or solar heating?

    What I want to know doesn’t work is direct conversion to microwaves.

    Let me explain a little email me if you need an explanation of teh idea iXXXaXXXnXXXbXXXuXXXrXXXrXXXoXXXwXXXsXXX_aXXXu XXX@XXX yXXXaXXXhXXXoXXXo . XXXcXXXoXXXm

    Here we go
    let incoming solar radition fall on half-mirror surface – most radiation enters cavity, little bounces off.

    Exit modes of cavity are at microwave wavelengths of choice – use wave guides to carry exited energy to collimator to beam to ground.

    Essentially we build a large flat cavity resonator tuned to emit microwave radiation at our preferred wavelengths.

    One – simple (hopefully) design, manufacture and setup – you could almost inflate such a design in the surface material requirements allow it.

    Two – no extra exotic (hopefully) materials.

    Three – low losses on conversion the incident radiation “heats up” the “cavity” and stays there until it finds an exit mode at microwave lengths – no second/thrid stages to get to microwaves.

  29. Joe Russo said

    Hello

    A good set of links I found in my notes to share with everyone if they have not seen it already.

    National Renewable Energy Laboratory. http://www.nrel.gov/
    Colorado School of Mines has an outreach program. http://www.mines.edu/outreach/cont_ed/iipa.htm

  30. Neil Cox said

    Louise post 2: I presume we have been looking for a micro black hole closer than Jupiter. If there are any likely candidates, it is being kept secret. Likely we cannot detect micro black holes farther away than Jupiter. I suppose their signature is very short wave length gamma radiation. Can lasers be pumped with gamma radiation? According to a perhaps unreliable source, a good laser can illuminate a spot one billion Earth diameters (minimum) at a distance of one billion light years. Assuming linear: 1% of an Earth diameter at 1% of a light year. 1% of a light year is 100 billion kilometers = 10E11 so that represents about the maximum distance that we can use a laser beam to send energy to Earth, or Mars. The energy beam could warm Mars with the beam, releasing volitiles into the atmosphere of Mars, as part of terraforming Mars. Not likely something we want to do this century. If we take the term micro litterally, the micro black hole would have about the mass of Earth = one millionth of the mass of our sun, so we are far from having the technology to change the speed or direction of a micro black hole. Neil

  31. Neil Cox said

    I think we should set about 2015 as the date to have a demonstration SBSP = space based solar power in LEO. All the materials need to come from Earth, as moon and asteroid mining and manufacturing are unlikely to be significant before 2040, unless there is a secret program already in progress. The demonstration should be optimised for military front lines, as we need some major technical advances to make domestic power from SBSP cost effective.
    Millimeter waves should be a fall back position if the diode lasers are not ready in another year or two. High altitude balloons should be the fall back technology if LEO looks unlikely in a year or two.
    My guess is safety is not a significant concern for the front lines in warfare, so we should think the highest beam density that is practical for other reasons.
    Assuming reasonable success of demonstrator SBSP, we can then consider off planet resources for future scale ups. Neil

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