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Space Power Technology

NSSO on Space Based Solar Power 198

Posted by samzenpus
from the it-is-always-sunny-50-miles-up dept.
apsmith writes "About a year ago some of the people at the US National Security Space Office began looking into space-based solar power (SBSP) as a technology in the near-term strategic interests of the United States. At first the participants were skeptical, and the "phase 0 study" went along with no official funding. In a rather innovative move, they organized the study as a series of internet-based (bulletin-board and email) discussions, with the wordpress site open to the public, and a closed experts-only discussion using Google Groups. Initially expecting only a dozen or so interested parties, the discussion grew to include over 170 people with past expertise and interest in the issues. The final report was released Wednesday morning; it provides an excellent broad-brush review of the status of SBSP, showing immense potential, but also a number of challenges that appear only surmountable with a strong government commitment to the project. The big question is where it goes from here — NASA? DARPA? The new ARPA-E? Or something new? I was able to attend the press conference, which included Buzz Aldrin in an announcement of a new alliance to push for implementing the recommendations of the report."
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NSSO on Space Based Solar Power More

NSSO on Space Based Solar Power

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  • cool (Score:3, Insightful)

    by spykemail (983593) on Wednesday October 10, 2007 @08:20PM (#20934487) Homepage
    Maybe the solar satellites can double as a baseball cap for the Earth :).

  • Ok, someone explain it to me (Score:5, Insightful)

    by iamlucky13 (795185) on Wednesday October 10, 2007 @08:25PM (#20934509)
    How is it better to lift your solar panels into orbit, generate your electricity, then beam it to the surface at (optimistically) 50% efficiency, and then receive the beamed power at (optimistically) 50% efficiency, meanwhile creating the navigational hazards of the power beams and still requiring distribution from receiving stations rather than simply generating it via panels at the point of use?

    Don't get me wrong, I'm all for finding ways to utilize space, but I don't see how this is even remotely economical, especially at our current technology levels.

    Convince me.
    • How about the same concept as the space elevator? All you have to do is get those carbon nanotubes to conduct electricity....

    • Re: (Score:2)

      by geekoid (135745)
      How about a series of mirrors to reflect in an orbit that keeps the side of the earth away from the sun lit up? then you could use standard solar panels.

      heh

      • Re: (Score:2)

        by Kadin2048 (468275) *

        How about a series of mirrors to reflect in an orbit that keeps the side of the earth away from the sun lit up? then you could use standard solar panels.
        That would not be a good idea. Lots of biological organisms -- including humans, but a lot more critical ones -- really don't like having direct sunlight 24/7. Lots of plants will just refuse to go into seed, for instance.

    • Re: (Score:3, Insightful)

      by apsmith (17989) *
      Saves on transmission and storage.

      No weather, and a clear view (no atmosphere at all in the way).

      That gives you a factor between 5 and 10 over on-the-ground systems to start with.

      If you really lose 50% in transmission *and* 50% in receiving the case is harder to make - most estimates seem to have higher numbers for overall system end-to-end efficiency, but of course nobody's buit one yet.

      • Re: (Score:2, Interesting)

        by modecx (130548)

        If you really lose 50% in transmission *and* 50% in receiving the case is harder to make - most estimates seem to have higher numbers for overall system end-to-end efficiency, but of course nobody's buit one yet.

        Actually, I'm quite sure someone has built an earth bound a set of devices capable of comparable beam energy density to a proposed orbit power system. IIRC, the efficiency of the receiving antenna can be around 90%, not sure about that of the transmitter.

        Personally, I'm sure an array of heat engine

    • Re: (Score:2, Interesting)

      by QuantumG (50515)
      Seeing as you seem to be a big fan of this 50% you speak of.. here's another one for you: at night, solar panels on the ground receive no sunlight whereas, get this, in space they do. Now, whereas I'm plenty doubtful of your claims to the use of 50% I'm pretty certain of the almost 50% split between day and night.

      Of course, I'm more of the belief that solar power satellites will not be practical until we have off earth resources to build them from and, as such, low tech heat exchange designs are a better s

    • Re: (Score:2)

      by Cecil (37810)
      There is no nighttime in space, nor any clouds, nor any seasons, nor any atmosphere. Solar panels in orbit deliver full power 24 hours a day 7 days a week 365 days a year with no need for fuel or maintenance. And they don't have to be, and probably shouldn't be, in orbit. Inject them into an orbit between Venus and Mercury, or closer still. Solar radiation falls off with the square of the distance. The closer we get them to the sun, the more power they will generate, by orders of magnitude.

      Obviously it's no

      • Re: (Score:3, Insightful)

        by timmarhy (659436)
        just how do you propose to get the electricity back to earth from venus.

        how do you propose we maintain them from that distance? yes, solar cells aren't this eternal source of power people think they are. expect to need to do rolling replacments every 10 years atleast, if not more under those conditions.

        • Robot equipment would perform the maintenance, powered by the array itself. When not working (although, they would probably ALWAYS be working), the robotic equipment would charge. Think of them as an army of advanced Roombas.

          • Robot equipment would perform the maintenance, powered by the array itself.

            ...and how will the robots create a new solar panel if a panel is damaged?

            Think of them as an army of advanced Roombas.

            Are they able to repair themselves, and if so, where do they get spare parts?

            As far as the idea is concerned, I'd not mind if they can do it cleanly. The S-G power delivery methods I'd heard of so far have been microwave-based; anyone think there'd be any impact to global warming?

            • Re: (Score:2)

              by fredklein (532096)
              how will the robots create a new solar panel if a panel is damaged

              1) Over-size the array, so a few dead/damaged panels wouldn't matter.
              2) Have a stock of spares. Robots cut bad panel loose, push into sun, slap spare panel into place.
              3) We could ship up a stack of spares every so often.
        • just how do you propose to get the electricity back to earth from venus.

          Interesting hard SF treatment of this in a fairly old set of novels. They were talking of communications, but the same rules apply. I recommend "The Complete Venus Equilateral" by George O. Smith.

      • Re:Ok, someone explain it to me (Score:4, Interesting)

        by Lloyd_Bryant (73136) on Wednesday October 10, 2007 @09:26PM (#20935001)

        There is no nighttime in space, nor any clouds, nor any seasons, nor any atmosphere. Solar panels in orbit deliver full power 24 hours a day 7 days a week 365 days a year with no need for fuel or maintenance. And they don't have to be, and probably shouldn't be, in orbit. Inject them into an orbit between Venus and Mercury, or closer still. Solar radiation falls off with the square of the distance. The closer we get them to the sun, the more power they will generate, by orders of magnitude.
        First off, putting them somewhere other than Earth orbit is silly - yes, you can get more energy from the Sun, but how do you transmit it to Earth? The microwave (or whatever) beam will also fall of with the square of the distance.

        And how exactly do you keep the power beam locked onto the target, when the target is on a sphere rotating once per day?

        Putting them in equatorial geostationary orbits is *much* simpler. You'll lose a small amount of generating time each day (while the station is in Earth's shadow), but if you schedule as much of your maintenance as possible during this time, the effect is minimal.

        And maintenance *will* be required, for the foreseeable future. Someday we may be able to build solar cells that don't need to be periodically replaced, but not today.

        Furthermore, it's been noted that Earth orbit is "halfway to anywhere in the solar system" (attributed to Heinlein). So we'll need serious orbital capability to build these things, regardless of where we put them.
        • First off, putting them somewhere other than Earth orbit is silly - yes, you can get more energy from the Sun, but how do you transmit it to Earth? The microwave (or whatever) beam will also fall of with the square of the distance.

          Actually, no.

          Light intensity from the sun drops off at the square of the distance because the sun radiates as a point source in all directions.

          If you put your collector array closer to the sun, you collect significantly more sunlight. Then you use that energy to power a laser. If

        • Re: (Score:3, Informative)

          by CrimsonAvenger (580665)

          Putting them in equatorial geostationary orbits is *much* simpler. You'll lose a small amount of generating time each day (while the station is in Earth's shadow), but if you schedule as much of your maintenance as possible during this time, the effect is minimal.

          No. An equatorial orbit only goes into Earth's shadow during two short periods a year, near the Equinoxes. Off the cuff, I think the sats will be able to enter Earth's shadow once daily for about three weeks every Equinox.

          The rest of the time,

        • meaning mainly, lower launch to orbit costs. Doing this not only gets us power, it gives us a platform for space industrialization.

        • Re: (Score:2)

          by AJWM (19027)
          First off, putting them somewhere other than Earth orbit is silly - yes, you can get more energy from the Sun, but how do you transmit it to Earth?

          I think it was Robert Forward who raised the possibility of putting the solar power stations on Mercury and just having them make antimatter. The antimatter is then shipped (nice, high energy density stuff that) to Earth.

          There are a few engineering details yet to be worked out, of course.

        • Re: (Score:2)

          by Cecil (37810)
          yes, you can get more energy from the Sun, but how do you transmit it to Earth? The microwave (or whatever) beam will also fall of with the square of the distance.

          No it most certainly doesn't. The kind of power loss I am talking about is the power loss due to dispersion. The sun radiates its light in all directions, so most of it is wasted. The further you go away from it, the more it has spread out and the smaller the available density of energy is.

          A perfectly collimated laser or maser (admittedly a practi
        • OR, you put up 2 sets of panels on either side of the earth and get power 24/7... when one panel is blocked, the other one is in full sunlight. Maybe the rub is to not transmit the power by a beam, but with a very long nanotube cable.

    • Because you don't need batteries... (Score:5, Informative)

      by Goonie (8651) <robert.merkel@nOSpam.benambra.org> on Wednesday October 10, 2007 @08:37PM (#20934635) Homepage
      There are several advantages space solar power has:
      • higher intensity sunlight than even a cloudless day, 24 hours a day
      • you've always got direct sunlight, so you can use cheap mirrors to focus the light on a very expensive but efficient solar cell (you can do this on Earth as well, but it doesn't work as soon as you get clouds)
      • No need for backup power. That's worth a lot of money.
      • The ground based gear is much smaller and lighter than equivalently-powerful terrestrial solar panels. This is a big advantage for the military, who are the proposed initial customers.

      I'm skeptical too, but it's not quite as crazy as it sounds.

      • Douglas Adams - "Mostly Harmless"
        - The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at and repair.

        Lets build in some redundancy shall we? (Just in case.)

        I think you covered the list pretty well but corrosion is also a factor that space should mitigate. Well, mostly aside from the wandering bit of space debris.

        I haven't RTFA, probably won't, but I'd

      • Re: (Score:3, Interesting)

        by polar red (215081)

        higher intensity sunlight than even a cloudless day
        And how are you going to transmit that energy from space through clouds ?

        • Re: (Score:3, Insightful)

          by Xiaran (836924)
          The earths atmosphere is transparent to certain microwave frequencies.
    • No worries about clouds and the supply will not be affected by the seasons.

    • Re:Ok, someone explain it to me (Score:5, Informative)

      by Jubedgy (319420) on Wednesday October 10, 2007 @08:49PM (#20934719)
      Portability and extensibility. The sun provides, about 1367 W/m^2 in space (courtesy, Space Mission Analysis and Design third edition, page 432) and about 250 W/m^2 on the Earth's surface (FTFA). In any case...

      Portability:

      By using an orbital energy collection system, you can simply re-route the beam to any place on the planet within the system's FOV...done right, you can get full 4*pi sr coverage of the Earth 24/7. Design a portable ground station, and you can provide power to a disaster area that has been removed from the rest of the power grid (paraphrased directly FTA).

      Extensibility:

      If, once in place and a standard orbital collection platform design has been established, more power is required, simply launch the spare unit. Proper formation flying techniques (something currently at about the cutting edge of orbital design) should allow the new unit to 'hook in' to the system to boost the amount of available power. This may be in the article, I have not finished reading it yet.

      The LISA mission provides a pretty good overview of how I see the entire system distributing power from the collectors to the emitters (the things that will transmit the power down to the surface), though I may be totally off base from what the authors have in mind. The LISA mission will consist of three satellites forming an equilateral triangle with leg lengths of 5 million Km shooting lasers at each other. Last time I checked, anyway.

      It is currently not economical, nor is it really achievable yet. I encourage you to at least browse through the article as it does discuss some of your questions in a more cogent manner than I have.

      • Re:Ok, someone explain it to me (Score:5, Informative)

        by QuantumG (50515) <qg@biodome.org> on Wednesday October 10, 2007 @09:51PM (#20935203) Homepage Journal

        The sun provides, about 1367 W/m^2 in space (courtesy, Space Mission Analysis and Design third edition, page 432) and about 250 W/m^2 on the Earth's surface (FTFA).
        Hmm.. the first number is correct, but we don't have 100% efficient solar panels and won't any time soon (if ever) so you've gotta down rate that.

        The second number, however is totally wrong. If you're going to talk about what "the sun provides", i.e., the theoretical 100% efficiency solar panel, then you get a figure of about 1000W/m^2 on the Earth's surface. You could say it is more like 800W/m^2 when you take cloud cover into consideration.. and then there's the fact that you only get that during daylight hours, so halve it to get 400W/m^2 but that's still a lot more than 250W/m^2. It *feels* like someone is downplaying the possible efficiency of solar panels on the Earth's surface vs the same solar panel in space in order to make their argument stronger. As you took that figure straight from the article, I'll give you the benefit of the doubt, but that's what it sounds like.

        It's still a heck of a lot of difference though. You're talking nearly 3.5 advantage to putting your solar panels in space over leaving them on the ground.. but there *are* losses to transmitting the power as microwaves through the atmosphere, and there is the astronomical cost of launching anything into space.

        Whenever I hear people talk about solar power satellites I'm reminded of the episode of Seinfeld where they stock the mail truck with bottles to collect the 5c deposit in the adjacent state. If you can get a free ride you might be able to make solar satellites work, but you've still gotta crunch a lot of numbers first, and no-one has done that successfully.

        • Re: (Score:2)

          by apsmith (17989) *
          250 is the average across Earth's surface, per unit surface area. If you were able to keep the array pointed directly at the sun all day long, you'd get 500 (1/2 of 1000, since half the time is still night-time). But that takes extra equipment, additional expense on the local side, and requires extra ground-area one way or another (that's a long shadow you're casting near sunries/sunset).

          • Re: (Score:2)

            by m2943 (1140797)
            250 is the average across Earth's surface, per unit surface area.

            Solar cells on earth aren't exposed to an "average" per unit area, you put them in the places where they work best, like high, cloudless deserts, and you steer them.

            1/2 of 1000, since half the time is still night-time

            And solar cells in orbit around the earth move through the earth's shadow. You can't put them into geostationary orbits (too crowded), and further out is expensive. Maybe we could build stators.

            If you were able to keep the arra

            • Re: (Score:2)

              by QuantumG (50515)
              Actually, geostationary orbits is exactly where they intend to put them.

              • Re: (Score:2)

                by m2943 (1140797)
                Actually, geostationary orbits is exactly where they intend to put them.

                Well, it ain't gonna happen: that space is too valuable and too crowded.

                • Re: (Score:3, Informative)

                  by QuantumG (50515)
                  Ya know, I think you should probably put down the crack pipe.

                  It's space, dude.

                  The orbit is 264,869 km around.

                • Re: (Score:2)

                  by AJWM (19027)
                  [gp] geostationary orbits is exactly where they intend to put them.

                  [p] ... that space is too valuable and too crowded.

                  You put the current communication satellite transponders (rather, their replacements) aboard the powersats. You give them bigger antennae. The bigger the antenna (at either end) the better the angular resolution.

                  The "too crowded" comes down to angular resolution, not actual distance. They're not (much) worried about collisions but about a receiver on Earth being able to differentiate betw

                  • Re: (Score:2)

                    by m2943 (1140797)
                    The "too crowded" comes down to angular resolution,

                    Of course.

                    They're not (much) worried about collisions but about a receiver on Earth being able to differentiate between adjacent satellites.

                    Well, duh! Next you'll tell us space is a vacuum! What more of those incredible insights do you have up your sleeve?

                    You put the current communication satellite transponders (rather, their replacements) aboard the powersats.

                    Brilliant idea! Let's put the receivers and transmitters right next to the gigawatt microwave a

                    • Re: (Score:3, Informative)

                      by AJWM (19027)
                      Brilliant idea!

                      Thank you, but it's not original.

                      Let's put the receivers and transmitters right next to the gigawatt microwave antenna! That will surely fix all those problems!

                      Yep. Unless you're trying to watch satellite TV in the middle of a rectenna farm, of course -- although even there they'd likely have the transponders for that particular region mounted on a different satellite. It's not like everything on the powersat has to point in the same direction, you know, or operate at the same frequency.

    • Re: (Score:2)

      by Dr. Spork (142693)
      In space, nobody needs to wash those things. I'm not trying to make a joke; dirt is a serious issue when we're talking about gigantic, fragile surfaces.

      Another advantage is that the array could be pointed directly at the sun permanently, whereas on Earth, you need to keep swiveling it.

      • Re: (Score:2)

        by timmarhy (659436)
        you do release there's lots of things flying about in space? what about the tiny meteor shower that we get every 50 years?
        • Who cares? We're probably just talking thin-film reflectors here. If they get enough holes punched in them that power output drops too much, just have your maintenance robots unfurl some more.

          • Re: (Score:2)

            by timmarhy (659436)
            and when you run out? the point i'm trying to impress on people here is that installations of this size require constant maintenance, it's in space it's expensive to do. it's a significant cost that must be addressed.

            idunno, it just seems like a massively complex, expensive solution to something we don't have a problem with, and won't have a problem with in the forseeable future.

            by all means reasearch, and if they can make it work and make economical sense, great. i'll remain skeptical until they solve th

            • it just seems like a massively complex, expensive solution to something we don't have a problem with

              We don't have a problem with shrinking available land mass, increasing dependency on oil?

              It's not that complex, the cost can be amortised easily enough, we do need clean energy, and you ended your sentence with a bl**dy preposition!

      • Another advantage is that in space, immensity can be bought very cheaply, once you have the infrastructure in place to build it. Put it this way: how much of every terrestrial structure is devoted to supporting said structure against Earth's gravity? The answer: most of it.

        Plus which, as others here have pointed out, in space solar power is something.

    • Re:Ok, someone explain it to me (Score:5, Insightful)

      by lgw (121541) on Wednesday October 10, 2007 @09:01PM (#20934803) Journal

      How is it better to lift your solar panels into orbit, generate your electricity, then beam it to the surface at (optimistically) 50% efficiency
      It's better because now you have a hugely powerful microwave cannon in orbit that can fry anyone you need it to. Thinking about an orbital power station other than as a weapon is probably misguided. This is probably a feature for the "National Security Space Office".
      • As china showed (and USSR, as well as America), it is easy to shoot a small sat out of the sky. Now put something of that size, and it is literally shooting at the broadside of a barn. And the brilliant pebble approach would work nicely for this.

        TO be honest, years ago, I thought the same thing, but if you think about it, we can simply use a nuke power plant on the ground and beam the energy to a set of sats to send the power. Just make the main receiver be at geo over USA, and then from there beam it aro

    • Re: (Score:2)

      by mikelieman (35628)
      Ok, consider this:

      The infrastructure developed to implement this project is pretty much the infrastructure needed to leave earth and visit other places on a regular basis.

      You get the Electricity, and Access to the Universe is gravy.
    • You're off on several items:

      How is it better to lift your solar panels into orbit, generate your electricity, then beam it to the surface at (optimistically) 50% efficiency, and then receive the beamed power at (optimistically) 50% efficiency, ...

      First: It isn't necessarily panels. Steam plants work just fine, and are much cheaper to build and lift.

      Second: There's 7 times the power per square foot available up there due to lack of atmospheric attenuation and the 24/7 nature of sunlight in space, compared
    • You can put up as many solar panels as you want, floating in space, aimed at the sun. No need to clutter up the landscape of earth. It scales up until the point you've got a Dyson Sphere,

      Then you transmit the power from the small panels to an space station in a geostable orbit around earth.

      Then you transmit the power from the space station to a matching ground installation on the earths equator.

      Then you transmit the power from there around the earth using whatever method is best.

      The strengths of such a sy

    • How is it better to lift your solar panels into orbit, generate your electricity, then beam it to the surface at (optimistically) 50% efficiency, and then receive the beamed power at (optimistically) 50% efficiency, meanwhile creating the navigational hazards of the power beams and still requiring distribution from receiving stations rather than simply generating it via panels at the point of use?

      Don't get me wrong, I'm all for finding ways to utilize space, but I don't see how this is even remotely economical, especially at our current technology levels.

      Convince me.

      The best ideas aren't solar panels in space, they're solar mirrors for heat turbines. You ever see that tower in the desert surrounded by mirrors? Up at the top they have a fluid that gets super-heated by the mirrors and it turns a turbine. Heating a fluid and letting it turn a turbine is the oldest form of power generation we have, it's just updating the heat source to solar.

      So the idea is that you put something like this in space and beam the power down with microwaves. At the moment, this sort of device

    • Isn't it going to be dead easy for china, russia, japan, most of europe to destroy any significant satellite? And possibly even anonymously.

      So I assume that many other more hostile nations will be able to within 50 years.

    • Re: (Score:2)

      by AJWM (19027)
      How is it better to lift your solar panels into orbit,

      Most solar powersat proposals don't actually suggest this (at least, not the ones I was looking at twenty years ago). The idea is to deploy sufficient systems (as automated and self-repairing/self-replicating as possible) on the Moon that the powersats are constructed from lunar materials. This avoids the costs of manufacturing them on Earth and lifting them to orbit. Some proposals just had leaving the panels on the Moon and beaming the power from

  • Beyond the Orange-Bellied Parrot (Score:3, Interesting)

    by Nefarious Wheel (628136) * on Wednesday October 10, 2007 @08:26PM (#20934525) Journal
    It's not really a bad idea, provided there are no orange-bellied parrots in the way. The real fun is when you have to explain to greenies that yes, it's really solar power, and yes, it's also thermonuclear.

    I like the idea of a separate organisation dedicated to this technology, as it's clear none of the existing organisations can do it. Set it in motion, get it done before the bloat sets in. Also like the idea of the solar-electric HEO ferry -- anyone have a link to an artist's perception of it (a real one I mean)?

    • Re: (Score:3, Interesting)

      by RyanFenton (230700)
      Indeed - and because of the potential for unparalleled amounts of energy that are possible with more and more direct forms of solar energy extraction, new things become possible. Dark matter-based energy storage systems and/or weapons become closer to practical, matter fabrication factories manipulating atoms using nuclear interactions (think renewable nuclear fuels), all kinds of uses for the astounding amounts of energy we can't practically transport directly back to earth, but have flowing out at all ti
      • Oops - meant anti-matter, not dark matter. Hate it when I make mistakes like that.

        Ryan Fenton
      • "I think we should stop targeting Cheyanne Mountain now."

        "Why?"

        "It isn't there any more"

        -- "The Moon is a Harsh Mistress", Robert A. Heinlein.

        Yep, lots of energy up there, and you don't have to produce it, just sort of funnel it. Large concentrating reflectors are quite easy to maintain in microgravity, just lots of metallised mylar film with supporting struts made of alfoil. Oh, and a guidance system of some sort. Some time back there were a few designs for manufacturing these as they unrolled from st

    • Re: (Score:2, Interesting)

      by jambox (1015589)
      FTA: "...then beamed toward a reference signal on the Earth at intensities approximately 1/6th of noon sunlight." Seems like they're intending to beam the energy back in a coherent, but rather diffuse beam to a large rectenna, rather than a tight, high intensity laser blast as is often assumed. Does this make sense? If the beam sent down to Earth is only 1/6th of the intensity of sunlight, what's the point? If this is true though, then the bird-slaughtering potential of SBSP is a misunderstanding. It'd
  • The big question is where it goes from here -- NASA? DARPA? The new ARPA-E? Or something new?

    By "something new", I'm sure you mean the formation of D.O.O.P.

  • showing immense potential, but also a number of challenges that appear only surmountable with a strong government commitment to the project.


    If I needed funding for my project I would say the exact same thing, especially if I had 170 other highly skilled fanboys to back up my idea.. ;-) Now it is a very cool idea, but there are alot of cool idea out there..
  • People here keep claiming that the more intense sunlight will result in high power generation, but i'm skeptical of this.

    solar cells here now aren't capable of extracting more then 35% of the light that makes it to earth now, so they won't do any better in space.

    the only type of solar generation that will produce more power in space due to the more intense soalr rays will be some form of mirror heating, and that present a whole bunch of other problems.

    i'm also curious as to how they will keep the solar a

    • Re: (Score:2)

      by apsmith (17989) *
      Well, if average sunlight falling on Earth's surface is 250 W/m^2 and average in Earth orbit is 1400 W/m^2, then 36% of 250 is a lot less than 36% of 1400. That's the difference there.

      The main proposed orbit is geo-stationary; these are very rarely shaded (for about 1 month of the year a satellite there gets about an hour's worth of shade every day, the rest of the year it's clear).

      Inexpensive space launch is definitely one of the technical challenges. The report calls for large-scale development and deploy

      • Re: (Score:2)

        by timmarhy (659436)
        my point is what makes you think the solar panel will generate more power with more light? they don't catch all the energy that falls on the earth, so more in space won't make a difference. your 160 watt panel on earth is still only going to be a 160 watt panel in space...

        • Re: (Score:2)

          by AJWM (19027)
          what makes you think the solar panel will generate more power with more light?

          This is exactly the way they work.

          Go get yourself one of those toy solar-powered cars, or a solar energy demo kit (solar cell and motor) from Radio Shack or someplace. Move the cell towards a light bulb; observe how the motor speeds up or slows down as the cell gets more or less light.

          Yes, there's an upper bound. Probaby shortly before the silicon starts to melt.
        • my point is what makes you think the solar panel will generate more power with more light? they don't catch all the energy that falls on the earth, so more in space won't make a difference. your 160 watt panel on earth is still only going to be a 160 watt panel in space...

          Bzzzt... wrong.

          PV panels can only extract electricity at a specific bandgap energy (although I believe recent developments allow multiple bandgaps, improving efficiency). Photons below that energy (i.e. longer wavelength) are not converte

    • Re: (Score:2)

      by Ironsides (739422)
      People here keep claiming that the more intense sunlight will result in high power generation, but i'm skeptical of this.solar cells here now aren't capable of extracting more then 35% of the light that makes it to earth now, so they won't do any better in space.

      On earth, you get ~250w/m^2, is space, you get 4-5 times as much. So, a solar cell in orbit at the same efficiency will produce 4-5 times as much power. It's not that they are more efficient, it's that they are getting more sunlight->more po
  • A big beam, needs a big mirror. Be it microwave, infrared or visible light it's a huge gun in orbit, untouchable by IEDs and lesser nations. It doesn't even need to work that well, just 10 x amplification from nominal and any spot on earth is unlivable. Or operate as a great psychological weapon when a given region is bathed in light 24 hours a day. It is a very bad idea, like SDI was a bad idea, like the further militarization of space is a bad idea.
    • Unless you could change the focal length of this mirror at will, I doubt the reflected light itself would be of any use as a weapon. Of course, the microwave or laser beam used to transmit the power to earth may be a different story, but there's an interesting refutation of that possibility here [slashdot.org].

      Besides which, I think it would be probably that the economic advantage of having this power would outweigh taking it offline willy-nilly to terrorize lesser nations...we can terrorize lesser nations quite adequate

  • Won't happen until one world, united. (Score:3, Insightful)

    by tygt (792974) on Wednesday October 10, 2007 @10:13PM (#20935371)
    Face it, we're already concerned about relying on an unstable Middle East for our energy.

    We're certainly not going to rely on a very fragile orbiting setup which is a sitting duck to anyone with a decent missile/launch vehicle.

    • Re: (Score:2)

      by timmarhy (659436)
      bullcrap, it's certainly a harder target then a power plant on the ground is. they will have to build multiple arrays, one shot won't take it out.
      • Didn't China whack one of their weather satellites with a missile not too long ago?

        Point being, even after a satellite has been destroyed, the shrapnel (debris) can remain in orbit and pelt/damage other satellites in the general orbital area. Unless you want to deal with all sorts of technical gremlins to hash out, the last thing you want is for your satellites to be damaged with space junk.

    • Re: (Score:2)

      by aug24 (38229)
      As this would be in geosynchronous, not low earth orbit, it would be a very decent missile/launch vehicle indeed. This would be way, way above ICBM maximum heights, for example.

      Justin.

    • Re: (Score:3, Insightful)

      by DerekLyons (302214)

      We're certainly not going to rely on a very fragile orbiting setup which is a sitting duck to anyone with a decent missile/launch vehicle.

      Nope.

      These things will be high up - in GSO, which takes it right out of the range of any ICBM based launcher. Unless you can figure out how to pack propulsion, power, guidance, and a Dangerous Payload into a five to ten pounds or so... (And no, the classic 'handful of sand' or 'paint chip' or 'styrofoam cup' won't cut it here - the interception geometry is diff

  • El Presidente Dwayne Elizondo Mountain Dew Herbert Camacho has a PLAN to save AMERICAH!

    He'll pick a bunch of SMART guys and they'll solve our ENGERNY problems and they'll do it all in ONE WEEK or he'll... uh... he'll uh... give them MORE TIME and MORE MONEY because its REALLY REALLY HARD to solve our ENGERNY problems! And then if they don't do it before they die then... uh... he'll pick some MORE SMARTER GUYS and let THEM solve our ENGERNY problems!

    Nothing like incentives [geocities.com]!

  • The US is proposing to put devices capable of aiming megawatt beams into orbit? And who exactly will control this?

    And the justification for this seems rather dubious, too. Capturing solar power in space has no obvious overall advantage over capturing it on the ground.

    • Re: (Score:2)

      by AJWM (19027)
      The US is proposing to put devices capable of aiming megawatt beams into orbit? And who exactly will control this?

      The US has been fielding megaton-range nuclear weapons (lately they're more sub-megaton) around the world for most of the last six decades (as have a few other countries). You're worried about a few megawatt beams?

      Capturing solar power in space has no obvious overall advantage over capturing it on the ground. ...other than being brighter (no atmospheric or cloud loss) and available 24 hours a d
  • The way to read TFA is to use the search function to look for "$". Then you can skip all the "it would work this way" stuff (this is R&D - just give it to them that they have something that MIGHT work) and get to the real feasibility.

    It's not about the watts per square meter, or the transmission feasibility or losses, skip to the final number: how many kilograms do you have to put into HIGH orbit to deliver a 1kW to the ground?

    I didn't find that number, but by searching on "$", 56 pages in to a 75 page

  • Jimmy Carter must be laughing his ass off (Score:5, Insightful)

    by theolein (316044) on Thursday October 11, 2007 @02:55AM (#20936861) Journal
    I remember, back in 1980 or so, when all the Reagan fans were jumping for joy because the actor was more popular than a naval nuclear engineer (yes; Carter actually knew his shit), Carter had proposed a system of orbital solar power stations [nss.org]. It would have been more or less the same thing as they are proposing today. Those of you who have access to Time magazine's archives will find an article on it.

    So, here we are today, some 27 years later, and the same proposal gets floated.

    Imagine if laziness hadn't dropped the issue back then. Iran, Iraq and the whole business of 9/11 would have been less critical than they now are.
  • FTFA:

    "Conflict prevention is of particular interest to securityproviding institutions such as the U.S. Department of Defense."

    Hmmmm - not on recent evidence!

There is always one thing to remember: writers are always selling somebody out. -- Joan Didion, "Slouching Towards Bethlehem"

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