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.

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my comments as “official” by any stretch of the imagination…please extend to me a degree of academic freedom and do not cite me, please.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.

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!

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.

Andreas

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!

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.

Andreas