(I expect it will take more energy to put into orbit than the solar panels will accumulate over their lifetime.)
This struck me as an interesting estimate so here's my attempt at checking it:
Wikipedia quotes 300W/kg solar cells. Medium Earth Orbit ranges from over 2,000km to 35,000km above sea level - let's pick a fairly low estimate of 6000km. Gravitational potential is 3.32 J for elevating a 1kg mass to 6000km from sea level. So the solar panel must operate for 1.28 days to recoup the energy cost of elevating the object. This is, of course, a lower bound (assuming perfect launch mechanism, no kinetic energy of orbit, etc. etc.), but it seems unreasonable to assume that launching solar panels has no benefit given this tiny lower bound. Furthermore, the fact that solar panels are routinely launched into orbit suggests that they do have a net energy production.
What about memory? Bits being flipped by cosmic radiation is an issue on Earth; I imagine it must be more significant in space, and annealing won't fix that.
What do existing computers-in-space do? Shielding of some sort?
So the solar panel must operate for 1.28 days to recoup the energy cost of elevating the object
The object- what about the rocket? (I also should have included the energy cost of making the solar panel in the first place, which tends to seriously reduce their attractiveness.)
Furthermore, the fact that solar panels are routinely launched into orbit suggests that they do have a net energy production.
Well, solar is cheap to get to space. (I know our recent Mars rover is using nuclear energy (powered by decay, not fission or fusion) rather than solar pan...
The following is intended as 1) request for specific criticisms regarding the value of time investment on this project, and 2) pending favorable answer to this, a request for further involvement from qualified individuals. It is not intended as a random piece of interesting pop-sci, despite the subject matter, but as a volunteer opportunity.
Server Sky is a an engineering proposal to place thousands (eventually millions) of micron-thin satellites into medium orbit around the earth in the near term. It is being put forth by Keith Lofstrom, the inventor of the Launch Loop.
Abstract from the 2009 paper:
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Some mildly negative evidence to start with: I have already had a satellite scientist tell me that this seems unlikely to work. Avoiding space debris and Kessler Syndrome, radio communications difficulties (especially uplink), and the need for precise synchronization are the obstacles he stressed as significant. He did not seem to have studied the proposal closely, but this at least tells us to be careful where to set our priors.
On the other hand, it appears Keith has given these problems a lot of thought already, and solutions can probably be worked out. The thinsats would have optical thrusters (small solar sails) and would thus be able to move themselves and each other around; defective ones could be collected for disposal without mounting an expensive retrieval mission, and the thrusters would also help avoid things in the first place. Furthermore the zone chosen (the m288 orbit) is relatively unused, so collisions with other satellites are unlikely. Also the satellites have powerful radar capabilities, which should lead to more easily detecting and eliminating space junk.
For the communications problem, the idea is to use three dimensional phased arrays of thinsats -- basically a bunch of satellites in a large block working in unison to generate a specific signal, behaving as if they were a much larger antenna. This is tricky and requires precision timing and exact distance information. The array's physical configuration will need to be randomized (or perhaps arranged according to an optimized pattern) in order to prevent grating lobes, a problem with interference patterns that is common with phased arrays. They would link with GPS and each other by radio on multiple bands to achieve "micron-precision thinsat location and orientation within the array".
According to the wiki, the most likely technical show-stopper (which makes sense given the fact that m288 is outside of the inner Van Allen belt) is radiation damage. Proposed fixes include periodic annealing (heating the circuit with a heating element) to repair the damage, and the use of radiation-resistant materials for circuitry.
Has anyone else here researched this idea, or have relevant knowledge? It seems like a great potential source of computing power for AI research, mind uploads, and so forth, but also for all those mundane, highly lucrative near term demands like web hosting and distributed business infrastructures.
From an altruistic standpoint, this kind of system could reduce poverty and increase equitable distribution of computing resources. It could also make solving hard scientific problems like aging and cryopreservation easier, and pave the road to solar power satellites. As it scales, it should also create demand (as well as available funding and processing power) for Launch Loop construction, or some other similarly low-cost form of space travel.
Value of information as to whether it can work or not therefore appears to be extremely high, something I think is crucial for a rationalist project. If it can work, the value of taking productive action (leadership, getting it funded, working out the problems, etc.) should be correspondingly high as well.
Update: Keith Lofstrom has responded on the wiki to the questions raised by the satellite scientist.
Note: Not all aspects of the project have complete descriptions yet, but there are answers to a lot of questions in the wiki.
Here is a summary list of questions raised and answers so far:
In his reply to the comments on Brin's post, Keith Lofstrom mentions using obsolete sats as ballast for much thinner sats that would be added to the arrays as the manufacturing process improves. Obsolete sats would not stay in use for long.
Ping times are going to be limited (70ms or so), and worse than you can theoretically get with a fat pipe (42ms), but it is still much better than you get with GEO (250+ ms). This is bad for high frequency trading, but fine for (parallelizable) number crunching and most other practical purposes.
It takes roughly 2 months for a 3 gram thinsat to pay for the launch energy if it gets 4 watts, assuming 32% fuel manufacturing efficiency. Blackbody cooling is another benefit.
Flash memory is acknowledged to be the most radiation sensitive component of the satellite. The solution would involve extensive error correction software and caching on multiple satellites.
Circuits will be manufactured as two dimensional planes, which don't short as easily. Another significant engineering challenge: Thermal properties in the glass will need to be matched with the silicon and wires (for example, slotted wiring with silicon dioxide between the gaps) to prevent circuit damage. Per Vanvier, it may be less expensive to replace silicon with other materials for this purpose.
Efficient power/cooling, increased communications, overall scalability, relative lack of environmental impact.
Yet to be answered:
Insightful comments: