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Size: 1896
Comment:
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Size: 1893
Comment: changed server-sat to thinsat
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| The theoretical energy cost of moving 3 grams to the 12789km m288 server sky orbit is derived from the 8667m/s launch delta V and the 1118 m/s insertion delta V, or 38MJ/kg . That works out to 1.14E5 Joules, which a server-sat makes in 8 hours. While no known technology can get there, systems such as [[ http://launchloop.com/ | the launch loop ]] can get within an order of magnitude of that. | The theoretical energy cost of moving 3 grams to the 12789km m288 server sky orbit is derived from the 8667m/s launch delta V and the 1118 m/s insertion delta V, or 38MJ/kg . That works out to 1.14E5 Joules, which a thinsat makes in 8 hours. While no known technology can get there, systems such as [[ http://launchloop.com/ | the launch loop ]] can get within an order of magnitude of that. |
Energy to Launch Server Sky
Assume that one million 3 gram server sats are launched with an Ariane 5ECA, and that each server sat produces 4 watts of usable power.
The 5ECA is a 3 stage vehicle:
Stage |
|
Fuel weight |
MJ/kg |
Energy J |
0 |
Solid (both) |
633,000 kg |
6 ? |
3.8E12 |
1 |
LOX/LH2 |
148,000 kg |
16 |
2.4E12 |
2 |
LOX/LH2 |
14,000 kg |
16 |
0.2E12 |
Total |
6.4E12J |
|||
The energies given are the chemical energies of the fuels. If we assume 32% fuel manufacturing energy efficiency, relative to generated electricity, then the total "electrical" energy needed to fuel an Ariane is 2E13 Joules. Server satellites can pay back that energy in 5 million seconds, or about 2 months. Not great, but not bad.
Possibilities
The theoretical energy cost of moving 3 grams to the 12789km m288 server sky orbit is derived from the 8667m/s launch delta V and the 1118 m/s insertion delta V, or 38MJ/kg . That works out to 1.14E5 Joules, which a thinsat makes in 8 hours. While no known technology can get there, systems such as the launch loop can get within an order of magnitude of that.
Most of the mass of a server sky satellite is a 50 micron glass substrate. With improved manufacturing techniques, the thickness can be reduced to 5 microns or less, with the mass reduced to 300 milligrams, and the above energy costs divided by 10. Later, if much of the glass and interconnect metal are made from lunar materials, the complex technical materials manufactured and launched from Earth can be reduced to a small fraction of that.
So, although Server Sky makes energy sense now, it can make vastly more energy sense in the future as technological improvement is driven by volume manufacturing.