[ExI] China SPS by 2025
hkeithhenson at gmail.com
Wed Feb 20 19:24:37 UTC 2019
David Lubkin wrote:
> I still have my copies of the GAO reports studying Solar Power
Satellites from forty years ago
> If they meet the 2030 goal, how soon before they can field a gigawatt facility?
Some things have not changed in 40 years or more. Between the
atmospheric window for microwaves and the physics (diffraction
optics), the minimum practical size is still around 5 GW Neither is
likely to change, though you do see some people proposing the rectenna
to be put on a StratoSolar type platform at 20 km.
The interest in China is driven by the reductions in cost to LEO that
reusable rockets allow. For a given target power cost, the capital
investment is about 80,000 times as much. So, 3 cent power would
require an investment of no more than $2400/kW.
The rectenna is estimated to cost $200/kW, the parts around $900/kW.
The lift cost is dependant on the specific power. The best estimate
for that is currently 6.5 kg/kW. Given the investment limit, that
sets $200/kg (to GEO) or, if you can build in LEO and selt-power them
up, $100/kg to LEO.
Power satellites have never been technically hard to do. They are
very hard to make them work economically. I spent the last ten years
working on the economics. It depends on progress by Reaction Engines
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