It's been known for decades that solar power satellites *can* send energy to the earth. Communication satellites do it every day, just not at levels useful for power.
The question is cost, and that's almost all due to the high cost of rockets to get millions of tons of power satellite parts to GEO. If you want to sell power on earth in serious competition with coal, the economics indicates you need to reduce the cost of getting parts to GEO by a factor of around 200. That's $20,000 per kg down to $100/kg. Unfortunately, the chemical energy in rocket fuel vs. the physics energy it takes to get to orbit just won't do it. Round numbers, the Falcon Heavy will put 50 tons in LEO or 25 tons in GEO for a cost of $100 M. That's a reduction to $4000/kg, a factor 5 but not enough. Launching one every hour might get the price down to $1000/kg which is still too high by five times. Skylon, the proposed rocket plane from Reaction Engines, at several flights per hour is expected to put 10 tons in LEO and 5 tons in GEO for a cost of $1.5 M or $300/kg. *Still* too high. A brand new concept starts with the sub orbital maximum load of 30 tons for a Skylon then uses 400 MW of laser power to get 10km/s exhaust velocity from a second stage. This will get 20 tons to GEO per flight. The estimated capital cost of the lasers ($4 B or $400 M/year) is under $2/kg. Spread over 480,000 tons per year it drives the lift cost for parts down to $100/kg. If we can get the lift cost down that far, a power satellite comes in at $1600/kW or $1.6 B/GW. At that capital cost, energy from space could sell for substantially less than energy from coal. The development could come in as low as $20 B. Any thoughts? Keith _______________________________________________ http://box535.bluehost.com/mailman/listinfo/brin-l_mccmedia.com
