If Power-Sats are to be built… Part 1.


For earth-orbiting power satellites to make a significant impact in the energy economy and the overall Earth environment, we’re looking at square kilometers in orbit. A rectangular photo voltaic array a thousand meters on a side we generate on the order of 100 megawatts of electric power. If we figure a kilo of mass per meter of collector area we’re looking at 500 tons of material in orbit, probably most of it silicon. How’s that going to get there?

After many years of thought on the topic it appears to me that there are basically three options.

1. Send material from the moon via catapult into nearer earth orbit. This was popularized by Arthur C. Clarke around 1962, more as a means of refueling interplanetary spaceships but other uses were implied. If a lunar catapult operates at 100 G.s it will need to be a bit over three Kilometers in length to toss loads at lunar escape velocity toward the Earth. If each load weighs only 50 KG, it will require at least 100 megawatts of power which will in turn require a square kilometer of photo voltaic cells (on the moon.) We’ll eventually need to learn to fab large numbers of solar cells on the moon but I suspect this is the hard way to start up a power-sat for Earth.

2. A small asteroid could be boarded and turned into a self-propelled rock barge. A huge solar collector, probably a balloon silvered on one hemisphere, could focus sunlight on one end of a huge heat engine while the asteroid itself functioned as the engine’s radiator. Such an arrangement could spew electrically-charged oxygen extracted from asteroid rock or bits of the rock itself to propel the asteroid toward an orbit around Earth. I confess I like this idea best but we would need to transport the engine, the collapsed collector and a good deal of mining and extraction equipment to the asteroid, which will require either an atomic rocket or one powered by laser from earth, Moon or an orbital position. Again a great deal of start-up technology before we can start building the power-sat.

3. Lifting stuff up from earth is the most direct and may well turn out to be the easiest way to proceed, especially once we get comfortable with the idea that we’re not talking about reusable cargo rockets but projectiles made of raw material delivered by small rockets getting an assist from a catapult launcher cited in a mountain location near Earth’s equator. In this manner we can minimize the size of both our catapult and the rockets we’ll need to provide final kick into orbit.


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