Hi All

From the research paper (not an "article" as I first stated) SM linked to, is a study of a supersynchronous SPS using 30 GHz microwaves to beam power from L2. While Landis finds it unsuitable for his specific analysis it still has a lot of advantages. What's interesting to me is the mass estimate ~ 1,300 tons for 1-2 GW power delivered. It's parked at L2 which might initially seem more expensive than GEO but the energy costs are similar, especially if a few lunar flybys are chucked into the orbit plan. Using chaos eventually it will get to L2 for about the same dV as GEO.

Using plasma drives the delivery cost goes right down, since they can be powered off a pre-deployed segment of the array. I estimate about 35% extra mass for fuel and propulsion making the total to LEO ~ 1755 tons. Specific power is 570-1140 W/kg. If array power costs are $0.5/ W and the SPS delivers power ~ 2/3 x 5 times more power than the best ground based solar that's an LEO delivery price of $1330 - $2660/kg to be equal in basic cost.

With cheaper LEO delivery the system gets more attractive. At $220/kg we're talking cost equivalence with coal power. With 50% efficiency PV cells and lighter structures the system mass might go down ~ 50%. Is $440/kg to LEO feasible in the near-term?

Adam

PS
Compare that to Zubrin's analysis ["Entering Space"] for a 1 GW [actually 500 MW reaches the ground] GEO SPS of 41,000 tons net mass and about ~ 3 times that for chemical delivery, hence ~ 123,000 tons to LEO. Specific power for the whole system is a mere 4 W/kg for mass delivered to LEO. He claimed that the system wouldn't break-even with minimum cost delivery to LEO ($100/kg, x1/100), plasma drives (x1/2) and panel mass reduction (x1/2) to cut costs - and I agree, but he obviously wasn't talking about realistic SPS designs.