...NASA would be the fatal albatross around the SE Project's neck.

Let's imagine otherwise... as for Brad Edwards' assessment of costs here's my guesstimates. He says an SE costs $7 - $10 G, which means the SE has to lift ~ 70,000 to 100,000 tons to GEO to break even at $100/kg. Initial plans are for the SE to carry ~ 20 t/wk, or just 1040 t/year, which is a SLOW way to get that much to GEO. I based my figures of ~ $500/kg on a cost of $15 G and 30,000 t haulled to GEO over the SE's lifetime. But future SEs would cost much less and have quicker rates to GEO. 100 t haulled at 1200 mph is a realistic goal, which will ultimately mean 20 hours to GEO and ~ 43,800 t/yr.

As for SPS... Good quality PV cells manage about 225 W/kg, which means a cost to GEO of ~$2.22/W @ $500/kg. Less than the actual cost of the cells. However being in space potentially gives the PV cells an advantage over terrestrial arrays of about ~ 4.3, hence they might be cheaper overall for the same amount of power installed. On Earth power per sq.m averages ~ 2500 KWh/yr at the very best with no cloudy weather. In space there are no clouds ever and 12,000 kWh/yr.

The energy costs to GEO are a fraction of the overall cost per kilo. I'm not overly sure what the actual figures are though, but with 100% efficiency energy expended to GEO is ~ 100 MJ/kg. Electrical motors get about ~ 85 - 95% efficiency, but the actual expended energy during the long climb could be a lot higher(?) Anyway assuming 10% that's 1 GJ/kg, which is ~ $13.90 @ $0.05/kWh. With matched payloads and some sort of coupling between rising and descending "sky-lifts" then the energy cost could go way down. But what are we haulling down from GEO at 43,800 t/year???

I'm sure you'd have some good ideas GB.

Adam