SSI Activity (and its rebirth?)

it) $10,000 per pound, to lift a 150 pound person to orbit is only $1.5
million Yes, but how many pounds do two mass-drivers and their power supplies weigh? How many pounds do the (admittedly small-scale) mining equipment weigh? How about the L-2 mass-catcher? How many pounds do the smallest-conceivable ore refinery, metal-working shop, and manufacturing facility weigh? I'm a frequent defender of the NASA-Ames study, but it's important to remember that the lift costs they were factoring in were the ones NASA was promising at the time, not the ones actually achieved. At the very least, its costing is way off. But you still say that we could proceed with space resource use with present lift costs? I'd be very happy to be proved wrong on this, but if so, what has been the hold-up for these many years? Just lack of imagination on the part of industry? But one point that we can agree on is that the space markets have to come first, and vastlyimproved lift costs will follow. And I disagree with those who say that we shouldn't even think about things like use of space resources until we have a space elevator, or laser propulsion, or some equally-exotic lift system. But still, I'd expect we'll need at least one order of magnitude improvement in lift costs before we start building an orbital ore refinery/manufacturing facility. But the encouraging thing here is that I'm convinced we can get to one order of magnitude improvement with chemical rockets and present-day technology, given some sensible engineering work toward that end and some economy of scale. I would also agree with you that self-replicating systems are vital.