SSI Activity (and its rebirth?)

are making. Why do you think a "clanking replicator" would be this big, I just expect replicators to start out big and then decrease in size as the technology improves, in much the same manner computers have. I expect the first replicator to be big based on the present size of a largely-automated factory for producing cars, bearing in mind that cars are probably going to be a lot simpler than a machine able to make a copy of itself. and why do you think Cheap-Access-To-Space would be easier to develop
than a shuttle-bay-sized clanking replicator? It depends on what we mean by CATS. If by that we mean a space elevator, or a laser-launcher, or perhaps evena scramjet, the replicator might well be more near-term. But if by CATS we mean bringing launch costs down to 1/10 or 1/20 current costs, that can probably be done without resort to new technology. My response to this is kind of like my response to the space elevator people, who are tending to go, "Look, carbon nanotubes! We'll have a space elevator in 15 years!" When we start riding elevators up and down skyscrapers with nanotube cables and driving cars across suspension bridges with nanotube cables, then it will be the time to start getting excited about the prospect of space elevators. By the same token, I expect to see replicators outremaking some desert somewhere before I expect to see them in space. That said, do I doubt that with some good engineering work, an ore refinery, metal-working shop, and fabrication facility could be miniaturized to 1/10 or 1/20 the mass of their Earthbound equivalents? Yes I do. And I think Gerry O'Neill did too, was very much into the idea of "seed" factories and self-replicating systems, and very much believed the High Frontierscenario stood or fell on these concepts. He just didn't expect themto get miniaturized to the point of fitting into a single Shuttle cargo bay in any near-term future. Also, even if it was the size of a small apartment building, and took
100 shuttle flight (so, about 100 billion dollars) in lift costs, well
doesn't that still show CATS is unneeded? If our only problem is that our scenario only needs 100 billion dollars, then I'd say that's a pretty big problem. Yes, I take your point that we've spent as much or more on other things. The cost of business as usual will be staggering. But the price tag for High Frontier is still a problem for us. CATS may not be the salvation of us all, or all things, and may well be a bit of the case of putting the cart before the horse, but I don't thinkit's a completely foolish endeavor.