You're getting right to the heart of the matter, Lee. We have to get away from thinking in terms of specific single programs of any kind, and think in terms of the system we need for general space transportation. We get tunnel vision thinking in terms of a single destination or in terms of a single vehicle. The important thing isn't to decide where to go first, but to declare our intention to go everywhere eventually, and plan accordingly.

If we architect a space system, we can starting thinking in terms of modularization and standardization. Propulsion and habitation requirements are different for short- and long-term missions, but we can define broad categories. We can apply what we already know about space vehicle cabins to design a generic short-haul habitation module for the Earth-Moon system; and what we've learned from ISS and the others to design a long-haul module for planetary missions. Then propulsion: Chemical engines for short-duration missions, maybe ion or other "advanced" technologies for long-duration. We might continue to get by with solar power in the inner solar system, but we'll need nuclear generators eventually. Fasten the habitation modules for a given mission type to a generic "keel", plug in the reactor or solar panels, and strap on as many of the type of engines required for the mass. The electronics could be as standardized as today's avionics.

Do our homework and set up production, and then when we decide where to go, it will take just a short time to assemble the pieces and just go.

Am I being wildly optimistic? I don't think so. It's true that we don't know everything we need to know to do it, but we know enough, and that's all we need to get started. How much more do we need to know, for example, about the long-term effects of living in space? We already know the general outlines of bone- and muscle-mass loss and radiation effects; how many more decimal places do we need before we get our butts in gear?

NASA's eternal quest for total knowledge and perfect control over all the unknowns would keep us forever in LEO. Maybe they can't help it, because they are, after all, a scientific and R&D organization; their charter is to learn, forever. I'm saying that we take what NASA's already learned, we do the best we can with it, and accept a certain level of risk. I'd risk my ass in a system like that, if anybody'd give me a chance. I'll bet that there are enough of the people who are actually qualified who will accept that level of risk.

Ad astra, dammit!