Suppose the US was satisfied with just 4-5 CEV flights a year. They would go to the ISS, or maybe just sit up in orbit doing little stuff. Or they could dock with one of the Bigelow stations and do stuff there, if they ever get built. Or we could build a minimalist, temporarily manned station to do stuff if ISS becomes unserviceable. No Ares, No missions beyond Earth orbit. Nothing beyond the CEV and the ISS or a new, minimalist station. Just good old fashioned shuttle style research would be left after the ISS wears out or is slowly bought out by private interests and/or other nations.
Yep, this would waste all of designed capacity of the CEV to support more ambitious missions. And a lot of the fixed cost of maintaining ANY manned program would remain. The scientific return per dollar would probably be lower than more ambitious missions...although, lets face it, the scientific return PER DOLLAR of manned space flight is ridiculously low anyway. If I had to bet, I would bet that this is true even considering "spinoffs" and engineering experience retained. More science could be done by allocating the money saved to unmanned missions or other science programs. And unmanned missions give spinoffs as well.
A case could be made for such a program. Nothing new would be learned. But we would not have to start from scratch if the money for more ambitious missions ever turned up. We would keep the capacity for manned space flight if it was ever needed for economic or military purposes. However, If manned space turns out to be just a waste of money for a very long time, we would have wasted as little money on it as possible. So to some it may seem a good way to hedge our bets - though I have my doubts.
Lets face it, unless someone other than NASA seriously threatens to do something big beyond earth orbit before us, this is the kind of space program we are going to get, so it makes sense to think about it, depressing as it may be.
1. How much would such a program cost compared to the full constellation program, or no program at all? There are so many fixed cost to having ANY manned program that the savings are probably smaller than one might expect.
2. Would it be better to abandon all government sponsored manned spaceflight rather than have a minimalist program?
3. Suppose manned space truly is not worth the cost but must be maintained for political and "bet hedging" purposes. would this kind of program be the best option? I suspect that the majority of the public takes this viewpoint toward the government sponsored manned space program.....