Speaking of which, do you think they'll have to pull Enterprise out of mothballs? At least to cover the shuttle missions that need to go up in future. Hard to say. I don't think the Enterprise is capable of powered flight. Are the main engines functional or just mockups? It was used for glide tests. Are the heat shield tiles capable of reentry from orbit? I'm not sure, since those releases from the 747 it was tested with didn't generate a lot of heat.
My guess is that NASA will have to get by with a reduced fleet. After Challenger there was a strong sense in Congress to appropriate funds to get a replacement. But that was '86, pre-9/11 and Iraq was only a distant cloud on the horizon. I don't get the same sense today. Congress seems to be saying we'll give to a few pennies (comparatively speaking) to tinker with some safety improvments on what you have left, but as far as anything new goes, forget it.
But as I said earlier NASA is going to have to do something to cover their collective a$$ as far as assurring survivability of their existing vehicles goes. If they drop another of these things, they're going to be looking at having essentialy zero capability of any kind of sustainable manned program. Then, its robots away (I'm sorry to say)...
Part of this problem goes back to the beknighted Seventies. Instead of a follow-on Mars Mission after the Apollo project, the budgeteers took over and gave us the Shuttle. Shuttle was supposed to be a means to an end, not an end in itself. As an aside, an engineer I once knew who graduated from Georgia Tech back in 1980 refused to even consider NASA, as he had heard the stories in the engineering community about the cutbacks and personnel layoffs that had occured after Apollo shut down.
Now we find only one alternative: the Orbital Space Plane concept, which will require some dandy engineering to get off the ground. For the time being, the remaining three shuttles will have to be watched and babied like hawks, and perhaps a polymer hardcoat put over the tiles as protection. Literally, it's all we've got. That 65 billion dollar ISS has to be serviced, after all.
Now, if someone would come up with the idea of using the ISS as a living quarter for construction crews who could assemble an interplanetary, nuclear powered Mars transit vehicle, then they'd be talking sense. A Mars transit vehicle is something you want built in orbit, not on the ground.
Be Seeing You,
Chris