What the hell does the Space Shuttle have to do with any of that? What is the Space Shuttle exploring? NOTHING. ITS A DAMNED PORK-BARRELING BOONDOGGLE! There seems to be a new political-correctness taking over FR: Anything that NASA does is sacrosanct. NASA is a just another bureacracy like the Dept. of Education or the Social Security Administration. The sooner it is abolished, the better!
If that is the conclusion you drew from my post, you need to work on your reading comprehension.
The shuttle is a failure, but NASA nor congress will admit it. NASA won't because, hey, when was the last time a bureaucracy said, "oops"? Congress won't because it mismanaged NASA and the shuttle to produce that failure.
NASA should be exploring, but instead it is wedged into low earth orbit like a 500lb man in a 24" door. Thirty years ago, private enterprise should have been starting a viable space industry. NASA should have spent the last twenty years paying for space on American Spacelines, not operating the shuttle.
That is why whatever replaces the shuttle must be designed around return on investment more than anything else.