The concept of the Shuttle--a reusable orbiting payload vehicle sounds like a good idea but it has never worked out with with our current technological and budget limits.
Simply put NASA has placed all its eggs in the Space Shuttle program and because of that our rocket technology and space exploration program has suffered. The Russians are still a generation ahead of us on rockets because they still produce them and rely on them.
Disposable rockets are 10 times cheaper and 100 times more structurally sound than a reusable space shuttle.
In addition the cargo bay of the space shuttle limits the payload capacity of the shuttle while on disposable rockets the payload is theoretically unlimited.
PS: A story I heard about the approach of the Russian and NASA space programs is very illuminating. The story goes like this, when a Russian space agency official was told by a proud NASA official about the expense and effort of its engineers that goes into desgining even the so called astronaut or space pen that allows it to be used in zero gravity the Russian replied "we use pencils."
It is time to start using disposable-reliable space vehicles and open up space to private industry.
For starters I would ask congress to authorize a bounty that it would reimburse any private organization that would send a manned mission to Mars and return its crew to Earth safely that would cover all expenses plus 15%.
Competition to Mars would capture and ignite the world's imagination.