Obama has gutted NASA to the extent that the only way our Astronauts can get to the space station is by hitching a ride on a Russian rocket.
As Neil mentions, the NASA budget at its peak was only one half penny for each tax dollar. The current entitlement spending is 43¢/tax dollar and therein lies a big part of our problem...
Just as with our industrial infrastructure, there is a fixed window of time in which we can rebuild NASA economically. Take too long and we have to start from scratch again, training people, building new infrastructure and establishing new research centers -- the cost would be prohibitive and we would have lost our foothold on the universe.