We came to Houston a day before our cruise to visit this museum. We paid $120 for 4 of us and we was going to spend there at least few hours. However, after an hour we realized, that there is not much left to do.
The only wow factor there is the faded 747 with the shuttle on top, but 15-20 minutes is more than enough to observe it.
It not even close to Space Museum in Washington, DC (with free admission btw)