[r9etb]

I had just read that the X-33 was 85% complete when the budget was pulled. I don't know why we pulled this when we could have at least tested one of these to learn more about shuttle flight.

IIRC, they were having serious delays and cost overruns on the propulsion system. That remaining 15% was 90% of the problem....

I don't know what the best Shuttle replacement would be. The answer to that question lies in what you really need to do. Is there really a need for a reusable spacecraft? If so, is there a crying need for one with a 50,000 lb payload capacity? How much of the Shuttle mission can be transitioned to the ISS? How much of it can be handled by big dumb boosters and one-shot manned capsules?

I think it's possible to build just about anything we need to build. The hard question is what you need, and whether you really need it.

[fooman]

I guess the genrally accepted needs are:

50,000 lb payload and reusablity and horizontal landing.