Steven from GameSpy had an interview with John Carmack, the guru of FPS game engines, main programmer of Id Software. The interview is not only about Doom III, also a little about Quake IV, and Id and John his future plans. Also a bit about the X-Prize.
GameSpy: Lets switch topics from your job to your hobby. Can you make a rocket to take two people in orbit?
John Carmack: Orbital is a lot more challenging. The X-Prize is about going up 100 kilometers and coming back down. You leave the atmosphere. You enter space and you remain weightless for 10 minutes or so. You come back in and it's world's tallest roller coaster ride. That would require about one-eighth of the energy required to go into orbit.
The X-Prize is absolutely obtainable. It is obtainable next year. There is little doubt in the technical ability on that and I think things are okay on the regulatory side. There are issues that we are working there, but we have plans and fallback plans.
Getting to is more fundamentally difficult, but it is not impossible. Rocket science has a mythology about it that isn't correct. Because of the way things evolved, we got our gigantic, expendable space vehicles.