[geoschmo]

Yeah, if you are talking about flying straight up under engine power, ala Yeager at the end of the right stuff, the lift isn't even such a big deal cause going straight up the wings aren't generating much lift. Well, they are, but it isn't helping to gain altitude anyway.

The problem is the jet engine needs air. I don't know how much oxygen it needs to be able to keep jet fuel burning and spinning the turbines. I am sure it needs some. But even if you could keep the turbines magically spinning somehow without oxygen you wouldn't get any thrust with no air to compress and push out the back.

That's why you need a rocket to keep generating thrust past a certain point. The rocket fuel has it's own oxygen in the form of a liquid or solid, and it generates thrust by the expansion of that fuel as it burns.

Geoschmo