Andrew Case wrote:
Ron Wanttaja wrote:

And when you come down, you have to get rid of all the 25,000 FPS. Orbital
spacecraft take some small portion away with rockets, and scrub off the
rest in atmospheric friction. The X-Prize folks have a far simpler
problem. Hopefully, that'll be addressed in the Y-Prize. :-)


you end up at zero altitude with nonzero
speed. This is called "lithobraking" :-)

Nice term. Like flying through cumulo-granite. : )

Coming in from orbit you can decelerate higher up, and take advantage of a
bit of lift to keep you in the thinner part of the atmosphere longer. A
ship like Rutan's can also do this to a certain extent since it will have
a substantial horizontal component of velocity.

The easy way is to come in like a capsule, with a throwaway, ablative
shield. The engineering is infinitely easier. OK, maybe not infinite,
but lots. The next NASA ship to fly will be capsule-like, I bet.