wlhaught wrote:
Alright, back to powered flybacks for first stages. Are jet engines
worth the trouble of extra systems?

As I recall, I read somewhere that the shuttle uses half its fuel to
reach 1,000 mph.


You sure?

I have a copy of a speed/height/time diagram of the shuttles ascend.
1000 mph would be 1600 km/h. The diagram says that this speed is
reached within the first minute of launch at a height of about 8-10
km.

Launch takes 8.5 minutes, boosters burn 2 minutes. If you would say
half of the boosters fuel is used up at 1000 mph that would fit. But
total fuel including the fuel of the big external tank?

Ok, solid booster rocket fuel is quite heavy, and the booster burns
faster in the beginning than at the end. So maybe overall this could
be true.

But what does it mean? Solid rocket boosters are not economic?

A somewhat related fact: the shuttle has to throttle its main engines
during ascent within atmoshpere, because the fragile orbiter wings
can't stand the wind pressure.

Does anone know how much of a performance penalty this means?
(And at what height/speed this happens)