Robert J. Chassell wrote:
>
> * An air-augmented chemical rocket. Currently, rockets carry all
> the oxygen they need with them. An air-augmented chemical rocket
> operates part of the time as a ram jet, taking in oxygen from the
> atmosphere. This reduces the mass of oxidizer the rocket must
> carry.
I don't see - philosophically - how this can be an advantage.
"Ramming" air is essentially a collision problem, that
significantly reduces the speed of the rocket. If you carry the
oxigen with yourself, it is moving with the speed of the rocket.
Yes, there are problems with a ram jet. But when you carry the oxygen
with yourself, you have to accelerate it. That takes a great deal of
oxidizer and fuel.
The best estimates I have seen are that a combined cycle rocket/ram
engine has the equivalent of a specific impulse in the 600s (i.e., the
equivalent of a pure rocket with an exhaust velocity of 6 km/sec,
although its actual exhaust velocity is lower), where a nuclear
thermal engine has a specific impulse of 800 - 900 (8 - 9 km/sec) and
a hydrogen-oxygen engine, like the Space Shuttle main engines, has a
specific impulse in the 400s, (4 km/sec) and its solid fuel rocket
engines -- which enable the shuttle to boost -- are have a lower
specific impulse.
--
Robert J. Chassell Rattlesnake Enterprises
http://www.rattlesnake.com GnuPG Key ID: 004B4AC8
http://www.teak.cc [EMAIL PROTECTED]
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