On Sunday 2004-01-18 13:08, Robert J. Chassell wrote: > 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.
First point: As I see it there are three ways to get things into orbit (or a battle) 1) Use a gun or variation on the theme of a gun. Cheapest if you want to put many payloads on targets. Hard on payloads. 2) Airplane. Intermediate 3) Missle (usu. a rocket) 2nd Point: Why couldn't you build a lauch vehicle with a fan-jet 1st stage (recoverable), Ram or scram jet 2nd stage (stage and recovery both optional) and a rocket 2nd or 3rd stage (disposible)? Then you wouldn't need a combination ram-jet/rocket. _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
