---------- > From: Trent Shipley <[EMAIL PROTECTED]> > To: Killer Bs Discussion <[EMAIL PROTECTED]> > Subject: Re: Martian Emotion > Date: Sunday, January 18, 2004 5:56 PM > > 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) 4) Space Elevator. And Ye call yeself a brin fan. _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
