space@mit-mc (02/25/85)
From: WOO IL LEE <lee@su-star> From "Aerospace Americe", Feb. 85, pg.1: .......Robert Cooper, director of the Defense Advanced Research Projects Agency, says that variable geometry hydrogen-burning supersonic-combustion ramjets (SCRAMjets) "using current state-of-the-art technology" could take off horizontally and accelerate to Mach 25, using existing Pratt & Whitney RL-10 rocket engines for final orbit injection. Motivation for their development, he said, is the need to reduce payload launch costs to $100/lb. ------
henry@utzoo.UUCP (Henry Spencer) (02/28/85)
SCRAMjet technology is mostly on paper. It is extraordinarily difficult
to test realistically, since airframe and engine have to be integrated
closely (or so I'm told), and nobody's felt like financing a dedicated
research aircraft just to check it out.
SSTO does not require SCRAMjets, or variable geometry either. It can
probably be done with an aerospike nozzle plus modern lightweight
structural materials, burning conventional propellants in a fairly
conventional way. There is little in the way of difficult or uncertain
engineering in this approach. (By contrast, variable-geometry SCRAMjets
sound like a recipe for horrendous complexity and expense.) And some
of the folks pushing this method think that $100/lb is a ridiculously
high cost to orbit and could be beaten easily.
--
Henry Spencer @ U of Toronto Zoology
{allegra,ihnp4,linus,decvax}!utzoo!henryal@ames.UUCP (Al Globus) (02/28/85)
> From: WOO IL LEE <lee@su-star> > > > From "Aerospace Americe", Feb. 85, pg.1: > > .......Robert Cooper, director of the Defense Advanced Research Projects > Agency, says that variable geometry hydrogen-burning supersonic-combustion > ramjets (SCRAMjets) "using current state-of-the-art technology" could take > off horizontally and accelerate to Mach 25, using existing Pratt & Whitney > RL-10 rocket engines for final orbit injection. Motivation for their > development, he said, is the need to reduce payload launch costs to $100/lb. > > > ------ It should be noted, however, that horizontal takeoff results in an orbiter with wings that are twice as heavy and a body half again as heavy as vertical takeoff. This data is in the same issue but a different article. The effect is caused by aerodynamic loads generated during pullup.
al@ames.UUCP (Al Globus) (02/28/85)
> ...And some > of the folks pushing this method think that $100/lb is a ridiculously > high cost to orbit and could be beaten easily. > -- It's amazing how cheap any easy things are when they're still on paper (or in the computer) and you haven't had to make them work yet. Remember when the shuttle would bring costs down to $500/lb to LEO? I think it runs around $3,000 and up in actuality.
henry@utzoo.UUCP (Henry Spencer) (03/05/85)
> > ...And some > > of the folks pushing this method think that $100/lb is a ridiculously > > high cost to orbit and could be beaten easily. > > It's amazing how cheap any easy things are when they're still on paper (or > in the computer) and you haven't had to make them work yet. Remember > when the shuttle would bring costs down to $500/lb to LEO? I think it > runs around $3,000 and up in actuality. Yup. But remember that the under-$100/lb cost for the scramjet shuttle is also a paper number, and is thus fair game for comparison. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry