Newsgroups: sci.space.shuttle
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: space news from Aug 15 AW&ST
Message-ID: <1988Sep13.170421.1849@utzoo.uucp>
Organization: U of Toronto Zoology
References: <1988Sep12.032459.25617@utzoo.uucp> <972@netxcom.UUCP>
Date: Tue, 13 Sep 88 17:04:21 GMT

In article <972@netxcom.UUCP> ewiles@netxcom.UUCP (Edwin Wiles) writes:
>>No attempt would be made to recover Shuttle-C's SSMEs; they would be
>>SSMEs that are near the end of their rated lives as shuttle engines.
>
>Am I correct in believing:
>	a) These are the 'main' liquid fuel engines for a shuttle?

Yes, SSME is Space Shuttle Main Engine.

>	b) That they would make it to the same orbit as the payload?

Yes.

>If so, these engines could be recovered in orbit, for use in 'scooters'.
>Some sort of small craft that didn't need much in the way of thrust, so
>that they could be run at something like 10% (or less) of their normal
>thrust...

This would not work, I'm afraid.  For one thing, there are limits to how
much you can throttle a rocket engine; I doubt very much that an SSME
would work at 10%.  Certainly they aren't rated for it and aren't designed
for it.  For another thing, most booster engines -- I think the SSMEs are
included -- are not restartable without an overhaul.  Their ignition
systems, in particular, are basically one-shot.  That is not a trivial
problem; starting a big engine safely can be quite tricky.

> If the Shuttle-C would have OMS engines as well, these would be
>even more useful in this capacity...

Now *that* sounds like a reasonable idea.  The OMS engines are down in a
practical thrust range, and they are restartable.  One possible wart:  I
don't know how easy it would be to refuel them in orbit.
-- 
NASA is into artificial        |     Henry Spencer at U of Toronto Zoology
stupidity.  - Jerry Pournelle  | uunet!attcan!utzoo!henry henry@zoo.toronto.edu