Path: utzoo!attcan!uunet!husc6!think!craig
From: craig@think.COM (Craig Stanfill)
Newsgroups: sci.space.shuttle
Subject: Re: Heavy Lift Capacity Boosters
Message-ID: <28994@think.UUCP>
Date: 3 Oct 88 16:18:15 GMT
References: <677@eplrx7.UUCP> <2240@ssc-vax.UUCP> <1402@viper.Lynx.MN.Org> <2248@ssc-vax.UUCP> <6936@ihlpl.ATT.COM> <1988Sep30.165056.18848@utzoo.uucp>
Sender: news@think.UUCP
Reply-To: craig@mneme.think.com.UUCP (Craig Stanfill)
Organization: Thinking Machines Corporation, Cambridge, MA
Lines: 29

One of the problems associated with shuttle-derived expendables
is the expense of the engines.  Getting them back to earth seems
to be a difficult problem.  For example, developing independent
re-entry pods for the engines seems a difficult undertaking.

Another near-possibility would be to recover the engines via
shuttle; after the shuttle's payload is deployed it would
be (conceptually) possible to grab a few engines, stash them
in the cargo bay, and bring them back down.  However, I see
several problems with this, and I doubt it is practical.

1.	Part of the point of shuttle-derived expendables is to 
	re-use the design of the aft part of the shuttle in the
	new vehicle.  Clearly, this pod would be too large to fit
	in the cargo bay, so the engines would have to be removed from
	the thrust structure first.  Unfortunatly, the engines are not
	designed to be jetisoned in-orbit, and making this possible is
	likely to require a major redesign of the thrust structures
	and connections.  This loses a major part of the
	attractiveness of the redesign.

2	Matching orbits might be a problem.

3.	It might considered too dangerous to put the engines into the
	cargo bay during re-entry.

This is the closest I can come to a method for recovering the engines,
but even here there are major problems.  I doubt the re-use of the
engines would justify the major re-engineering efforts.