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Date: Sat, 20 Jan 90 01:30:27 -0500 (EST)
Subject: SPACE Digest V10 #446

SPACE Digest                                     Volume 10 : Issue 446

Today's Topics:
		    Re: SSX Concept not a 'Steal'
		      Re: Shuttle fuel reserves
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Date: 19 Jan 90 16:51:29 GMT
From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo!henry@tut.cis.ohio-state.edu  (Henry Spencer)
Subject: Re: SSX Concept not a 'Steal'

In article <9001190742.AA05456@zit.cigy.> jcp@cgch.UUCP (Joseph C. Pistritto) writes:
>...  Mr. Hudson has confirmed,
>however, that he doesn't hold any 'rights' to the design that
>would inhibit it's development by another organization.

Which is just as well, since he didn't really invent it!  Rocketdyne and
McDonnell-Douglas, I believe it was, put a lot of effort into aerospikes
and single-stage-to-orbit concepts in the late 60s and early 70s; they
hold all the basic patents on the aerospike, although most of those have
probably expired by now.  Phoenix and SSX bear strong family resemblances
to a lot of their concepts, although details are different and innovations
did creep in.

>... These are similar pressure regimes as used on the
>Saturn V's F1 engines, which were good for a LOT longer than
>they actually were used for...

The F-1 specs in fact said that the engine was to be good for something
like 50 firings.  Now that was a durable engine, probably the best big
rocket engine the US has ever built.  There's no secret as to how this
was achieved, either:  the specs were most explicit that the F-1 was not
to push technology in any way, except insofar as sheer size (the F-1 was
a huge leap upward in size and thrust) absolutely demanded it.  Apart
from its enormous size, it was a very plain and unremarkable engine.
That's the way to build reliable hardware.
-- 
1972: Saturn V #15 flight-ready|     Henry Spencer at U of Toronto Zoology
1990: birds nesting in engines | uunet!attcan!utzoo!henry henry@zoo.toronto.edu

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Date: 18 Jan 90 01:30:21 GMT
From: van-bc!rsoft!mindlink!a752@ucbvax.Berkeley.EDU  (Bruce Dunn)
Subject: Re: Shuttle fuel reserves


     The shuttle uses nitrogen tetroxide as the oxidizer and MMH
(mono-methyl-hydrazine) as the fuel.  One of the reasons that mono methyl
hydrazine is used rather than hydrazine or unsymmetrical dimethyl hydrazine is
that at the optimum fuel:oxidizer ratio, the fuel and oxidizer tanks are
essentially the same size.  Hydrazine would give a slightly better performance,
but tends to be less safe (it is self-decomposing) and gives fuel and oxidizer
tanks which are not the same size possibly complicating tank layout.
     The shuttle normally uses the rear OMS engines for de-orbit burns, but has
the capability of using essentially any of the smaller thrusters to do the same
job (although of course burning longer).

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End of SPACE Digest V10 #446
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