Path: utzoo!utgpu!attcan!uunet!lll-winken!lll-tis!helios.ee.lbl.gov!pasteur!ucbvax!decwrl!decvax!tektronix!reed!douglas
From: douglas@reed.UUCP (P Douglas Reeder)
Newsgroups: sci.space.shuttle
Subject: rockets with nozzles at the top
Message-ID: <10142@reed.UUCP>
Date: 26 Aug 88 05:06:21 GMT
References: <1001@scicom.alphacdc.com> <44700006@pyr1.cs.ucl.ac.uk> <6204@ihlpl.ATT.COM>
Reply-To: douglas@reed.UUCP (P Douglas Reeder)
Organization: Reed College, Portland OR
Lines: 22

In article <6204@ihlpl.ATT.COM> knudsen@ihlpl.ATT.COM (Knudsen) writes:
>
>Robert Goddard used this upside-down design in his early
>liquid rockets of the '20s; since the nozzle pulls rather than
>pushes the ship, you get free stability without servos, gimbals,
>and all that other failure-prone stuff.

   The problem, as Goddard found out, was that a FIXED nozzle at the top
is just as bad as one at the bottom.   If the connection is flexible
then it works like you expect.  This is not obvious, but consider carefully:
a nozzle at the front a fixed frame rocket pushes in EXACTLY the same
direction as one at the back.

   An unrelated question:   Why is it not possible to use the OMS thrusters
to make a powered landing on the shuttle, if unpowered landings are so 
undesirable?  Extra fuel would be required, cutting into payload,
unfortunately.

-- 
Doug Reeder                           USENET: ...!tektronix!reed!douglas
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