Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!ucsd!nosc!crash!pro-canaveral.cts.com!gandalf
From: gandalf@pro-canaveral.cts.com (Ken Hollis)
Newsgroups: sci.space.shuttle
Subject: Re: SSME's
Message-ID: <5817@crash.cts.com>
Date: 22 Nov 90 22:56:07 GMT
Sender: root@crash.cts.com
Lines: 72

Greetings and Salutations:

>From: henry@zoo.toronto.edu (Henry Spencer)
>Subject: Re:  New Shuttle Engines
>People have explored more devious schemes, like variable-length nozzles,
>but no real use has been made of them yet.

The MX Missile uses a 2 piece extendible, variable length nozzle.

>>... If this is a heavy constraint, why light
>>the SSMEs at sea level at all ...
>
>One very important practical reason is that the #1 time for engine trouble
>is at ignition.  Lighting the SSMEs on the pad means that the more benign
>kinds of engine failures simply cause a pad abort.  There may also have been

You also would have a center of gravity that would be way off since this is an
asymmetrical launch vehicle.

(In another article...)

>>The Main Engine Controller is a major upgrade for the engine, with
completely
>>new programming & components.
>
>If I'm not mistaken, though, its external behavior is more or less identical.

Increased memory & CPU speed allows more parameter monitoring at a faster
speed.  This could be critical for shutting the SSME down faster if needed.

>Given that the MEC isn't a problem area of the engine, I think it fair to
>class this as an incremental improvement.

Some other improvements (You be the judge on incremental or not...)

Pratt & Whitney Turbopumps : Longer life expectancy between changeouts,
beefier & heavier.

Large throat MCC (Main Combustion Chamber)


>competitive procurement.  Considering how badly Rocketdyne's SSME has
>failed to meet its promises, one might suspect that the next big engine
>"Not to worry."                        |  henry@zoo.toronto.edu   utzoo!henry

At least give them credit for getting the performance requirements to 109% of
design.  While I will agree that the maintenance was not as expected, the
design was pretty ambitious.

>From: brettvs@blake.u.washington.edu (Brett Vansteenwyk)
>Subject: Re:  New Shuttle Engines
>My impression was (especially from reading Feynman's book) that the SSMEs
were
>virtually rebuilt after each launch--the component parts going into a system
>of inspection and repair such that when a given engine was rebuilt, many
>of the pieces in the new build came from other engines that were also in the
>rebuild process at the time--the original engine's parts by and large
would...
>             --Brett Van Steenwyk

I now see what you are referring to.  Currently about the only thing that is
removed each flight for inspection is the HPOTP (High Pressure Oxidizer
Turbopump).  However parts from one engine are removed (whether they failed or
are needed on another engine) and used in other places.  Each part has a
serial number, and they are all interchangeable.  But for the most part SSME's
do not have a lot of part swapping.

Ken Hollis

ProLine:  gandalf@pro-canaveral         
Internet: gandalf@pro-canaveral.cts.com
UUCP:     crash!pro-canaveral!gandalf