Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!usc!ucselx!crash!pro-canaveral.cts.com!gandalf
From: gandalf@pro-canaveral.cts.com (Ken Hollis)
Newsgroups: sci.space.shuttle
Subject: SSME's
Message-ID: <5667@crash.cts.com>
Date: 15 Nov 90 10:36:14 GMT
Sender: root@crash.cts.com
Lines: 96

Greetings and Salutations:

I don't always catch reply's to messages, so if I miss something you wish for
me to see, just send it & I will try to answer.

Now in particular:

>From: brettvs@blake.u.washington.edu (Brett Vansteenwyk)
>Subject: New Shuttle Engines
>
>Not long ago it was noted that the first of Endeavour's engines had 
>arrived at KSC.  Some mention was made that these engines were "new and 
>improved".

The "New & Improved" was mostly the new Block II engine controller, going from
an Honeywell old fighter (F-100? Super Saber?) jet fire control computer (can
you believe discrete components, plated wire memory...) To a REAL MC68000
micro (space hardened, of course...).  Other changes are from the HPFD (High
Pressure Fuel Duct) changing from Titanium to Inconel (This had already been
implemented) and other misc changes (nothing major).

>[1].Are these new engines useable in the older shuttles?  It would seem

Yes, these engines are LRU's (Line Replaceable Units)

>[2].Are these engines part of a more "mature" system? 

Currently Pratt & Whitney is working on a second generation HPFTP (High
Pressure Fuel Turbopump) and HPOTP (High Pressure Oxidizer Turbopump).  These
are also LRU's, but P&W has integrated advances in manufacturing techniques,
for example less welding.

>[3].(Slight rehash from [2]).  While the SSME's have not been a 
>particular safety problem (in hindsight, at least relative to the 
>SRB's), their turnaround launch to launch has been a nightmare for 
>costs--so much of each engine needs to be rebuilt.

Oh? About the only thing that has to be "worked on" is the HPOTP.  Other than
that, they are really not that much different than the rest of the shuttle for
turnaround.

>  This seems to stem 
>from the fact that this design pushed the envelope for efficiency and 
>thrust to weight ratio. This engine has been in use for almost 10
>years, and it would seem that it could be classified as a "mature" 
>system by now--a learning curve with subsequent reduction in 
>refurbishment costs as well as a more reliable engine.  Is there 
>evidence to indicate that this has happened?

Yes, it has happened, and they are still learning new things every day.  This
is part of the reason for the new P&W HPOTP & HPFTP.  Please remember that it
takes YEARS to qualify anything for NASA on the shuttle.  Changes are made
gradually so that you don't screw anything up by fixing one small problem to
create a BIG new problem.

     .
     .
     .

>[4].Whenever I see any discussion about new launcher development, I 
>never, or almost never see any suggestion to using the SSME's, nor do I 
>see any indication of an engine derived from SSME technology.  The 
>tendency is to discuss systems originating 25 or even 30 years back.  I 
>am assuming that the SSME was the most recent major engine development.  
>Has all the time and talent spent to make the SSME work been wasted on 
>what is now considered an evolutionary dead-end?  While it may seem 
>disconcerting, it seems where the evidence is pointing.
>

The SSME is made for a MAN RATED rocket.  Redundancy, double checks, etc.  It
was also created as a singe stage to orbit rocket, able to work both at sea
level & in the vacuum of space.  When the unmanned rocket motors are designed,
they don't need all of the safeguards, and they are designed to operate only
within a certain part of the atmosphere (the section they are active for) not
the whole way.  The SSME's are EXPENSIVE, not to be used on expendables (But
if you were riding that roman candle, wouldn't you be rest assured that the
gov't bought the BEST low bid equipment they could... ;->).

>[5].If not the evolutionary dead-end as postulated in [4], could there be
>an SSME derivative for an expendable launcher, or a restartable version
>for purposes similar to the Saturn 3rd stage system? 

Indeed, you find Rocketdyne using the experience gained from the SSME's to
design cheap engines for the expendables (By the way, Rocketdyne makes MOST of
the engines for the expendables anyway...).

>        Just some random thoughts.
>             --Brett Van Steenwyk

Just some random answers.....

Ken Hollis

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