Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!wuarchive!uunet!stanford.edu!eos!aio!icarus.jsc.nasa.gov!dbm
From: dbm@icarus.jsc.nasa.gov (Brad Mears)
Newsgroups: sci.space.shuttle
Subject: Re: Shuttle computers (Really, "Drop the landin' gear, Jed!")
Message-ID: <1991May7.162403.566@aio.jsc.nasa.gov>
Date: 7 May 91 16:24:03 GMT
References: <1991May1.162201.16502@zoo.toronto.edu> <1076@igor.Rational.COM> <1991May3.111445.1@vf.jsc.nasa.gov> <1082@igor.Rational.COM>
Sender: dbm@gothamcity.jsc.nasa.gov (Brad Mears)
Organization: Barrios Technology @ NASA/JSC; Houston
Lines: 65

In article <1082@igor.Rational.COM>, wab@rutabaga.Rational.COM (Bill Baker) writes:
|> >	Why do you need to raise the landing gear.  Is the shuttle going to
|> >	wave off and go around again on a landing.?
|> 
|> I had no scenario in mind when I asked the question, but an obvious
|> one occurrs to me now:  What do you do when the gear deploys
|> partially?  Hasn't this already happened or is my memory playing
|> tricks?  I seem to remember a Shuttle touching down without the nose
|> gear down and scrubbing its nose pretty good.  

Wrong.  If that had happened, it would have done more than scrub the nose.


|> My problem with the robustness of the Shuttle system is that it seems
|> to be designed to deal with just one major failure at a time.  NASA's
|> answer to those highly unlikely scenarios combining two major failures
|> is to say that the crew is SOL.  

Wrong.  The basic design goal for shuttle has *always* been that it should be
able to withstand two failures and still assure crew safety.  This level of
fault-tolerance exists for *most* failures.  It is a harsh reality that you
can't protect against some failures.  For example, what do you do if a wing
falls off?  Deploy the backup wing?   


|> Still, that or another scenario could
|> occur in which it would be desirous to raise the gear.

Why don't you make a list of the scenarios in which it is desirous to raise the
gear?  Compute the probability for each of these happening.  Now compute the
risk you've *added* by introducing all this new equipment (motors, hydraulics, etc).
Do you still want that capability?


|> I'm sure you NASA guys (contractors are close enough) are tired of
|> getting ribbed about the Shuttle, 

I'm tired of irresponsible flamage.  If you ever want to have a *serious*
discussion about shuttle, give me a call.

|> but the fact is that anyone who has
|> followed the program these many years knows the problems.  Everyone
|> from NASA to USA Today has discussed the SRBs and turbo pumps.  In
|> other words, you don't have to be a rocket scientist to know what's
|> wrong with the Shuttle, at least with regard to the major problem
|> components.  

You may not have to be a rocket scientist, but you need a better source of
information than USA Today.

 
|> Wouldn't you
|> want to decrease that possibility as you increase its likelihood?

Do YOU have an infinite supply of money?

-- 
Brad Mears
dbm@icarus.jsc.nasa.gov

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