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From: v071pzp4@ubvmsd.cc.buffalo.edu (Craig L Cole)
Newsgroups: sci.space.shuttle
Subject: Re: Shuttle computers (Really, "Drop the landin' gear, Jed!")
Message-ID: <75299@eerie.acsu.Buffalo.EDU>
Date: 7 May 91 15:15:56 GMT
References: <1991May1.162201.16502@zoo.toronto.edu> <1076@igor.Rational.COM> <1991May3.111445.1@vf.jsc.nasa.gov> <1082@igor.Rational.COM>
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In article <1082@igor.Rational.COM>, wab@rutabaga.Rational.COM (Bill Baker) writes...
>In article <1991May3.111445.1@vf.jsc.nasa.gov> kent@vf.jsc.nasa.gov writes:
>>> 	* Landing gear that only goes in one direction
>>
>>	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.

Pardon me, but when did _this_ happen? The only landing related failure
was the last KSC landing pre-Challenger. One of the shuttle's brakes
locked, blowing one of the tires. This led to the ending of KSC landings
until the nosewheel steering system was installed (done) and new
carbon-carbon brakes were isntalled (done, but still being tested)

> 
> [Scenario for raising gear deleted]
> 
>I don't see why this would make it more difficult to raise the gear.
>Presumably it would make it more difficult to close the gear bay
>doors.

I've always been told that the landing gear mechanism is designed to
be simple -- it'll only open once (per trip), but it'll always
open _right_.

An interesting sidenote - I've always understood that the shuttle
can land completely autonomously, but someone has to be there to
at least lower the landing gear, since the shuttle computers are
in no way in control of it. The reason that the computers aren't
able to lower them, is _because_ they only open once. NASA didn't
want a computer glitch to lower the landing during launch (really
ugly thought) or in orbit (still ugly). The shuttle couldn't
survive reentry with its landing gear down.

I can't quite agree with NASA on this one. Having landing gear you
can raise would have made the system a little more complex and maybe
a bit heavier, but the one-shot gear opens up a couple of new
problems:

1) Inability to test gear in orbit before landing.
2) Inability to land (safely) should the astronauts become
   incapacitated.

That, of course, is only true if the shuttle can land completely
autonomously. Correct me if I'm wrong...

Craig Cole
University at Buffalo
V071PZP4@UBVMS.CC.BUFFALO.EDU
V071PZP4@UBVMS.BITNET