Newsgroups: sci.space.shuttle
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Shuttle computers (Really, "Drop the landin' gear, Jed!")
Message-ID: <1991May2.230207.20055@zoo.toronto.edu>
Date: Thu, 2 May 1991 23:02:07 GMT
References: <1991Apr26.111139.1@vf.jsc.nasa.gov> <1991Apr30.171707.27685@isc.rit.edu> <1991May1.162201.16502@zoo.toronto.edu> <1076@igor.Rational.COM>
Organization: U of Toronto Zoology

In article <1076@igor.Rational.COM> wab@rutabaga.Rational.COM (Bill Baker) writes:
>Why in the *hell* can they only *lower* the landing gear?
>Theoretically, I suppose, you only need to lower it in flight, but it
>still seems like bonebrain engineering to me.

No, it's minimum-weight engineering.  Being able to raise the gear again
needs extra machinery.

It's common in spacecraft for actions that go only one way to be implemented
with machinery that is only capable of going one way, but is simpler and
lighter than two-way machinery.  Pyrotechnic valves are an example:  the
valve opens when you fire a small explosive charge, which makes for a very
lightweight and reliable valve actuator that only goes one way.
-- 
And the bean-counter replied,           | Henry Spencer @ U of Toronto Zoology
"beans are more important".             |  henry@zoo.toronto.edu  utzoo!henry