Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: shuttle payload bay doors??
Date: Tue, 20 Feb 2001 16:42:26 GMT

In article <3a927360.1668656@news1.on.sympatico.ca>,
noone <noone@sympatico.ca> wrote:
>...I understand that there are time restrictions for
>cooling reasons as to how long they can remain closed before they must
>either land or abort landing and open them up again.

Correct.  The radiators on the inside of the doors are the orbiter's main
cooling system, and the auxiliary systems used for descent have quite
limited operating times.

>What would the contingency be if one or both the doors failed to
>either re-open before and aborted landing OR more importantly failed
>to close properly. Since they close them only hours before landing
>this doesn't seem like enough time to me to mount an EVA to fix a
>problem for that landing opportunity.

If the doors fail to close, probably they miss that landing opportunity
while they troubleshoot.  If they're short on consumables and can't wait,
or troubleshooting fails, they do an emergency spacewalk to crank the
doors shut manually.  Yes, this is somewhat risky due to the lack of
prebreathing time, so they may load up on painkillers in advance.  (Even
the normal spacewalk preparations include taking aspirin as a precaution
against minor decompression sickness.)

I'd guess that an idle orbiter could get by with only one door open.  If
neither of them open, then you declare an emergency, and either cancel the
wave-off and come down anyway, or if the weather's just too nasty, pick
the closest emergency landing site that has acceptable weather.
--
When failure is not an option, success  |  Henry Spencer   henry@spsystems.net
can get expensive.   -- Peter Stibrany  |      (aka henry@zoo.toronto.edu)