Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!apple!uokmax!jabishop
From: jabishop@uokmax.ecn.uoknor.edu (Jonathan A Bishop)
Newsgroups: sci.space.shuttle
Subject: Re: apollo 13
Message-ID: <1990Dec16.053427.23566@uokmax.ecn.uoknor.edu>
Date: 16 Dec 90 05:34:27 GMT
References: <90346.083237TACON019@ysub.ysu.edu> <1990Dec14.053652.4228@cimage.com>
Organization: Engineering Computer Network, University of Oklahoma, Norman, OK
Lines: 33

gregc@cimage.com (Greg Cronau) writes:

>In article <90346.083237TACON019@ysub.ysu.edu> TACON019@ysub.ysu.edu (Fred Ullom) writes:
[Discussing Apollo 13 return]
>The CSM/LEM never went into earth orbit after return from the moon. They were
>targeted for a direct reentry from translunar flight. The SM and LEM separated
>and went straight into the atmosphere and burned up. The CM skimmed the upper
>atmosphere on a tangental trajectory and then pulled up back out of the upper
>atmosphere to shed some of the heat from the heat shield. It then fell back
>into the atmosphere at a steeper angle due to the lost velocity from the first
>encounter. It was able to pull up through a combination of it's trajectory and
>a certain amount of aerodynamic lift provided by it's shape. It is sort of an
>aerobraking manuever. I *think* all the returning Apollo moon flights used this
>method of reentry. I don't believe there was a need to first attain earth orbit
>on return from translunar flight.

     You are correct.  You just plunge right in.  Bit of trivia:  Apollo 10 had
the fastest re-entry; I don't recall what the speed was, but it was the fastest
man has ever gone.
     Another note: Apollo 13 did use the skip or 'lift vector up' re-entry;
they were also very near the edge of the corridor where this was safe; if they
had been approaching the atmosphere at a slightly shallower angle, they would
have had to change to a 'lift vector down' re-entry, which means they would
have entered to 'bite' into the atmosphere rather than skip.  There was some
debate in Mission Control just prior to re-entry over whether the profile
should have been changed; fortunately, the correct decision was made.
     The above information is from memory from reading "13: The Flight that
Failed."
-- 
jabishop@uokmax.ecn.uoknor.edu

"Ground Control to Major Tom: Your circuit's dead; there's something wrong.
Can you hear me, Major Tom?" -- David Bowie