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From: fcrary@lightning.Berkeley.EDU (Frank Crary)
Newsgroups: sci.space.shuttle
Subject: Re: STS-40 Press Kit
Message-ID: <1991May17.034042.16781@agate.berkeley.edu>
Date: 17 May 91 03:40:42 GMT
References: <91136.092515TNEDDERH@ESOC.BITNET>
Sender: root@agate.berkeley.edu (Charlie Root)
Organization: ucb
Lines: 43

In article <91136.092515TNEDDERH@ESOC.BITNET> TNEDDERH@ESOC.BITNET (Thorsten Nedderhut) writes:
>1. Does there exist more Space Shuttle abort modes? Can you give me more
>   detailed information about them?

Pulling this out of the Rodgers Commision Report (pp178-184):

Return-to-Launch-Site Abort (RTSL): Used if a main engine fails in the
first four min. of flight. After the Soild Rocket Boosters burn out, (if
the failure was in the first 2 min.) and after "excess propellant" is 
burned. The shuttle turns around (its still in the atmosphere) and lands at
its launch site.

Transatlantic Landing Abort (TAL): Used if the engines fail later, or
less completely, that in the case of a RTSL. The shuttle alters its
launch profile so that it will fly a ballistic "hop" to a landing site
in Europe or Africa (I believe the primary site is in Spain).

Abort-Once-Around (AOA): If the shuttle works well enough to go into
orbit, but is unable to reach a stable orbit (e.g. so low that atmospheric
drag is a major factor.) The shuttle flys ONE orbit, then re-enters and
lands at Edwards. (Better hope the landing conditions are OK.)

Abort-TO-Orbit (ATO): Occurs in the event of a very late or limited
failure of a main engine. In this case, the shuttle goes into a low, but
stable, orbit. This may or may not cause a mission failure. A zero-gravity
science mission would not care that they were not in the intended orbit,
so long as it is a stable and recoverable orbit (Which the ATO is. If the 
orbit isn't, they Abort-Once-Around.) Some missions (Earth  observing, 
spacecraft launch, etc. ) may be sensitive to the final orbit. In such a
case the mission would be a failure. (I believe the ATO orbit is too low
to modify significantly with the OMS rockets.)
This abort mode was flown once. Flight 19 (51-F), orbiter Challenger, 
(If I'm wrong it was Flight 17(51-B) of Challenger) made an Abort to
Orbit in 1985.

These also exist emergency modes, such as ditching the orbiter in the
ocean. This, of course, destroyes the orbiter, but might save the crew.

After the Challenger loss, these modes were improved to make them safer, 
but I belive the main aspects (as I discribed above) were not changed.

				     Frank Crary
				     UC Berkeley