Path: utzoo!attcan!uunet!cs.utexas.edu!samsung!brutus.cs.uiuc.edu!psuvax1!psuvm!ricevm1.bitnet!barry
From: BARRY@RICEVM1.BITNET
Newsgroups: sci.space.shuttle
Subject: Re: Shuttle roll maneuver
Message-ID: <1601BARRY@RICEVM1>
Date: 4 Nov 89 19:48:32 GMT
References: <1758@cfa237.cfa250.harvard.edu> <7255@ingr.com> <1989Nov4.073508.10143@utzoo.uucp>
Organization: Rice University - ICSA
Lines: 32

As a Space Shuttle Flight Controller, I feel compelled to respond to the
roll maneuver controversy.

The launch pads are indeed retrofitted for the Shuttle program, and as
noted in previous messages, some sort of maneuver would have to be performed
from any *fixed* platform for a given orbital inclination.  The launch pads
are so big that I can't imagine rotating them, along with the flame trench,
cryogenic recirculation lines, etc.  There are only three DOD missions
remaining (on the current manifest), so secrecy is not a concern.  Besides,
the inclination is obvious just after liftoff.  The folks in the Launch
Control Center at KSC like to be able to see the orbiter, too.

The orbiter is carried underneath the stack for several reasons.  The
heads-down configuration is more stable for roll and pitch than the
heads-up configuration; thus it's more efficient with propellant.  The crew,
regardless of displays, like to have a horizon reference.  The antennae
for communications with Merritt Island Launch Area (MILA) and Bermuda
during ascent must point to the ground, and the external tank must not
block the transmission path.  [You say, "What about TDRSS?"...]

One note for interested parties: for intact launch aborts (the Return To
Launch Site (RTLS) and Trans-Atlantic Landing (TAL) modes), the orbiter
actually winds up in the heads-up configuration prior to main engine
cutoff in order to separate from the external tank by simply dropping it.
In nominal separation modes, the orbiter remains in the heads-down
configuration and translates away from the external tank from underneath
it.  Most of the time spent on-orbit is in the heads-down attitude.

Don't think that the ascent design folks haven't thought about the
alternatives!

Matt Barry (barry@ricevm1.rice.edu, mbarry@nasamail.nasa.gov).