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From: eder@ssc-vax.UUCP (Dani Eder)
Newsgroups: net.columbia
Subject: Re: Telling When Launch Will Occur
Message-ID: <314@ssc-vax.UUCP>
Date: Mon, 7-Jan-85 15:29:21 EST
Article-I.D.: ssc-vax.314
Posted: Mon Jan  7 15:29:21 1985
Date-Received: Tue, 8-Jan-85 05:38:53 EST
References: <3241@alice.UUCP>
Organization: Boeing Aerospace Co., Seattle, WA
Lines: 28

> Discovery was rolled to the pad today, in preparation for the
> 23 January military launch.  The Pentagon will only say that
> the launch time will be between 1315 and 1615 EST, and the
> public will know more specifically only ''when the engines
> ignite.''
     When might a sightseer be able to predict the launch time?
Well, normally about 2 hours before launch, the crew enters the
orbiter.  You might catch the astronaut convoy driving out to the
pad.   The External Tank normally begins chilldown at T-5 hr, and
is filled over a number of hours.  There will be vapors around the
tank once it begins to be filled.  The support crew leaves at
T-30 min.  Their trucks might be observed leaving the pad area.

     At T-9 min the automatic sequencer is started.  Beyond this
point there is a five minute hold capability.  At T-7 min the
crew access arm begins retracting.  At T-3 min the Space Shuttle
Main Engines are gimballed to start position.  At T-2 min 30 sec
the External Tank vent arm is retracted.  Beyond this point there
is only a two minute hold capability, and the count would have
to be recycled to T-9 min.  At T-18 sec the SRB nozzles are
swiveled.  Of course, at T-3.46 sec the Main Engines are
started.

     Happy Observing.


Dani Eder / Boeing Aerospace Co., Advanced Space Transportation Organization
"Tommorrow, you can be anywhere" / uw-beaver!ssc-vax!eder / (206)773-4545