Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!necntc!frog!john
From: john@frog.UUCP (John Woods)
Newsgroups: sci.space.shuttle
Subject: Re: Orbiter/SRB separation
Message-ID: <1156@X.UUCP>
Date: 24 Jun 88 00:17:00 GMT
References: <1869@bigtex.uucp> <3330005@hpindda.HP.COM> <2259@phred.UUCP>
Organization: Servants of the Great White Frog
Lines: 53

There has been a lot of discussion about this.  Just to throw more LH on the
fire, I thought I'd quote from the Report of the Presidential Commision on the
Space Shuttle Challenger Accident, Volume 1, page 20-21:

   "The first visual indication that swirling flame from the right
Solid Rocket Booster breached the External Tank was at 64.660 seconds
when there was an abrupt change in the shape and color of the plume.
This indicated that it was mixing with leaking hydrogen from the
External Tank.  Telemetered changes in the hydrogen tank pressurization
confirmed the leak.  Within 45 milliseconds of the breach of the
External Tank, a bright sustained glow developed on the black-tiled
underside of the Challenger between it and the External Tank.
   "Beginning at about 72 seconds, a series of events occurred extremely
rapidly that terminated the flight.  Telemetered data indicate a wide
variety of flight system actions that support the visual evidence of
the photos as the Shuttle struggled futilely against the forces that
were destroying it.
   "At about 72.20 seconds the lower strut linking the Solid Rocket
Booster and the External Tank was severed or pulled away from the
weakened hydrogen tank permitting the right Solid Rocket Booster to
rotate around the upper attachment strut.  This rotation is indicated
by divergent yaw and pitch rates between the left and right Solid
Rocket Boosters.
   "At 73.124 seconds, a circumferential white vapor pattern was
observed blooming from the side of the External Tank bottom dome.
This was the beginning of the structural failure of the hydrogen tank
that culminated in the entire aft dome dropping away.  This released 
massive amounts of liquid hydrogen from the tank and created a sudden
forward thrust of about 2.8 million pounds, pushing the hydrogen tank
upward into the intertank structure.  At about the same time, the
rotating right Solid Rocket Booster impacted the intertank structure
and the lower part of the liquid oxygen tank.  These structures
failed at 73.137 seconds as evidenced by the white vapors appearing
in the intertank region.
   "Within milliseconds there was massive, almost explosive, burning
of the hydrogen streaming from the failed tank bottom and the liquid
oxygen breach in the area of the intertank.
   "At this point in its trajectory, while traveling at a Mach number
of 1.92 at an altitude of 46,000 feet, the Challenger was totally
enveloped in the explosive burn.  The Challenger's reaction control
system ruptured and a hypergolic burn of its propellants occurred
as it exited the oxygen-hydrogen flames.  The reddish brown colors
of the hypergolic fuel burns are visible on the edge of the main
fireball.  The Orbiter, under severe aerodynamic loads, broke into
several large sections which emerged from the fireball."

Reading the telemetry report was kind of interesting.  The Challenger
control systems were indeed making a valiant effort to cope with the
bizarre goings on, right up until the radio stopped...
-- 
John Woods, Charles River Data Systems, Framingham MA, (617) 626-1101
...!decvax!frog!john, john@frog.UUCP, ...!mit-eddie!jfw, jfw@eddie.mit.edu

	Guns don't kill people; I kill people.