Conference 7.286::space

155.0. "CHALLENGER 51-L Chronology" by PYRITE::WEAVER (Dave - Laboratory Data Products) Thu Feb 20 1986 11:44

Newsgroups: net.columbia
Path: decwrl!decvax!tektronix!teklds!zeus!bobr
Subject: highlights of the Challenger disaster
Posted: 17 Feb 86 05:11:44 GMT
Organization: Tektronix, Beaverton OR
 
An AP wire story by Howard Benedict recounts a report presented by NASA
spokesman Jim Mizell, which gives the following chronology:
 
  -- At 0.445 of a second after launch, a plume of black smoke burst from the
side of the right-hand booster and was visible for about 12 seconds before
disappearing.  It was near a joint sealed by a pair of rubber O-rings
intended to prevent hot gases from escaping from between two segments of the
booster.
 
  -- At 58 seconds, smoke appeared on the side of the right-hand booster
near a strut that attached it to the external liquid fuel tank.  At 59.249
seconds, an intense plume of flame appeared in this area, and the chamber
pressure in the booster rocket started to fall.  Because of the pressure
difference, the left-hand booster had more power and began tugging the
shuttle slightly off course.
 
  -- At 62.484 seconds, the shuttle's computers tried to compensate for the
difference by moving the right wing flap.  Mizell said the flap was moved so
abruptly that it created a "spike" in radio data, indicating that the flame
must have broken through the right-hand booster in explosive fashion.
 
  -- At 63.924 seconds and at 65.524 seconds, the computers directed first
the right-hand main engine nozzle and then the left-hand main engine nozzle
to swivel to try to compensate for the off-course motion.
  Mizell said this subjected Challenger to an up-and-down motion "like a
porpoise moving through water."
 
  -- At 66.174 seconds, bright spots and then a large glow appeared on the
side of the right-hand booster.
 
  -- At 67.684 seconds, pressure dropped in the oxygen tank that fed the
system of small jet thrusters that steer the shuttle, indicating that one or
more of the jets were firing to try to keep Challenger on course.
 
  -- Between 72.01 and 72.281 seconds, Challenger was rocked severely when
the two boosters began working against each other.  One tried to move left
and the other right and then suddenly, one pitched slightly up and the other
down and the spacecraft moved sideways.  Mizell said the crew probably felt
this but had no time to report it.
 
  -- At 73.175 seconds, a puzzling cloud, perhaps from the liquid hydrogen
fuel tank, appeared alongside the external tank.
 
  -- At 73.201 seconds, fire flashed between the shuttle and the external
tank.
 
  -- At 73.226 seconds, the external tank exploded near the forward
attachment strut.
--
Robert Reed, CAE Systems Division, tektronix!teklds!bobr