from Morton Thiokol, the contractor that built the
shuttle’s solid-rocket booster engines. Engineers
warned that if the O-rings that sealed joints in these
engines reached a temperature below 53 degrees
Fahrenheit, there was no guarantee that they would
perform properly. NASA officials, aware that the
many delays were resulting in bad publicity, decided
that it was safe to proceed with the launch.
The Short Flight Challengerfinally lifted off at
11:38 a.m. eastern standard time (EST) on January
- A later examination of launch film showed the
first sign of a problem less than 0.7 seconds into
the flight, when puffs of dark smoke were emitted
from the right-hand solid-rocket booster. Investiga-
tors later determined that the smoke resulted from a
leak in a joint between sections of the booster. Dur-
ing the stress of liftoff, metal parts bent away from
each other, the primary O-ring was too cold to seal,
and hot gases vaporized both the primary O-ring
and a secondary O-ring that served as a backup.
Particles of aluminum oxide rocket fuel are be-
lieved to have temporarily sealed the gap. But, about
fifty-eight seconds into the flight,Challengerencoun-
tered an intense wind shear, a sudden change in
wind speed and direction. This was the most severe
wind shear recorded up to that time in the shuttle
program. The resulting force broke the temporary
seal. Within a second, a plume of rocket exhaust
penetrated the joint, striking the shuttle’s externalThe Eighties in America Challengerdisaster 195
The crew of the space shuttleChallengerposes for its official portrait on November 15, 1985. Back row, from left: Ellison S. Onizuka,
S. Christa McAuliffe, Gregory B. Jarvis, and Judith A. Resnik. Front row: Michael J. Smith, Dick Scobee, and Ronald E. McNair.(NASA)