Engineering Disasters: Space Shuttle Challenger (1986)

  • 7 astronauts died when the space shuttle Challenger exploded shortly after launch in January 1986.
  • The space craft was destroyed following a gas leak on the Solid Rocket Boosters
  • The root cause was erosion to the o-ring seals by combustion gases. The o-rings were not designed to work at low temperatures. The overnight temperature of the launch site was −8 °C
  • NASA was AWARE of the potential problem as early as 1977

ChallengerThe launch of the shuttle Challenger on January 28, 1986 was a huge television event, largely because one of the astronauts was New Hampshire’s Christa McAuliffe, a member of the Teacher in Space program. This was a NASA program announced by Ronald Reagan in 1984 to inspire students, honor teachers, and spur interest in the flagging space exploration program. Teachers would travel into space as Payload Specialists (non-astronaut civilians), and return to their classrooms to share the experience with their students.

The project was cancelled after the disaster.The mission did not get off to a good start. The launch had already been postponed several times due to mechanical problems and bad weather. Throughout the morning, the Morton Thiokol engineers responsible for the design of the O-rings were concerned about the low temperatures, as the O-ring joints on the Solid Rocket Boosters (SRBs) were not designed to function at temperatures lower than 4 °C (39 °F). The overnight low temperature at the launch site was (−8 °C (18 °F).

There were earlier concerns about the O-rings as early as 1971 where a test showed that when pressurized water was used to simulate the effects of booster combustion, the metal parts bent away from each other, opening a gap through which gases could leak. This made it possible for combustion gases to erode the O-rings. In the event of widespread erosion, a flame path could develop, causing the joint to burst and destroying the shuttle.

Challenger crew

“Obviously a major malfunction”

The NASA Space Shuttle Challenger broke apart 73 seconds into its flight and killed all 7 astronauts on board. The investigation proved that the shuttle began to break apart at liftoff.  The O-ring failed, as had been the concern of the engineering team, leading to the separation of the right-hand SRB’s field joint attachment, which caused the structural failure of the external tank. Aerodynamic forces then proceeded to break up the shuttle.

Mitigation

The Presidential Commission on the Space Shuttle Challenger Accident, subsequently known as the Rogers Commission, was formed to investigate the disaster. The commission found that the Challenger accident was caused by the O-rings failing to seal a joint on the right solid rocket booster, which allowed pressurized hot gases and eventually flame to “blow by” the O-ring and make contact with the adjacent external tank. This caused structural failure. The failure of the O-rings was attributed to a faulty design whose performance could be too easily compromised by factors including the low temperature on the day of launch.

Surprisingly, the commission found that NASA and Morton Thiokol had been aware of the deficient joint design since 1977, but rather than redesigning the joint they decided to define the problem as an acceptable flight risk.

Shuttle flights were suspended awaiting the results of the Rogers Commission investigation. The Rogers Commission finally offered nine recommendations on improving safety in the space shuttle program, and NASA was directed by President Reagan to report back within thirty days as to how it planned to implement those recommendations.

About: William Tyrell

Mr. Tyrrell has over 40 years of project management, design and engineering experience in industries as diverse as ports, bulk handling facilities, offshore production and drilling, petrochemical and refineries, bauxite and nickel mining, mineral concentrators, pressure vessel fabrication, wood products, pulp and paper, microelectronics, and food processing.

Leave a Reply

CLOSE
CLOSE
Skip to toolbar