read and watch - answer a question
The Challenger Disaster
A Case-study in Engineering Ethics
• Shuttle Components
– Orbiter
– Liquid Rocket
Booster
– Solid Rocket
Booster
Shuttle Components
Chronology of the Related Events
• 1974
– NASA contracts Morton Thiokol
• 1976
– NASA accepts the design based on the Titan missiles
– The joints are sealed by
• Two synthetic rubber O-rings,
• 177 clevis pins,
• Heat shield putty
The Cause of the Disaster
Early Problems
• 1977
– Tests at Thiokol show O-ring leakage
– Joint is made stronger by changing sizes
• 1981
– Post-launch investigation showed O-ring
erosion due to hot gages.
Early Problems
• January of 1985 launch
– First cold-weather launch
– Post-launch investigation showed joint failure
– Tests showed O-rings inability to fill the gap
due to joint rotation at lower temperatures
Early Problems
• July 1985
– Thiokol redesigns the joints w/o O-rings – The
design was not ready for Challenger launch
Political Climate
• Congress is unhappy with NASA
• Competition with Russians to be the first to
observe Halley’s comet.
• Pressure to launch before President
Reagan’s State of the Union Address
Days before Launch
• First launch attempt postponed
• The next launch date was set and was to be
attended by Vice President Bush.
• The temperature at launch: 29 degrees F.
Days Before Launch
• NASA starts an investigation of the effect
of low temperatures on the O-ring seals
• Organization involved
– NASA
– Marshall Space Flight Center
– Morton Thiokol
Engineering Investigation Before
Launch
• Players at NASA
– Larry Mulloy: SRB Project Manager at Marshall
• Players at Thiokol
– Roger Boisjoly: A SRB engineer
– Arnie Johnson: A SRB engineer
– Joe Kilminster: SRB engineering manager
– Alan McDonald: SRB engineering director
– Bob Lund: Vice president for engineering
– Jerald Mason: General manager
Engineering Investigation Before
Launch
• Boisjoly and Johnson recommend the
launch to be postponed.
• Bob Lund, the VP for engineering agrees
and makes a similar recommendation.
Investigation Before Launch
• Larry Mulloy, the NASA manager of SRB
asks Joe Kilminister, the SRB manager at
Thiokol, for his opinion.
• Kilminister agrees with other Thiokol
engineers and recommends a launch delay.
Investigation Before Launch
• After discussion with Mason
• Lund reverses his decision regarding
launch!
• Thiokol recommend the launch to proceed
The Launch in January 1986
• The overnight temperatures drop to 8 F
• The temperature of SRB at launch is 28 F
• There is an immediate blow-by of hot gas at
launch. The seal fails quickly over an arc of
70 degrees.
The Launch in January 1986
• The by-products of combustion forms a
glassy oxide that reseals the joint.
• The brittle oxide is shattered
• Hot gases quickly burn through the liquid
rocket booster
The Aftermath
• Causes of the accident are attributed to
– Inability of the O-rings to expand and seal at
low temperatures.
– Heat shield putty did not perform at low
temperatures
– Fits and seating of the O-ring was affected by
low temperature.
The Aftermath
• After all the testimonials
– Biosjoly is taken off the project and subtly
harassed by Thiokol management.