The Normalization of Deviance at
NASA
Background
• January 28, 1986
• Shuttle engineers were worried about launching
at the predicted temperature of 31 degrees
• O-rings – their job was to keep hot gases from
spreading to different parts of the solid rocket
boosters where unspent fuel was stored
• Evidence suggested that the rubber O-rings failed
in cold weather
– They wouldn’t seal joints properly
Background
• The decision was made to launch despite the cold weather
• Primary and secondary O-rings failed, which led to the
explosion
• The disaster was viewed as a technical failure
• The Presidential Commission also suggested
– Managerial wrongdoing
• Economic pressures led managers to focus too much on keeping to the
launch schedule
– Flawed decision making processes at NASA
• Middle managers violated safety rules by not passing technical
information up to top technical decision makers
• Is this correct? What other factors may have played a role?
Videos
• The launch
– http://www.youtube.com/watch?v=j4JOjcDFtBE
• CBS Evening News coverage
– http://www.youtube.com/watch?v=COZ-GKfwQX8
• Technical explanation for the cause from NASA
– http://www.youtube.com/watch?v=MKG4bvZGWag
• “The Last Flight of Space Shuttle Challenger” and
other videos:
– http://www.youtube.com/playlist?list=PL6738973930178A
5D
Report of the Presidential Commission
•
http://science.ksc.nasa.gov/shuttle/missions/51-l/docs/rogers-commission/table-of-contents.html
•
Chapter 4 - THE CAUSE OF THE ACCIDENT
•
The consensus of the Commission and participating investigative agencies is that the loss of the
Space Shuttle Challenger was caused by a failure in the joint between the two lower segments of
the right Solid Rocket Motor. The specific failure was the destruction of the seals that are intended
to prevent hot gases from leaking through the joint during the propellant burn of the rocket motor.
The evidence assembled by the Commission indicates that no other element of the Space Shuttle
system contributed to this failure. In arriving at this conclusion, the Commission reviewed in detail
all available data, reports and records; directed and supervised numerous tests, analyses, and
experiments by NASA, civilian contractors and various government agencies; and then developed
specific scenarios and the range of most probable causative factors.
•
CONCLUSION In view of the findings, the Commission concluded that the cause of the Challenger
accident was the failure of the pressure seal in the aft field joint of the right Solid Rocket Booster.
The failure was due to a faulty design unacceptably sensitive to a number of factors. These factors
were the effects of temperature, physical dimensions, the character of materials, the effects of
reusability, processing and the reaction of the joint to dynamic loading.
Discussion Points
• Sociology and the Challenger Disaster
– How did the larger context (at NASA, in the engineering profession, in the
aerospace industry) impact the work groups (i.e., engineers and managers)?
• Why is risk sociological?
– Arnoldi says that risks are social for at least three reasons; how do these
pertain to the Challenger disaster?
• Objective and subjective probabilities
– How is risk assessed at NASA?
– What are the sources of engineering disagreements about risk?
– How do engineers solve disagreements about risk?
• Cognitive science
– Risk perceptions – what role did they play?
– What were the higher order impacts of the Challenger disaster?
• Can you describe what Vaughan means by the ‘normalization of
deviance?’
• The basic idea of the chapter (and book) is that the post tragedy
review simplified the causes of the tragedy; the decision to launch
and failure to redesign were not based on deviant acts by actors
within NASA, but reflected the overall culture at NASA and were
embedded within/products of the organization, common practice,
and process for evaluating risk
• The main themes to pay attention to:
– Overall view of risk regarding space travel and the space shuttle
system
– Risk assessment
• Organizational structure of NASA – engineers, project managers, contractors
• Basic rules and procedures for dealing with risk (i.e., Acceptable risk process
and the flight readiness review)
• How actors dealt with engineering disagreements
• Sources of engineering disagreements over risk assessments
• Stages of risk regarding the solid rocket boosters (e.g., failsafe, concerns over
joint rotation, escalated risk, review of evidence, formalization of risk)