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Note On Outliers: The Space Shuttle Challenger Example

The Space Shuttle Challenger disaster was caused by the failure of an O-ring seal on the right solid rocket booster due to unusually low temperatures prior to launch. On the night before the launch, temperatures of 31F were recorded and engineers discussed the effect of low temperatures on O-ring performance. While some thermal distress in O-rings was expected, the final decision was made to launch as planned. A post-accident commission noted that flights with zero O-ring incidents were excluded from the analysis, which could have provided more complete information on the temperature effects. Including all the data and quantifying the relationship between temperature and O-ring failure may have helped improve the risk assessment and launch decision making process

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89 views2 pages

Note On Outliers: The Space Shuttle Challenger Example

The Space Shuttle Challenger disaster was caused by the failure of an O-ring seal on the right solid rocket booster due to unusually low temperatures prior to launch. On the night before the launch, temperatures of 31F were recorded and engineers discussed the effect of low temperatures on O-ring performance. While some thermal distress in O-rings was expected, the final decision was made to launch as planned. A post-accident commission noted that flights with zero O-ring incidents were excluded from the analysis, which could have provided more complete information on the temperature effects. Including all the data and quantifying the relationship between temperature and O-ring failure may have helped improve the risk assessment and launch decision making process

Uploaded by

Debora Kasp
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Note on Outliers:

The Space Shuttle Challenger Example

In the late 1970s, NASA strived for a lighter weight orbiter. Space Shuttle Challenger was the second

Space Shuttle orbiter that was put into service after Columbia. But before its first flight a test vehicle was

needed to ensure the lighter airframe could handle the stress of space flight. Computer software at the time

was not yet advanced enough to accurately predict how the new, optimized design would respond to intense

heat and stress. The best solution was to submit the vehicle to a year of intensive vibration and thermal

testing.

Its maiden flight was on April 4, 1983, and it completed nine missions before breaking apart 73 seconds

after the launch of its tenth mission, on January 28, 1986, resulting in the death of all seven crew members.

It broke up mid-flight in the second minute of its tenth mission. The accident led to a two-and-a-half year

grounding of the shuttle fleet, with missions resuming in 1988 with the launch of Space Shuttle Discovery

on STS-26. The cause was ultimately found to be the failure of an O-ring seal on the right solid-fuel rocket

booster (SRB). Its failure was mainly due to unusually low temperatures prior to lift off.

The Background Story:

The failure of an O-ring seal was determined to be the cause of the Space Shuttle Challenger disaster

on January 28, 1986. On the night before the launch, exceedingly low air temperatures were recorded and

a 3-hour discussion took place. The discussion was about the forecasted low temperature for the next day

of 31F, and the effect of low temperature on O-ring performance (O-rings seal joints). In their discussion

they utilized the the relationship between the number of O-rings having some thermal distress and the

temperature to decide whether the shuttle should take-off as planned. The final decision was to launch the

shuttle as planned.

Post-tragedy, a commission noted that a mistake in the analysis of the data was that the flights with

zero incidents were left off because it was felt that these flights did not contribute any information about
the temperature effect.

What may have helped in the decision making process?

- use off all the data (rather than using data conditional on the occurrence of an incident)

- quantification of the relationship between temperature and O-ring failure

- prediction of the probability of O-ring failure at 31F

1
References

1. en.wikipedia.org, “Space Shuttle Challenger”

2. nasa.gov, “Space Shuttle Overview: Challenger (OV-099)”

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