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Challenger Memorandum

An engineer at Morton Thiokol Inc. recommends delaying the launch of the space shuttle Challenger due to the forecasted low temperatures. Tests showed that the O-rings used to seal the shuttle's rocket booster segments lost effectiveness and did not re-seal properly at temperatures below 75°F, putting the shuttle at risk of catastrophic failure. Data from previous launches also showed O-ring erosion when temperatures were below 66°F. The engineer urges delaying the launch until temperatures reach at least 66°F to avoid potential disaster and loss of the shuttle and crew.

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170 views3 pages

Challenger Memorandum

An engineer at Morton Thiokol Inc. recommends delaying the launch of the space shuttle Challenger due to the forecasted low temperatures. Tests showed that the O-rings used to seal the shuttle's rocket booster segments lost effectiveness and did not re-seal properly at temperatures below 75°F, putting the shuttle at risk of catastrophic failure. Data from previous launches also showed O-ring erosion when temperatures were below 66°F. The engineer urges delaying the launch until temperatures reach at least 66°F to avoid potential disaster and loss of the shuttle and crew.

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MEMORANDUM

Luke Schwarz
Engineering Department
Morton Thiokol Inc.
2475 Washington Blvd.
Ogden, Utah 84401
(801) 629-2270

December 27, 1985

Staff and Management


Marshall Space Flight Center
Huntsville, AL 35811
(256)-544-2121

Subject: ​Me and my team of engineers strongly recommend that the launch of the Challenger
shuttle be delayed. We feel this way because our research shows that launches at lower
temperatures have a tendency to sustain more damage to the O-rings. With the temperature
being forecasted at about 26-29 °F our fear is that launching the shuttle in these conditions will
result in a catastrophic failure and possibly loss of life.

Details: ​There are primary and secondary O-rings in the SRB. The purpose of the primary
O-rings are to seal the segments of the SRB together and stop glasses from leaking and the
secondary O-rings are there as backups in case they fail. The O-rings are made to seal under
the pressure of the gases, but they don’t always perform as intended in colder weather. We
tested the rubber used for the O-rings by clamping it and putting in ice water. As we unclamped
the rubber it had clearly lost its resiliency and would not seal properly (Tufte 1997). If the
O-rings fail to perform the hot gases will leak from the SRB and cause massive complications.

Our team of engineers have run tests on these O-rings at various temperatures and the results
were shocking. “At 100 °F the o-ring maintained contact. At 75 °F the o-ring lost contact for 2.4
seconds. At 50 °F the o-ring did not re-establish contact in ten minutes at which time the test
was terminated” (Winsor 1988). This clearly shows that the O-rings do not perform correctly at
low temperatures and put the shuttle at great risk. Also, the data from previous shuttle launches
shows that all shuttles launched at temperatures lower than 66 °F suffered some level of o-ring
erosion.

Solution: ​It is crucial that the launch of the Challenger shuttle be delayed until the temperature
is at least 66 °F in order to avoid a major disaster resulting in the loss of the Challenger shuttle
and it’s passengers.
Key
= Forecasted Temperature Of The Challenger Launch (26-29 ​°F)

= Predicted Damage To The Challenger’s O-rings

= Shuttle Launches
= Trend Line
References

Tufte, E. R. (1997). ​Visual and statistical thinking: Displays of evidence for making decisions ;
displays of evidence for making decisions​. Graphics Pr.

Winsor, D. (1988). Communication failures contributing to the Challenger accident: An example


for technical communicators. ​IEEE Transactions on Professional Communication,31​(3),
101-107. doi:10.1109/47.7814

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