Memorandum
To:Rock Etman
Launch Programs Head, Marshall Space Launch Facility
T-54321 Lift-off Way, Havelift, OFF 10226
From:Skye Campbell
MTI Lead Engineer, MTI Headquarters
98723 Asdf St. Plain, WA 98826
Date:Jan. 21, 1986
Re:Delay Challenger launch due to high potential for o-ring failure.
Background
If we launch the Challenger Shuttle in one week, as is currently planned, the rocket has a high likelihood to have
a major malfunction and potentially explode. It must be delayed. Throughout all of the launches that we have
executed so far, several launches have produced results of erosion in the joint-sealing O-rings due to them sealing
improperly. I have collected all of the temperature and erosion data from previous launches. This data is
assembled in a chart attached to the bottom of this memo for your convenience.
As you can see, there are a few outliers, but other than those few cases, the majority of O-ring erosion was
during launches with sub 66 degree ambient temperatures. The trend lines provided on the graph show that
with the decrease in temperature, there is a major increase in erosion.
Once the primary O-ring is sealed, the pressure equilibrium will be established and everything will run
smoothly, but until then there is a window of time where, if the secondary O-ring is not sealed, then there will
be a complete joint failure. On tests concerning the secondary O-ring’s sealing capabilities “At 100 degrees F the
O-ring maintained contact. At 75 degrees the O-ring lost contact for 2.4 seconds. At 50 degrees the O-ring did
not re-establish contact for 10 minutes, at which time the test was terminated.” (Winsor 105) Next week’s
predicted temperatures are below 30 degrees F. This kind of temperature can easily cause the secondary O-ring
to not seal correctly, leading to erosion, and then complete failure of both primary and secondary O-rings.
Recommended Action
My urgent suggestion is that we must forego the launch until the ambient temperature is at least 66 degrees
minimum. We cannot guarantee the safety of the launch and crew in the temperature conditions of the planned
launch date. The coldest completed launch so far was in temperatures more than double next week’s
temperatures at 66 degrees, and that launch’s O-rings sustained heavy erosion and damage. Continuing to
launch the Challenger as planned has a high risk of a failed launch and loss of life.
Works Cited
Tufte, Edward. Visual and Statistical Thinking: Displays of Evidence for Making Decisions. Graphics
Press, 2003. Print.
Winsor, Dorothy. C ommunication Failures Contributing to the Challenger Accident: An Example for
Technical Communicators. Jeee Transactions on Professional Communications. 31.3 (1988).
PDF File.
