Observations on the Loss of the Challenger

Observationso Engineering processes (the

decision-making process to arrive at the launch decision) need continuous review.

o Learn to recognize when external pressures or conflicting interests (profits, prestige,…) cause deviations from usual engineering processes.

Observationso Be wary of incrementally increasing

risks by normalization of deviance.o Learn to recognize, and be especially

cautious in the operation of, tightly coupled and complexly interactive engineering systems.

o Learn to differentiate between Primary Engineering Decisions (PED) and Primary Management Decisions (PMD)

Normalization of Devianceo When 1977 tests indicates some joint

opening, contrary to joint designers’ expectations, a sealing putty “fix” was added, and the anomaly was considered an “acceptable risk”.

o When a 1981 launch resulted in blow-by through the putty, this anomaly was explained as a result of improperly applied putty.

o When 1984 and 1985 launches caused more leakage, this leakage had come to be expected, and acceptable.

Normalization of Devianceo If the initial seal designers were asked

whether any leakage through the seal was acceptable, they probably would have not accepted any leakage.

o Every instance of gas blow-by was contrary to the initial seal designers’ expectations and, yet came to be acceptable, almost expected. A “fix”, not a redesign, was always the remedy.

o Deviations from initially expected behavior should always be reexamined very carefully.

Tightly Coupled & Complexly Interactive

Systemso Processes are said to be tightly coupled when

one process can rapidly affect another process.o Processes are said to be complexly interactive

when they interact in unanticipated ways.o Risk is more difficult to estimate in tightly

coupled and complexly interactive processes.o The solid booster seals and the shuttle fuel

storage/delivery system are an example of a tightly coupled and complexly interactive system.

The Effects of Low Ambient Temperature

o The low ambient temperature was a concern during launch review.

o The critical interaction between low temperature and seal behavior was not foreseen (complexly coupled behavior).

o Launch was approved in spite of the concerns about low temperature because no data existed to indicate a hazard (normalizing deviance). (No data existed to confirm the safety!--review the purpose of the pre-launch engineering process!)

Writing Assignment 1

Persuasive Writing Exercise

o You are asked to take the position of Morton Thiokol engineer Roger Boisjoly after he learns his recommendation against launching of the Shuttle Columbia has been rejected. The rejection is not final, however, as your verbal arguments have been successful in delaying Morton Thiokol’s final launch decision until the next morning. You are asked to prepare, overnight, a short (maximum two pages, double spaced) executive summary of the reasons for your recommendation against a launch decision. Prepare this in the form of a memorandum addressed to Mr. Robert Lund, P.E., Vice-President of Engineering, Morton Thiokol. (The memo will carry your name, not Mr. Boisjoly’s name.)

o This assignment is due Friday, Sept. 19, at recitation.