Presentation on theme: "Observations on the Loss of the Challenger Observations o Engineering processes (the decision- making process to arrive at the launch decision) need."— Presentation transcript:
Observations on the Loss of the Challenger
Observations o 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.
Observations o 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 Deviance o 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 Deviance o 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 Systems o 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!)
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.