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Roger Boisjoly-The Challenger Disaster

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Year 1987
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Memo from A.R. Thompson on the Flight Seal

Morton Thiokol, Inc

Wasatch Division

Interoffice Memo

2871:FY86:141

22 August 1985

TO: S.R. Stein, Project Engineer

CC: J.R. Kapp, K.M. Sperry, B.G. Russell, R.V. Ebeling, H.H. McIntosh, R. M. Salita, D.M. Ketner

FROM: A.R. Thompson, Supervisor Structures Design

SUBJECT: SRM Flight Seal Recommendation

The O-ring seal problem has lately become acute. Solutions, both long and short term are being sought, in the mean time flights are continuing. It is my recommendation that a near term solution be incorporated for flights following STS-27 which is currently scheduled for 24 August 1985. The near term solution uses maximum possible shim thickness and a .292 +.005/-.003 inch dia O-ring. The results of these two changes are shown in Table 1. A great deal of effort will be required to incorporate these changes. However, as shown in the Table the O-ring squeeze is nearly doubled for the example (STS-27A). A best effort should be made to include a max shim kit and the .292 dia O-ring as soon as it is practical. Much of the initial blow-by during O-ring sealing is controlled by O-ring squeeze. Also more sacrificial O-ring material is available to protect the sealed portion of the O-ring. The added cros-sectional area of the .292 dia O-ring will help the resilience response by added pressure from the groove side wall.

Several long term solutions look good; but, several years are required to incorporate some of them. The simple short term measues should be taken to reduce flight risks.

A. R. Thompson

ART/jh

Cite this page: "Memo from A.R. Thompson on the Flight Seal" Online Ethics Center for Engineering 8/29/2006 OEC Accessed: Sunday, September 24, 2017 <www.onlineethics.org/Topics/ProfPractice/Exemplars/BehavingWell/RB-intro/33759/FlightSeal.aspx>