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 4:55:00 PM
National Academy of Engineering
Accessed: Tuesday, January 06, 2009
<www.onlineethics.org/CMS/profpractice/exempindex/RB-intro/FlightSeal.aspx>