The Challenger Disaster

July 15, 2009

To: The Design Groups working on O-ring Failure Problem on the SRB’s
NASA, Morton Thiokol, Inc., and The Marshall Space Flight Center

From: Marshall Space Flight Center Engineering and Design Group

Subject: The failure of the O-rings on the SRB’s Joints

Dear Robert M. Boisjoly:

We at Marshall Space Flight Center have some serious concerns over the recent test results on the rubber o-ring seal on the SRB’s. We had demonstrated these concerns since 1979 and earlier at the inception of the program.

The test data and other pertinent information have been communicated to your group in memos starting in 1977. As we all know, those o-rings are a major factor in the safe completion of any shuttle mission. The tolerances are more than the manufacturer recommends. Therefore, a serious possibility of an explosion during liftoff could occur.

The MTI group had started testing these o-rings as early as 1977 with the test results being unsatisfactory. Your group wanted to relax the standards for these tests. While the Marshall group wanted to change the design of the o-ring and materials used in its manufacture. All managers received a copy of the memo and Mr. Eudy did not attach the significance of the memo to this problem.

In February 6, 1979, Mr. Eudy and Mr. Ray took the test data and visited Precision Rubber Corporation and Parker Seal Company. The test data indicated that there was a possibility of the primary seal failure and along with that the secondary seal failure. The information gathered from the visits to these two manufacturers caused MTI to become more concern about the o-ring problem.

The problem has taken so long in becoming solved, that NASA has gone to other venders seeking new products that will solve the o-ring problem. This is stated in a memo from Roger M. Boisjoly dated July 22, 1985. He was so concerned over the problem that he recommended that the flights be put on hold.

The main failure factor in the o-ring was the temperature and reseating after the expansion. On cooler temperatures the o-ring could not reseat itself properly in the SRB’s and clevis joint. The test data can be found on a memo from MTI dated August 9, 1985 Brian G. Russell, SRM ignition System Manager. This memo breaks down the test results. Still at this late date MTI does not accept the fact that a failure could be fatal to a shuttle mission.

We at Marshall conclude that immediate steps should be put in place to make sure that the flights are put on hold to more data could be retested. This has been an ongoing problem of both our groups not accepting the other’s evidence or lack of as a problem. Gentlemen we have to do something now before it’s too late. The other memos that we have sent has fallen on deaf ears and we really believe that this is a major safety concern. If you do not have copies of these memos and reports, contact me and I will sent the complete file over to your group.


Sincerely,

Gordon Palmer