What is the main trend, bottom line, and how might this bottom line have been be

Question

What is the main trend, bottom line, and how might this bottom line have been better emphsized in the answer of question 2?
70 Memo from Brian Russell, MITI Engineer to NASA's Jim Thomas August 9, 1985 DATE: SUBJECT: Actions pertaining to SRM Field joint Secondary seal Per your request, this letter contains the answers to the two questions you asked at the July Problem Review Board telecom: l. Question: If the field joint secondary seal lifts off the metal mating surfaces during motor pressurization how soon will it retum to a position where contact is re-established? Answer: Bench test data indicated that the oring resiliency (its capability to follow the metal) is a function of temperature and the rate of case expansion. MTI measured the force of the O-ring against Instron platens, which simulated the nominal squeeze on the o-ring and approximated the case expansion distance and rate. At 100 F the O-ring maintained contact. At 75 F the O-ring lost contact for 2.4 seconds. At 50 Fthe O- ring did not reestablish contact for ten minutes at which time the test was terminated. The conclusion is that the secondary sealing capability in the SRM field joint cannot be guaranteed 2. Question: If the primary oring does not seal, will the secondary seal seat in sufficient time to prevent joint leakage? Answer: MTI has no reason to suspect that the primary seal would ever fail after pressure equilibrium is reached, i e., after the ignition transient. If the primary oring were to fail from 0 to 170 milliseconds, there is a very high probability that the secondary oring would hold pressure since the case has not expanded appreciably at this point. If the primary seal were to fail from 170 to 330 milliseconds, the probability of the secondary scal holding is reduced. From 330 to 660 milliseconds the chance of the sccondary scal holding is small. This is a direct result of the oring's slow response compared to the metal case segments as the joint rotates. Please call me or Mr. Roger Boisjoly if you have additional questions concerning this issue.

Explanation / Answer

100oF is the safe temperature for seocondary seal to perform as the temperature goes down to 75oF, the sealing response become erratic and failure rate enhances further as temperature goes down further. So, 100oF is the cut-off temperature for present design of the seal and if requirement is to go down then sean require to be redesigned.

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