OK. Thank you, Horace.lSQ

¶1361bid., p. 296.

¶136Jbid., p. 297.

¶137Bid., p. 299.

¶lJsIbid., p. 302.

¶ISs Bid., p. 305.

¶There is no documentation to describe the method by which the ullage pressure transducers were qualified to "10 degrees." No al- ternative analysis is described on the launch commit criteria to support use of this low temperature as a rationale for approving a waiver.

¶This example indicates that NASA personnel do not necessarily employ a sufficiently rigorous engineering analysis to the waiver of launch commit criteria during countdown. There also appears to have been some confusion as to the effect of exceeding the redline temperature. Ullage pressure readings may be critical parameters if fed to the Main Engine controllers during flight. According to NASA:

Following engine ignition at about T-4 seconds, the ullage pressure is supplemented using propellant gases va- porized in the engine heat exchangers and routed to the two ET propellant tanks. The tank pressure is maintained based on data inputs from ullage pressure sensors in each tank to control valves in the Orbiter. A combination of ullage and propellant pressure provides the necessary net positive suction pressure to start the engines. The net posi- tive suction is the pressure needed at the main engine pump inlets to cause the pumps to work properly. The pumps, in turn, supply high-pressure liquid oxygen and liquid hydrogen to the thrust chamber. Acceleration pres- sure is added for operation. Fuel is forced to the engines primarily by tank pressures and, to a lesser degree, by gravity.140

¶Inaccurate readings from these sensors might cause the engines to operate improperly.

¶Also, according to the launch commit criteria, violations of launch redlines may also have occurred on the Auxiliary Power Unit (APU) gearbox lube oil (minimum redline temperature 42 deg F), and the fuel test lines (minimum temperature 41 deg F), if in fact the actual temperature were lower than minimum.141

¶There was also no mention of the 34.2 deg F minimum redline temperature for the SRB recovery batteries or what the tempera- ture of the batteries was at 1 a u n ~ h . I ~ ~

¶Under "Remarks," this criterion states, "Violation of this redline shall require an assessment to determine if a hazard exists which jeopardizes the Shuttle. . . ."¹⁴³¹⁴³ bid.: June 18. 1986, P. 100. 144 %id.; p. 101. '

¶Mr. Mulloy testified before the Commission that:

Mr. MULLOY."I had a discussion on my SRB loop with the SRB people dealing with the question of a 24-hour turnaround to attempt to launch again at 9:38 on the 28th and the effect that the predicted cold temperatures for the night of the 27th might have on that. The input was received back both to Mr. Reinartz and myself that we were looking at the Launch Commit Crite-

¶1*0 NASA,"Space Shuttle News Reference," !?81, p. 2-40. 1'1 "Lauch Commit Criteria and Background, Amendment 20, p. G-23. Ira hid., p. G-1 143 hid.

¶64-420 0 - 86 - 9

250

ria relative to temperatures. It was felt there was a need to look at the recovery battery temperatures that are in the forward skirt of the SRB and the fuel service module temperatures that are in the fuel service modules for the thrust vector control system in the aft skirt of the solid rocket booster. The input received back by me was that they did not

¶feel that would be of any concern. They were going to continue to look at it, and if any concern arose they would let me know.

¶I went to the 2:OO Mission Management Team and reported that there were no constraints to the solid rocket booster for a 24-hour turnaround, that we had taken a look at the recovery battery temperatures and the fuel service module. We did not feel at this time that there would be any Launch Commit Criteria for the low temperature limits that were established for those systems, but that we were continuing to assess that; should anything change in that regard, I would so report that."

¶Chairman ROGERS. "You referred to the Launch Commit

¶Criteria. What were they as far as you knew in terms of weather conditions? Any?"

Mr. M u m y . "In terms of weather conditions, yes, sir, I'm aware that there is a Launch Commit Criteria for the system for weather. There are a number of factors in that Launch Commit Criteria. One of them is the ambient temperature, which is established at 31 degrees. Another is the sea state and winds in the SRB recovery

¶area. Another is the cross-winds at the return to landing site runway at Kennedy Space Center. Another is the trans-Atlantic landing site weather, and another is severe weather, which is related to lightning and thunderstorms in the area."

¶Chairman ROGERS."And when you say there were no constraints in the 2:OO meeting, does that mean that as far as you could see there were no problems in those areas?"

¶Mr. M u u o ~ ."NO, sir, I did not evaluate those areas of the Launch Commit Criteria. What I was looking at was the specific Launch Commit Criteria items that are on the solid rocket booster and the effect that the low temperatures would have on that.

¶I would expect Mr. Aldrich would normally make the judgements on, and his people at the Johnson Space

¶Center, would make the judgements on crosswinds and trans-Atlantic weather and the general ambient environment for launch." 14*

¶While there is no reason to believe that these waivers directly contributed to the cause of the accident, the low temperatures during the night of the 27th and morning of the 28th most prob- ably did. Committee staff learned in discussions with Thiokol personnel 145 that liquid hydrogen apparently remained in the Exter- nal Tank throughout the night of January 27. This most likely played a role in the joint seal failure, since it permitted heat trans- fer through the ET/SRB aft attachment strut throughout the night. Of equal interest, however, is the fact that ET requires an eight-hour recovery period between tanking cycles, measured from the time the hydrogen tank low-level sensors are dry.14s

251

¶If the hydrogen tank was never emptied during the turnaround procedure, this would represent a violation of those criteria. Had the criteria been observed, STS-51L would have required an after- noon window on January 28, or it might have been necessary to at- tempt the launch on January 29. This has not been independently confirmed, however.

W o n with Carver Kennedy,ThioLol Wasateh Operations, Brigham City, Utah. Sep

¶tember 4.1986. General Kutyna aL0 nded thb in the Commimion'r hearing on February 14.

¶Cornmimion Ibpon Volume N. 660). l S a0s ( 7 r

¶141 Channel 245, p. 218.

¶p.