LAUNCH REDLINES

¶Section VI.B.1.b. of this report describes the rationale for devel- opment of certain criteria that serve to indicate when the Shuttle system is experiencing problems during the countdown. On the morning of January 27 and 28, during the countdown for STS 51-L, the launch crew in the Firing Room wrote waivers to certain of these criteria in order to permit launch of the Shuttle. Tapes and transcripts from the Operational Intercommunication System dem- onstrate that, at least in one instance, the technical analysis au- thorizing the use of a backup procedure did not account for ambi- ent temperatures below the limits specified for this procedure. Thus, a waiver should not have been granted.

¶Revision C, Amendment 18 of the Launch Commit Criteria speci- fied 45 degrees Fahrenheit as the minimum redline temperature for the External Tank nose cone.lZ4

¶But the ambient temperatures during the countdown were well below that. On January 27, while the Shuttle waited for liftoff, con- versations indicated that the nose cone heaters were not able to maintain proper temperatures. Excepts from the transcript of this discussion follow.

¶CF. Okay, go ahead, Fred.

¶FH. Okay, we may have a problem with propellant temperatures at that low level. We're about three degrees away from red line and losing ground right now.

¶CF. Because of the amount of heat that the ground system's able to put in there?

¶12 2 Mr. George Jeffs, President, North American Space Operations, Rockwell International.

¶L z 3 Cmte. H,p., Transcript, July 25, 1986, pp. 71-74.

¶I24NASA, Launch Commit Criteria and Background," Revision C, Amendment 18, JSC- 16007, December 1 , 1982, p. 5.1-4. See Appendix VIII-K. FH. That's right, they're giving us all they can right now. . . . I z 5

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¶DIRECTOR. . . . What do you guys feel about all the temperatures we saw today, like nose cone, and all those? Think about that so we can talk about that a little bit.

¶M. Yeah, that's another thing we're not happy about. We think we could probably still get by with it, but we're marginal.

¶UKN. You know, nose cone temp. Horace, is probably gonna be down in the low ~O'S,maybe even below 20.

¶M. I think the intertank we ought t o be able to keep it up high enough. . . . I z 6

¶DIRECTOR. . . . Okay. You guys think that nose cone heater is putting out all we gonna be able to get out of it?

¶UKN. Yep. You got it full blast. You're gonna be down 18-20" tomorrow on the nose cone. And the waiver we wrote today said we're only good down to 28. That was today's. . . .

¶UKN. And Horace, the [intertank] heater was running full bore for quite awhile. And we were running at least 10"below the set point temperature.

¶DIRECTOR. What about Fred Heinrich? He on 245?

¶FH. I'm here, Horace.

¶DIRECTOR. Fred, what do you think about the flow rate, I mean the RCS temps?

¶FH. Okay, Grady said they can crank that thing up locally and get outside the OMRSD [Operations Maintenance Requirements and Specifications document] limit, which may-be enough, but we need td get started as soon as we get in there. Other- wise, we can't get the tank warm enough. We're going to lose ground all throughut the cry0 load.

¶DIRECTOR. Okay.

¶FH. We're about 3" away from red line right now. We lost some during this cry0 load with full bore on the heaters.

¶DIRECTOR. Okay.

¶R. Horace, this is Robinson, We'll have to check with JSC about the upper limit on this temperature.

¶DIRECTOR. What do you mean?

¶R. -right now OMRSD is not in-it may be something else other than Fred Hein- rich's temperatures.

¶DIRECTOR. Okay. Then you don't have no problem picking it up, though, that's the only requirement we got, right?

¶R. That's afirmative.l27

¶The waiver referred to in this conversation offered the following technical rationale: "NO visible ice buildup on the nose cap fairing exit area. Temperature is 12 deg F below redline."12*

¶The waiver also read, "For STS-33 [51-L] Min LCC acceptable is 28 deg F (was 45 deg F). Ullage transducers are acceptable down to 28 deg F (was 40 deg F). Refer Note A, LCC 5.1-4." l Z 9

¶Note A read:

"The following purge temps are backup measurements. GLOT 4104A PRI Nose Cone Heated Purge Temp. GLOT 4604A SEC Nose Cone Heated Purge Temp."¹¹ For the purpose of this report, a procedure is a formal set of instructions designed to guide and assist in the performance of a technical or management function. g8 mid., July 24, 1986, p. 11. 1 9 9 Ibid., June 25, 1986, p. 52. 3 0

¶These refer to telemetry data channels. As the temperatures are received via telemetry, they are to be interpreted by means of a curve shown on page 5.1-4B.13'

¶It is important to note that Note A applies only if the ambient temperature is between 40 and 99 degrees F. Otherwise, the redun- dant procedure is invalid.

¶As for the effect of exceeding this redline, the launch commit cri- teria reads:

¶12501s Channel 245, p. 217.

¶'*@Ibid. 218.

¶12' 01s &annel 245, pp. 219-20.¹¹ For the purpose of this report, a procedure is a formal set of instructions designed to guide and assist in the performance of a technical or management function. g8 mid., July 24, 1986, p. 11. 1 9 9 Ibid., June 25, 1986, p. 52. 2 8 See Appendix VIII-L. '2OIbid.

¶130 "Launch Commit Criteria and Background," p. 5.1-4.

¶131 bid., p. 5.1-4B. See Appendlx VIII-K.

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"The minimum redline was established for two reasons. A. LO2 ullage pressure transducers calibrated to 40 deg F. B. Avoid ice buildup at nose cone fairing exit." ''Consequences of exceeding redline; 1. Ice build up and possible impact to Orbiter. 2. Inaccurate ullage pressure readings." l 3

¶Engineering support communications continued with the follow- ing:

¶M. Horace, 245.

¶DIRECTOR.Yeah, go ahead.

¶M. Okay, one other thing's been brought to my attention. The, the LOX, the LOX ullage pressure transducers are calibrated to a minimum of 40 degrees and maxi- mum of 140, which is what sets our minimum in the nose cone. Below that, we may get some variations in reading.

¶FH. No, that's not true, Mark.

¶M. Well, okay.

¶FH. (garbled) see I got some measure readings here from Mark was. . . .

¶M. That's what's on the LCC backup page.

¶UKN. Read the LCC backup page on the lower limit.

¶M. It says 40 degrees.

¶FH. It says for reasons of ice and frost at that the exit on the fairing.

¶M. Yeah.

¶MAC. Test on 245. (garbled). . . 245.

¶DIRECTOR. Go ahead, Mac.

¶MAC. Hey, are you guys reading this LCC that the consequences of exceeding the nose cone temp redline? The sheet we have over here says that we will get inaccu- rate ullage pressure readings.

¶DIRECTOR. Okay, Mac, we understand, thank you.

¶On the morning of January 28, the following discussions between engineering support personnel were also directed toward waiving the launch commit criteria on the External Tank nose cone.

¶UKN. Dave, they were, of course, expecting to violate those ET nose cone purge temps LCCs again. It's 20 degrees colder today than it was yesterday.

¶D. Well, I guess we'll be going down the line producing a waiver to the same effect that we produced yesterday.

¶UKN. How did we just define it yesterday for 51L? Or for this attempt for 51L?

¶D. Copy your whole question. Say again?

¶UNK. I thought we just annotated it yesterday as for 51L only.

¶D. That may be it, I l l check the waiver log. . . .

¶UNK. Dave? 161.

¶D. Go ahead.

¶UNK. Yeah, it is effectively 51L, I think we are in good shape.