Report of the PRESIDENTIAL COMMISSION on the Space Shuttle Challenger Accident


Volume 4 Index


Hearings of the Presidential Commission on the Space Shuttle Challenger Accident: February 6, 1986 to February 25, 1986



[740] [Ref. 2/25-1 1 of 24] Typed version of handwritten notes of A. J. McDonald, Manager Shuttle Rocket Motor Project, Morton Thiokol, Inc.





Notes from January 27, 1986

Late afternoon on January 27th


While staying at Carver Kennedy's residence in Titusville, Florida, I received a call from Bob Ebeling, Manager, Solid Rocket Motor Project Officer, Igniter and Final Assembly [Thiokol, Utah], about concern of low temperature predicted at the Cape for the launch of [shuttle launch] STS-51L the next morning. Concern was associated with performance of the field joint O-rings. I told him I would obtain the latest weather information and predicted temperatures up to launch time and call him back. Carver Kennedy, Vice President Space Services at Kennedy Space Center for Morton Thiokol, Inc., called the Launch operations Center and received the latest recorded temperatures and temperature predictions up to the planned launch time of 0938 EST on 28 January 1986. Freezing was expected to occur before midnight with a minimum temperature of 22° F expected by 6:00 a.m. with around 26 ° F at launch time. I transmitted this data back to the plant and said I would set up a meeting on this subject as soon as possible with Kennedy Space Center and Marshall Space Flight Center. I told Bob to make sure Bob Lund, Vice President, Engineering [Thiokol, Utah] was involved in making this decision because it should be an engineering decision not program management. I felt that I was not in a position to make the assessment or recommendation. I told Bob Ebeling that engineering needs to prepare some charts on this matter and FAX [telefax] them to Kennedy Space Center and Marshall Space Flight Center. I told Bob to make sure engineering is prepared to recommend an acceptable launch temperature with the data and rationale supporting the


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recommendation. I then called Larry Mulloy, solid Rocket Booster, Project Manager [Marshall Space Flight Center] at the Holiday Inn at Merritt Island [Florida] and they could not reach him. I then called Cecil Houston, Marshall Space Flight Center/Resident Manager Office at Kennedy Space Center and told him our concern abort the low temperatures on the O-ring seals. Be said he would set up a 4-wire teleconference on this subject with Marshall Space Flight Center and Morton Thiokol, Inc. through his conference room in Complex C at Kennedy Space Center. The teleconference was set up for 8:15 p.m. EST and I told Cecil Houston I would support the conference at that time. I relayed this message to the plant.


8:15 P.M. EST.

I then left Carver Kennedy's house and went to Cecil Houston's conference room arriving about 8:15 p.m. Those present were Cecil Houston, Larry Mulloy, Stan Reinartz, Shuttle Project Manager [Marshall] Jack Buchanan, Manager Kennedy space Center Operations for Morton Thiokol Inc, and myself. The charts from Morton Thiokol Inc. had not been received and the 4-wire call came in shortly thereafter and we suggested all parties hold because the FAX transmittal had not yet been received at Kennedy Space Center. The FAX started coming through around 8:40 p.m. (EST) and we waited several minutes until most of the charts were transmitted and copies made for distribution to attendees. The meeting started just before 9:00 p.m. (EST) before all the charts, were received. The conclusions and


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recommendations were not received until approximately 9:30 p.m. (EST).

The presentation was made by Mr. Bob Lund, Vice President, Engineering at Morton Thiokol Inc. (I think). The charts that he used presented the history of O-ring erosion and blow-by of the primary seal in the field joints, reasons for concern at lower temperatures, results of subscale tests, previous flight and static tests of Solid Rocket Motors and conclusions and recommendations. The data presented by Morton Thiokol Inc. showed that the timing function to seal the o-rings would be slower due to lower temperatures (Chart 2-2) and that the worst blow-by part a primary O-ring occurred on SRM-15 (STS-51C) [solid Rocket Motor-15 on Shuttle Flight STS-51C on January 24, 1985 1:5O p.m. EST] which was flown about a year ago and had the coldest O-rings of any of the flight motors (Chart 6-1). Morton Thiokol Inc. recommended not to fly STS-51L (SRM-25) 51L with Solid Rocket Motor-25 scheduled for launch next morning on January 28) until the temperature of the O-rings reached 53° F or higher. This temperature must be calculated based upon local ambient temperature and wind conditions. This recommendation was basically made on our successful experience base.

NASA (George Hardy (I think), Deputy Director Science and Engineering at Marshall Space Flight Center) said he was "appalled" by Morton Thiokol Inc.'s recommendation. Larry Mulloy then commented that we were trying to establish a new Launch Commit Criteria which we couldn't do: Launch Commit Criteria's are pre-established sets of constraints.


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Stan Reinartz, also commented that he was under the impression that the Solid Rocket Motor was qualified from 40 ° F to 90° F and the 53° F recommendation was not consistent with that. Larry Mulloy also commented that if we live to a 53 ° F requirement then we will never make 24 launches per year because many of the launches occur early in the morning where 53 ° F is not uncommon. Furthermore, we may never get a launch off at Vandenburg Air Force Base under the 53 ° F constraint levied by Morton Thiokol Inc. and we don't know when we will ever get STS-51L launched [planned January 28 launch]. Cecil Houston commented that it would probably be Thursday, January 30th before morning temperatures (i.e., 9:36) would reach that condition.

NASA challenged Morton Thiokol Inc.'s 53 F recommendation based on the data presented on Charts 1-1 and 6-1. These charts showed that the next worst blow-by of a primary O-ring occurred on SRM-22 (STS-61A) [Solid Rocket Motor-22 on Shuttle Flight 61A launched on October 31, 1985 at 11:00 a.m. EST] which had the highest temperature (75° F) and that we had static tested motors (DM-4) at even lower temperatures (36° F) with no observed blow-by or O-ring erosion. Based on these data, NASA felt the temperature effects on the O-rings were inconclusive. "I commented that I didn't believe that the static


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test history was a valid test for the O-rings because the blow-by holes observed in the zinc chromate putty after assembly and leak check were manually filled prior to static test.. Someone from Morton Thiokol Inc. commented that even though SRM-22 [75° F] was the second worst blow-by observed, the severity of the blow-by was not nearly as pronounced as SRM-15 [53 ° F]. Soot observed behind the primary O-rings on SRM-15 was much blacker, covered a larger area, and there was some heat affect [effect] without any measurable erosion observed on the secondary O-ring of SRB-15.

Further discussion centered around the inconsistency of the data presented in the charts relative to temperature effects. The data presented in the charts, namely Chart 1-1, 4-3 and 6-l were considered inconclusive and NASA suggested that Morton Thiokol Inc. reassess their recommendation of 53 ° F for a launch temperature based upon a re-examination of all the data. George Hardy (I think) said he would not consider flying without Morton Thiokol Inc.'s concurrence. "I commented that lower temperatures are in the direction of badness for both O-rings because it slowed down the timing function but that the affect [effect] is much worse for the primary O-ring compared to the secondary O-ring because the leak check forces the primary O-ring into the wrong side of the groove


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while the secondary O-ring goes in the right direction and that this condition should be evaluated in making the final decision for recommending the lowest acceptable launch temperature. Based on the data prescribed in Chart 2-1 I considered this very important because depending on how much delay one has in getting a good reliable primary seal affects the capability of the secondary O-ring to seal.

Morton Thiokol Inc. decided at that time to hold a caucus off-line to re-evaluate all the data they had at their disposal and come back with a re-assessment of the temperature conditions acceptable for launch. Morton Thiokol Inc. planned to be off-line for approximately five minutes but were actually in a caucus in the MIC No. l at Wasatch for nearly a half hour.

While we were waiting at Kennedy Space Center for Morton Thiokol, Inc. to Caucus, Mr. Mulloy, Mr. Reinartz and myself engaged in a discussion concerning the qualification temperature of 40° F to 90° F for the Solid Rocket Motor." I told them that I wasn't involved in the qualification of the steel case Solid Rocket Motor's but based upon my experience with the Filament Wound Case-Solid Rocket Motor,


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I don't believe that every component and element of the solid Rocket Motor is qualified to 40° F. My interpretation of the Spec is that 40' F to 90° F is the operating temperature range and Includes all components of the solid Rocket Motor.» Larry Mulloy commented that the 40° F requirement applies to Propellant Mean Bulk Temperature only and that we will be at 55° F for Propellant Mean Bulk Temperature at time of launch. He said that means other components could be below 40° F as long as the Propellant Mean Bulk Temperature never dropped below this value. I told him that is ridiculous because the propellant is such a massive insulator that it never changes Propellant Mean Bulk Temperature even with tremendous external temperature extremes and I'm sure the Spec didn't mean that.

While we were waiting for Morton Thiokol Inc.'s response, I suggested that NASA recommend delaying the launch until late afternoon when temperatures are expected to reach 48-50 ° F. I told them that I understand that this would be an acceptable launch window since the original launch time for STS-51L was set at 3:45 P.M. (EST.). I was told that this was considered and rejected because of problems with weather and/or [shuttle flight] visibility at one of the TAL [Trans Atlantic Landing] abort sights, I believe Dakar [Senegal].


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Since the temperature data appeared to be inconclusive based on the charts presented, I expected Morton Thiokol Inc. to either find some more supporting information for the 53° F temperature requirement or evaluate lower temperatures and make a recommendation and that's why it was taking so long. I really suspected that the new recommendation would be 40° F because of the discussion concerning the qualification requirements for the motor unless some new calculations could be made to obtain a better number.

Morton Thiokol Inc. finally came back on and said that they had re-assessed the data and concluded that even though the lower temperatures were concerning that the temperature affects were inconclusive and therefore Morton Thiokol Inc. recommends launching. I believe Mr. Joe Kilminster, Vice President, Space Booster-Programs, at Morton Thiokol Inc. was the speaker. Mr. George Hardy (I think) suggested that Morton Thiokol Inc., put that in writing and send it by FAX to both Kennedy Space Center and Marshall Space Flight Center to be available by morning. I told Mr. Mulloy that I would not sign the letter that it would have to come from the plant.


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Joe Kilminster (I think) said that they would draft a letter and send it out right away on the FAX to both Kennedy Space Center and Marshall Space Flight Center. I was instructed to stay and receive the letter and deliver it to Mulloy, Reinartz, and Houston. I asked Cecil Houston where the FAX was and he told me it was at the other end of the building.

While we were waiting for the signed FAX, I made several comments to Mr. Mulloy, Mr. Reinartz, and Mr. Houston with Jack Buchanan present. I told them I didn't feel good about the recommendation and that based upon the data presented no one could really define an exact temperature at which this seal problem may be unacceptable. However, even though I did not agree with the position that all components of the Solid Rocket Motor were really qualified to 40° F, I understand that many people at both Morton Thiokol Inc. and NASA signed up to that based upon the CDR [Critical Design Review] and DCR [Design Certification Review] for the steel case motor. I was surprised that NASA accepted a recommendation to fly at a temperature well below the qualification temperature; predicted temperatures at launch time (9:38 a.m. EST.) were expected to be around 26° F.


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I further stated that I may be naive about what generates a Launch Commit Criteria but I was under the impression that it was generated based upon launching within the qualified environments of all elements and subsystems of the Space shuttle. Because of that, I don't understand why NASA would allow a Shuttle launch below 40 F. I told them that if anything happened, I sure wouldn't want to be the person who had to explain to a Board of Inquiry why it was all right to launch at a temperature below that at which the system was qualified to. No one in the room commented on that statement. I was still so upset at the decision that I asked for reconsideration for postponement of the launch because there were other considerations which were bad in addition to the O-ring seal problem. I stated that if I were the Launch Director, I would cancel the launch for tomorrow morning for three reasons:


(1) The possible effects of the O-ring sealing problem at low temperatures that we just discussed.

(2) I had just left Carver Kennedy's house to come to this meeting and had just received a report from the booster recovery ships.


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The ships were in a absolute "survival" mode in 30 foot seas, sustained winds of 50 knots gusting to 70 knots, pitching 30 degrees and they thought the rough seas may have damaged some of the recovery equipment on the back of the ships. The ships were heading straight into the wind toward shore for survival and could not support tomorrows planned launch at 0938 A.M. (EST). The ships had been moving away from the booster impact area at approximately three knots for sometime and didn't know when conditions would be safe enough to attempt to turn around. I then reminded everyone that this was the first launch with apogee separation of the nozzle exit cone and separation of the parachutes from the boosters at water impact. Launching early the next morning would put the booster recovery at some risk and would most likely eliminate any reef possibility of recovering the frustrums and parachutes.


(3) The third reason for not launching was the expected formation of ice in the Launch Complex area. I told them that I did not know what affects that this may have on accoustics, debris, or structures but it didn't seem prudent to launch under these unknown conditions.


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I was told that these were not my problems and that I shouldn't concern myself with these. I responsed that maybe one of these problems was not being considered sufficient to cancel the launch but that all three of them combined should be more than sufficient to delay the launch. The NASA folks indicated that they would pass this information on in advisory capacity. Mulloy then asked me where the signed FAX was and I told him I would go check on it.

The FAX had not come in yet so I waited at the FAX machine for a while and wondered if it was working because it had been sometime since the teleconference had been completed. The FAX finally come in at 11:27 p.m. (EST) while I was waiting at the machine. I took the FAX to Jack Buchanan's office where he reproduced several copies for distribution to the attendees, of the meeting.

I returned to Cecil Houston's office where Mulloy, Houston and Reinartz were on a telecon. I believe with Mr. Arnie Aldrich. They were discussing the condition of the booster recovery ships at sea


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and concluded that a launch decision would have to be made based upon the reasonably high probability that the parachutes and frustrums (approximately S1 million of hardware) would not be recovered but there was was no significant increase in risk of retrieving the boosters. Mulloy was asked if the could tolerate the less of the parachutes and frustrums and still support the launch schedules and he said yes. A decision was made to proceed with the launch without the recovery ships in the area and to make sure we didn't jeopardize the safety of the ships by trying to return to the recovery area in such bad sea conditions.

They also briefly discussed the ice issue in the launch complex area and were told that the ice issue had been addressed earlier in the day. Mr. Mulloy and Mr. Reinartz made it clear that they were acting in an advisory capacity only and wanted to make sure that all this information was made available. The decision was to proceed with the early morning launch and the telecon was concluded. I did not hear any conversation on the o-ring concerns but I presume that discussion occurred while I was at the FAX.


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I gave copies of the FAX signed by Joe Kilminster with the recommendation by Morton Thiokol Inc. to proceed with the launch of [shuttle flight] STS-51L on 28 January 1986. I was surprised that the FAX did not address any temperature conditions at all. It contained a brief summary of some of the Pro's and Con's associated with colder temperature and recommended proceeding with the launch on 28 January 1986 without reference to any particular temperature or time. The meeting broke up and I spent a few more minutes with Jack Buchanan and returned back to Carver Kennedy's house in Titusville arriving there between 12:30 and 1:00 a.m. (EST.] on 28 January 1986.


A.J. McDonald




Since recording the events the night before the launch I came across a piece of paper in my suit pocket that was written by me when Morton Thiokol Inc. made their final recommendation. I have included as page 14A in these notes.


A.J. McDonald



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