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Interview

by Rick Boos

with Charlie Stevenson

Charlie Stevenson was employed by NASA at the Kennedy Space Center in 1965. He was a member of the test checkout and launch team for all manned space flights.

Challenger 51-L Accident

TESTIMONY OF CHARLES STEVENSON. MR. STEVENSON: We did it both days. Okay, I am Charles Stevenson, and I have been employed by NASA at the Kennedy Space Center since 1965. During the past 20 years I have been a member of the test checkout and launch team for all manned space flights. CHAIRMAN ROGERS: Would you move the mike over a little bit? MR. STEVENSON: Starting with the Gemini program and running through Apollo and into the Shuttle program. I am a graduate of North Carolina State University, and I have a degree in engineering mechanics, a B.S. degree, and a B.S. degree also in physics and applied mathematics. I am currently the section chief for the external tank and the solid rocket booster mechanical systems section. In regards to the questions I am anticipating, I am also responsible for TPS, ice, frost and debris damage on the Shuttle. MR. DAVIS: I am Billy K. Davis. I have been [956] 1705 with NASA since 1960. I have a degree in mechanical engineering from the University of Alabama, and I started in the manufacturing/engineering area for Marshall Space Flight Center, and then systems engineering, and post that, I have been in the Chief Engineering Office for the External Tank, and in that area, I have been responsible for development of the manufacturing processes, the facilities and the other things that go with the external tank insulation system, and as a part of that, was instrumental in seeing to it that we got a development that could provide us with knowledge as to whether or not we would make ice, and at what time we would have ice, and how we could detect it. And so, for that reason, for each launch I have been the senior test representative for the external tank and work with Mr. Stevenson in the ice and debris area. CHAIRMAN ROGERS: Colonel Kolczynski, I think I mislabeled you as a member of the ice team. I understand that you are the Air Force weatherman, is that correct? COLONEL KOLCZYNSKI: Yes, sir, that is true. I am Lieutenant Colonel Edward F. Kolczynski. I am Commander of Detachment 11, 2d Weather Squadron at Patrick Air Force Base. In that capacity, I provide 1706 support to the Eastern Test Range, Eastern Space and Missile Center, Air Force Tactical Applications, and then, of course, to NASA in support of all Shuttle operations up to and including launch. My expertise is I have been in the Air Force 19 1/2 years, and for 18 1/2 of those years I have been a meteorologist. I have a bachelor's degree in mathematics, a master's degree from Texas A&M in meteorology, and I've got some doctoral work at the University of Maryland, also in meteorology. My experience has been as a forecaster at Grand Forks Air Force Base for my early days in the Air Force, then as a staff meteorologist consulting on weather support to developing systems like the F-15 and the A-10 aircraft at Wright-Patterson Air Force Base. I worked at Studies and Analysis in the Pentagon in operations research doing force deployment issues, trade-off analyses and simulations. And of course, at Headquarters, Air Weather Service at Studies and Analyses. And classified Special Projects. And finally a year at the Kennedy Space Center. CHAIRMAN ROGERS: Thank you very much. Mr. Stevenson, would you proceed? Do you have a statement or do you want to proceed to just narrate what happened on those two days? 1707 MR. STEVENSON: Okay, let me-I will do both. As a TPS ice, frost and debris team we have really seven major activities, and I would just name the seven, and then I will get into the ones we are really interested in. We initially do a pre-launch pad debris and vehicle familiarization walkdown to familiarize all the people with the possibilities of debris issues and to familiarize them with the latest configuration of the vehicle. That is for the advantage of some of the people who normally do not work the vehicle every day but come to us from off-Center. We then conduct during the launch a T-3 hour ice/frost walkdown where again we look at the vehicle for ice/frost conditions, TPS anomalies, and any last minute debris that we may find. Following launch, we immediately go to the pad again and do a postlaunch debris assessment. The purpose of this mainly is to determine if there is any flight hardware on the pad or any damage that may have occurred to the vehicle as a result of some pad debris. [957] We then do a postflight photo analysis in which we again look at the vehicle, that is, as it is launched through the launch film, to see if there is any 1708 damage to the vehicle. We also review the SRB for postflight debris assessment, and we review the orbiter once it returns. In regards to the launch day activities, I guess I should just read a statement. CHAIRMAN ROGERS: Okay. MR. STEVENSON: The members of the ice/frost team made three assessments of the icing conditions on the FSS, the RSS, the MLP deck and Pad B apron during the STS-33 prelaunch activities. Due to a drop in temperatures to below freezing during the preceding day and night, the freeze protection plan last used for STS-20 on January 24, 1985 was implemented to protect the various facility systems. Two actions within the plan were intended to limit the ice debris which could potentially cause damage to the Shuttle vehicle during the launch. The first action involved adding 1450 gallons of antifreeze into the over-pressure water troughs. CHAIRMAN ROGERS: Which day now are you speaking about, please? MR. STEVENSON: I am talking about launch day. CHAIRMAN ROGERS: January 28, launch day? MR. STEVENSON: Yes. 1709 CHAIRMAN ROGERS: If you would speak a little bit more into the mike, I have just a bit of trouble hearing you. MR. STEVENSON: Okay. The water troughs in both SRB holds have a total capacity of 6,580 gallons. The resulting antifreeze to water ratio is calculated to be at approximately 21.3 percent, which protected the water troughs from freezing down to an ambient temperature of 16 degrees. The second action involved the draining, where practical, of all water systems. Several systems, such as the fiex, the deluge, the emergency shower and eye wash were not drained. These systems were opened slightly and allowed to trickle into the drains. The trickling water was found to cause the drains to overflow, and the high wind gusts spread the water over large areas, and it then froze. Based upon those conditions, when we came into the firing room on the day of launch and had a call to stations, the ice, frost, TPS and debris team observed the icing conditions which were on the FSS and notified our upper management. A decision was made at that time to send the ice/frost team to the pad for an assessment of the facility icing conditions. The team arrived at the pad at approximately 1710 0130 in the morning and remained there for approximately one and one half hours. CHAIRMAN ROGERS: And who was the team? MR. STEVENSON: The team at this time consisted of B. K. Davis, myself, and two facility members who were familiar with the water system. CHAIRMAN ROGERS: Was that unusual to have you go to the pad at that time? MR. STEVENSON: Yes, it is. CHAIRMAN ROGERS: Had it ever been done before? MR. STEVENSON: Once before when we had a similar condition. CHAIRMAN ROGERS: Okay. Proceed. [958] MR. STEVENSON: Okay. Upon arrival at the pad we noted the following conditions, and I will just more or less summarize those. As far as the pad apron was concerned, ice was concentrated in an area under the RSS and covered approximately 3,000 square feet. The ice ranged in thickness from one fourth of an inch to about three inches. On the MLP deck itself, we had a sheet of ice mostly on the west side between the left hand SRB exhaust holes and the west side, or the east side of the 1711 FSS. This ice-the sheet ice was approximately one-eighth inch thick, and the secondary overpressure water troughs, we found that we had ice which was estimated to be approximately one half inch thick. And the density of that ice was estimated to be approximately 25 pounds per cubic foot. As for the fixed service structure between the 100 and 220-foot levels, we had a large quantity of icicles which averaged approximately five-eighths inch in diameter and ranged from six inches to one foot long. We had ice on all panels, such as distribution panels, structural members of the facility, valve panels. This ice averaged approximately one-eighth to one-half inch thick. Upon returning to the LCC, of course, we immediately held a meeting with our upper management, and members of the management system were probably Mr. Aldrich and Horace Lambreth, who is Director of Shuttle Engineering. CHAIRMAN ROGERS: Mr. Aldrich and who else? MR. STEVENSON: Horace Lambreth, Director of Shuttle Engineering, and several other key management people who I don't have the names of right off. The results of that meeting was that we 1712 immediately started the engineering effort to calculate the trajectories of ice which would be falling off of the FSS. We concluded that the ice which we had seen in the water troughs, the overpressure troughs, would not be acceptable for launch based on our previous experience of debris coming out of the water troughs. We decided to send a facility technician, group of technicians with us to the pad again when we went during our normal three-hour inspection, and we proceeded to make a second assessment during the T-3 hour hold on the conditions we found there, we left the LCC- MR. HOTZ: What time did you go out on the pad the second time? MR. STEVENSON: We arrived at the pad at 0654 in the morning, and we departed at 0844. Again, the team was augmented by several facility personnel to aid us in the removal of ice from the water troughs, which we had determined to be unacceptable for launch. Our temperatures, our ambient temperatures as we recorded them on our consoles and found them during the time we were there ranged from 26.1 to 30.1 degrees Fahrenheit. The ice was found in the troughs to have thickened and was solid. These are the overpressure water troughs. 1713 A fish net was employed to break up the ice and remove it. Approximately 95 percent of the ice was removed using this method. The ice and unfrozen antifreeze solution was measured at that time with the infrared pyrometer and found to have a temperature between 8 degrees and 10 degrees Fahrenheit. Those temperatures have since been corrected to read between 14 and 16 [959] degrees. Also most of the icicles that we had seen or reported earlier on the left hand SRB aft skirt were removed during this period. As far as the FSS goes, the ice had increased, but the overall extent of the ice was generally the same. Upon returning to the LCC, we immediately held a second meeting with about the same members present. We had at that time completed our trajectory calculations which predicted that the ice falling from the FSS, if it fell at ignition, would probably impact the MLP deck at a distance of approximately 20 feet from the FSS. These calculations did not include the effects of aspiration, which was unknown. We had decided in the meeting that if we had ice falling away from the vehicle, that aspiration would not draw ice into the water trough holes, and therefore, that the ice on the FSS was not a safety of flight 1714 issue. We proceeded back to the pad for a third inspection, and the reason we went back for the third inspection-and this would not normally be an inspection we would conduct-was to remove all of the ice off of the MLP deck on the west side of the MLP deck, which would have a potential for getting-being drawn in by aspiration or by vibration of the deck. MR. HOTZ: Could you give us the times on that again? MR. STEVENSON: That time was between 10:30 and approximately 11:00 a.m. We again carried the facility crew with us who aided us in the removal of all of the ice on the west part of the MLP deck away from the left hand SRB. The conditions of the ambient temperatures, as measured in the firing room, too, by our instrumentation for this period of time ranged from 34.8 to 36.2 degrees Fahrenheit. We also found that there was again a little bit of ice in the overpressure water troughs, and again, we fished that ice out, and we returned to the LCC at approximately T-20 minutes. CHAIRMAN ROGERS: Your function was to make the inspections that you referred to and report back to Mr. Aldrich, is that it? MR. STEVENSON: I report back normally to the 1715 launch director. CHAIRMAN ROGERS: In this case, who was he? MR. STEVENSON: In this case the launch director was Mr. Gene Thomas, but in our normal report we do it over the communications system, which also includes whatever top management. CHAIRMAN ROGERS: But in this case who did you report to? MR. STEVENSON: In this case, each time we held a special meeting off-line to discuss the ice issues and what we should be doing about it. CHAIRMAN ROGERS: Was that because it was a little worse than previous launches? MR. STEVENSON: Yes, sir. CHAIRMAN ROGERS: Did the low temperature readings cause any concern among the ice team members? MR. STEVENSON: You mean our scanner readings? CHAIRMAN ROGERS: Yes. MR. STEVENSON: Well, we took a considerable amount of readings using the IR scanner. We normally take a lot of readings using the IR scanner. We are charged with the responsibility [960] of and use the IR scanner mainly to determine the temperatures on the ET skin because the ET surface is where we are really 1716 expecting ice, and the icing conditions, and that is really what we look for when we make an ice inspection is the ice that is normally on the tank that will cause damage to the orbiter during flight. CHAIRMAN ROGERS: But in this case you did something more? MR. STEVENSON: Well, we took the-in this case we took readings that we normally take. We take more readings than we are required to take, if that is your question. CHAIRMAN ROGERS: Did you take readings on the SRBs? MR. STEVENSON: Yes, sir. CHAIRMAN ROGERS: Do you normally do that? MR. STEVENSON: Yes, sir. CHAIRMAN ROGERS: And were there differences in the readings between the left and the right booster? MR. STEVENSON: Approximately 14 degrees delta. CHAIRMAN ROGERS: And what were those readings? MR. STEVENSON: The uncorrected readings were 9 degrees and 23 degrees. We have since scaled those up to 19 degrees and 33 degrees. CHAIRMAN ROGERS: So the right was 19 degrees, 1717 you think, and the left was 33 degrees? MR. STEVENSON: Yes, sir. CHAIRMAN ROGERS: And was there any discussion about those readings with other members of the launch team? MR. STEVENSON: With other members of the launch team, no, sir. CHAIRMAN ROGERS: And what were those discussions? MR. STEVENSON: We did not discuss those specific temperatures with other members of the launch team. CHAIRMAN ROGERS: Did you report those temperatures to others? MR. STEVENSON: No, sir, not those specific temperatures. CHAIRMAN ROGERS: Why not? MR. STEVENSON: Because, in our opinion, first-well, two reasons, I guess. Number one, the vehicle was operating within the red lines that we have, the guidelines that we have to go by, and when we go out and make our inspection, we are required to report on anomalies, number one, and having no anomalies, you report on the points of interest. Since the vehicle is operating within its red 1718 lines, within my guidelines, within its Launch Commit Criteria, within the OMRSD requirements, that was not a point to report. CHAIRMAN ROGERS: Mr. Davis, did I see you about to say something? MR. DAVIS: Well, when you first asked the question earlier, did we discuss it among ourselves, Charlie and I did discuss it at the time and concluded that this 9-degree reading probably might not be exactly right, and felt that the set of readings that you get on the left-hand booster was more representative of what the true conditions were. [961] As far as the temperature readings taken on the tank itself, they followed fairly close to the predictions that we had, although right at the bottom the temperature readings were somewhat further than normal away from the predicted readings. They were colder, but they were not so much colder that it would cause any particular consternation or anything because our insulation is quite capable of working at liquid hydrogen temperatures, and in fact, you can immerse it in liquid hydrogen and it really doesn't do anything to it other than it just takes a while for it to get cold in the middle. So as far as the tank was concerned, and all 1719 of the things that it normally would be expected to do, it was doing it in fact better than usual because we had ice in smaller amounts in places that we normally had a lot of ice, like interfaces between the orbiter and the tank and the interface between the solids and the tank. They had ice in the regular places but it was and there are certain places where it is quite acceptable to have them. In this case we had much less than usual, and it can be attributed to the fact that there was no atmospheric moisture available to be forming on it. CHAIRMAN ROGERS: In other words, the icing conditions were not as bad on this flight as on others? MR. DAVIS: That is correct. MR. STEVENSON: As far as the vehicle is concerned. CHAIRMAN ROGERS: As far as the vehicle is concerned. MR. STEVENSON: Right.

Challenger lifts into orbit on 29 April 1985-Mission STS-51B. Photo Credit: NASA

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