Paul, Hans G.
Dublin Core
Title
Paul, Hans G.
Source
University of Alabama in Huntsville Archives and Special Collections, Huntsville, Alabama
Rights
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Format
.MP4
Language
en
Type
Interviews
Audio
Identifier
ohc_stnv_000032_A
Oral History Item Type Metadata
Interviewer
Bilstein, Roger E.
Interviewee
Paul, Hans G..
Transcription
[00:00:00] Hans Paul: You tell me what you want to, what you're interested in. I don't know.
I have not...
[00:00:08] Roger Bilstein: I think we’re interested in everything you said [inaudible]. [laughs]
[00:00:11] HP: I have not prepared anything for this [inaudible]. It might be good; it might be bad. I don't know.
[00:00:21] RB: Well, we have lots of questions. Perhaps we can just call you back sometime.
[00:00:25] HP: Are you ready now?
[00:00:26] RB: Yeah, go ahead.
[00:00:27] HP: What I wanted to say…I made it a point that many people think the [rapid?] engine is the whole of the [propulsion system?], and it is not. It is a very essential and a very important part, but there are many, many other aspects that are equally important, which cannot be neglected [inaudible]. I tried to illustrate this. The thermal engineering was extremely important, as was the orbital restart of the J-2 engine. Again, on the S-IVB. You know, they run up [inaudible] and say, “You cannot [inaudible] orbit extremely difficult.” Furthermore, on the ground, you have still the atmosphere. If you are not careful, the atmosphere is [cool?] You don't see it; you don't pay for it. And orbit, [inaudible] [and what happened?]
[00:01:22] HP: First of all, we insisted that we run our test in…Now if I say so, I might [inaudible]...We felt that we should simulate orbit in the Tullahoma test facility [inaudible]. Then we had to prove it, I guess, for three months. Presentation after presentation. Finally [inaudible] “You’re sure about this?” [Inaudible] Are you familiar with it? You know, you can fire the J-2 engine, the vacuum, up to and so-and-so many thousand of feet. And what did we find? We found that the cross-over duct [overheated?]. There was heat [soaked?] back [or whatever?] it was. During restart, so oxygen pump—or turbine first—got more energy than intended or designed for. If you do so, then you change, during the start-up, the mixture. You get more oxygen in your gas generator and in your gas generator mainly. This increases your temperature, so you exceed the upper temperature. If you do so, then you burn up your turbine [case?], and there is no second start.
[00:02:58] HP: So we found this out. Then, of course, after you have this proof, then you can sit down…And then the contractor, of course. They analyze it. They should have done this before. They didn’t because they are confident that during their tests on the ground, they never really have a problem like this. An engineer must never be overconfident. He must always be suspicious. He must be skeptical by profession, otherwise he is [inaudible]. What I wanted to say is that our thermal properties, [inaudible] the whole propulsion system—from the lowest temperature, the [reach?] or [real?], close to zero, up to the highest temperatures, which can be handled at the present time technologically—they play a very important part. Regardless of which new project comes in [inaudible] the temperature control, the astronaut basically brushes off the radiator, then turns around and brushes himself off and brushes the dust back on the radiator again, which causes low temperatures and the missing [inaudible] after take off temperature problems. This aspect is extremely essentially the point. It is not normally as a rule realized by, except for the few who are intensively involved in it [inaudible].
[00:04:37] RB: Did you get involved very much with insulation problems then too?
[00:04:41] HP: Oh yeah, we do. We call it the high temperature heat protection. On the lower end, the conservation of hydrogen, we call it cryopropellant preservation. We do this. I think we are on the forefront.
[00:05:00] RB: I was curious about the difference in design—if you want to comment about it—between the S-IVB, which had the internal insulation, and the S-II, which had the external.
[00:05:09] HP: I can show it to you. This is the data—the evaporation, lots of liquid hydrogen storage. The hydrogen evaporation is [inaudible] day is shown here, and here is the storage volume, liters. So if you have a container that is 100 liters, and you lose one percent, then it’s here. If you lose ten percent, it’s here. If you lose 100 percent a day, then it’s here. Is that clear? Can [inaudible].
[00:05:41] HP: Now you asked about the S-IV. The hydrogen loss of the internal insulation on the S-IV is 0.9 here. In orbit, it is down here. On the S-II stage, with the external insulation, the helium-purged foam on the S-II stage on the ground is here. The NAPCO spray foam insulation, we consider this on the ground, because the attitude is not high enough. The pressure is too high. But it's here. Does this answer your question?
[00:06:16] HP: In other words, the S-IV on the ground would have an evaporation loss of over 100 percent. The S-II, there’s not much difference. It's at 100 percent, but it is a little bit better.
Whereas in orbit, the S-IVB—now this would be in orbit it would be better too—it has ten, I would say it is probably fifteen, around fifteen or twenty percent.
[00:06:50] HP: Now you asked what we are doing in insulation. We just tested a few weeks ago this 105 inch in diameter liquid hydrogen storage tank. It's 10,000 liters, a little bit more than 10,000 liters capacity. You see it is less than one percent, it is 0.3 percent. In thirty days, you would have ten percent loss. That is [inaudible].
[00:07:23] RB: Excuse me, going back to the S-II, there is a problem because you really don't consider it lost in orbital mode.
[00:07:28] HP: Let me tell you, this insulation was not available at the time [this stage had been built?] ten years ago. This insulation was not in [inaudible]. For the time being, you must say that if you are on the ground you can always replenish. It's a short flight of five minutes, doesn't amount to anything. I think it was adequate. It was very adequate. But the improvement from year to year if you show it on a log scale is peanuts. What we need now. I should not interrupt you. You asked a question.
[00:08:07] RB: The S-IVB was a little…Can you say that the S-IVB was a little more efficient then?
[00:08:13] HP: No, because on the ground, it was even…Let’s see…We are nitpickers who say, [“Was it working?”] I would say—if you ask me—I would say the S-IVB and the S-II were the state of [inaudible]. It served the purpose.
[00:08:30] RB: Okay, that's what I'm getting at, I guess.
[00:08:32] HP: It served the purpose. And now, the requirements are greatly increasing and are much tougher. These insulations for orbital storage would not be good enough. Unfortunately, we have been able to reduce this by roughly two orders of magnitude. Let me explain. You see, in a storage container, the surface area of the volume changes with the third rule of the volume.
[00:09:12] RB: I’ll take your word for it.
[00:09:12] HP: In other words, what it loses…Take a sphere. If you have a small sphere, then the external area is relatively large compared to the content. If you have a big sphere, then the volume can hold increases faster [compared to surface area?]. For a storage container, a big container is always [at an advantage?]. I have shown this by plotting in here the one-third power of the volume. In other words, if you take this volume here, you go three or you could go three over here. One, one, two, three. This line would come from here to here. In other words, if you have 100,000 instead of 100, then your loss comes down by the third rule of thousands, which is [inaudible]. That is exactly what we choose here. In other words, what I should not do, I should not compare the loss of a small container to that of a big container. I have to normalize it. This is what these lines do.
[00:10:33] John Stuart Beltz: Excuse me, I hate to interrupt. We've run over our time, and we also have no energy.
[tape ends]
I have not...
[00:00:08] Roger Bilstein: I think we’re interested in everything you said [inaudible]. [laughs]
[00:00:11] HP: I have not prepared anything for this [inaudible]. It might be good; it might be bad. I don't know.
[00:00:21] RB: Well, we have lots of questions. Perhaps we can just call you back sometime.
[00:00:25] HP: Are you ready now?
[00:00:26] RB: Yeah, go ahead.
[00:00:27] HP: What I wanted to say…I made it a point that many people think the [rapid?] engine is the whole of the [propulsion system?], and it is not. It is a very essential and a very important part, but there are many, many other aspects that are equally important, which cannot be neglected [inaudible]. I tried to illustrate this. The thermal engineering was extremely important, as was the orbital restart of the J-2 engine. Again, on the S-IVB. You know, they run up [inaudible] and say, “You cannot [inaudible] orbit extremely difficult.” Furthermore, on the ground, you have still the atmosphere. If you are not careful, the atmosphere is [cool?] You don't see it; you don't pay for it. And orbit, [inaudible] [and what happened?]
[00:01:22] HP: First of all, we insisted that we run our test in…Now if I say so, I might [inaudible]...We felt that we should simulate orbit in the Tullahoma test facility [inaudible]. Then we had to prove it, I guess, for three months. Presentation after presentation. Finally [inaudible] “You’re sure about this?” [Inaudible] Are you familiar with it? You know, you can fire the J-2 engine, the vacuum, up to and so-and-so many thousand of feet. And what did we find? We found that the cross-over duct [overheated?]. There was heat [soaked?] back [or whatever?] it was. During restart, so oxygen pump—or turbine first—got more energy than intended or designed for. If you do so, then you change, during the start-up, the mixture. You get more oxygen in your gas generator and in your gas generator mainly. This increases your temperature, so you exceed the upper temperature. If you do so, then you burn up your turbine [case?], and there is no second start.
[00:02:58] HP: So we found this out. Then, of course, after you have this proof, then you can sit down…And then the contractor, of course. They analyze it. They should have done this before. They didn’t because they are confident that during their tests on the ground, they never really have a problem like this. An engineer must never be overconfident. He must always be suspicious. He must be skeptical by profession, otherwise he is [inaudible]. What I wanted to say is that our thermal properties, [inaudible] the whole propulsion system—from the lowest temperature, the [reach?] or [real?], close to zero, up to the highest temperatures, which can be handled at the present time technologically—they play a very important part. Regardless of which new project comes in [inaudible] the temperature control, the astronaut basically brushes off the radiator, then turns around and brushes himself off and brushes the dust back on the radiator again, which causes low temperatures and the missing [inaudible] after take off temperature problems. This aspect is extremely essentially the point. It is not normally as a rule realized by, except for the few who are intensively involved in it [inaudible].
[00:04:37] RB: Did you get involved very much with insulation problems then too?
[00:04:41] HP: Oh yeah, we do. We call it the high temperature heat protection. On the lower end, the conservation of hydrogen, we call it cryopropellant preservation. We do this. I think we are on the forefront.
[00:05:00] RB: I was curious about the difference in design—if you want to comment about it—between the S-IVB, which had the internal insulation, and the S-II, which had the external.
[00:05:09] HP: I can show it to you. This is the data—the evaporation, lots of liquid hydrogen storage. The hydrogen evaporation is [inaudible] day is shown here, and here is the storage volume, liters. So if you have a container that is 100 liters, and you lose one percent, then it’s here. If you lose ten percent, it’s here. If you lose 100 percent a day, then it’s here. Is that clear? Can [inaudible].
[00:05:41] HP: Now you asked about the S-IV. The hydrogen loss of the internal insulation on the S-IV is 0.9 here. In orbit, it is down here. On the S-II stage, with the external insulation, the helium-purged foam on the S-II stage on the ground is here. The NAPCO spray foam insulation, we consider this on the ground, because the attitude is not high enough. The pressure is too high. But it's here. Does this answer your question?
[00:06:16] HP: In other words, the S-IV on the ground would have an evaporation loss of over 100 percent. The S-II, there’s not much difference. It's at 100 percent, but it is a little bit better.
Whereas in orbit, the S-IVB—now this would be in orbit it would be better too—it has ten, I would say it is probably fifteen, around fifteen or twenty percent.
[00:06:50] HP: Now you asked what we are doing in insulation. We just tested a few weeks ago this 105 inch in diameter liquid hydrogen storage tank. It's 10,000 liters, a little bit more than 10,000 liters capacity. You see it is less than one percent, it is 0.3 percent. In thirty days, you would have ten percent loss. That is [inaudible].
[00:07:23] RB: Excuse me, going back to the S-II, there is a problem because you really don't consider it lost in orbital mode.
[00:07:28] HP: Let me tell you, this insulation was not available at the time [this stage had been built?] ten years ago. This insulation was not in [inaudible]. For the time being, you must say that if you are on the ground you can always replenish. It's a short flight of five minutes, doesn't amount to anything. I think it was adequate. It was very adequate. But the improvement from year to year if you show it on a log scale is peanuts. What we need now. I should not interrupt you. You asked a question.
[00:08:07] RB: The S-IVB was a little…Can you say that the S-IVB was a little more efficient then?
[00:08:13] HP: No, because on the ground, it was even…Let’s see…We are nitpickers who say, [“Was it working?”] I would say—if you ask me—I would say the S-IVB and the S-II were the state of [inaudible]. It served the purpose.
[00:08:30] RB: Okay, that's what I'm getting at, I guess.
[00:08:32] HP: It served the purpose. And now, the requirements are greatly increasing and are much tougher. These insulations for orbital storage would not be good enough. Unfortunately, we have been able to reduce this by roughly two orders of magnitude. Let me explain. You see, in a storage container, the surface area of the volume changes with the third rule of the volume.
[00:09:12] RB: I’ll take your word for it.
[00:09:12] HP: In other words, what it loses…Take a sphere. If you have a small sphere, then the external area is relatively large compared to the content. If you have a big sphere, then the volume can hold increases faster [compared to surface area?]. For a storage container, a big container is always [at an advantage?]. I have shown this by plotting in here the one-third power of the volume. In other words, if you take this volume here, you go three or you could go three over here. One, one, two, three. This line would come from here to here. In other words, if you have 100,000 instead of 100, then your loss comes down by the third rule of thousands, which is [inaudible]. That is exactly what we choose here. In other words, what I should not do, I should not compare the loss of a small container to that of a big container. I have to normalize it. This is what these lines do.
[00:10:33] John Stuart Beltz: Excuse me, I hate to interrupt. We've run over our time, and we also have no energy.
[tape ends]
Duration
0:10:37
Files
Collection
Citation
“Paul, Hans G.,” The UAH Archives and Special Collections, accessed July 9, 2026, https://oralhistory.uah.edu/items/show/629.