Bauer, Harold E.

Bauer, Harold E.

This Bauer oral history interview focuses on the technological evolution of Douglas Aircraft’s S-IV and S-IVB rocket stages, emphasizing how experience from the earlier S-IV program directly informed the simpler, more efficient S-IVB design. Harold Bauer explains that the two stages shared fundamental technologies, including common bulkheads, internal insulation, structural concepts, valve systems, and pressurization methods, while the S-IV used six RL-10 engines and the S-IVB employed a single, more powerful gimbaled J-2 engine. A major technological advance was the introduction of liquid hydrogen, which required new approaches to insulation, structural design, and the storage of very cold helium for efficient tank pressurization. Bauer also describes the stage’s lightweight structural design, including externally mounted stringers protected from aerodynamic heating by a thermal coating called Korotherm, noting that aerodynamic drag was less important during the brief atmospheric portion of a Saturn V flight than structural strength, weight, and ease of manufacturing. The interview highlights how the S-IVB’s design eventually contributed to the Skylab concept: engineers recognized that the large, empty liquid-hydrogen tank could serve as a valuable orbital workspace, initially providing a safe environment for practicing extravehicular activities and eventually inspiring the concept of a pressurized orbital workshop. Logistics also influenced the location of Douglas facilities near Seal Beach and air and sea transportation routes. Bauer discusses the importance of precision welding, particularly because the S-IVB depended on welded joints for both structural strength and leak prevention, unlike conventional aircraft construction, which relied more heavily on riveting and bolting. Elaborate welding fixtures and carefully controlled inert-gas welding processes were developed to ensure consistent, high-quality joints, while the fiberglass-aluminum common bulkhead represented one of the most demanding aspects of the manufacturing process but ultimately became routine. The interview also covers the Sacramento test facilities, including the Beta I and Beta III stands, where S-IV and S-IVB stages underwent acceptance testing. Overall, Bauer portrays the S-IVB as the product of accumulated engineering experience, emphasizing that its success resulted not from radical departure from the S-IV but from refining proven technologies, simplifying the design, improving manufacturing efficiency, and recognizing opportunities to extend the usefulness of the stage beyond its original role as a launch vehicle.

University of Alabama in Huntsville Archives and Special Collections, Huntsville, Alabama

This material may be protected under U. S. Copyright Law (Title 17, U.S. Code) which governs the making of photocopies or reproductions of copyrighted materials. You may use the digitized material for private study, scholarship, or research. Though the University of Alabama in Huntsville Archives and Special Collections has physical ownership of the material in its collections, in some cases we may not own the copyright to the material. It is the patron's obligation to determine and satisfy copyright restrictions when publishing or otherwise distributing materials found in our collections.

.MP4

en

Interviews

Audio

ohc_stnv_000003_A

Bilstein, Roger E.

Bauer, Harold E.

[00:00:02] Roger Bilstein: Okay, yeah, is there here something special with this illustration?

[00:00:07] Harold Bauer: Earlier we had talked about progression from Thor to the S-IV and S-IVB stages. I think in context it's well to point out the technical progression from the S-IV to the S-IVB. That's what this chart really shows. We really learned practically all of the key technological steps in the S-IV. The insulation, the common dome, the structural features were all basic to the S-IV. The S-IV was more complicated by having six RL-10 engines instead of the single J-2. That was a very fine engine, worked quite well for us. I would say that the experience that we gained on the S-IV program was very important to us in being able to carry off the S-IVB program with the efficiency that I believe we did. In a sense, the S-IVB is a more simple configuration although it has greater demands on it. One of the things we learned as we progressed from S-IV to S-IVB was to simplify things, make things more likely to work, more effective. We ended up with a very efficient stage. In fact, when we later on we were pressed to think in terms of how to reduce costs, make the stage for less money, it became very difficult to find really basic techniques of configuration adjustment that would lead to a lesser cost stage. I think that is a tribute to the efficiency of the design.

[00:02:38] RB: We heard some place or somebody mentioned it, the S-IVB was really a much different flight article because of the engines maybe, or because of the feed lines, etc., because of its diameter. Do you really see it that way? They're trying to say that the Thor is to the S-IV as the S-IVB is to the S-IV. Just a different vehicle.

[00:03:12] HB: I don't really feel that way about it. Although I can see why a person could take that position. The geometry is different on the S-IVB than the S-IV, but the basic design principles are essentially the same. By that, let me be specific. Common bulkhead, internal insulation, structural concepts, valve actuation devices, pressurization systems were essentially the same. I consider them to be quite similar in nature and that the S-IV was the technical precursor to the S-IVB and directly applicable. The packaging was different, but that's a minor thing.

[00:04:33] RB: The RL-10 came out of this Centaur program didn't it?

[00:04:36] HB: Yes, it's a fine little engine.

[00:04:40] RB: The J-2 gave you a higher specific impulse.

[00:04:43] HB: Well, yes, but mostly the large thrust that was involved and a much more efficient packaging, single engine versus six or more small engines. It was a much more efficient device.

[00:05:02] RB: Was that J-2 on the S-IVB, is that a gimbaled or is that [stationary?]?

[00:05:06] HB: Yes, it's a gimbaled. The roll control is handled by the auxiliary propulsion systems that are attached to the skirts.

[00:05:22] RB: Did you have any particular difficulties in achieving interfaces with the S-II stage and the IU unit?

[00:05:29] HB: No, no, that was very straightforward. As a matter of fact, that was one of the simplest jobs we had. This chart sort of goes back to the main theme we've been talking about, which compares Thor to S-IV and to S-IVB. It notes that we launched our first Thor in September 1957. The first launch on S-IVB was January 1964, which was a considerable time period. The first launch of S-IVB was February ‘66, only two years after the first launch of the S-IV. The first launch of the Saturn V version of the S-IVB was November 1967. The common theme that goes through all of these stages, of course, is the liquid oxygen technology. The type of engine, although changing from oxygen/kerosene to oxygen/hydrogen, the fundamentals are essentially the same. Liquid hydrogen being introduced in 1964 was the big step, which led to the insulation and some structural adjustments to accommodate the very cold liquid hydrogen, and the pressurization system, which we introduced with cold helium internal to the liquid hydrogen tank as a concept of improving the efficiency and packaging—if you will—of the helium, which is the pressure it will run in the valves and actuating the pneumatic systems.

[00:07:29] RB: The fuel pressurization then was kind of a new thing?

[00:07:33] HB: Yes, that's right. This enables you to put very, very cold helium gas in the liquid hydrogen tank and keep it cold. As you draw on that gas, you then permit it to expand by warming up to the ambient conditions that exist, which permits a very efficient packaging and storage capability of the helium.

[00:08:13] RB: Was anything like that used on the Centaur? They used a pump for the propellant utilization, didn't they?

[00:08:21] HB: I think that's correct. I do not know that Centaur uses cold helium as we do. But that was a very clever approach and a very logical one. This particular slide shows the types of joints, types of fittings, and stringers, and tank walls that we have developed. This is very fascinating to a structural engineer. I'm not sure how fascinating it is to others. It really presents a picture of a rather efficient design concept that has led to a good, rugged design that has not given us any problems.

[00:09:37] RB: On the skirt sections here, the stringers are external?

[00:09:46] HB: Yes, that's right.

[00:09:48] RB: In the S-II, there are some external stringers too? [Inaudible] they finally included that insulation with the cork material on the outside of those to reduce the aerodynamic heating. Do you have any problems with this?

[00:10:08] HB: There is some aerodynamic heating, and we do coat these stringers with heat protection devices such as korotherm, which is a thick paste type of paint which permits the heat that is generated during exit to be contained, so that we don't increase the temperature of the stringers to the point where they lose their strength.

[00:10:48] RB: It's contained in the paint base?

[00:10:50] HB: Yes, paint becomes a thermal barrier in the same fashion as the insulation inside of the liquid hydrogen tank although it's working in the other extreme.

[00:11:04] RB: What's this stuff called? Korotherm?

[00:11:09] HB: Korotherm. K-O-R-O and “therm” like in thermal.

[00:11:16] RB: Korotherm.

[00:11:18] HB: It's just a thick paint, almost paste-like in nature, which applies quite readily to these structural devices.

[00:11:32] RB: Was it just simpler to build a skirt with these external stringers rather than put them on the inside?

[00:11:38] HB: Yes.

[00:11:40] RB: [Inaudible] thinking that flash riveting has been around for quite a while.

[00:11:44] HB: We don't need that. These stringers are all pretty much within the very thick boundary layer so drag-wise we're not contributing much more drag.

[00:11:56] RB: Oh, I see.

[00:11:57] HB: The design parameter is not drag, it's simply structural strength with lightness and then efficiency and ease of construction. It became more economical to put the simple half-stringers on the outside. The only design criteria that had to be met then was to provide the thermal protection during the brief moments of high heating during exit.

[00:12:34] RB: Well, it always kind of bothered me, I guess, because we heard so much about getting in the structure, getting out of the atmosphere pretty fast, these aerodynamic features and qualities. It kind of bothered me to see these stringers out there.

[00:12:50] HB: [It wasn’t necessary?] to have a smooth surface as you would on the wing of a transport. Now the reason for that is fairly simple. The amount of time that we were within the high drag atmosphere was reasonably short. If we were flying for literally hours like a DC-8 or a DC-10, then that drag experienced over a long period of time would be quite meaningful, and, of course, is the reason why we have gone to laminar flow type of wings and very smooth skin surfaces on the rutted areas of transport airplanes because that has a tremendous payoff in fuel consumption. It is not that sort of a thing in the only short period of time that we're going through the atmosphere on something like a Saturn V. It just is not necessary to have one of those techniques.

[00:13:57] RB: Looking at it from this picture, it reminded me again of the Skylab configuration and the Apollo applications program. When you were designing, [inaudible] the S-IVB, were you kind of thinking of the Skylab at the same time, or any inputs that you were designing because of the possible Skylab configuration?

[00:14:22] HB: Oh yes, as early as 1964. In 1964, we began to think in terms of the use of the liquid hydrogen tank as a work area or experiment area or activity area for the astronauts when something like the Saturn IB was in Earth orbit. The point there was that the S-IVB does remain in orbit for a considerable period of time—weeks, months, a year—depending on what orbital altitude is selected. The device is up there, it is a huge thing: twenty-one feet in diameter, and the hydrogen tank is probably some thirty to forty feet in length, if you include the dome. We had a large opening at the top of the hydrogen dome for manufacturing reasons. There came an occasion in 1964—I guess actually the latter part in 1963—when we had occasion to increase the diameter of that opening at the top of the hydrogen tank for ease of manufacturing and better loading characteristics. It was sized to permit workmen to enter or exit. We got with Dr. von Braun and agreed on a diameter for that new opening that would match an astronaut and his gear going through. He said, “Now if at any time we want to use the spent S-IVB stage as an activity area, it would be easy for us to permit ready access of the astronauts to the liquid hydrogen tank.” The original concept was that extra-vehicular activities could be performed in the confines of this tank without anybody being worried about drifting off and being lost in outer space, such as would be the case of [inaudible] departed for any reason during some of these spacewalks. There were some experiments being contemplated of maneuvering units, maneuvering aids, little handles, implanting jet gases that would assist astronauts in moving around in extra-vehicular activity. These could all have been tested inside the liquid hydrogen tank. From that concept in 1963-64, gradually developed the concept of the Skylab as we know it now.

[00:18:25] RB: I see now because I remember seeing some other things about using just this empty tank and I couldn't figure out really…It didn't come through to me what you would be doing in there, just to test these EVA things [inaudible]...

[00:18:36] HB: [Inaudible] doing all sorts of EVA type of activity in pressurized suits in that tank and not be concerned with being injured or being left in space. Then it became pretty clear that we could also repressurize that tank and think in terms of living in a [short sleeve?] environment. The original concept of the global workshop was to use a spent liquid hydrogen tank.

[00:19:16] RB: So the things from the start though originally designed purely as a rocket, and you got into design ways and realized you could do something?

[00:19:30] HB: [Inaudible] opportunity for other uses since it was up there and represented a considerable resource moving around in orbit, the question was let's get smart and see how much use we can put to it.

[00:19:53] RB: Before you get on to that, were there certain times too when you designed this thing, sheer logistical problems closed certain avenues until you realized you couldn't carry it down a highway or under a bridge or maybe carry it in a certain mode and so you had to redesign it somehow?

[00:20:11] HB: No. [laughs] It helped us select the location of this facility. [laughs] Quite seriously.

[00:20:19] RB: Well, some place I read—it was in the trade journal, however—-that the S-IV something they began to think of logistics as a parameter of its original design.

[00:20:34] HB: Yes.

[00:20:37] RB: There's nothing in the location of the plant that was…

[00:20:40] HB: We were [inaudible], if you will, compared to the S-II and the S-IC, we thought we could solve our problems quite readily. It did, in thinking in terms of future programs, the logistics consideration did have an important influence on the location of this facility. We are close to Seal Beach as a port and close to the Naval Air Station as a means of getting air transportation. Those two things had to be considered in the location of this facility. They had some [inaudible] in the location of the Seal Beach facility for North American for the same reasons.

[00:21:27] RB: Excuse me, go on with the…

[00:21:30] HB: Well, I have some photographs here of the several tankage and membrane joints. We can look a little bit more at the common bulkhead and how it is, the simplicity of its attachment to the liquid oxygen tank, and the attachment to the liquid hydrogen tank. I think the important thing that this chart shows is that the structural simplicity that came out of the design concepts is impressive. These are not difficult welds. They lend themselves to easy inspection and good quality control. The most complex part of this thing is the fitting of the aluminum surfaces to the fiberglass common bulkhead. That is probably the most difficult job we have and perhaps the most demanding one as far as workmanship is concerned. That was considered at one time to be the big worrisome feature of the design. In fact, in practice, it has turned out to be most routine. After the first few articles were manufactured, that settled down to a very routine process and has been no trouble whatsoever.

[00:23:17] RB: Well, you had some special processes, didn't you, to shape the common bulkhead for this?

[00:23:26] HB: That is a very elaborate process, and I would prefer to get an expert on that to discuss that with you [when you’re ready?] to talk about that. That has reduced itself to a very clever methodology of fitting and sizing the fiberglass center section, so that it matches very precisely to the two aluminum domes and lends itself to good adhesive characteristics and excellent quality control. I am very pleased with the outcome of that.

[00:24:11] RB: Some of these welds, were these fairly common as far as aircraft construction or they were kind of unique for the space program and less straightforward?

[00:24:22] HB: However really unique due to the application, it had not been common to use weldments of this nature for major structural joints in aircraft. The joints were all riveted or bolted. Here we had a situation where we departed from that and were depending entirely upon the integrity of the welds for both structural attachment and for sealing. We could not have any leakers, if you will. Leakers being passed for molecules of hydrogen to pass through, not boiling leaks. We don’t have to have anything but a path of migration of molecules of hydrogen into the common bulkhead and mix with molecules of oxygen from the liquid oxygen tank to have a very distasteful situation [both laugh] in the common bulkhead.

[00:25:32] RB: Was the inert gas welding technique used anywhere in the aircraft industry? That was fairly common?

[00:25:41] HB: Yes. The main reason for that is that you just cannot stand to have just common atmospheric gases around the arc. The oxygen and hydrogen, or the hydrogen I guess is the worst offender, tends to embrittle the welds.

[00:26:06] RB: Okay, [you have to move?]

[00:26:11] HB: Yes. I think the most impressive part of the early portion of the program was the design of the welding fixtures. What I have here are some of the large welding devices that were used to do these precision welds. In this case, we are welding the liquid oxygen tank to where I take to be the liquid oxygen tank. This is the dome of the liquid oxygen tank, which is the cylindrical section of the liquid hydrogen tank.

[00:27:02] RB: They are inside the tank here?

[00:27:04] HB: That's right.

[00:27:05] RB: This will be coming down through that top opening, I suppose?

[00:27:09] HB: That's correct. [Inaudible] travels now automatically and is doing the circumferential weld of the cylinder to the liquid oxygen tank extension.

[00:27:23] RB: This whole beam coming down here and the two supports coming in forms kind of a triangular…?

[00:27:28] HB: That's right.

[00:27:29] RB: It rotates all around the inside of the tank. This is the problem with the shop area, but of course nothing was going on with the solid fixtures, and sometimes they didn't have a better idea of how they operated.

[00:27:43] HB: For two-man operation that's pretty good.

[00:27:47] RB: Does this just work on a geared track here sometime, and [inaudible] observe it and guide it?

[00:27:54] HB: They are controlling the feeds, and one of them is watching the welding process. This is our Sacramento test facility where we did the acceptance firings on these two stands, Beta stands we call them. This is a facility that we at NASA developed for the conduct of the S-IV and the S-IVB activities. This is now for all practical purposes closed down.

[00:28:42] RB: Beta I and Beta II test stands? Three?

[00:28:45] HB: Beta III.

[00:28:46] RB: Beta I and Beta III?

[00:28:50] HB: There were going to be Beta I, Beta II and Beta III, but we only made Beta I and Beta III. I think we skipped Beta II for some reason. I think I'm right on that.

[00:29:04] RB: Now on the test program there were a couple of explosions, weren't there?

[00:29:08] HB: No. There was one on the S-IV program and there was one on the S-IVB program.

[00:29:13] RB: Excuse me here…

[tape ends]

0:29:19