Christensen, David ("Dave")
Dublin Core
Title
Christensen, David ("Dave")
Description
David Christensen describes how the Saturn program relied on a network of experienced aerospace vendors to develop and supply specialized components, emphasizing that this approach had long been standard in the aircraft industry. Rather than competing primarily on price, vendors sought to demonstrate superior reliability, technical performance, and compliance with stringent NASA specifications, particularly for liquid oxygen (LOX) compatibility. Marshall Space Flight Center engineers worked closely with contractors and suppliers to test competing products, develop specifications, and ensure the highest-quality components were selected. Christensen explains that successful vendors often invested their own resources to qualify products, collaborated directly with engineers during research and development, and sought to have their components named in procurement specifications, giving them a competitive advantage while still allowing equivalent products to compete. He uses Aircraft Porous Media (later part of Pall Corporation) as a case study, describing how the company developed advanced porous metal filters and Rigi-Mesh material through in-house research and close collaboration with the Air Force and Huntsville engineers. These technologies became critical for hydraulic systems and, later, rocket engine applications such as the J-2 engine injector, illustrating how government-industry partnerships, rigorous testing, and sustained technical collaboration drove innovation and reliability throughout the Jupiter and Saturn programs.
Source
University of Alabama in Huntsville Archives and Special Collections, Huntsville, Alabama
Rights
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.
Format
.MP4
Language
en
Type
Interviews
Audio
Identifier
ohc_stnv_000007_A
Oral History Item Type Metadata
Interviewer
Bilstein, Roger E.
Interviewee
Christensen, David
Transcription
[00:00:16] Roger Bilstein: Was the kind of operation where—you used a term, I've forgotten what it was—but they're the vendor entrepreneurs—the guys that come around and really sell things. I wonder if you could start there and talk about that a little bit first.
[00:00:26] David Christensen: Okay. Well, I guess this is fairly standard that you have a lot of peddlers pushing their wares, you know, big programs. It's kind of interesting to me on the Saturn program to see the techniques that we used in developing new components and hardware. These were done by the so-called vendors. That's the common term. This is also fairly common to aircraft development. It has been for years. For example, the Parker fittings were used on the Ryan Spirit of St. Louis and developed by a Mr. Parker of Cleveland, Ohio, I believe. This later became part of Parker Hannifin Corporation, which is one of the larger pneumatic and hydraulic component system manufacturers in the world. One of their divisions was developed in Los Angeles called Parker Aircraft, actually located next to the aircraft industry in California. That would be a typical example. Another one might be Pesco Products— which later became a division of Borg-Warner right there in Cleveland—supplying, for example, the hydraulic filters as hydraulic systems became applied to aircraft. Of course, Cleveland being another aircraft center. Thompson Products would be another one.
[00:01:48] DC: These are typical vendors that have historically supplied parts and, in my opinion, done pioneering work in the component development for aircraft. This just naturally evolved into—of course—guided missiles, rockets in the post-war period, and eventually the Saturn program. There's nothing unique to Saturn about this particular approach. But it was to me quite interesting to see the efforts that were made by these vendors to get their wares into the Saturn vehicle. I was more involved in mechanical components. This included fittings, filters, hydraulic filters for your servo control systems, tubing, hydraulic pumps, for example.
[00:02:41] DC: One of the problems you had, of course, in the Saturn is that you might go to someone like Rocketdyne Division of North America to develop the engine itself. You'd have certain vendors that were their favorites, you might say, working closely with them on the West Coast. Then you'd have others coming into Huntsville. They were interested in getting their wares on board. Really the only thing they had to sell is, of course, better quality, that being the order of the day. Price did not seem to be quite that much of a consideration in those days. It was quite a bit of concern of reliability and meeting very rigid specs, for example. One of the critical specification requirements was LOX compatibility, which was sort of the new term. In the aircraft industry, you really didn't have that particular problem, not using liquid oxygen.
[00:03:34] DC: Anyway, these vendors might come in and say, “Well, we have a better valve than what Rocketdyne is proposing to use on the engine. How do we get it into the system?” Usually that was a very difficult task. More likely they would supply components for, say, the interconnection of the engines on the Saturn or the pre-valves or the flexible ducts that are above the engine pump inlets and this sort of thing. There were a number of, you might say, pet vendors then developed by the Huntsville team. In some cases these were the same, for example, as Rocketdyne might use. In other cases they might not be.
[00:04:15] DC: But one thing that was very apparent is Huntsville did have, you know, influence over the reliability of the whole system. Naturally these people would try and get on board. For example, you would get a situation like on the S-II stage being built by North American with prime responsibility. But yet Huntsville writing the specifications for that stage and working closely with the North American people because it was a size of a liquid hydrogen and oxygen structure that had never been developed before. It had to be somewhat a team effort. Expanding on the vendor thing, you might have somebody like Parker Aircraft working closely with North American out there in California. By the same token, working closely with the Huntsville people here so that their hydraulic control package or accumulator or whatever it might be would be accepted by both parties. This is what it would probably take to become, you know, on board the Saturn vehicle. I'm referring now to Saturn V.
[00:05:28] DC: I think we may have talked about some other aspects of this, but you did have a lot of vendors running in and out, pushing their wares, saying, “We've got a better product than this. Let's take a look at it.” You had a lot of test programs going on. You had a heck of a lot of component testing going on to evaluate one of these products against the other and come up with test criteria, so you could select the best component or hardware.
[00:05:54] RB: Would there be a situation where some vendor got a hold of the specs or something and said, “Hey, we got something that will fit in here,” and they would come down, and maybe Marshall hadn't heard of them before or wasn't aware of their new product. So they would work hard to sell that.
[00:06:06] DC: Yes. Then they might have to, on their own investment, develop a valve that would meet those same specifications, you know, and say, “Look, this is equal to your spec and is acceptable, and we've proven it. If you don't believe us, you test it.” In some cases, Marshall, NASA, or before that the Army would do that. On the spec sheet itself, then you would state you such and such a part are equivalent. Normally, they would always list one naturally, maybe two, if two are equal, you know, in quality, or then they would put the little word “are equivalent.” If you could qualify, then you could still compete. Then it became if you were technically acceptable, you could meet this all the specs and then demonstrated this. Then it became a matter of price, which I think was a healthy situation. You didn't have a stranglehold or a monopoly by one particular company, but free enterprise was still allowable.
[00:07:04] DC: The big problem was in this big morass of documentation and people, this was always a problem of how did the vendor find out who to go see and what's the network and the sequence of events he's got to go through and how long does it take to implement this thing. In a lot of cases, they would hire consultants and representatives to help them in this regard. That was one of the things that I did here with several companies was to assist them. In some cases, not just to get on board or compete, but to more or less limit the competition. In other words, by doing such an outstanding job that sole source—that's always the ultimate ideal situation is to be sole source—so you're named in the RFQ or the spec or whatever it is as the supplier. That's always the objective, you might say. As an alternative, at least be either/or equipment supplying these things.
[00:08:09] DC: It was quite an interesting relationship in that, like I say, you had first of all, management by Marshall, you had test teams here—component test teams—they were heavily involved in that. You even had designers right on the board working with some of these vendors, working closely with them, hand in hand almost. In some cases, the vendor was under contract. In a lot of cases—Flexonics on the flexible connectors—had actually R&D contracts to develop some of these systems because they had only one application, obviously. How many other ways can you use a flexible duct between your propellant tanks and the piggyback turbopump on an H-1 engine? I mean, that's it. In other cases, you had…I guess companies had many applications for their pressure switches, so they would try and bring their products on board also.
[00:09:06] DC: But again, it boiled down to the problem of knowing the right person, knowing the sequence of events. In a lot of cases, you had commercial firms even that did not have that much government experience. In the main case, most of these vendors were former aircraft vendors that did know the ropes, and it was just a new market for them to tap, you might say, even though it was a limited market as far as production numbers as well.
[00:09:31] RB: So in some cases, the guy would come in with the product, and he would say, “This is a good product, we tested it and so on.” Then part of the idea is to get when the RFQ or spec comes out to get that product named then?
[00:09:44] DC: Yeah, that's your objective is to try and…
[00:09:46] RB: The government could protect itself by saying X company or equivalent.
[00:09:50] DC: Yeah, right.
[00:09:52] RB: But you're still ahead of the game if you get your name in the spec first time?
[00:09:55] DC: Right. Because then you're requested to bid on this thing. Usually, it would be difficult for another company to come along and in the short time frame between the time the purchase order went out and he had to turn his bid in to analyze really what's involved in that spec. In other words, you've got to look at that spec and look at all the parameters and see what's your closest sets of valve or a pressure switch in your catalog, which one is closest to that spec, then look at the differences between your closest model and the exact spec that's required. Then further, how much in-house effort you've got to perform: how many parts have you got to change, how long does that take, how many man hours have you got to pump into it. Normally the alternate vendor would just say, “Well, it's just not worth the trouble for half a dozen parts” or whatever it might be. As a result, you'd probably only get one bid. That would be more likely than not.
[00:11:01] RB: Okay. Can you go into the end of the Pall Corporation, how the Rigi-Mesh got into the Pratt & Whitney engine, the J-2, and so on? And too, would you explain about the Pall Corporation doing their R&D in-house and selling that?
[00:11:18] DC: Yeah, right, okay. Some of these vendor firms were more interested in—I can name a few like Park Aircraft, Flexonics, I'm sure there's a lot of others—that were interested in getting their research and development funded by the government. In other words, they would solicit contracts to advance the state of the art, which I think is a healthy situation for them and the government. The government can oversee these efforts, but it puts the company in a very good position then to be the supplier when the parts are developed. This was the case in certain development of low leakage fittings, for example, the mechanical connectors on the propellant systems, pneumatic systems. This was the case in a lot of the valves themselves that were, the pre-valves, for example. Particularly, you could say the large sophisticated types of components and hardware, the pre-valves that would stop the propellant flow prior to going into your engine operation.
[00:12:20] RB: H-1 and F-1?
[00:12:21] DC: Yeah. Historically, most rockets do have pre-valves, which allow you to shut these things down on a test stand. They're primarily needed for static testing. Not so much for main stage, but they still keep them in sometimes on the flight operation.
[00:12:39] DC: Anyway, the Pall Corporation, which is the one I was familiar with, had a division called Aircraft Porous Media. The philosophy of the Pall Corporation as a whole was to do their own internal R&D and meet specs that were required primarily for hydraulic pneumatic filters. That was their main business. They were also an aircraft-oriented firm. That's how they got into the metal filter business because their philosophy was with the higher temperatures and vibrations and operational parameters of aircraft, particularly jet aircraft after World War II, that the normal types of filters and strainers and so forth that had been used up to that point were just not of high enough quality.
[00:13:26] DC: They worked very close with the Air Force at Wright Field in developing a whole new family of filters for aircraft, and then expanded from that base into the commercial fields and then into missile and rocket fields. It was a very interesting company to watch. They originally got into that business through the efforts of Dr. David Pall, who founded the company. He originally worked with the Atomic Energy Commission in World War II in developing porous metal materials for gas diffusion processes for your development of the atomic energy program, atomic bombs, and so forth. All of your nuclear programs that are now used in nuclear reactors came out of this research.
[00:14:15] RB: He was a research scientist?
[00:14:17] DC: As far as I recall, he was either a consultant or a research scientist. He did materials research. That was his forte. As you may know, other ways of doing this are now becoming known using centrifugal diffusion. I think the Japanese have been doing this, which is less expensive way of separating your U-235.
[00:14:41] DC: He felt there was a need then after experimenting with this material, and he thought there were other applications, so he started working with controlled porosity of metals. This is done by taking woven metal, similar to what you have a woven piece of cloth with certain twill patterns and weaving patterns. A lot of this has been done over the years in such countries as Germany for industrial applications. Metal screen mesh is not a new material. The fact that Dr. Pall worked with the sintering, making this a rigid material by almost reaching the melting point and then allowing it to cool before it completely melted, you actually become almost like an integral piece of material, little tiny holes in it. By layering this and rolling it, you can then get any thickness and practically any porosity you need for any given application. The first application that he proposed for this was aircraft filters, hydraulic filters. One of the advantages would be not only, let's say, apply with extreme operational parameters, but also you can re-clean it rather than throw it away. There you became like a reusable application for these filters.
[00:16:10] RB: You know, these hydraulic actuators in flaps and landing gear and things like that?
[00:16:16] DC: Yeah, yeah, yeah. All your hydraulic control circuits needed these things. One of the problems you get into if you don't filter your hydraulic fluid is you have excessive wear on your hydraulic pumps, your piston pumps, and your gear driven pumps made by such companies as Pesco—one of the other old line vendors. This was really an advantage to the Air Force because it gave you longer operational life. The other vendors may not have liked it that much because they didn't sell as many parts. [laughs]
[00:16:45] RB: But it also creates structural rigidity to the component then too, if you've got a metal filter in there. Was that part of it at the time?
[00:16:52] DC: Well, yeah, actually it's sort of an independent floating part, if you're familiar with how filters are made.
[00:16:57] RB: Okay, I was jumping ahead to the engine systems then.
[00:17:00] DC: Yeah. These things are normally…Another thing you can do with these is you can pleat them into a series of corrugations. What this means, you get more exposed area, so you have more filtered area. Then you can take these things and put them in an ultrasonic cleaner with certain fluids and then clean them up and then use them over and over again. That was one of the big advantages.
[00:17:21] RB: Getting back to our story in Huntsville…There had been some background with the Air Force and aircraft filters. When the Jupiter program started, which was around ‘55, say, ‘56, then it was decided to go to a gimbaled hydraulic system on the Jupiter. Before that, there had been some, I think, hydraulic packages on some of the other Army rockets too. Possibly the Nike, I'm not sure on that. And certainly the Hawk. At that time, the Army missile programs were getting involved with hydraulic control systems in a big way on the Jupiter because it obviously had to have two large actuators to gimbal the complete engine. I'm sorry, to gimbal the thrust chamber below the gimbal point in this case. Also these things were used for the roll control system, which I mentioned, meaning your turbine exhaust gas is overboard, had to require a servo mechanism. The people at Aircraft Porous Media started coming down to Huntsville and talking to engineers here, who for the first time, were getting heavily involved in hydraulic control systems because in the Redstone and V-2 before that, there were no hydraulic systems. It was a new area, you might say, for the von Braun team to get involved in. Therefore, a lot of in-house efforts started going into hydraulic system cleanliness specifications and standards. The people from Aircraft Porous Media started working closely with test people and engineering people here in Huntsville to help them develop the specs that were needed to purchase parts and components and so forth for these systems.
[00:19:18] RB: Who would have been involved? Was Weidner in there and Hans Paul?
[00:19:21] DC: Yes, those were the two main people involved. There were other people like, at that time, Jim Thornton. There was another fellow around that became involved named Vic Neiland, who's still around. He was heavily involved in this whole story. One of the key guys was a chemical engineer named Bill Riehl. He's still here. He was not only interested in hydraulic contamination problems, but also LOX impact sensitivity. That was another thing he worked heavily in.
[00:19:48] RB: How do you spell that?
[00:19:49] DC: R-H-I-E-L. R-I-E-H-L. One of them. It's Riehl. R-I-E-H-L.
[00:19:54] RB: How do you spell Neiland?
[00:19:55] DC: N-E-I-L-A-N-D. Or I-E. I’ve got to check. I’ve forgotten.
[00:20:00] RB: What's his name again now?
[00:20:01] DC: Victor.
[00:20:02] RB: Vic Neiland?
[00:20:03] DC: Yeah.
[00:20:04] RB: Okay.
[00:20:05] DC: So those are the two guys that could give you the background on early hydraulic system development.
[00:20:09] RB: Yeah.
[00:20:10] DC: This continued, and the people from APM—Aircraft Porous Media—continued to work closely and have developed these specs. It was a good case history of how a vendor, you might say, worked hand in hand with the people here in Huntsville to come up with good specs that supposedly would give you a good high reliability on your hydraulic system.
[00:20:34] RB: Was this a case where they kind of wrote themselves into this?
[00:20:37] DC: Yes, very definitely.
[00:20:38] RB: Were you doing that for the...
[00:20:39] DC: No, I was on the other side of the fence at that time working in the engine group.
[00:20:43] RB: Okay, yeah.
[00:20:44] DC: I was doing such things as designing these hydraulic systems and working from that side. Incidentally that was one system that was never touched by Rocketdyne. They tried many times to get into engine control systems. In this case it was done completely in house, which is kind of interesting. As well as such things as your missile propellant pressurization systems, all of your heat exchanger developments, all of your pre-valve systems, all of your electrical relay systems, all of this was developed by Huntsville. In other words, the interface was sort of “Rocketdyne, you build this engine, you test it and develop it. We'll run acceptance testing on it, and you deliver it to us or you deliver it to Chrysler”—whichever the case may be—”and we'll plug it in and take it over from there.”
[00:21:40] RB: This is Jupiter?
[00:21:41] DC: Yeah, and this is also applied to the H-1 and the Saturn type of relationship.
[00:21:46] RB: Rocketdyne wasn't getting into the hydraulic actuators?
[00:21:49] DC: No.
[00:21:50] RB: But they were taking the government-furnished equipment?
[00:21:52] DC: Yeah.
[00:21:53] RB: Okay.
[00:21:54] DC: That's right. All of the control aspects, all the mechanical control as well as guidance and electronic, and all these other control systems were developed out of Huntsville. Of course, they went to vendors for certain pieces, but the systems engineering was strictly done by the Huntsville teams. No question about it. From Jupiter then evolved the larger numbers of actuators and hydraulic packages and pumps, what have you. Incidentally, the pump received its power in both cases from the turbo machinery of the engine. A tight interface there, of course. This pump in turn had to have an accumulator so that it had a reservoir reserve. In other words, in designing a hydraulic system, you have a basic energy input, in this case from the pump. You also have to have a surplus storage device, which in this case is an accumulator, so that when you have extreme actuation, you don't starve the pump more or less. You have to have reserve. It's like a storage battery in an automobile type of thing. That'd be your electrical analog. This evolved into the Saturn program, and then the company continued to work closely with the people, and they were involved. When the Saturn V came along, there were a few difficulties, but in general they stayed all the way through the program. This is a good situation, or a good case of getting in early and riding the program all the way through.
[00:23:32] RB: So APM was in on Jupiter and they got in on the H-1 then? And got in on the F-1.
[00:23:37] DC: Mm-hmm. The Saturn I, and then on the F-1. Now the F-1 was a different kind of beast in that you used fuel for the actuators. I may be wrong. I know that we were looking at it. I think you had a big fuel pump using kerosene/RP. This applied through the actuators also, so you'd require a different type of filter. This was sort of a new ball game, and frankly I was kind of getting out of it at that time, so I'd have to refresh my memory and check a few things on that.
[00:24:10] RB: When did you become the representative for APM?
[00:24:13] DC: It must have been about ‘61. So I left in ‘60, about ‘61. Also with Parker Aircraft about that same time.
[00:24:26] RB: So when you became the rep for APM, you were selling actuator filters?
[00:24:32] DC: Well, I was not a rep. I'll have to take that back. They had what they call a manufacturing representative. I was in a little different league. They called me a government liaison representative. My function was more liaison and communication as opposed to sales. I never was involved in direct sales. It was more like a consulting type thing.
[00:24:54] RB: I see.
[00:24:55] DC: The same thing held true with Parker. It was more of a consulting and advice and liaison as opposed...In other words, they had their own salesmen. I didn't get directly into that loop at all of writing purchase orders and what have you. That was a separate marketing function. It was to advise those people who to go see and what was going on and who should they go see at North American to make sure their hydraulic systems or filters are applied to the second stage, who should they see a Douglas and this sort of thing.
[00:25:26] DC: In a lot of cases they knew and already had worked with these people, so it was just tightening up, you might say, the communication loop. Which competitors are sniffing around, we better keep an eye on type of thing. [laughs] But there was a lot of that going on. Like I say, there were literally dozens and dozens of reps running around at that time. In fact, it got pretty bad at times where they'd almost have to close the doors and make it a strict appointment because at one time these guys were like fleas. I was on the other side of the fence, and I know how it is when they come marching in on you. [laughs] That was really, I think, an interesting sideline here. I think that was one reason for more of the security consciousness that developed more so than worried about classification of material. It was just for protection of the poor engineers so they could get some work done. I tried to make it my own policy not to bother people unless I really had something of interest to them or vice versa. I've tried to maintain that relationship over the years. When I felt I could contribute something or a company could, I thought it was worthwhile to pursue it, which I think is very important to maintain a long-term relationship.
[00:26:47] RB: Well, looking at the Rigi-Mesh application and engines, by ‘61 Pratt & Whitney had already gotten into it.
[00:26:53] DC: Yes, through the Lewis testing and the Rigi-Mesh being the trade name for this same porous material. I might mention there were a number of things looked at for this material. This particular application was for the injector face on the liquid hydrogen propelled rocket motors. The advantage being that you get a transpiration cooling effect through the porous material. It gives you sort of a boundary layer on the combustion wall similar to the old film cooling techniques used on the V-2. This was an early recognized problem that you can burn up an exposed material unless you have cooling on it. In the case of the injector, it's not like the outer wall where you have a heat exchange effect and you have a continuous flow of propellants that gives you a cooling effect. In this case, you're just oozing, you might say, right through the porous material to get that same effect. It's similar, but not the same. Also other things were looked at with this material. The Air Force, for example, has always been for a long time been interested in boundary layer control and actually, let's say, sucking off on the leading or upper edge.
[Interruption, tape cuts out and restarts]
[00:28:18] DC: We were talking about Rigi-Mesh, and I was mentioning the other applications for this material. Another application that, let's say, evolved out of this material was for noise suppression. For example, a lot of the big jet engines now have a outer layer of the same type of porous material cut down on the noise level. But anyway, you're right, Pratt & Whitney had been using this material and run their own tests down at...I'm not sure if they were in Florida at that time or not. I know they did run some testing down there later. I know they started, you know, buying this material, running tests. They determined it was very useful for this application. Another application I'll mention quickly, it has been considered for quite a few years for re-entry nose cone purposes, sweat cooling, where you actually have a material oozing through this during re-entry to give you a film cooling layer. It's efficient from that standpoint, except for the loss of the cooling fluid. This is one of the disadvantages. The trend has been more to your solid ablative type, you know, materials that liquefies every entry and get the film cooling from that. So the outgas are…
[tape cuts out]
[00:29:42] DC: In the meantime, the Pratt & Whitney engine was developed primarily under Air Force contract for the Atlas-Centaur application. That's where it's still being used. At that time also, I think Huntsville gave Douglas a contract for the S-IV stage as the second stage for Saturn I, which would be called Saturn I-B. I'll correct that. The six Pratt & Whitney engines were used on Saturn I as the second stage. The S-IVB actually used in the J-2 engine as well as the S-IVB stage, which was the third stage for Saturn V.
[00:30:30] DC: In that period—I'd say ‘60-’61, I'll have to check—the specs were written for this larger LOX/hydrogen engine, and there was competition between primarily Pratt & Whitney and Rocketdyne for the engine. Rocketdyne was awarded the contract. I'd have to go back and check my...You're probably more familiar with now than I am, but I think this was even before the Apollo was announced that this was going on. I do recall working very hard on the specs for that engine. I left in June of 1960, so that means those specs were being worked on quite early as well as the upper stages, the S-IVB and the S-II stage, yeah.
[00:31:15] DC: The specs are being prepared better today. In other words, there was enough knowledge to know that these are the kind of pieces of hardware, and this was going back to the C-2 program probably that you would need these. Very likely the specs didn't have the final configuration. They didn't have some of the basic dimensions and systems that were required, and we were at that time starting to write those specs, particularly the engine specs.
[00:31:42] DC: I left about that time, and about that time Rocketdyne got the engine contract, J-2. In their original concept, I don't think they accepted the Pratt & Whitney injector design for obvious reasons. They had to be unique, you know? But yet they were still allowed to give them the contract. To make a long story short, I did continue to follow this program, more or less as its government liaison role. As a matter of fact, this came somewhat later, maybe a year later, before I actually got into that position. Even at that time, there was questions on...
[interruption, tape cuts out and restarts]
[00:32:31] DC: One of the questions that came up on using Rigi-Mesh for the J-2 engine was the availability of the material because it was sort of a sole source for proprietary material. It was manufactured in sintering furnaces there in Glen Cove, New York. That was the source. The question came up on availability. I don't recall all the details, but I do recall one story of Dr. von Braun visiting Rocketdyne, as he frequently did in these product improvement reviews and engine status program reviews and what have you. I was told—I wasn't there at the time—but I was told that he just asked them point blank, why don't they just go ahead and use what had been proven—namely the Pratt & Whitney injector system and material. And they did it. Then the whole thing was settled from there on out. It was just a matter of supplying the hardware then, I mean the material, to Rocketdyne. Let them shape it, you know, machine it. It can be handled just like a solid piece of material in the same thickness.
[00:33:37] RB: Do you remember who was there and heard von Braun?
[00:33:40] DC: I think Jerry Thomson mentioned this to me. He would be the best one just to ask for more details on that particular point.
[00:33:48] RB: Well now, were you here at Huntsville, were you talking to somebody in the engine program office about Rigi-Mesh and trying to encourage them to use it?
[00:33:57] DC: Yes, I think I continued to keep some contact with local engine people. I think I did propose this, you know. Would they consider this, and they were considering it. The people here were sort of in favor of it, but I think it was Rocketdyne that was dragging their heels. I don't know all the factors there, you know, what else they were looking at. Frankly, I know they were looking at some of their own unique injector designs, and probably they were, you know, trying to somewhat justify whatever they had proposed. There was a period there of almost a year when after I left the propulsion group, and then got more heavily involved in this consulting type activity that I'm not that familiar with everything that did happen. But by the time I was back in the loop, they still had not made a final decision, I don't think, on the Rigi-Mesh.
[00:34:47] RB: Were you talking to Thomson here then?
[00:34:51] DC: Yeah, yeah, yeah, because I was going back into that same old group that I had worked in and was talking to them about filters and Rigi-Mesh applications. I became also involved with Pesco Products, division of Borg-Warner, with their [more or less consulting?] rep in Huntsville. They were involved in the boost pumps for the Centaur engines, so they were in liquid hydrogen. Yes, I was in that direct propulsion and propellant system loop. We were also involved in the pre-conditioning pumps. I think they were electrically driven for the S-IV stage and eventually the S-IVB and S-II stage. You have to pre-chill or pre-condition the temperature of the lines before you go into main stage on a liquid hydrogen engine. These little pre-chilling pumps would perform that function. They would actually start up before you go in, you know, start engine operation to cool down so you don't get a gasification ram effect from cold propellants hitting hot lines. So that's another story.
[00:36:09] RB: This is kind of off the subject a little bit, but I'm interested in it. I haven't run it down yet. Where were those Pesco pumps used in the Saturn and what for?
[00:36:16] DC: They were used upstream of the liquid hydrogen propellant feed lines
coming from your propellant tanks to your engines. They were used, as I say, to pre-condition those lines and chill them down. In other words, to get a dynamic flow going through there
because under just a static condition with no flow, you don't get much of a chill down. You have to actually flow the stuff because it boils off so quickly, you see?
[00:36:45] RB: Were they using the LOX lines too or just hydrogen?
[00:36:48] DC: Primarily hydrogen. I think there were possibly some LOX chill down. I know there were hydrogen. It's not as critical on the LOX side. You know, temperature is not near as low, of course. Hydrogen, it is quite critical. With LOX, it's not that critical.
[00:37:08] RB: Okay, so they're upstream of the propellant feed lines to pre-chill those lines.
[00:37:12] DC: So what you have to do...
[00:37:13] RB: Is that involved with the engine pre-chill too?
[00:37:15] DC: Yeah, you go down as far downstream as you can, then what you do, you open up a valve during the pre-chill sequence and then circulate it back up again, you say, to your propellant tank. What it means, you have a closed loop circulation. But if you didn't have that, if you had just a static condition, you wouldn't have any place to go, you say.
[00:37:37] RB: But they not only chilled the lines then, that Pesco pre-chilled the engine too?
[00:37:41] DC: Yeah, as much of the engine as you could.
[00:37:43] RB: Yeah, that's what I mean.
[00:37:44] DC: This was the same function that the boost pumps had on the Centaur, still have. Pesco designed under contract with the Air Force and provided this same role for the Centaur vehicle.
[00:37:58] RB: Okay, so when you're talking about engine pre-chill pumps, for example, a J-2 restart, they have to go through the pre-chill cycle?
[00:38:04] DC: Yeah.
[00:38:05] RB: That's a Pesco pump that's doing that?
[00:38:06] RB: Not necessarily. I know it was on the S-IVB. I'll to have to go back and refresh my memory because I'm confusing in my own mind the S-IV, S-IVB, the S-II, and even the S-I, I think it did have some blocks chilled down pumps. I'll have to look at some schematics, so I'll beg off.
[00:38:26] RB: I had some Pesco products, but they talk about it in such general terms, I just couldn't figure out exactly where they were used.
[00:38:31] DC: Yeah, that was a function, and I could dig that out for you.
[00:38:35] RB: Okay, do you remember anything more about the manufacturing process of Rigi-Mesh, a little bit how they went into that and how they did it?
[00:38:44] DC: Yeah, first, in some cases they would weave their own material; in other cases they would just purchase it as an industrial wire cloth type of thing. In that form it's flexible in that there's no interconnection between the individual strands. This is used for strainers, and wire cloth is used in a lot of industrial applications. They even, I think, purchased a few of their own weaving companies like in Ireland and possibly Germany to supply the raw material to make sure you could always have an adequate supply, which when you're getting big demands you have to meet the demands, and then you have to prepare yourself.
[00:39:25] DC: The next step then is to take this and go through a furnace at almost a melting point. So really it's just like a sintering furnace on a conveyor belt. You go through this thing, and the two critical items are the temperature and the time frame—how long it's in there. If you get these things tuned up, it's quite an art. One of the reasons more people aren't doing this is it takes a lot of experience. It's kind of like the old guy in the steel mill, he knows just when to pour it off. When you do this, out it comes, and it's just like a flat sheet of solid material except it has little holes in it. In that form you can use it for certain applications. Then say you want to go to the injector face, you need, of course, more thickness. You might have to require seven or eight layers of this wire cloth. They seem to favor what they call the Dutch twill weave, which is a specific weave that has a little more rigidity in an even, normal state. It gives you additional strength when it's sintered.
[00:40:28] DC: The next step is then to take, say, X number of layers of this stuff after you individually process them, and then stack them up and run them through all together in a combined form, a combined composite, or matrix of layers. Then that again is quite a tricky process because of your heat transfer rate not being uniform from the outside of the thing to the interior. It's like cooking a potato.
[00:40:58] DC: So all of these things had to be considered in the sintering process. Like I say it's somewhat proprietary. Other people do it. It's not…They're not…They don't have monopoly on this technique. For example, Bendix, [Purolator?] division got into it in a big way. They're still involved in this stuff. They call their material [poor alloy?], I believe. But as a matter of interest, [Purolator?] used to have all the aircraft filter business.
[00:41:29] RB: Does APM have it now?
[00:41:31] DC: Yes, and I think Dr. Pall went to [Purolator?]. That was one of the companies he approached to get their interest up. He went to a number of others and didn't get any response. So he just said, “Dammit, I'll do it myself!” And that's what he did. He went into the filter business. He ended up with the majority of the world market in aircraft filters, which they probably still have today. I haven't checked lately, but I know they did five years ago.
[00:41:53] RB: So [he was applied?] to British corporations, and French corporations, and so on?
[00:41:57] DC: Yeah, yeah, he was worldwide. He had worldwide representatives, fed him this stuff all over the world. Anyway, getting back to Rigi-Mesh…Then you take the stuff out of the furnace, and you test it to make sure it doesn't peel, and it's all centered together properly. Then you have to come up with a given porosity. You do this by taking it and rolling it through two steel rollers and decreasing the thickness, which increases the delta P—or pressure drop—across the plane. The more you squeeze it, the less porosity you have. That step means you can control the, you know, customize more or less whatever type of material you want to develop. Then if you want to further modify it, you can even then take a little tiny material—stainless steel, which in most cases it was—you can take little tiny stainless steel particles and deposit them on the top and even get a filtration action if you like. In some of their cases, they would combine powdered metallurgical type processes with woven wire processes, integrate this into the same material. It means you end up with a structurally strong material because of the weaving. You end up with in-depth filtration because of the tiny little balls that are stacked up and centered together and integrated with the woven material. We call this super mesh.
[00:43:38] RB: Yeah. [laughs]
[00:43:43] DC: So that's how the Rigi-Mesh started.
[00:43:46] RB: Well, they supplied it then, what, just sheets of material?
[00:43:48] DC: Yeah, yeah. And still do to people like Pratt & Whitney, GE…I can't think of any other big engine…Allison, I guess. I don't know if they're still in the act or not. But this same material then, it was and is being used for noise suppression because it is porous and absorbent and cuts down the dB level by dampening out the high frequency vibration
from your compressors and turbine blades. It's somewhat self-cleaning in that you can, you know, purge it out and you can use it for…Well, one thing that I always thought was interesting was to use this material for cooling turbine blades to operate at higher temperatures. And this was considered in World War II by the German Junkers people and their jet engine development. Navy got interested and there has been...
[00:44:48] RB: The US Navy?
[00:44:49] DC: Yeah, US Navy. I think they captured that particular group of engineers and brought them over here. There's a lot of that going on, you know, right after World War II. Over the years, I think the Air Force, NASA-Lewis probably, I know NASA-Lewis, Navy, and other people have looked at this possibility of using porous turbine blades. To me, that would be one of the more outstanding applications if and when it evolves because then you can raise your combustion temperature and operate it at a much higher temperature. It’s giving you much more compact and efficient turbines, jet turbines.
[00:45:32] RB: Off hand, do you know of any other rocket engines besides the RL-10 and the J-2 that it was used in?
[00:45:36] DC: No, but I was quite heavily involved personally in a lot of experimental work that was going on here. Looking at the so-called toroidal thrust chamber, there was a lot of experimental work there. Rocketdyne eventually built, you know, some of these engines under contract. That was one of the materials being considered there for the injector on the inside of the engine. There were some others, small engine concepts that were played around with here.
But as it turned out, these never were used.
[00:46:10] RB: There's something else I was going to ask you too. In making the J-2 injector base, they used electrical discharge machining. So the Rigi-Mesh is the material they were working with. Is that right? And they would just go through…Then they would put in another...
[00:46:24] DC: Mm-hmm. Orifice.
[00:46:25] RB: Orifice, solid for the oxidizer to go in?
[00:46:28] DC: Yeah.
[00:46:29] RB: Okay, so that explains that.
[00:46:31] DC: That's almost identical to the Pratt & Whitney system. Oh, the other big application was the M-1 engine. Aerojet bought quite a quantity of the same material into this under a NASA contract and developed a large million pound thrust liquid hydrogen engine. Originally, it was a Nova upper stage engine. That program eventually died out. I'm not sure on the NERVA engine, you know, which is the Aerojet Westinghouse nuclear engine whether Rigi-Mesh was used or not. I'm not sure, but I kind of doubt it because it's just a P engine. All you're doing is dumping liquid hydrogen into it and expanding it, you know, in the form of gas for your thrust. In that case, I don't think the injector face is that critical. I'm not sure. But the M-1 would have been on the big application.
[00:47:26] RB: That's a really beautiful story, Dave. It's really a nice one. I like that. Cheers.
[tape ends]
[00:00:26] David Christensen: Okay. Well, I guess this is fairly standard that you have a lot of peddlers pushing their wares, you know, big programs. It's kind of interesting to me on the Saturn program to see the techniques that we used in developing new components and hardware. These were done by the so-called vendors. That's the common term. This is also fairly common to aircraft development. It has been for years. For example, the Parker fittings were used on the Ryan Spirit of St. Louis and developed by a Mr. Parker of Cleveland, Ohio, I believe. This later became part of Parker Hannifin Corporation, which is one of the larger pneumatic and hydraulic component system manufacturers in the world. One of their divisions was developed in Los Angeles called Parker Aircraft, actually located next to the aircraft industry in California. That would be a typical example. Another one might be Pesco Products— which later became a division of Borg-Warner right there in Cleveland—supplying, for example, the hydraulic filters as hydraulic systems became applied to aircraft. Of course, Cleveland being another aircraft center. Thompson Products would be another one.
[00:01:48] DC: These are typical vendors that have historically supplied parts and, in my opinion, done pioneering work in the component development for aircraft. This just naturally evolved into—of course—guided missiles, rockets in the post-war period, and eventually the Saturn program. There's nothing unique to Saturn about this particular approach. But it was to me quite interesting to see the efforts that were made by these vendors to get their wares into the Saturn vehicle. I was more involved in mechanical components. This included fittings, filters, hydraulic filters for your servo control systems, tubing, hydraulic pumps, for example.
[00:02:41] DC: One of the problems you had, of course, in the Saturn is that you might go to someone like Rocketdyne Division of North America to develop the engine itself. You'd have certain vendors that were their favorites, you might say, working closely with them on the West Coast. Then you'd have others coming into Huntsville. They were interested in getting their wares on board. Really the only thing they had to sell is, of course, better quality, that being the order of the day. Price did not seem to be quite that much of a consideration in those days. It was quite a bit of concern of reliability and meeting very rigid specs, for example. One of the critical specification requirements was LOX compatibility, which was sort of the new term. In the aircraft industry, you really didn't have that particular problem, not using liquid oxygen.
[00:03:34] DC: Anyway, these vendors might come in and say, “Well, we have a better valve than what Rocketdyne is proposing to use on the engine. How do we get it into the system?” Usually that was a very difficult task. More likely they would supply components for, say, the interconnection of the engines on the Saturn or the pre-valves or the flexible ducts that are above the engine pump inlets and this sort of thing. There were a number of, you might say, pet vendors then developed by the Huntsville team. In some cases these were the same, for example, as Rocketdyne might use. In other cases they might not be.
[00:04:15] DC: But one thing that was very apparent is Huntsville did have, you know, influence over the reliability of the whole system. Naturally these people would try and get on board. For example, you would get a situation like on the S-II stage being built by North American with prime responsibility. But yet Huntsville writing the specifications for that stage and working closely with the North American people because it was a size of a liquid hydrogen and oxygen structure that had never been developed before. It had to be somewhat a team effort. Expanding on the vendor thing, you might have somebody like Parker Aircraft working closely with North American out there in California. By the same token, working closely with the Huntsville people here so that their hydraulic control package or accumulator or whatever it might be would be accepted by both parties. This is what it would probably take to become, you know, on board the Saturn vehicle. I'm referring now to Saturn V.
[00:05:28] DC: I think we may have talked about some other aspects of this, but you did have a lot of vendors running in and out, pushing their wares, saying, “We've got a better product than this. Let's take a look at it.” You had a lot of test programs going on. You had a heck of a lot of component testing going on to evaluate one of these products against the other and come up with test criteria, so you could select the best component or hardware.
[00:05:54] RB: Would there be a situation where some vendor got a hold of the specs or something and said, “Hey, we got something that will fit in here,” and they would come down, and maybe Marshall hadn't heard of them before or wasn't aware of their new product. So they would work hard to sell that.
[00:06:06] DC: Yes. Then they might have to, on their own investment, develop a valve that would meet those same specifications, you know, and say, “Look, this is equal to your spec and is acceptable, and we've proven it. If you don't believe us, you test it.” In some cases, Marshall, NASA, or before that the Army would do that. On the spec sheet itself, then you would state you such and such a part are equivalent. Normally, they would always list one naturally, maybe two, if two are equal, you know, in quality, or then they would put the little word “are equivalent.” If you could qualify, then you could still compete. Then it became if you were technically acceptable, you could meet this all the specs and then demonstrated this. Then it became a matter of price, which I think was a healthy situation. You didn't have a stranglehold or a monopoly by one particular company, but free enterprise was still allowable.
[00:07:04] DC: The big problem was in this big morass of documentation and people, this was always a problem of how did the vendor find out who to go see and what's the network and the sequence of events he's got to go through and how long does it take to implement this thing. In a lot of cases, they would hire consultants and representatives to help them in this regard. That was one of the things that I did here with several companies was to assist them. In some cases, not just to get on board or compete, but to more or less limit the competition. In other words, by doing such an outstanding job that sole source—that's always the ultimate ideal situation is to be sole source—so you're named in the RFQ or the spec or whatever it is as the supplier. That's always the objective, you might say. As an alternative, at least be either/or equipment supplying these things.
[00:08:09] DC: It was quite an interesting relationship in that, like I say, you had first of all, management by Marshall, you had test teams here—component test teams—they were heavily involved in that. You even had designers right on the board working with some of these vendors, working closely with them, hand in hand almost. In some cases, the vendor was under contract. In a lot of cases—Flexonics on the flexible connectors—had actually R&D contracts to develop some of these systems because they had only one application, obviously. How many other ways can you use a flexible duct between your propellant tanks and the piggyback turbopump on an H-1 engine? I mean, that's it. In other cases, you had…I guess companies had many applications for their pressure switches, so they would try and bring their products on board also.
[00:09:06] DC: But again, it boiled down to the problem of knowing the right person, knowing the sequence of events. In a lot of cases, you had commercial firms even that did not have that much government experience. In the main case, most of these vendors were former aircraft vendors that did know the ropes, and it was just a new market for them to tap, you might say, even though it was a limited market as far as production numbers as well.
[00:09:31] RB: So in some cases, the guy would come in with the product, and he would say, “This is a good product, we tested it and so on.” Then part of the idea is to get when the RFQ or spec comes out to get that product named then?
[00:09:44] DC: Yeah, that's your objective is to try and…
[00:09:46] RB: The government could protect itself by saying X company or equivalent.
[00:09:50] DC: Yeah, right.
[00:09:52] RB: But you're still ahead of the game if you get your name in the spec first time?
[00:09:55] DC: Right. Because then you're requested to bid on this thing. Usually, it would be difficult for another company to come along and in the short time frame between the time the purchase order went out and he had to turn his bid in to analyze really what's involved in that spec. In other words, you've got to look at that spec and look at all the parameters and see what's your closest sets of valve or a pressure switch in your catalog, which one is closest to that spec, then look at the differences between your closest model and the exact spec that's required. Then further, how much in-house effort you've got to perform: how many parts have you got to change, how long does that take, how many man hours have you got to pump into it. Normally the alternate vendor would just say, “Well, it's just not worth the trouble for half a dozen parts” or whatever it might be. As a result, you'd probably only get one bid. That would be more likely than not.
[00:11:01] RB: Okay. Can you go into the end of the Pall Corporation, how the Rigi-Mesh got into the Pratt & Whitney engine, the J-2, and so on? And too, would you explain about the Pall Corporation doing their R&D in-house and selling that?
[00:11:18] DC: Yeah, right, okay. Some of these vendor firms were more interested in—I can name a few like Park Aircraft, Flexonics, I'm sure there's a lot of others—that were interested in getting their research and development funded by the government. In other words, they would solicit contracts to advance the state of the art, which I think is a healthy situation for them and the government. The government can oversee these efforts, but it puts the company in a very good position then to be the supplier when the parts are developed. This was the case in certain development of low leakage fittings, for example, the mechanical connectors on the propellant systems, pneumatic systems. This was the case in a lot of the valves themselves that were, the pre-valves, for example. Particularly, you could say the large sophisticated types of components and hardware, the pre-valves that would stop the propellant flow prior to going into your engine operation.
[00:12:20] RB: H-1 and F-1?
[00:12:21] DC: Yeah. Historically, most rockets do have pre-valves, which allow you to shut these things down on a test stand. They're primarily needed for static testing. Not so much for main stage, but they still keep them in sometimes on the flight operation.
[00:12:39] DC: Anyway, the Pall Corporation, which is the one I was familiar with, had a division called Aircraft Porous Media. The philosophy of the Pall Corporation as a whole was to do their own internal R&D and meet specs that were required primarily for hydraulic pneumatic filters. That was their main business. They were also an aircraft-oriented firm. That's how they got into the metal filter business because their philosophy was with the higher temperatures and vibrations and operational parameters of aircraft, particularly jet aircraft after World War II, that the normal types of filters and strainers and so forth that had been used up to that point were just not of high enough quality.
[00:13:26] DC: They worked very close with the Air Force at Wright Field in developing a whole new family of filters for aircraft, and then expanded from that base into the commercial fields and then into missile and rocket fields. It was a very interesting company to watch. They originally got into that business through the efforts of Dr. David Pall, who founded the company. He originally worked with the Atomic Energy Commission in World War II in developing porous metal materials for gas diffusion processes for your development of the atomic energy program, atomic bombs, and so forth. All of your nuclear programs that are now used in nuclear reactors came out of this research.
[00:14:15] RB: He was a research scientist?
[00:14:17] DC: As far as I recall, he was either a consultant or a research scientist. He did materials research. That was his forte. As you may know, other ways of doing this are now becoming known using centrifugal diffusion. I think the Japanese have been doing this, which is less expensive way of separating your U-235.
[00:14:41] DC: He felt there was a need then after experimenting with this material, and he thought there were other applications, so he started working with controlled porosity of metals. This is done by taking woven metal, similar to what you have a woven piece of cloth with certain twill patterns and weaving patterns. A lot of this has been done over the years in such countries as Germany for industrial applications. Metal screen mesh is not a new material. The fact that Dr. Pall worked with the sintering, making this a rigid material by almost reaching the melting point and then allowing it to cool before it completely melted, you actually become almost like an integral piece of material, little tiny holes in it. By layering this and rolling it, you can then get any thickness and practically any porosity you need for any given application. The first application that he proposed for this was aircraft filters, hydraulic filters. One of the advantages would be not only, let's say, apply with extreme operational parameters, but also you can re-clean it rather than throw it away. There you became like a reusable application for these filters.
[00:16:10] RB: You know, these hydraulic actuators in flaps and landing gear and things like that?
[00:16:16] DC: Yeah, yeah, yeah. All your hydraulic control circuits needed these things. One of the problems you get into if you don't filter your hydraulic fluid is you have excessive wear on your hydraulic pumps, your piston pumps, and your gear driven pumps made by such companies as Pesco—one of the other old line vendors. This was really an advantage to the Air Force because it gave you longer operational life. The other vendors may not have liked it that much because they didn't sell as many parts. [laughs]
[00:16:45] RB: But it also creates structural rigidity to the component then too, if you've got a metal filter in there. Was that part of it at the time?
[00:16:52] DC: Well, yeah, actually it's sort of an independent floating part, if you're familiar with how filters are made.
[00:16:57] RB: Okay, I was jumping ahead to the engine systems then.
[00:17:00] DC: Yeah. These things are normally…Another thing you can do with these is you can pleat them into a series of corrugations. What this means, you get more exposed area, so you have more filtered area. Then you can take these things and put them in an ultrasonic cleaner with certain fluids and then clean them up and then use them over and over again. That was one of the big advantages.
[00:17:21] RB: Getting back to our story in Huntsville…There had been some background with the Air Force and aircraft filters. When the Jupiter program started, which was around ‘55, say, ‘56, then it was decided to go to a gimbaled hydraulic system on the Jupiter. Before that, there had been some, I think, hydraulic packages on some of the other Army rockets too. Possibly the Nike, I'm not sure on that. And certainly the Hawk. At that time, the Army missile programs were getting involved with hydraulic control systems in a big way on the Jupiter because it obviously had to have two large actuators to gimbal the complete engine. I'm sorry, to gimbal the thrust chamber below the gimbal point in this case. Also these things were used for the roll control system, which I mentioned, meaning your turbine exhaust gas is overboard, had to require a servo mechanism. The people at Aircraft Porous Media started coming down to Huntsville and talking to engineers here, who for the first time, were getting heavily involved in hydraulic control systems because in the Redstone and V-2 before that, there were no hydraulic systems. It was a new area, you might say, for the von Braun team to get involved in. Therefore, a lot of in-house efforts started going into hydraulic system cleanliness specifications and standards. The people from Aircraft Porous Media started working closely with test people and engineering people here in Huntsville to help them develop the specs that were needed to purchase parts and components and so forth for these systems.
[00:19:18] RB: Who would have been involved? Was Weidner in there and Hans Paul?
[00:19:21] DC: Yes, those were the two main people involved. There were other people like, at that time, Jim Thornton. There was another fellow around that became involved named Vic Neiland, who's still around. He was heavily involved in this whole story. One of the key guys was a chemical engineer named Bill Riehl. He's still here. He was not only interested in hydraulic contamination problems, but also LOX impact sensitivity. That was another thing he worked heavily in.
[00:19:48] RB: How do you spell that?
[00:19:49] DC: R-H-I-E-L. R-I-E-H-L. One of them. It's Riehl. R-I-E-H-L.
[00:19:54] RB: How do you spell Neiland?
[00:19:55] DC: N-E-I-L-A-N-D. Or I-E. I’ve got to check. I’ve forgotten.
[00:20:00] RB: What's his name again now?
[00:20:01] DC: Victor.
[00:20:02] RB: Vic Neiland?
[00:20:03] DC: Yeah.
[00:20:04] RB: Okay.
[00:20:05] DC: So those are the two guys that could give you the background on early hydraulic system development.
[00:20:09] RB: Yeah.
[00:20:10] DC: This continued, and the people from APM—Aircraft Porous Media—continued to work closely and have developed these specs. It was a good case history of how a vendor, you might say, worked hand in hand with the people here in Huntsville to come up with good specs that supposedly would give you a good high reliability on your hydraulic system.
[00:20:34] RB: Was this a case where they kind of wrote themselves into this?
[00:20:37] DC: Yes, very definitely.
[00:20:38] RB: Were you doing that for the...
[00:20:39] DC: No, I was on the other side of the fence at that time working in the engine group.
[00:20:43] RB: Okay, yeah.
[00:20:44] DC: I was doing such things as designing these hydraulic systems and working from that side. Incidentally that was one system that was never touched by Rocketdyne. They tried many times to get into engine control systems. In this case it was done completely in house, which is kind of interesting. As well as such things as your missile propellant pressurization systems, all of your heat exchanger developments, all of your pre-valve systems, all of your electrical relay systems, all of this was developed by Huntsville. In other words, the interface was sort of “Rocketdyne, you build this engine, you test it and develop it. We'll run acceptance testing on it, and you deliver it to us or you deliver it to Chrysler”—whichever the case may be—”and we'll plug it in and take it over from there.”
[00:21:40] RB: This is Jupiter?
[00:21:41] DC: Yeah, and this is also applied to the H-1 and the Saturn type of relationship.
[00:21:46] RB: Rocketdyne wasn't getting into the hydraulic actuators?
[00:21:49] DC: No.
[00:21:50] RB: But they were taking the government-furnished equipment?
[00:21:52] DC: Yeah.
[00:21:53] RB: Okay.
[00:21:54] DC: That's right. All of the control aspects, all the mechanical control as well as guidance and electronic, and all these other control systems were developed out of Huntsville. Of course, they went to vendors for certain pieces, but the systems engineering was strictly done by the Huntsville teams. No question about it. From Jupiter then evolved the larger numbers of actuators and hydraulic packages and pumps, what have you. Incidentally, the pump received its power in both cases from the turbo machinery of the engine. A tight interface there, of course. This pump in turn had to have an accumulator so that it had a reservoir reserve. In other words, in designing a hydraulic system, you have a basic energy input, in this case from the pump. You also have to have a surplus storage device, which in this case is an accumulator, so that when you have extreme actuation, you don't starve the pump more or less. You have to have reserve. It's like a storage battery in an automobile type of thing. That'd be your electrical analog. This evolved into the Saturn program, and then the company continued to work closely with the people, and they were involved. When the Saturn V came along, there were a few difficulties, but in general they stayed all the way through the program. This is a good situation, or a good case of getting in early and riding the program all the way through.
[00:23:32] RB: So APM was in on Jupiter and they got in on the H-1 then? And got in on the F-1.
[00:23:37] DC: Mm-hmm. The Saturn I, and then on the F-1. Now the F-1 was a different kind of beast in that you used fuel for the actuators. I may be wrong. I know that we were looking at it. I think you had a big fuel pump using kerosene/RP. This applied through the actuators also, so you'd require a different type of filter. This was sort of a new ball game, and frankly I was kind of getting out of it at that time, so I'd have to refresh my memory and check a few things on that.
[00:24:10] RB: When did you become the representative for APM?
[00:24:13] DC: It must have been about ‘61. So I left in ‘60, about ‘61. Also with Parker Aircraft about that same time.
[00:24:26] RB: So when you became the rep for APM, you were selling actuator filters?
[00:24:32] DC: Well, I was not a rep. I'll have to take that back. They had what they call a manufacturing representative. I was in a little different league. They called me a government liaison representative. My function was more liaison and communication as opposed to sales. I never was involved in direct sales. It was more like a consulting type thing.
[00:24:54] RB: I see.
[00:24:55] DC: The same thing held true with Parker. It was more of a consulting and advice and liaison as opposed...In other words, they had their own salesmen. I didn't get directly into that loop at all of writing purchase orders and what have you. That was a separate marketing function. It was to advise those people who to go see and what was going on and who should they go see at North American to make sure their hydraulic systems or filters are applied to the second stage, who should they see a Douglas and this sort of thing.
[00:25:26] DC: In a lot of cases they knew and already had worked with these people, so it was just tightening up, you might say, the communication loop. Which competitors are sniffing around, we better keep an eye on type of thing. [laughs] But there was a lot of that going on. Like I say, there were literally dozens and dozens of reps running around at that time. In fact, it got pretty bad at times where they'd almost have to close the doors and make it a strict appointment because at one time these guys were like fleas. I was on the other side of the fence, and I know how it is when they come marching in on you. [laughs] That was really, I think, an interesting sideline here. I think that was one reason for more of the security consciousness that developed more so than worried about classification of material. It was just for protection of the poor engineers so they could get some work done. I tried to make it my own policy not to bother people unless I really had something of interest to them or vice versa. I've tried to maintain that relationship over the years. When I felt I could contribute something or a company could, I thought it was worthwhile to pursue it, which I think is very important to maintain a long-term relationship.
[00:26:47] RB: Well, looking at the Rigi-Mesh application and engines, by ‘61 Pratt & Whitney had already gotten into it.
[00:26:53] DC: Yes, through the Lewis testing and the Rigi-Mesh being the trade name for this same porous material. I might mention there were a number of things looked at for this material. This particular application was for the injector face on the liquid hydrogen propelled rocket motors. The advantage being that you get a transpiration cooling effect through the porous material. It gives you sort of a boundary layer on the combustion wall similar to the old film cooling techniques used on the V-2. This was an early recognized problem that you can burn up an exposed material unless you have cooling on it. In the case of the injector, it's not like the outer wall where you have a heat exchange effect and you have a continuous flow of propellants that gives you a cooling effect. In this case, you're just oozing, you might say, right through the porous material to get that same effect. It's similar, but not the same. Also other things were looked at with this material. The Air Force, for example, has always been for a long time been interested in boundary layer control and actually, let's say, sucking off on the leading or upper edge.
[Interruption, tape cuts out and restarts]
[00:28:18] DC: We were talking about Rigi-Mesh, and I was mentioning the other applications for this material. Another application that, let's say, evolved out of this material was for noise suppression. For example, a lot of the big jet engines now have a outer layer of the same type of porous material cut down on the noise level. But anyway, you're right, Pratt & Whitney had been using this material and run their own tests down at...I'm not sure if they were in Florida at that time or not. I know they did run some testing down there later. I know they started, you know, buying this material, running tests. They determined it was very useful for this application. Another application I'll mention quickly, it has been considered for quite a few years for re-entry nose cone purposes, sweat cooling, where you actually have a material oozing through this during re-entry to give you a film cooling layer. It's efficient from that standpoint, except for the loss of the cooling fluid. This is one of the disadvantages. The trend has been more to your solid ablative type, you know, materials that liquefies every entry and get the film cooling from that. So the outgas are…
[tape cuts out]
[00:29:42] DC: In the meantime, the Pratt & Whitney engine was developed primarily under Air Force contract for the Atlas-Centaur application. That's where it's still being used. At that time also, I think Huntsville gave Douglas a contract for the S-IV stage as the second stage for Saturn I, which would be called Saturn I-B. I'll correct that. The six Pratt & Whitney engines were used on Saturn I as the second stage. The S-IVB actually used in the J-2 engine as well as the S-IVB stage, which was the third stage for Saturn V.
[00:30:30] DC: In that period—I'd say ‘60-’61, I'll have to check—the specs were written for this larger LOX/hydrogen engine, and there was competition between primarily Pratt & Whitney and Rocketdyne for the engine. Rocketdyne was awarded the contract. I'd have to go back and check my...You're probably more familiar with now than I am, but I think this was even before the Apollo was announced that this was going on. I do recall working very hard on the specs for that engine. I left in June of 1960, so that means those specs were being worked on quite early as well as the upper stages, the S-IVB and the S-II stage, yeah.
[00:31:15] DC: The specs are being prepared better today. In other words, there was enough knowledge to know that these are the kind of pieces of hardware, and this was going back to the C-2 program probably that you would need these. Very likely the specs didn't have the final configuration. They didn't have some of the basic dimensions and systems that were required, and we were at that time starting to write those specs, particularly the engine specs.
[00:31:42] DC: I left about that time, and about that time Rocketdyne got the engine contract, J-2. In their original concept, I don't think they accepted the Pratt & Whitney injector design for obvious reasons. They had to be unique, you know? But yet they were still allowed to give them the contract. To make a long story short, I did continue to follow this program, more or less as its government liaison role. As a matter of fact, this came somewhat later, maybe a year later, before I actually got into that position. Even at that time, there was questions on...
[interruption, tape cuts out and restarts]
[00:32:31] DC: One of the questions that came up on using Rigi-Mesh for the J-2 engine was the availability of the material because it was sort of a sole source for proprietary material. It was manufactured in sintering furnaces there in Glen Cove, New York. That was the source. The question came up on availability. I don't recall all the details, but I do recall one story of Dr. von Braun visiting Rocketdyne, as he frequently did in these product improvement reviews and engine status program reviews and what have you. I was told—I wasn't there at the time—but I was told that he just asked them point blank, why don't they just go ahead and use what had been proven—namely the Pratt & Whitney injector system and material. And they did it. Then the whole thing was settled from there on out. It was just a matter of supplying the hardware then, I mean the material, to Rocketdyne. Let them shape it, you know, machine it. It can be handled just like a solid piece of material in the same thickness.
[00:33:37] RB: Do you remember who was there and heard von Braun?
[00:33:40] DC: I think Jerry Thomson mentioned this to me. He would be the best one just to ask for more details on that particular point.
[00:33:48] RB: Well now, were you here at Huntsville, were you talking to somebody in the engine program office about Rigi-Mesh and trying to encourage them to use it?
[00:33:57] DC: Yes, I think I continued to keep some contact with local engine people. I think I did propose this, you know. Would they consider this, and they were considering it. The people here were sort of in favor of it, but I think it was Rocketdyne that was dragging their heels. I don't know all the factors there, you know, what else they were looking at. Frankly, I know they were looking at some of their own unique injector designs, and probably they were, you know, trying to somewhat justify whatever they had proposed. There was a period there of almost a year when after I left the propulsion group, and then got more heavily involved in this consulting type activity that I'm not that familiar with everything that did happen. But by the time I was back in the loop, they still had not made a final decision, I don't think, on the Rigi-Mesh.
[00:34:47] RB: Were you talking to Thomson here then?
[00:34:51] DC: Yeah, yeah, yeah, because I was going back into that same old group that I had worked in and was talking to them about filters and Rigi-Mesh applications. I became also involved with Pesco Products, division of Borg-Warner, with their [more or less consulting?] rep in Huntsville. They were involved in the boost pumps for the Centaur engines, so they were in liquid hydrogen. Yes, I was in that direct propulsion and propellant system loop. We were also involved in the pre-conditioning pumps. I think they were electrically driven for the S-IV stage and eventually the S-IVB and S-II stage. You have to pre-chill or pre-condition the temperature of the lines before you go into main stage on a liquid hydrogen engine. These little pre-chilling pumps would perform that function. They would actually start up before you go in, you know, start engine operation to cool down so you don't get a gasification ram effect from cold propellants hitting hot lines. So that's another story.
[00:36:09] RB: This is kind of off the subject a little bit, but I'm interested in it. I haven't run it down yet. Where were those Pesco pumps used in the Saturn and what for?
[00:36:16] DC: They were used upstream of the liquid hydrogen propellant feed lines
coming from your propellant tanks to your engines. They were used, as I say, to pre-condition those lines and chill them down. In other words, to get a dynamic flow going through there
because under just a static condition with no flow, you don't get much of a chill down. You have to actually flow the stuff because it boils off so quickly, you see?
[00:36:45] RB: Were they using the LOX lines too or just hydrogen?
[00:36:48] DC: Primarily hydrogen. I think there were possibly some LOX chill down. I know there were hydrogen. It's not as critical on the LOX side. You know, temperature is not near as low, of course. Hydrogen, it is quite critical. With LOX, it's not that critical.
[00:37:08] RB: Okay, so they're upstream of the propellant feed lines to pre-chill those lines.
[00:37:12] DC: So what you have to do...
[00:37:13] RB: Is that involved with the engine pre-chill too?
[00:37:15] DC: Yeah, you go down as far downstream as you can, then what you do, you open up a valve during the pre-chill sequence and then circulate it back up again, you say, to your propellant tank. What it means, you have a closed loop circulation. But if you didn't have that, if you had just a static condition, you wouldn't have any place to go, you say.
[00:37:37] RB: But they not only chilled the lines then, that Pesco pre-chilled the engine too?
[00:37:41] DC: Yeah, as much of the engine as you could.
[00:37:43] RB: Yeah, that's what I mean.
[00:37:44] DC: This was the same function that the boost pumps had on the Centaur, still have. Pesco designed under contract with the Air Force and provided this same role for the Centaur vehicle.
[00:37:58] RB: Okay, so when you're talking about engine pre-chill pumps, for example, a J-2 restart, they have to go through the pre-chill cycle?
[00:38:04] DC: Yeah.
[00:38:05] RB: That's a Pesco pump that's doing that?
[00:38:06] RB: Not necessarily. I know it was on the S-IVB. I'll to have to go back and refresh my memory because I'm confusing in my own mind the S-IV, S-IVB, the S-II, and even the S-I, I think it did have some blocks chilled down pumps. I'll have to look at some schematics, so I'll beg off.
[00:38:26] RB: I had some Pesco products, but they talk about it in such general terms, I just couldn't figure out exactly where they were used.
[00:38:31] DC: Yeah, that was a function, and I could dig that out for you.
[00:38:35] RB: Okay, do you remember anything more about the manufacturing process of Rigi-Mesh, a little bit how they went into that and how they did it?
[00:38:44] DC: Yeah, first, in some cases they would weave their own material; in other cases they would just purchase it as an industrial wire cloth type of thing. In that form it's flexible in that there's no interconnection between the individual strands. This is used for strainers, and wire cloth is used in a lot of industrial applications. They even, I think, purchased a few of their own weaving companies like in Ireland and possibly Germany to supply the raw material to make sure you could always have an adequate supply, which when you're getting big demands you have to meet the demands, and then you have to prepare yourself.
[00:39:25] DC: The next step then is to take this and go through a furnace at almost a melting point. So really it's just like a sintering furnace on a conveyor belt. You go through this thing, and the two critical items are the temperature and the time frame—how long it's in there. If you get these things tuned up, it's quite an art. One of the reasons more people aren't doing this is it takes a lot of experience. It's kind of like the old guy in the steel mill, he knows just when to pour it off. When you do this, out it comes, and it's just like a flat sheet of solid material except it has little holes in it. In that form you can use it for certain applications. Then say you want to go to the injector face, you need, of course, more thickness. You might have to require seven or eight layers of this wire cloth. They seem to favor what they call the Dutch twill weave, which is a specific weave that has a little more rigidity in an even, normal state. It gives you additional strength when it's sintered.
[00:40:28] DC: The next step is then to take, say, X number of layers of this stuff after you individually process them, and then stack them up and run them through all together in a combined form, a combined composite, or matrix of layers. Then that again is quite a tricky process because of your heat transfer rate not being uniform from the outside of the thing to the interior. It's like cooking a potato.
[00:40:58] DC: So all of these things had to be considered in the sintering process. Like I say it's somewhat proprietary. Other people do it. It's not…They're not…They don't have monopoly on this technique. For example, Bendix, [Purolator?] division got into it in a big way. They're still involved in this stuff. They call their material [poor alloy?], I believe. But as a matter of interest, [Purolator?] used to have all the aircraft filter business.
[00:41:29] RB: Does APM have it now?
[00:41:31] DC: Yes, and I think Dr. Pall went to [Purolator?]. That was one of the companies he approached to get their interest up. He went to a number of others and didn't get any response. So he just said, “Dammit, I'll do it myself!” And that's what he did. He went into the filter business. He ended up with the majority of the world market in aircraft filters, which they probably still have today. I haven't checked lately, but I know they did five years ago.
[00:41:53] RB: So [he was applied?] to British corporations, and French corporations, and so on?
[00:41:57] DC: Yeah, yeah, he was worldwide. He had worldwide representatives, fed him this stuff all over the world. Anyway, getting back to Rigi-Mesh…Then you take the stuff out of the furnace, and you test it to make sure it doesn't peel, and it's all centered together properly. Then you have to come up with a given porosity. You do this by taking it and rolling it through two steel rollers and decreasing the thickness, which increases the delta P—or pressure drop—across the plane. The more you squeeze it, the less porosity you have. That step means you can control the, you know, customize more or less whatever type of material you want to develop. Then if you want to further modify it, you can even then take a little tiny material—stainless steel, which in most cases it was—you can take little tiny stainless steel particles and deposit them on the top and even get a filtration action if you like. In some of their cases, they would combine powdered metallurgical type processes with woven wire processes, integrate this into the same material. It means you end up with a structurally strong material because of the weaving. You end up with in-depth filtration because of the tiny little balls that are stacked up and centered together and integrated with the woven material. We call this super mesh.
[00:43:38] RB: Yeah. [laughs]
[00:43:43] DC: So that's how the Rigi-Mesh started.
[00:43:46] RB: Well, they supplied it then, what, just sheets of material?
[00:43:48] DC: Yeah, yeah. And still do to people like Pratt & Whitney, GE…I can't think of any other big engine…Allison, I guess. I don't know if they're still in the act or not. But this same material then, it was and is being used for noise suppression because it is porous and absorbent and cuts down the dB level by dampening out the high frequency vibration
from your compressors and turbine blades. It's somewhat self-cleaning in that you can, you know, purge it out and you can use it for…Well, one thing that I always thought was interesting was to use this material for cooling turbine blades to operate at higher temperatures. And this was considered in World War II by the German Junkers people and their jet engine development. Navy got interested and there has been...
[00:44:48] RB: The US Navy?
[00:44:49] DC: Yeah, US Navy. I think they captured that particular group of engineers and brought them over here. There's a lot of that going on, you know, right after World War II. Over the years, I think the Air Force, NASA-Lewis probably, I know NASA-Lewis, Navy, and other people have looked at this possibility of using porous turbine blades. To me, that would be one of the more outstanding applications if and when it evolves because then you can raise your combustion temperature and operate it at a much higher temperature. It’s giving you much more compact and efficient turbines, jet turbines.
[00:45:32] RB: Off hand, do you know of any other rocket engines besides the RL-10 and the J-2 that it was used in?
[00:45:36] DC: No, but I was quite heavily involved personally in a lot of experimental work that was going on here. Looking at the so-called toroidal thrust chamber, there was a lot of experimental work there. Rocketdyne eventually built, you know, some of these engines under contract. That was one of the materials being considered there for the injector on the inside of the engine. There were some others, small engine concepts that were played around with here.
But as it turned out, these never were used.
[00:46:10] RB: There's something else I was going to ask you too. In making the J-2 injector base, they used electrical discharge machining. So the Rigi-Mesh is the material they were working with. Is that right? And they would just go through…Then they would put in another...
[00:46:24] DC: Mm-hmm. Orifice.
[00:46:25] RB: Orifice, solid for the oxidizer to go in?
[00:46:28] DC: Yeah.
[00:46:29] RB: Okay, so that explains that.
[00:46:31] DC: That's almost identical to the Pratt & Whitney system. Oh, the other big application was the M-1 engine. Aerojet bought quite a quantity of the same material into this under a NASA contract and developed a large million pound thrust liquid hydrogen engine. Originally, it was a Nova upper stage engine. That program eventually died out. I'm not sure on the NERVA engine, you know, which is the Aerojet Westinghouse nuclear engine whether Rigi-Mesh was used or not. I'm not sure, but I kind of doubt it because it's just a P engine. All you're doing is dumping liquid hydrogen into it and expanding it, you know, in the form of gas for your thrust. In that case, I don't think the injector face is that critical. I'm not sure. But the M-1 would have been on the big application.
[00:47:26] RB: That's a really beautiful story, Dave. It's really a nice one. I like that. Cheers.
[tape ends]
Duration
0:47:50
Files
Collection
Citation
“Christensen, David ("Dave"),” The UAH Archives and Special Collections, accessed August 24, 2026, https://oralhistory.uah.edu/items/show/568.