How to Build a Rocket Engine

How do you build a rocket engine without blowing your factory up? Vern Estes took on this assignment as one of his first tasks in the family business of model rocket manufacturing. In today’s podcast episode, he recalls reaching the challenging goal of creating a machine that could quickly, and safely, pack model rocket engines to keep up with the voracious demand from a public eager to launch their own kits into the atmosphere.

Full Shownotes and transcript after the player

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00:00:00

SEAN MOBLEY:       The Flight Deck is made possible by the generous donors supporting the Museum of Flight. You can support this podcast and the Museum of Flight’s other initiatives across the United States and the world by visiting museumofflight.org/podcast.

[Music]

SM:     Hello. And welcome to The Flight Deck, the podcast of the Museum of Flight in Seattle, Washington. I am your host, Sean Mobley. Now, if you grew up here in the U.S. and had a passing interest in space, there’s a really good chance that at some point you launched a model rocket. And also, a good chance that the rocket had the name Estes on it. Today’s podcast is an interview with Vern Estes himself, the founder of Estes Industries taken from his oral history where he talks about his early assignment creating a machine that would create the tiny rocket engines that power the modeling hobby.

00:01:00

When you consider the explosive nature of the engines, creating a machine that didn’t blow up the whole planet was harder than you might have realized. Vern was interviewed at the Museum of Flight by Bill Stine who you will hear throughout the episode as well. And with that, I’ll turn it over to Vern and Bill.

[Music]

VERN ESTES:           Well, it was an ambitious project, particularly since I didn’t have any idea as to how I go about doing it. And Harry did provide me with some information on the basic instruction of the model rocket motors. And so, with that, and then I began to conduct experiments to find out what it’s going to take to make satisfactory motors. And then after I learned a few things about it, I—

BILL STINE:  Give me some examples of what you learned. Was it things like the amount of pressure necessary to compact the propellant sufficiently so that it wouldn’t blow up? Was it dwell time? What were the types of things—

00:02:16

VE:      Yeah.

BS:      Because this was all unchartered unknown territory.

VE:      Yeah. It was totally unknown to me. And the black powder that we used was normal black powder. We bought it from DuPont. And it would be compressed into the cylindrical tubes. And so, some of the things I had to learn was what size of a nozzle, and what it was going to take to compress that powder so it would burn from end to end through the tube rather than exploding, and how we would add a component for time delay and an injection charge. And there were whole series of things we had to learn.

And so, it required building some test equipment so we could test the engines that we were making and see if they would, how they performed. And then, making adjustment and so-on. Then, after I had built some, a hand-press so to speak. And then in order to get it in production, decided to build a machine called Mabel. And Mabel was the first automated equipment to manufacture model rocket engines. And I didn’t really have much money or anything to build it with. So, many of the components and things came from a junk yard. And so, it took me several months to build the equipment.

00:04:04

And so, finally, Mabel’s ready to work, and was able to start turning out motors at the rate of about one every five and half seconds or so. And that turned out to be more than Model Missiles could use at the time. And so, later on, we decided then, following up with – to go actually into the [unintelligible 00:04:43] business.

BS:      We being you and your wife, Gleda.

VE:      Me. And my wife, Gleda. Right. Yeah. So, we were more or less alone at the time doing this. I had some help that I did hire, but.

BS:      So, can you tell us, do you remember, why Mabel? What’s the significance of your choice of the name Mabel?

VE:      Well, it was after… The name Mabel came from a guy that I had hired to operate her. And he had known – and the machine was a bit stubborn sometimes. And it didn’t always work just like you wanted it to. And—

BS:      So, she kind of had a mind of her own?

VE:      And, kind of, a mind of her own. And so, it reminded him of some lady he had known. And so, he started using the word Mabel for our machine. And that stuck. [Chuckles]

BS:      Do you remember his name?

VE:      I don’t right now.

00:05:41

BS:      Okay. Okay. So, Mabel was a phrase that was a nickname assigned to the machine by an early, if not your first employee.

VE:      An early employee. One of the first ones to run the equipment. Right. Yeah.

BS:      So, tell me about some of the mechanical challenges you had in designing. So, for example, was there prior science or prior art in regards to deciding that it should be a rotary indexing machine, or was that something that you, through practical application of mechanical knowledge, decided that would be the best way to devise the machine?

VE:      You know, this goes back to a job I had in high school. And I was working at a bottling plant part time in Denver. And that machine was on, basically, a rotary table that put the bottles on the, feed it onto the table and then add different things with syrup and so-on. And put the cap on and complete it. And that had some similarity.

BS:      Certainly. You could make—

VE:      …to the way that we’re going to have to—

BS:      …a lot of analogies between the process.

00:07:03

VE:      Right. We’re going to have different components and different things that had to be a part of the rocket engine. And so, I decided that putting it on a rotary table with different stations, it would do different things as the table rotated would be a good way to go. And so, that’s kind of the way I got started on it.

BS:      Was Mabel a hydraulic machine, or was she pneumatic?

VE:      The power to compress the powder was by the use of hydraulics. And, but the automation on it was all pneumatic, or compressed air so that the valves would sense operations being completed and the advance on to do the next operation and so-on.

The hydraulics that I used came I guess you’d say from a junk yard. I found a couple of power steering pumps at a junk yard. And I rigged with two different motors; one of them would use high volume, low pressure and so it would move cylinders fast to get from one place to another. And then, the other one then would switch in and. But then, the high pressure them to do the final compression. That was a very low-cost way of getting to where I needed to be, and within my budget at the time.

BS:      Hm-hmm. [affirmative]

VE:      And the rotating table, that was the piece that I found at another junkyard, and so-on, and so-on. It was assembled more or less from very inexpensive [chuckles] type equipment. And Mabel did a good job for a number of years. I think ‘til about 1965. That was ’58.

00:09:23

And our demands were just so great that Mabel couldn’t keep up any longer. And so, we’d started developing additional equipment at that time. That was after we had moved to Penrose.

BS:      Can you recall any of the… You seem to have a great recollection of the mechanics and design of the machine. I know one of the things in later years for many decades after Mabel was difficult was the ejection of the pressed motor casing for on the machine because the process of pressing the black powder into the paper casing expanded the casing. And it always created difficulty in how you’d get this expanded casing out of the vestibule that was holding it? So, can your recall how you first solved that?

VE:      The first production, what I now refer to as Mabel I, the original, didn’t have any sport for the casings. And so, we had a relatively thick wall of casing in order to provide support when you put high pressure internally.

The next generation of building Mabel II, we used a clamping mechanism to clamp around the casing so that it could not expand. And that made a much smoother external to the rocket engine at that time.

00:11:13

The original Mabel, the operation was basically would have a hopper where the tube would be picked up, be put on the machine, and the nozzle would material. The clay nozzle would first be put in in the press. And then there would be various stages of the black powder compressed because you had to compress it in increments and you couldn’t just fill the tube and press it. It had to be done in increments. And then the delay charge would be put in and compressed, and ejection charge. And initially then we used a paper cap on the end. Later, Mabel used just a clay cap on the end instead. But initially we had the paper cap, then as the engine was completed, then it would drop through a printer, and the printing on the casing then, that would designate the type of motor it was and so on. And that completed the operation.

BS:      Okay. The clamping mechanism that you’d described, was it something that kind or worked like this?

VE:      Yeah. Hinged, kind of, clamping that… And that was very effective in maintaining the outside diameter in spite of the relatively high pressure. So, it had to be put on the internal compression.

BS:      So, with the description you’ve given of Mabel, I can picture this machine, and a guy in a pair of greasy overalls with an oil can oiling and keeping her running. Did she have a unique sound? What did she sound like when she was operating?

VE:      Well, compressed air when you operate a valve and you’ll have an exhaust sound. So, every time an operation would complete, you’d hear a sound there. And whenever the tube feeder would operate, it would come down, make kind of a banging noise.

00:13:43

You’d hear the hydraulic motors hum and switch from high pressure to low pressure and so-on. Had a distinct sound. I don’t have a sound recording right.

BS:      Okay. Well, I’m not going to ask you to make the sounds.

VE:      No. I wouldn’t be very successful with that. [Chuckles]

BS:      Do you recall any early mishaps on the machine where perhaps you had an accidental ignition or something on the machine, and how it happened, and what you learned from it—

VE:      Well—

BS:      …to correct it and make it more safe?

VE:      We had an early accident in Denver. Gentleman that was running the equipment had something go wrong. We don’t know the source, why it went wrong. But on that machine, there was quite a bit of powder, of black powder exposed in containers there that were used where the feed mechanisms were. He was severely burned. And it took him quite a while for recovery. And so, at that point, we decided, well, we’ll modify Mabel. And so, we put different means of containing with vents out, containing the powder. So, it was loaded into something that was – if it did explode or something went wrong, all of the powder would vent out, the explosion would vent out through the roof. If you have pipes going up through the roof. But… And that was fairly satisfactory. But we did have John Schutz.

00:15:33

He’s the guy that invented the first model rocket glider, was working for us. We had the controls for turning Mabel on and off, were on the outside of the building. We had made some new rules. Don’t stay in the building when Mabel’s running, plus all the venting and everything.

BS:      Hm-hmm. [affirmative]

VE:      And then one day, the wind was blowing hard. And John’s spending his time inside. And something went wrong. He suffered minor injuries because of what we had done solved a lot of that problem. But in our next generation of Mabels, we isolated even further how the operator was separated from any quantity of propellant. And now there was the concrete barrier. The roof of the building was made with concrete. And the propellant was up on top. And the operator of the machine was in the building. And even if an explosion occurred or something went wrong in the powder, it would simply make a big noise. And the operator was quite safe.

BS:      Your recollection was that the powder was actually housed in a Styrofoam building.

VE:      In a Styrofoam jack if you will or something on top that had a metal frame, Styrofoam. And we did have some events occur that had the operator been there next to it rather than in the building where the machine was, it would have been serious.

00:17:24

BS:      So, you went through several generations of Mabel. How many Mabels actually got made?

VE:      I think it’s seven. The original Mabel I would liked to have kept for, perhaps, something for a museum or something.

BS:      Hm-hmm. [affirmative]

VE:      We were on a trip. I think we were in Europe or some place at the time. And we came back. And it had been disposed of as a piece of junk. [Chuckles] Went to the junk yard.

BS:      So, I’m assuming you’re referring to, at that point, that was under Damon’s ownership.

VE:      I think that’s when Damon owned the company. Right. Yeah. That was, would have been in the 1970’s.

BS:      So, seven machines producing a rocket engine every five seconds. Did you run 24/7?

VE:      We ran 24/7.

[Music]

00:18:29

SM:     Thank you for tuning into this episode of The Flight Deck, the podcast of the Museum of Flight in Seattle, Washington. Special thanks to those of you who have supported the podcast financially. Your gift makes this show possible. You can become a donor by clicking on the yellow ‘Donate’ button at museumofflight.org/podcast.

Now, this is only a short snippet of Vern Estes’ oral history. If you would like to access the entire oral history, it’s available in our archives. And details on how to request the oral history are in the show notes of this episode at museumofflight.org/podcast along with a link to all the oral histories currently available to stream for free 24/7.

If you’re interested in rocketry, we have a lot of rocketry related items in our digital collection. Link in the show notes. And, of course, our archives have even more available if you want to dive into some research.

The oral history collection is made possible by Michael and Mary Kay Hallman. If you want more rocketry-related podcast episodes, I’ll include a link to a recent episode where we talked about some of the great photos of rocketry meets in our collection. And what’s really interesting, at least to me, is that the information that we gathered for those photos about the photos themselves was crowdsourced directly from the rocketry community.

And, of course, we have several exhibits about rocketry here at the museum, especially in the Charles Simoni Space Gallery. Check those out next time you visit.

00:20:02

If you like what you heard, please rate and review the podcast on Apple Podcasts, or wherever you downloaded us from. It’s the easiest way to support the show. You can also contact us at podcast@museumofflight.org. Until next time, this is your host Sean Mobley saying to everyone out there on that good Earth, we’ll see you out there, folks.

END OF PODCAST