Fire and Ice: The Flight of the Versa Rocket

Fire and Ice: The Flight of the Versa Rocket

This is a story about how a small town boy built the first ever 3D printed reusable solid propellant rocket engine, the challenges along the way, and the future of the underlying essence of that dream...

It was a cold winter day, snow was on the ground and all around, but as I purused the depths of the internet an idea had set root in my mind and was festering slowly. Video after video I watched countless attempts at home built rocket engines, some dangerous failures and some surprising successes, but the thing that was becoming clear to me was that you absolutely didn't need to be a rocket scientist to take on this slightly daughting adventure so it was around this time I began to think that just maybe I could build my very own rocket engine. 

I'd always had a boundless passion for anything that had to do with space or aviation and ever since reading an article about Burt Rutan and SpaceShipOne winning the Anasari X Prize back in 2004 I got it in my head that anyone could pursue this universal dream of touching the stars and that just maybe in my lifetime I could see my childhood dream of going to space realized. I'd grown up in a small rural town in northern Wisconsin, which seemed about as far away as anyone could get from the distant glimer of a future where anyone can go to space, but none the less I set my sights on a path I thought could get me there. In the fall of 2013 I found myself 2,000 miles from home in the mountains of Arizona as a dreamy eyed freshman aerospace engineering student at Embry-Riddle Aeronautical University. In my time at Embry-Riddle I found my interests and work leaning more and more towards UAV's and a long ways away from space as I had even then 14+ years of experience in RC, but all the while the dream of getting to space was in the back of my mind. For a number of reasons it had become clear that I was not destined to be an aerospace engineer, nor was it really what I wanted and after my first year out in Arizona I found myself moving 2,000 miles again, this time to take a position with Cirrus Aircraft in Duluth, MN as an Experimental Technician working on building the first couple of their SF50 jet aircraft.

Above image property of Cirrus Aircraft

I was in this role for about five months and during that time my projects outside of work continued on along the path of UAV's and remote control aircraft. It was only shortly after I moved to the engineering team at Cirrus as a designer working on production tooling for the jet that my interests drifted back towards those machines that make all the fire and smoke as they shoot upwards into the skies.

I'd always wanted to get into larger model rockets as a kid(and was never able to due to the cost and hassle) and rockets that I could fly as frequently as my model aircraft so that I could share the experience with many people and get them interested in space as well and as I dove into the depths of the internet and began to believe that I might be able to teach myself how to build rocket engines, I thought I saw a glimmer of hope, and a path that might just lead me to a reusable model rocket engine for everyone...

This journey began with humble origins and my very first attempts were far from successful with the end result being much closer to flares than rocket engines, but I was determined and didn't give up. I started in February of 2015 and bared the cold of winter to take my creations outside and test them time and time again until I finally began to make progress. 

Even as I was starting to see some success though it was clear that the nozzle was failing prematurely and that I would need to find a better solution than a washer bonded to the flat of the PVC end closure.

Around this time I took a break from the brutual cold of the midwest and flew out to see some of my old engineering friends who still resided in Arizona. I was out there for about a week and during that time we launched a model of my friends concept for a super sonic rocket glider as well as worked on my nozzle issue. As the week closed and I boarded a plane back to the frozen tundra I had a good idea of what direction I was going to go next. 

Alas some success. I first found true success in my rocket engine building when I crafted a De Laval Nozzle out of hydrolic anchoring cement by shaping a converging and diverging section around the washer and end closure. I would later go on to make a similar multi part nozzle out of clay inserts that I baked in an oven and then bonded into the PVC closure that I would ultimately use the most for my disposable engines as it was a much quicker process than allowing cement to cure. 

With my new found success in amatuer rocket engine building I was eager to fly something, however as my motor didn't have a parachute charge and I didn't have an aircraft suitable for rocket power I needed a much simplicer solution if I wanted to get something airborne and thus I turned to the tried and true classic of rocketeering, the bottle rocket. A stable and amazingly simple way to flight test an engine, it seemed a good option as I had ample room down range for the rocket to fall safely. 

From here I continued to refine the XR29 engine and I started pushing the performance envelope questing for more and more thrust, seeing what was possible within the confines of a PVC engine.

I soon found the limit and countless explosions later I realized I needed something far more consistant in performance than what I had with these motors as well something much simpler to build/fuel and safer if I ever wanted to be able to share my creation so I took what I had learned from the XR29 and began to design the XR58. This was intended to be the holy grail of rocket glider engines.

Intending to make a vast leap in technology from motors that cost no more than a couple dollars a test to a motor that could cost me a couple hundred dollars a test should it fail I knew I needed an intermitent step to prove the new design before an actual XR58 would be built and thus was born the XR58E, the E signifying that this motor was expendable. I created with PVC couplers, clay, and a trusty washer an anolog of the XR58 design that was almost identical in all of it's critial dimensions including the nozzle and cross section of the pressure vessel that would house the propellant and while certainly more expensive than the XR29 engine, the XR58E was significantly cheaper than an actual XR58 would be and significantly lowered the financial risk in building the first prototype of a completely unknown design. 

The test was flawless and with renewed confidence I ordered the first XR58 from a supplier in Europe, this one being made out of 3D printed ceramic in an effort to save cost and weight despite my intuition which suggested it would be too brittle to handle the pressure. After a long wait the first engine arrived and with much anticipation I prepared it for its first test. 

Unfortunately as I had predicted, 3D printed ceramic was no where near up to the job and the first test firing ended with the engine failing in multiple places. 

Reluctantly I dug a little deaper into my pockets and ordered just the nozzle portion of the XR58 design 3D printed out of stainless steel thinking that maybe, just maybe I could get away with a plastic pressure vessel and steel nozzle based on my experiences with PVC rockets so that's what I tried.

This did not end up working either to my dismay, so finally I went ahead and ordered the stainless steel pressure vessel for my engine. 

While the first test with the entirely steel motor went much better than the first, the motor still suffered a failure, this time blowing out the seal between the two halves of the motor and erroding a bit of the nozzle.

In going from the XR58E to the actual XR58 I had tried to up the trust slightly by adjusting the dimensions of the nozzle, though clearly after the first test with the actual XR58 the chamber pressure was too high and I ended up drilling the nozzle back out to the original dimensions and wallah. Success(albiet a slightly asymmetrical success due to the residual errosion on the nozzle from the previous attempt). I had built the first ever reusable 3D printed solid propellant rocket engine.

It was around this time that 3D Print saw fit to do a brief article on the XR58. I fired the engine five more times to prove that it could withstand repretitive use as was intended. I also took the time to build a test stand to fire the motor on so that I could get actually perfomance numbers to help refine the design of the engine and size an aircraft for it to fly further down the line. 

Althought that stand would later be destroyed by a test of a high thrust varient of the XR58...

Anyway, back on point. 

From there I went back to my computer to design the next iteration, aiming to address the nozzle durability issue, and reduce the weight so that the engine could actually fly an RC aircraft. And so was born the XR58 v2; the realization of the original vision for what this motor could be. 

The new motor performed beautifully in the test stand time and time again... So as I approached ten consecutive firings of the motor without issue I knew it was time. The XR58 needed to grow wings and take to the sky where it belonged. It had been a long road coming, but I finally had the engine I'd always wanted for flying rocket powered gliders. With a cost of just $1.13 per flight in propellant I could hardly contain my excitment and I was eager to strap this engine to about anything you could make rocket powered and share my creation. 

I took my newly proven engines from my parents where I'd been testing them back north to where I worked at Cirrus and with a coworker we got ready to fly the XR58 engine for the first time on a pair of rocket gliders. 

We had two engines fueled and ready to go. Two vehicles ready to go. Twice the chance of success. The purpose built rocket wing was up first and sadly it came off the launch ramp sideways and enveloped the stand in a cloud of smoke beating the airframe against the ground until there were only the tattered remains of what was once a foamboard plane left. 

Next was the turn of the Versa Rocket. 

As the XR58 engine lit with a pop from the igniter, the Versa Rocket leapt forth on a column of smoke and flame, clawing at the sky, trying to fly, like a phoenix rising from the ashes... 

It tipped it's nose skyward and struggled along, but it was too much for a first attempt and with a nasty tip stall the Versa Rocket found itself sitting down range while it the depleated the remainder of the fuel. 

With the winter weather not being the least bit cooperative weeks passed and eventually we decided to deal with the poor weather and light the Versa Rocket so we could fly it late at night after we got done with work.

It was already dark out when we started. We'd just finished a 10+ hour day at Cirrus and the weather was anything but ideal. We were determined though to fly the Versa Rocket successfully this time after all the promise that that first attempt had held.

As we mounted the Versa Rocket on the rail, the misty freezing rain falling around us in the dark of night after a long days work, snow crunching beneath our boots, and the soft glow of the distant garage light where we'd fueled the motor, I couldn't help but feel like for me this moment was akin to standing on the beaches of kitty hawk about to witness man taking flight for the first time. 

We'd been so close to success last time that I felt like this time it had to work. This flight of passion was not meant to be though. The first attempt found the aircraft getting hung up on the rail only to faulter and land in the snow near the pad were the motor burned out it's fuel. No matter though, we already had a second motor fueled up and ready to go. We made a dash out into the freezing rain to grab the Versa Rocket and swapped out the old motor for the new.

This time something was different though...

A crack in the grain had gone unnoticed and it was apparent at the second of ignition that something was wrong. We ducked for cover as the Versa Rocket ripped off the launch ramp at light speed where it momentarly streaked to the left before a loud bang echoed followed closely by a metallic clang as the shrapnel and remains of the Versa Rocket impacted the nearby barn. The XR58 had been designed to fail safely with the fasteners being sized so that they would break before the pressure vessel would burst but this time around because this engine had been fired so many times before, fatigue won out and the pressure vessel ruptured splitting the Versa Rocket's airframe in half and sending chunks of rocket engine flying. 

With the Versa Rocket in pieces and the second XR58 v2 ever ruined we waited. I'd only had one retainer ring for the nozzle despite having two pressure vessels so while we waited for a replacement we brought the Versa Rocket airframe back to life. 

Months passed and as the snow finally began to thaw we were ready to try it once more. We got the recently reconstituted Versa Rocket with it's brand new XR58 set up and ready to go. Little did we realize this would be the final flight of the Versa Rocket. In the core of this engine was a massive void. I had noticed it upon inspecting the engine(in an effort to avoid a repeat of the last flight) and we debated what to do. The engine was fueled and everything was set up. We didn't know when we would get another chance to fly, but we also knew if we tried it in the standard configuration it would rupture so with an educated guess we decided to swap out the .3125" inch nozzle for a .406" diameter one hoping that that would compensate for the additional surface area burning, but to no avail. The void was far more extensive than we could have possibly know and shortly after ignition, that was all she wrote. 

So that was it. The Versa Rocket was destroyed and we knew we couldn't go on like this. Things were quickly approaching a level of danger and expense that just wasn't acceptable so we made the decision to go back to the drawing board and try to figure out how to solve the propellant woes of the XR58 before we tried to fly any more engines. Over the months that followed we made some progress, demonstrating multiple times that we could produce a propellant grain without anomolies but we were never able to reproduce the void/cracks that had ultimately lead to the death of the Versa Rocket leaving us to wonder what the true cause was of the voids and cracks. 

In addition to the concerns about safety with the fuel, I was battling a never ending qualm with quality control issues in the 3D printed engines and I was doubting whether I had a viable price point for my target audience with this process. I had recieved two replacements from the supplier, but every single one except for the second engine(the first one that was destoryed) had an unacceptable defect due to the nature of the design and the manufacturing process. I was also being painfully reminded of the resistance to change in a hobby dictacted by a demographic set in their ways, detatched from the infacy of their love affair with the hobby, and afraid to lose their hobby to something they deemed unsafe and unappealing as I began to share what I had created with others. 

So it seemed as though the dream of building a truly affordable and reusable rocket engine for RC aircraft would have to wait for a different time in history...

Dismayed I found myself thinking about how as a young boy I'd always wanted to get into rockets bigger than an Estes rocket and couldn't. Even someone who's only flown Este's rockets knows how expensive they are on a per flight basis and I've believed for a long time that that needed to change and it still does.

How can we expect to inspire a new generation of space enthusiasts when model rockets are prohibitively expensive and the regulatory enviroment is so entrenched that it almost seems like too much effort to think about launching a rocket? Whether I will be the one to change that or not is yet to be seen, but I have to believe that someday someone will and I think it will bring about a change in the hobby on the level of how Flite Test has changed the RC world.

Until then though, I just want to let the amatuer rocketeers and space cadets out there know that they're not alone and we're all in this together. Be safe and press on! We just have to keep trying and we can't give up because if we don't do it, who will?

Even now as I bring this article to a close, I have a suspicion that I'm not done with this one... I do after all still have three unused engines just waiting to take flight... and no shortage of ideas for the next one.