The Improvised Rocket Car

by Sandy Antunes, PhD

"Everyone have safety glasses?  5… 4… 3… 2… 1… ignite!" The car's rocket engine kicked in, even though just an hour before, it hadn't even been an idea. The starting thought had been "should I change my major?"

The petitioner was Jorge Rodriguez, a Computer Engineering (CE) major who had a soul searching moment when he realized he was more interested in car racing than sitting at a computer all day. CE is an interesting major, straddling the worlds of software and hardware, with a degree of flexibility not all majors enjoy. Jorge's discussion of the technology of car racing led to a natural evolution of how he might be able to meld this new racing direction with his current studies.

Unfortunately, he was talking to me, an Astronautical Engineering (AE) professor, neither a car racer nor a formal CE. Fortunately, AEs are known for always having model rocket engines within arms' reach. Between the two of us, an idea for a senior project was conceived: if you put a model rocket engine into a remote-controlled (r/c) car, could you actually, you know, control it? Or would you just have a low, flat missile?

There's history to this. Alumnus Anh Ho, back when he was a freshman, did the first take on this experiment. Fearing the car would be uncontrollable, he used the weakest engine available and his test took place on friction-heavy grass. The result itself was anticlimactic. Which is to say the engine ignited, the car didn't move, then the car flipped over and sat there for the remaining seconds of engine burn. Having a default of "it's hard to get it to move" was a good starting point.

Knowing this shifts the experiment from whether it's safe, to how to get it to move and whether you can steer it when it does. This is where the CE senior project work comes into play. By adding air foils and control surfaces, it is theoretically possible that you could make a steerable-- maybe even self-driving-- rocket car. Success required that we find just the right engine to make it move in a stable fashion.

Fortunately, after about 10 minutes of talking and thinking, we decided to just head up to the Fusion Lab to prototype it. Another bit of luck, Christian Michael, an AE major and our resident rocket guru, was both around and willing to help. He ran a quick calculation on weight versus engine strength, then we began hunting up parts. An old r/c car, pieces of model rockets, an engine with igniter (Christian wisely had us dial down the engine strength for the first test), some glue and duct tape later, and the Improvised Rocket Car was born.

Outside we went, to try the first, fateful launch. The count range out, the trigger was pushed, and the car zoomed off into the distance! Well, a distance of about ¼ of the parking lot, which was pretty much what we'd predicted for that engine power. We may be spontaneous, but we aren't stupid.

What is particularly beautiful is how the right combination of people and parts can go from 'idea' to 'experiment' in less time than it takes to get lunch. The strength of a college campus is in the depth of what you can do outside of classes. And, it's great to watch a tiny car noisily blow across a couple of parking spaces just with rocket power, and know it's a prelude to the future.