Most students at the University of Colorado choose to live in town, but I’m one of the guys who traded accessibility for lower rent and a lot more room. I live roughly 10 miles south of Boulder, Colorado in Broomfield. It’s great. On a good day it takes me about 15 minutes to get to CU where I’m the testing lead of the HYSOR graduate project, and when I get home, I can put my feet up without hitting the wall. It’s getting to that part of the semester though when I bypass feet-up-putting for the bed. We have a very test-heavy semester as we work our way toward the static test fire that will show our rocket has the requisite thrust profile for our mission. Our first rocket is designed to blast off to a 10 kilometer altitude, two-thirds of the distance I cross to get to work, before releasing its payload. “It’s not rocket science” takes on a different meaning when the distance it takes to sing a couple of Adele songs in your car is covered in 30 seconds by the rocket you’re working on, and it’s working against gravity.
For the uninitiated, HYSOR is an aerospace engineering graduate project at CU now in its fifth semester of high pressure, high decibel, high thrust rocketry goodness. HYSOR stands for HYbrid SOunding Rocket, and we’re building one of the first. If our launch is successful next year we’ll be the first university team to launch a hybrid rocket. Most rockets out there are either solid or liquid, but the gist to any rocket design is that a fuel mixed with an oxidizer at sufficient temperature produces gobs and gobs of thrust, whether it’s 5-year-old Timmy’s model rocket or the space shuttle’s main engines.
A solid rocket is built with the fuel and oxidizer mixed together in a fuel grain. The fuel grain burns away once it is lit, producing thrust until the fuel is spent. Model rocket motors are good examples of solid rockets. A liquid rocket shoots liquid fuel and oxidizer together to produce thrust. Each has its pros and cons of course: solid rockets benefit from being less complex than liquid rockets because of the lack of rocket plumbing, but they aren’t as efficient (rockets have their own gas mileage, you know).
The fuel is cast like a solid rocket motor in our design, but it doesn’t have the oxidizer mixed into it like a traditional solid rocket does. That’s because we are using liquid rocket architecture to inject oxidizer into the fuel grain; hence the hybrid designation. Naturally we get an attenuated mix of the pros and cons of using the typical systems, and we need to understand how both work in order to be successful. Last year brought us to a total of five cold flow tests and three static test fires to bridge the gap between what we predict will happen and what the rocket will actually experience in its flight to glory.
The goal of this semester is to have a successful static test fire. We light the rocket on fire but hold it in place, measuring the amount of thrust produced. That gives us a correlation between thrust and burn time that we can pop back in our models to determine if we’ll make our altitude requirement. As the saying goes, all things that go up must come down, and we need to make sure that we reach 10 kilometers before our rocket starts heading in the opposite direction.
So here we are, the final push toward our first flight. All the models, the machining, the two-week fuel casts…it’s coming to a head. Watch the skies that you might catch sight of HYSOR.