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Odysseus: Mach Rocket

posted Feb 24, 2013, 4:39 AM by Sean M. Messenger   [ updated Apr 6, 2014, 3:59 PM ]

ENGR 80: Experimental Engineering at Harvey Mudd College is a sophomore-level, experimental, lab-based course that covers a variety of engineering disciplines. E80, as it is called, is a core class in the engineering major and is always taken second semester sophomore year by engineer majors. The course focuses on instrumentation and measurement techniques, good lab report practice, technical report writing, and the usage of experimental results in complex analysis and modeling. Normally, teams of four students work through labs that teach basic experimental techniques and the use of sensors that could be used in rockets. The final project for the course is an open-ended, experimental project where students are asked to use what they have learned through labs, lectures, and outside material to design an experiment, take data, and analyze some aspect of rocket flight. Teams have tested the accuracy of integrating acceleration as measured by an accelerometer and compared the predicted position with altitude sensors, modeled and calculated drag force at different speeds, et cetera. Ultimately, the project is open-ended with students using kits and G, H, and maybe I motors for thrust. These rockets typically do not even get close to breaking the sound barrier. The field experience includes two trips to the desert for a total of four launches for data acquisition.


My team includes Chris Hirlinger, Chris Miro, and Taylor Peterson. Teams were arbitrarily chosen at the beginning of the course by the section professor. We decided very early on that we felt our group was very strong, and realized that we all wanted to do something special, unique, and challenging: we wanted to make a supersonic, or Mach, rocket. A supersonic rocket is a rocket that breaks the sound barrier (traveling faster than the speed of sound, Mach 1). For example, a bullet fired from a gun typically travels faster than the speed of sound.

Proposal, Build, and First Launch

On 26 February, the team presented a proposal to Professor Spjut requesting permission to do our own final project. Normally, teams build from a kit and customize the analysis and data collection methods. We proposed building a full rocket from scratch. Professor Spjut approved our proposal, but requested that we launch at the upcoming Rocketry Organization of California's (ROC) launch in two weeks in order to show proof of completion and progress. This milestone set two goals: fly a rocket with minimal electronics to get experience, and get Tripoli Rocketry Association Certification for one team member (chosen to be Hirlinger) in order to launch the higher thrust rockets necessary for our project plan. 

The planning, build, and launch process is documented in the group's First Flight Report. More pictures of the launch are available in my Picasa Web Album.


Modifications and Second Launch

After the first launch, the group had a functional (albeit with some small issues) rocket presumably capable of supersonic flight. The on-board electronics at this point were not the E80 set, so that had to be incorporated. The group divided up into two teams, one for mechanical modifications and manufacturing, the other for electronics and flight modeling. Taylor and myself worked on the manufacturing while both Chris' worked on electronics.


The second flight was scheduled for April 13, again at a ROC event at Lucerne Valley. When we went to the pad to prep the electronics, the data acquisition board would not turn on. After struggling with it briefly, we decided to launch the rocket without electronics to make sure we fixed the hardware issues from the first launch. The rocket took off beautifully, but we lost track of it on its way down. Again. This time, though, the rocket went higher and did not come down nearly as close to the launch site. We packed up and spent most of the rest of the day searching the lake bed for it. In the process, we found someone else's rocket who was also out looking. We returned it to them, but couldn't find our rocket. We gave up and started heading back to campus, planning what we would do next.

About 5 minutes down the road, we got a call from the same person whose rocket we found saying he found ours. We went back, recovered it, and went back to campus ecstatic. But the rocket still didn't work properly. More issues to fix, more things to test, and more lessons learned.

Modifications and Third Launch

This was the first official launch of E80. This is the first time the other teams were launching their rockets. We already had two launches under our belt, so to speak, but none of them were entirely successful. This launch was no exception. We got all the way out to the site without our GPS receiver. It would have been 2 hours to go back to campus and return with it, and we thought we would be fine without it. We calculated the battery on the rocket was good to last 4 hours, so if we did lose it someone could go back for the receiver and return, no problem. We launched the rocket, it flew beautifully, but then lost it in the sun. No one saw it come out, deploy a parachute, or land. We could never find the rocket again.

Final Tests and Presentation

The course was about experimental engineering, which we had done a significant amount of. The project, however, was to study supersonic fin flutter. We didn't get any data from the launches and only had a fin can left over. We decided to do what tests we could in the wind tunnel, see if it matched our model, and then propose a future launch to confirm our theory.

Here is our final report and final presentation. Rockets are fun, there is a lot to learn, and no better way than trial by fire. That project was worth every penny of the $1,000 we put into it.

Started: 26 February 2013
Finished: 6 May 2013