Relevant Files
Project
Details
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Date: Spring 2024
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Organization: Personal Project
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Objective: Learn foundational engineering skills, build a flyable rocket
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Key elements: Nosecone, fins, avionics, motor mount, support equipment
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Role: Personal project
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Achievements:
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Designed and built components for a fully custom rocket
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Familiarized with engineering tools and skills
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Familiarized with fundamental rocket design
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Low-Powered Rocket Design
Notes
The main goal for my freshman year in university was to get as much practical engineering experience as possible, especially in the world of aerospace. As my first institution did not have an established rocketry team, I pursued my own personal project to give myself an introduction to rocketry. I gave myself a goal to design and build a 3-inch diameter rocket by the summer. I also added two secondary goals: As much of the rocket as possible should be designed myself, and it should have a flight computer to save flight data and deploy parachutes. I worked on this project simultaneously with the autonomous robot, thus, I had very little actual engineering skills going into the project, and this would serve as a practical testbed for getting experience. Before beginning design, I did research into the general principles of amateur scale rocketry, which informed by decision to split the rocket up into 4 main sections: Recovery, avionics, fins, and the motor.
The second section was recovery. This section had the most commercial parts out of any section in the vehicle. This was necessary to build a secure platform to reliably recover the vehicle, with many bolts and the parachute itself being purchased. It consisted of a 3d printed bulkhead which would separate the recovery section from the avionics, along with a 3d printed piston above it to eject the parachutes safely. The bulkhead would be mounted directly above the avionics bay with dedicated slots for small ejection charges to be triggered by the computer. The piston would then sit above these charges, preventing direct contact with the parachute itself. The parachute would then be placed between the piston and the nosecone, folded inside of a fire blanket. The whole system was connected using a nylon shock cord, with a U-bolt mounted to the bulkhead and an eye-bolt mounted to the nosecone securing everything. Due to the layout of the vehicle placing the motor behind the avionics, it was necessary to remove the built in charge to most commercial motors before flight, with recovery responsibility being fully placed with the flight computer.
Once I had determined a layout, the first main section I worked on was the avionics. I built my avionics section around an Easy-Mini flight computer. This small board was easy to work with, had downloadable software to connect the computer to a laptop, had multiple connections for recovery charges, and was perfect for my use case. The board was so small, however, that it required a separate on-off switch, as well as a dedicated battery. The avionics section of the vehicle was designed around these constraints. It consisted of two circular mounting points on the top and bottom, as well as the middle portion where the computer would be kept. On one side there were mounting tabs for the board, as well as an indent where the switch could be secured. The other side had a slot to snugly fit the battery, with a bracket on top to keep it in place, and pass throughs for wires to reach the computer. The computer side of the avionics would have a hole cut through the body tube to allow for access to the switch, which would be armed immediately before launch.
The final main section was the motor. The motor itself would be bought, however the motor mounting tube was a custom made, 3d printed piece. It consisted of a long outer shaft which was mounted directly to the body tube. The motor would be placed inside the tube, and then secured using a custom screw in retainer at the very aft of the vehicle, integrated with the motor tube. I originally intended the vehicle to be able to fly with multiple motor sizes, thus an adaptor ring could also be placed inside the motor mount to snugly fit any motor size.
The third section was the fin assembly. The fins were designed and sized in accordance with stability simulations ran in a software called Openrocket, which automatically gave a stability rating taking into account the center of pressure and mass on the vehicle. The fins were intentionally oversized to account for any possible errors made when building the model. The fins were then epoxied onto the motor tube through slots, with extra epoxy being placed on the body tube to ensure a secure hold. This was done with the aid of a custom made fin-jig to align the fins during the cure time.
While this project never took off, I don’t consider it a failure. Rather, it served its purpose as a stepping stone to better designs. Because of this project, I greatly refined my skills with computer modeling, and learned to get much more comfortable with the process of test and iteration. While there are so many things I would have done differently had I started again, it is only because I made those mistakes that I understand how to fix them. In the future, I plan to build another rocket like this one and implement all the changes needed to make a safer and reliable vehicle.
By the end of the semester, after much trial and error, I had done enough work to consider the rocket in a completed state, and even completed a parachute deployment test (seen on the right). However, this vehicle never ended up flying. This was due to a number of technical reasons which, when added up, meant I simply was not confident that the rocket would be safe. For my first attempt at a model rocket, the goals I set for myself were incredibly ambitious in hindsight. With the knowledge I have gained since then, I can point out several key areas which would need improvement before flight. For one, the 3d printed parts were heavy and never fit securely to the body, yet also porous and not well suited to drilling. The fins, even with the help of the jig, were attached messily, with epoxy residue leaving bumps and imperfections. The motor tube was printed out of PLA, as it was the only material available in the lab, and had the possibility to melt through due to the high temperatures experienced, even with a short burn time. And finally, relying on avionics for parachute deployment as a beginner was a big risk. I simply did not feel comfortable loading the vehicle with charges while at a launch weekend.
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