AUG. '17 - DEC. '17
In Fall of 2017, industry giant Bayer put out word of a rocketry competition that they and the Big Ten were going to co-run. Myself and a few other members of the University of Minnesota Rocket Team decided to devote our lives to winning this competition... and win we did. After uncountable sleepless nights and an unfathomable amount of Alka Seltzer tablets later, we set the Guinness World Record for the "highest launch of an effervescent tablet rocket" at 429 feet and carried home a $25,000 check from Bayer. We decided to put this money back into the Rocket Team, aiding our annual funds tremendously.
Link to a news article reporting the record here.
After several design iterations and simulations in OpenRocket, we settled on a design that was going to give us a good compromise of stability and drag. Because this is not your usual rocket, which typically carries its propellant, we were not able to simply scale down the design of one of our full-sized rockets from past competitions.
Due to the characteristics of our Alka Seltzer fuel (high-impulse, but extremely short 'burn' time) we new that we wanted our rocket to be very light while having the strength to withstand the abrupt force of our pressurized gas. We considered several materials that fit these requirements including fiberglass, carbon fiber, acrylic, aluminum, and various plastics. Because of being the most versatile, low-cost, and the easiest to work with option, we decided on 3D-printing most of our components. This also allowed us to make design changes very rapidly, which was essential in designing the most efficient rocket possible in the small amount of time given.
When deciding how we wanted to utilize our fuel to power our rocket we had to main design options. One option would be to design a 'typical' rocket, which has an integrated fuel tank and carries its propellant, releasing its pressurized gas as it accelerates upward. The second option would be to leave the fuel tank on the ground, dumping all our our pressure at once and firing our rocket upward with a single, rapid, release of gas. We found that the second option was going to be superior to the first for our rocket, as a design this small simply could not fit an integrated fuel tank with anywhere near the thrust potential of a larger tank fixed to the ground.
This method of propulsion was very unique in the field of rocketry, and forced us to think about much more in our design process than in your typical rocket; we now had to consider expansion speeds and capacities of our gas, maximum attainable pressure, aerodynamics of a projectile, and much more. This also gave us confidence, as our design was very much 'outside of the box' and we felt as though this would give us a leg up on the competition.
The flight computer is the brains of the rocket. It records our flight data which we use for post-flight analysis, allowing us to easily identify possible issues and make improvements to our rocket. Additionally, the flight computer is responsible for triggering our parachute recovery system.
Since our rocket design was so compact, we decided to create our own custom flight computer using an Arduino Nano and several data-collecting components. Additionally, this would enable us to add any functionality we wanted, including features pulled from various commercially available units, giving us the exact performance we needed without any unnecessary components.
DEC. '17 - DEC. '18
Upon conclusion of the first Alka-Rocket Challenge, the two lead members of our Alka team graduated. Our Rocket Team as a whole held an election to determine the new Alka lead member. After delivering our speeches, I was elected as the new Alka project lead out of many running for the position
I immediately got to work putting together a new Alka project team, coming up with design changes, and delivering new ideas. After 10 months of hard work we qualified for the final round of the competition, and again took 1st place. Following last year's footsteps, we again elected to put our prize money (which was raised to $30,000) back into our Rocket Team to help fund our larger projects.
Building off of our knowledge from last year, we knew that our rocket had to be as small and light as possible, while remaining strength and stability.
Having more time for project development, we were able to explore more options for our rocket materials. We moved away from 3D-printing the body tubes and instead laid up our own fiberglass ones on a custom mandrill we lathed out of steel. This allowed us to produce substantially stronger and lighter rockets. For the same reasons, we switched to fiberglass for the fins as well.
We would have liked to move away from 3D printing the nose cone and boat tail of our rocket as well, but were not able to because of their more complex shapes and our strict schedule. This is an improvement we hope to incorporate into our rocket next year.
Again, using our knowledge from the previous year to our advantage, we knew that it was most efficient for us to have a propulsion system that remained stationary on the ground rather than one that was carried with the rocket.
The most major design change to our launcher was barrel length. Through some gas expansion problem-solving and lots of trial and error, we were able to find the optimal barrel length for maximum acceleration. Additionally, we found that PVC inconsistencies and shrinkage in cold weather was negatively affecting our rocket's performance. Because of this, we switched to using a poly-carbonate barrel which eliminated shrinkage and reduced drag, resulting in a massive performance boost.
Additionally, we used our increased budget of money and time to rebuild almost every component of our pressure chamber using higher quality materials and with more care than the previous year. This ensured that our system was both as safe and reliable as possible.
Because we wanted an easier and more solid method of communicating with our flight computer, we decided to use a Raven rather than our own Arduino-based computer. We also upgraded to batteries with much higher capacities. This meant an increase in weight, but we decided it was worth the trade off of being able to now affix every component of our avionics bay more permanently and without the worry of needing to disconnect the batteries to charge or swap them. Additionally, all components were connected in a much more solid, compact manner, making it substantially easier for us to insert and remove the avionics system as a whole from our rocket.
DEC. '18 - DEC. '19
After winning the Alka-Rocket competition for two consecutive years, I was renamed lead for the 2019 competition team.
This time around we lost no current members, so hitting the ground running on the next iteration of our rocket was a breeze. After another 10 months of continuous trial and error, we had come up with our most impressive rocket yet and took home 1st place for the third year in a row. We again elected to put our prize money ($25,000) back into our Rocket Team to help fund our larger projects.
With more experience with composites under our belts, we decided to take an ambitious approach to this year's rocket. We moved on from fiberglass to laying up our own carbon fiber components, resulting in an even stronger rocket body.
In addition to material changes to the body of the rocket, we improved the other components as well. Rather than 3D printing with typical PLA filament, we printed this year's nose cone and boat tails out of SLA. This is done using a resin printer, which results in much finer resolution prints, and even stronger parts.
Finally, we revamped our recovery system. Rather than attempting to separate a part from our rocket to deploy the parachute as we had done in previous years, we now created a dedicated parachute bay at the tail-end of our rocket. This allowed us to secure our rocket body much more thoroughly, and drastically increased the reliability and effectiveness of our parachute recovery system.
Since the launcher from our system was so effective last year, we decided to go with the exact same one for this year's competition.
There was a minor change in the competition rules that placed a size limit on a team's overall launch system, so we had to shorten our polycarbonate barrel slightly. Other than that, no additional changes were made to the launcher.
Similar to our situation with the launcher, our flight computer was very reliable and effective in our design from last year. Because of this, we did not feel the need to do any major redesigning of this portion of our system.
We were able to place the flight computer components on a smaller platform, which decreased overall size and increased ease of assembly when inserting into our rocket body. We also decided to get rid of a power switch in favor of a "twist and shove" method. This allows us to assemble the entire rocket without needing to have the flight computer turned on during the process. Once assembled, we can simply twist two wires together and shove them through a small hole in the rocket body so arm our system.
At this year's competition we flew to an altitude of 535 feet, besting the previous maximum height achieved with successful recovery, which we set at 226 feet last year.
Here is an awesome ultra slow-motion shot of our rocket launching, captured on an Ametek Phantom Ultrahigh-Speed camera.
After winning the competition for the third consecutive year, we were invited out to New York City to do an interview with Cheddar at their New York Stock Exchange location.