Shake, Rattle a Little, and Hopefully We Won’t Roll

The space craze has made a comeback with the formation of SpaceX and Blue Origin competing to build reusable rockets, driving the imagination of many aspiring engineers. I happen to be one of those aspiring engineers and a bit of a space nut too, which led me to the University of Washington – Seattle’s rocketry club. I have been a part of the Society of Advanced Rocket Propulsion (S.A.R.P.) since I began the mechanical engineering program at UW – Seattle in the autumn of 2017.

While the foundations of being an engineer are laid out in the coursework that spans the years at college the practical application of those fundamental skills builds more than just character and problem-solving skills. So, I set out to challenge myself knowing the importance of applying one’s knowledge to real-world situations. And after my first year of S.A.R.P. and watching a video of our rocket only to watch it do summersaults before crashing down, the team decided that creating a sub-team that focuses on testing the following year would be a good idea.

This year we will be performing vibration testing in hopes of preventing another structural failure on the rocket.

Let’s Build a Rocket

As listed on the SARP webpage, sarpuw.edu, each year the team sets out on the daunting task of building a 14-foot-tall rocket using our engineering coursework and the assistance of professors and professionals in the industry (sarpuw.com). The team consists of over 200 undergraduate students and is broken into various sub-teams.

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“We participate in the Experimental Sounding Rocket Association’s (ERSA) Intercollegiate Rocket Engineering Competition (IREC). In 2018, we placed first in the highest altitude category at 30,000 feet with a student-researched and designed propulsion system.” (sarpuw.com) This year I have chosen to work on the Avionics and Recovery sub-team of the Flight Test team, which was created in response to a dramatic failure in the 2018 competition launch.

SARP Rocket 2018

If at First, You Don’t Succeedto, You Probably Should Have Tested It

While we may have won first place at last year’s competition for our propulsion design a structural failure caused our recovery system to fail to result in a crash landing. Unfortunathe tely, when the structure failed on the rocket it caused a chain reaction of failures in our parachute recovery system that caused our main parachute to shred to pieces. For the main parachute to deploy successfully the drogue parachute, a smaller parachute than the main one built of stronger material, is first deployed to slow the descending rocket down to speeds sustainable by the main parachute. So, this year the leads of SARP decided to form a flight test team to provide testing options to prevent future failures.

The harm that could befall spectators from a 14-foot-tall rocket, possibly still containing combustible fuels, is something that we as a team want to avoid as much as possible. Taking special considerations in the safety of the launch by performing tests on not only important structural components but also the recovery systems, such as parachutes and avionics, brings the perspective of what it means to be a diligent engineer into the light. Avionics refers to the electronics that will control various components and record flight data for the rocket. One of the main tests being performed this year will be the vibrational testing of structural and avionics systems. Each test is geared to verify a parameter and validate the intended operation of the system at test.

Catastrophic Failure of Recovery Coupler

Shake It As You Mean It

Vibrational testing is as it sounds, things being subjected to rapid jerking motions or vibrations, but with a deeper mathematical model driving it. A thick plate used as the mounting fixture for components is connected to an electromagnet that is powered by high voltages and controlled by a specific computer algorithm, the mathematical model. This algorithm allows the table to move at various rates and distances, the algorithm can make the table move smoothly like the vibrations of a washing machine or erratically as if bricks had been thrown in the wash as well. This testing provides an ideal simulation of how the rocket would vibrate due to the engine firing in the launch. Vibration testing can also exert extreme gravitational forces, commonly referred to as G’s, like that of pilots turning tight corners. Those extreme gravitational forces are what we suspect to be the root cause of our rocket failure last year. An important component called the recovery coupler, a connecting and storage point between the main fuel storage and the parachute storage, had a manufacturing defect that when subjected to the large force of the engines pushing the rocket up and Earth wanting to pull it back down caused it to buckle. So, we will be testing the structural integrity of our recovery coupler as well as verifying the proper operation of our avionics under vibrations. This will allow us to review the current design and make modifications before the final assembly and launch.

Vibration testing can provide us with important feedback for the performance of our parts and systems so we can improve the overall design and safety of our rocket. There will be plenty of challenges ahead, but it will allow us to someday recover and possibly reuse parts of our rocket. And applying the academic knowledge we have gained in our classes helps us to be stronger engineers in our future endeavors, be it to infinity or beyond.