Work

Rocket Engine Thrust Tester

A DIY thrust test stand I built so we could make our model rocket engines a bit more scientifically.

  • Taoyuan Vocational HS (NTUT-affiliated)
  • HS Year 1
  • 2022
  • Team project
A DIY rocket engine test stand made of two wooden boards fixed together at 90 degrees

Background

It all started when I watched Taiwanese YouTuber 胡子 (Huzi)’s homemade rocket videos, which got me hooked on model rockets. I rounded up a few classmates and we started building sugar rockets (potassium nitrate + sugar). Step one was making the fuel, but once we’d made it we were too scared to just launch it, in case it flew straight to the moon (overthinking it lol). So I figured I’d build a thrust test stand first.

The first problem: what sensor do you even use to measure thrust? I assumed there’d be some kind of professional force gauge, but apparently not. After a while of searching online I still came up empty, and the only thing I found on Shopee was the load cell used in scale modules. It didn’t feel very professional, but I went with a load cell anyway.

Build Process

  1. Used my basic woodworking skills to cut a mounting frame
  2. 3D printed a fuel holder
  3. Attached the load cell to the 3D-printed part
  4. Wrote an Arduino program to read the load cell and send the data to Python
  5. Wrote a Python program to log the data
  6. Wrote a Python program to process the data and run the calculations

How to Use It

  1. Secure the fuel in the holder
  2. Start the Python logging program
  3. Ignite the fuel
  4. Stop the logger once the fuel has burned out
  5. Load the logged data into the Python calculation program to get the results

Reflections

This build involved a lot of rocket engine formulas, like total impulse, average thrust, peak thrust and burn time, so I learned a ton of rocket engine basics. It was also my first time using pyserial for serial communication between Python and Arduino, which has helped me in a lot of projects since.

The biggest letdown was that the motor fired downward onto the load cell, so it also weighed the fuel itself. We didn’t have a way to figure out how the fuel’s mass drops over time, so we couldn’t calculate the true thrust. But at least we learned the thrust wasn’t very big, so after that we skipped the thrust tests and just went straight to flying lol

If I ever build it again, I’d probably switch to a horizontal setup on a slide rail, so the fuel’s mass wouldn’t matter anymore!