Rocket Thrust Testing

My neighbor, Dr. Grant, has been experimenting with different types of rocket fuels for a while. The last rocket we tried to launch exploded, so we knew we had too much pressure inside the engine casing. The more pressure we have, the more thrust we can produce. So, we would like to maximize it if we can. We decided to create an apparatus to test different nozzles and fuels. We can use the maximum thrust produced by the rocket to find the pressure inside of the engine casing. Our plan is to compare the actual pressure to the engine's pressure rating. After all the testing, our goal is to find the fuel and nozzle combination that will give us the maximum amount of energy without blowing up the engine. Below, I will give a few details about our testing methods.

Helpful Links:

CLICK HERE for software

CLICK HERE for load cell amplifier

CLICK HERE for the load cell

CLICK HERE to download the library for the HX711

Credits:

Chemist: Dr. Grant

Fabricator: Sawyer

Developer: Taylor Burton

The Lever Arm:

The lever arm pivots in the center. The rocket thrusts downward and then the arm pushes upward onto the load cell. The load cell collects data and sends it to an arduino which communicates with the computer.

Lever arm with engine casing read to thrust downward

The end with the load cell and the cord going to the arduino

Load cell:

We used the HX711 amplifier with our load cell. There are many load cells out there that work with the HX711. Each load cell will be calibrated differently, but most libraries for them work very well. The load cell we used was the TAS606. If you end up using my code with a different load cell, you will have to calibrate the sensor for it to work properly. The libraries for the HX711 should detail this. Wiring the sensor is pretty easy. If you can't figure it out from the picture below, go to the Spark Fun website. They have a very detailed tutorial over this product.

The HX711 connected to an arduino nano

Software:

The firmware was uploaded to an arduino nano and it communicated through a USB to the computer. I created a GUI using Processing, which is basically Java. However, I find it easier and faster to create a simple GUI using Processing. The GUI prompts the user to select a COM port and then waits for a test to begin. It plots the live data on a graph and then asks the user if he or she would like to save the data as a text file. At the end of the test, it will display the maximum thrust and total amount of energy produced from the rocket's engine. Below is an example of what the GUI looks like after the test is done. It is just waiting for the user to click save data. CLICK HERE to get to the code. You will need to have Processing and the Arduino IDE downloaded as well.

Note: The screenshot below is a little outdated. Instead of work, it should be change in momentum. The new software on GitHub should reflect this change.

The GUI at the end of a test