Hybrid Rocket Fuel Grain

During the summer of 2021, I worked with the Cal Poly Aerospace Shop Technician Cody Thompson as his assistant to maintain the lab spaces as well as prepare for upcoming experiments that would be done by 400 level students in the upcoming Fall Quarter. One task, as shown below, included manufacturing fuel grains for the hybrid rocket test stand.

Using a fuel grain that was already manufactured, I took measurements and created a 3D CAD model of it using Solidworks. From this 3D model, it was easy to create an engineering drawing that could be referenced throughout the manufacturing process of the new fuel grains.

Using the Haas TL-1 CNC Lathe, I manufactured a total of 20 hybrid rocket fuel grains complete with a centered hole, tapered ends, and chamfered edges.

The fuel grains were secured and used on the hybrid rocket test stand, as shown below. The stand uses propane to ignite oxygen that runs through the grain. The grain is fitted into two hinges that allow it to swing back and forth so that the force of the grain can be measured a strain gauge.

Initially, the strain gauge wasn't properly calibrated in the software "Labview", which was used to display measured values from the test stand. To fix this, I used weights to produce and record outputted voltage values in order to plot them against each other and create a calibration curve, as shown below. This least squares regression line equation was then inputted back into the software to create a much more accurate reading of force values by the strain gauge.