HTPE/PLA Test on 09-23-2022

The objective of this test was to examine the effect of an optimum expansion ratio on the coefficient of thrust. The optimum expansion ratio at sea level is ~ 1.7. By cutting off ~ 4 mm from the end of the nozzle, I get an expansion ratio of ~ 1.8. I had a steady average thrust of ~ 19.3 N with a burn time of ~ 4.4 seconds. Ignition occurred in ~ 1.4 seconds. Although I had a really good thrust, my thrust coefficient efficiency was ~ 75%. However, my O/F ratio was ~ 5.2, way to high (theoretical at 2.75). So, there is room for improvement!