Test Evaluation

Upon reviewing the data that was gathered, it seemed that the load cell was calibrated incorrectly and as can be seen below, has a zero point of roughly (2.6) kg. It also shows that the maximum thrust produced topped off at just over (5) kg (11 lbf). This would mean that the engine only produced 22% of the thrust it was designed for. This outcome is entirely plausible, however, as the injector redesign was poor but necessary. The video of the test fire clearly demonstrates the engine chugging. This phenomenon is due to poor combustion stability which would be the outcome of a single hole injector design. Unfortunately, a pressure transducer could not be integrated in to the design of the engine. Chamber pressure data could confirm intense pressure fluctuations that may have also contributed to the chugging. I theorize that the pressure in the chamber would rise above the injection pressure for a brief moment causing back pressure on the feed line thus closing the fuel check valve. This would starve the engine for only a few milliseconds but enough to almost entirely cease new combustion. Upon reopening, the residual hot combustion products would relight the fresh fuel and oxidizer mix, starting the process over again. Video review from the front of the engine seems to show sustained combustion but it is not clear enough to support the theory of the pressure fluctuations. The 'pulses' are visible in the thrust data by the erratic thrust levels during the (3) second test firing seen in the graph below.  

There is still work being done to attempt to back calculate the raw data to possibly extract the voltage values from the load cell and re-plot the thrust curve.