Engine Ablation Rate Code

 One of the first tasks I was given on the team was to determine the material for the ablative chamber for the engine. Since the burn time of rocket we were designing was double that of the previous rocket, the effects of throat ablation would be more pronounced. As the throat increases, the chamber pressure decreases, which decreases thrust and efficiency, which would decrease our predicted final altitude. To reduce this, we were considering using a graphite throat, which would reduce the throat ablation. To determine which was the better solution, I implemented code that simulated the effect of throat ablation in the team’s 1 degree of freedom (1dof) model for sizing the rocket. The code iteratively ran so that, as the throat increased, the chamber pressure decreased, which slightly decreased throat ablation rate, etc. until burnout. I then implemented a mass increase for the graphite throat, and compared the results. Counterintuitively, the pure silica-phenolic ended up having the higher altitude. While graphite did reduce the ablation rate of the engine, the effects of throat ablation were not so severe, and the additional mass of the graphite throat decreased the final altitude by 3,000ft. Raw performance was not the only factor considered, as a graphite insert would ablative at a different rate compared to the chamber and nozzle, as well as have the potential of being “ripped” out of the engine during flight, if the ablation rates differed significantly enough. So, I made the decision to proceed with a pure silica-phenolic engine.