Analysis of FDM-Enabled Thermoplastics as Hybrid Rocket Fuel

In this analysis, materials capable of being 3D printed such as acrylonitrile-butadiene styrene (ABS), polyethylene terephthalate-glycol (PETG), and polylactic acid (PLA) were analyzed mathematically to determine their potential application as a fuel source for a hybrid rocket engine currently being developed by Daedalus Astronautics. By developing a 3D printed fuel option, new fuel grain geometries can be manufactured and tested that have the potential to greatly improve regression and flow characteristics of hybrid rockets. In addition, 3D printed grains have been shown to greatly reduce manufacturing time while improving grain-to-grain consistency. In the end, it was found that ABS, although the most difficult material to work with, would likely provide the best results as compared to an HTPB baseline. This is because after conducting a heat conservation analysis similar to that employed by NASA's chemical equilibrium with applications code (CEA), ABS was shown to operate at similarly high levels of specific impulse at approximately the same oxidizer-to-fuel ratio, meaning the current Daedalus test setup for HTPB would be applicable to ABS. In addition, PLA was found to require a far lower oxidizer-to-fuel ratio to achieve peak specific impulse than any of the other fuels analyzed leading to the conclusion that in a flight-ready engine it would likely require less oxidizer and pressurization mass, and therefore, less overall system mass, to achieve thrust levels similar to ABS and HTPB. By improving the thrust-to-weight ratio in this way a more efficient engine could be developed. Following these results, future works will include the hot-fire testing of the four fuel options to verify the analysis method used. Additionally, the ground work has been set for future analysis and development of complex fuel port geometries which have been shown to further improve flight characteristics.