Combustion of alane-based solid fuels

In this study the combustion behavior of solid fuels loaded with micron-sized aluminum, nanoaluminum, and aluminum hydride with loadings of 10, 20, and 40 mass % are compared directly using pure oxygen as the oxidizer. An opposed flow burner was used to screen the various fuels at various oxidizer flow rates. Regression rates were gathered over oxidizer impingement velocities ranging from approximately 40 to 160 cm/s (strain rates of 80-320 s^-1). Fuels loaded with aluminum hydride were found to have regression rates comparable to or better than that of the baseline hydroxyl terminated polybutadiene (HTPB) fuel. In addition, the regression rate increased with increasing aluminum hydride content. Conversely, the regression rates of fuels loaded with micron-sized aluminum were found to decrease with increasing aluminum content. Emission spectroscopy revealed that under most conditions the aluminum in the fuels loaded with micron-sized aluminum did not ignite within the immediate vicinity of the solid fuel sample. Temperature measurements determined from thermal emission support this conclusion as well. Finally, a lab-scale hybrid rocket motor was used to compare the combustion performance of the fuels relative to each other. It was found for the same oxidizer mass flow rate, pressure and thrust were highest for alanized fuels. Data included were thrust, pressure, regression rate, and mass burning rate.