Enhancement of regression rates in hybrid rockets with HTPB fuel grains by metallic additives

2015, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Low regression rates in hybrid rockets limit their use and capability. In the current paper, the implementation of micro- and nano-Aluminum and Boron particles as a regression rate enhancer is assessed on a lab-scale motor. Additive particles were individually assessed at mass loadings of 5% in hydroxyl terminated polybutadiene (HTPB) fuel grains. The combination of nano-Aluminum and Boron was also assessed at loadings of 2.5% each for a total additive loading of 5%. Test fuel grains had a length of 15.24 cm; had initial combustion port diameters of 25.4, 10, or 2 mm; and were burned in gaseous oxygen at low pressures (< 1 MPa) and moderate oxidizer mass fluxes (1-18 g/cm2-s). Traditional temporally and spatially averaged techniques and resistive-based sensor methods were applied to determine the average regression and fuel mass loss rates of plain and additive HTPB motors. The addition of nano-Aluminum (100 nm) to hybrid motors increased the surface regression rate and mass loss rate. At the conditions of this study, the effects of micro-scale Aluminum (24 m) were negligible, and the effects of the Boron additive (100 nm-5 m) were unfavorable to motor performance. The formulation containing both nano-Aluminum and Boron exhibited performance between the pure nano-Aluminum and pure Boron additive formulations.

Enhancement of regression rates in hybrid rockets with HTPB fuel grains by metallic additives Conference Paper