Characterization of HTPB-based solid fuel formulations: Performance, mechanical properties, and pollution

Features such as safety, low-cost, and throttleability make hybrid rocket engines an attractive option for suborbital flights and space exploration missions in general. While the domain of possible liquid oxidizers is well characterized, the choice of a suitable solid fuel is still a matter of investigation. Space Propulsion Laboratory (SPLab) at Politecnico di Milano has developed a series of proprietary techniques to evaluate, on a relative grading, the quality of innovative solid fuels while visualizing at the same time their flame structure. But a serious alert was recently notified that soot emission from hydrocarbon fuels has the potential to contribute to global climate change. In this paper, HTPB polymer has been taken as baseline and characterized at laboratory level in terms of ballistic properties, mechanical testing, and thermochemical calculations.

► Hybrid micro-burner and optical setup for solid fuel combustion. ► Characterization of ballistic and mechanical properties of solid fuels. ► Measurement of HTPB instantaneous and time-average regression rates. ► Extinction and spontaneous reignition of HTPB. ► Soot formation and environmental impact.