Hybrid Propulsion In-Situ Resource Utilization Test Facility Results

Hybrid rockets present a promising alternative to conventional chemical propulsion systems for In-Situ Resource Utilization (ISRU) and in-space applications. While they have many benefits for these applications, there are still many small details that require research before they can be adopted into flight systems. A flexible test facility was developed at JPL to test operation of hybrid motors at small scale (5 cm outer diameter fuel grains) over a range of conditions. Specifically, this paper studies two of the major advantages: low temperature performance and throttling. Paraffin-based hybrid rockets are predicted to have good performance at low temperatures. This could significantly decrease the overall system mass by minimizing the thermal conditioning required for Mars or outer planet applications. Therefore, the coefficient of thermal expansion and glass transition of paraffin are discussed. Additionally, deep throttling has been considered for several applications. This was a natural starting point for hotfire testing using the hybrid propulsion ISRU test facility. Additionally, short length to diameter ratio (L/D) fuel grains are tested to determine if these systems can be packaged into geometrically constrained spaces