Designing high-performance hypergolic propellants based on materials genome

A new generation of rocket propellants for deep space exploration, ionic liquid propellants, with long endurance and high stability, is attracting more and more attention. However, a major defect of ionic liquid propellants that restricts their application is the inadequate hypergolic reactivity between the fuel and the oxidant, and this defect results in local burnout and accidental explosions during the launch process. We propose a visualization model to show the features of structure, density, thermal stability, and hypergolic activity for estimating propellant performances and their application abilities. This propellant materials genome and visualization model greatly improves the efficiency and quality of developing high-performance propellants, which benefits the discovery of new advanced functional molecules in the field of energetic materials.

Propellant Off-Gassing and Implications for Triage and Rescue

INTRODUCTION: Hypergolic propellants can be released in large amounts during space launch contingencies. Whether propellant-contaminated suit fabric poses a significant risk to rescue crews, due to off-gassing, has not been explored in detail. In this study, we addressed this issue experimentally, exposing space suit fabric to propellants (dinitrogen tetroxide [N2O4] and monomethyl hydrazine [MMH]).METHODS: The NASA Space Shuttle Program Advanced Crew Escape System II (ACES II) is similar to the NASA Orion Crew Survival System (OCSS) and was utilized here. Suit fabric was placed and sealed into permeation cells. Fabric exterior surface was exposed to constant concentrated hypergolics, simulating permeation and leakage. Fabric was rinsed, and permeation and off-gassing kinetics were measured. Experimental parameters were selected, simulating suited flight crewmembers during an evacuation transport without cabin air flow.RESULTS: The fabric allows for immediate permeation of liquid or vaporized MMH and N2O4. NO2 off-gassing never exceeded the AEGL-1 8-h level (acute exposure guideline level). In contrast, MMH off-gassing levels culminated in peak levels, approaching AEGL-2 10-min levels, paralleling the drying process of the fabric layers. DISCUSSION: Our findings demonstrate that MMH off-gassing is promoted by the drying of suit material in a delayed fashion, resulting in MMH concentrations having the potential for adverse health effects for flight and rescue crews. This indicates that shorter decontamination times could be implemented, provided that suit material is either kept moist to prevent off-gassing or removed prior to medical evacuation. Additional studies using OCSS or commercial crew suits might be needed in the future.Schwertz H, Roth LA, Woodard D. Propellant off-gassing and implications for triage and rescue. Aerosp Med Hum Perform. 2020; 91(12):956961.