Preignition Behavior and Combustion Stability of Storable Propellants for Deep Space Missions

Storable propellants are critical to the success of NASA’s deep space and low earth orbit missions because they provide a small impulse bit, high performance, and simplicity while being able to sit unused on a spacecraft for large periods of time prior to and after operation. Storable propellants are also well known for their high cost due to toxicity of hydrazine propellants, and combustion instabilities capable of destroying a thruster. Technology roadmaps 2.1.1 and 2.1.2 address NASA’s need to develop new green bipropellants and monopropellants. Technology roadmap 2.1.1.1 (monopropellants) addresses the need to develop higher thrust classes of the green monopropellants able to perform in regimes similar to hydrazine. The new propellants must also improve on the reliability of hydrazine systems. Current green monopropellants like AF-M315E, GEM, and LMP-103S are under development but have only been applied to thrusters on scales much lower than typical hydrazine systems and have not demonstrated higher reliability. To develop the next generation of storable propellant thrusters, I will develop diagnostic techniques to investigate a thruster operating during a deep space mission. The first phase of the study will be to conduct attenuated total reflectance (ATR) analysis of various propellants as they react to provide real-time information about the preignition reactions that occur. Second, I will conduct through transmission FTIR analysis while various green monopropellants and bipropellants are combined inside of a chamber and allowed to react at relevant temperature and pressures while the reaction is recorded using high-speed cameras. Next, the condensed products will be exposed to temperature gradients similar to what would occur in a thruster after it is shut down and thermal soak back occurs. All samples will be tested for explosive potential to determine whether they are particularly likely to contribute to combustion instabilities when allowed to remain inside of a thruster. Finally, computational chemistry techniques will be used to generate theoretical IR spectra for comparison to experimental results and comparison of proposed reaction mechanisms. The combination of these tasks will develop new diagnostic techniques for storable propellants and provide information about storable propellant reactions under relevant conditions for improved stability and development of next-generation green propellants.

Storable propellants are critical to the success of NASA’s deep space and low earth orbit missions because they provide a small impulse bit, high performance, and simplicity while being able to sit unused on a spacecraft for large periods of time prior to and after operation. This project will develop new diagnostic techniques for storable propellants and provide information about storable propellant reactions under relevant conditions for improved stability and development of next-generation green propellants.

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