Alternative Propellant Nuclear Thermal Propulsion Engine Architectures

What is it about?

Recently, NASA’s Artemis Program has considered sustainably returning humans to the Moon with In-Situ resource utilization (ISRU) as the central focus and considers hydrogen-based Nuclear Thermal Propulsion (NTP) to be a viable propulsion system candidate for deep space missions. The Lunar Crater Observation and Sensing Satellite (LCROSS) discovered the abundancy of water, ammonia, and other volatiles in permanently shadowed regions on the Moon. Since NTP can theoretically use any fluid as a propellant, water and ammonia are two potential alternative propellants to hydrogen which do not require post processing to be used directly In-Situ. Alternative propellant NTP (A-NTP) engine models were developed to examine the performance of water and ammonia. It was found that these in-situ propellants can significantly increase the thrust of an engine but at much lower efficiency than hydrogen. However, it was found that water degrades the engine materials much faster than either hydrogen or ammonia which decreases the engine life significantly. Therefore, different temperatures were used to understand the effects of material degradation.

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