<p>Compared with traditional chemical energy rockets, nuclear thermal propulsion (NTP) is a more ideal power device for deep space exploration. With high specific impulse and using single-component propellant, NTP could achieve a large space vehicle final velocity to reduce the flight time and provide a low initial effective payload mass to reduce the spacecraft ground launching mission costing. Usually, hydrogen is employed as propellant to enhance the specific impulse of NTP systems. However, the low boiling point and light density leads to several significant issues related to safety and storage, such as increased size of propellant tank and additional systems for in-orbit cryogenic fluid management. From the perspective of reactor physics, thermal hydraulics, material compatibility, and experience in the aerospace field, ammonia is the alternative propellant to replace hydrogen. Generally, the aim of increasing the specific impulse is to save the propellant, but in missions such as orbital transfer and rapid maneuvering, more thrust is required to provide sufficient acceleration. Therefore, different missions have different performance requirements for NTP spacecraft. To analyze the impact of propellant on the specific impulse and thrust of the spacecraft, the hydrogen expander cycle NTP system analysis program PANES is improved. The thermophysical properties library of ammonia has been increased, and the stability of program calculation has been enhanced. Based on the same mission conditions, the design and analysis of NTP systems with other single-component propellant are carried out, and the effects of different propellants on the specific impulse and thrust of the spacecraft are given. The thermophysical properties and high temperature decomposition of ammonia provide a thrust greater than hydrogen. Therefore, ammonia can replace the hydrogen to effectively provide greater thrust while reducing the initial volume of the propellant in the same NTP system. This paper improves the PANES program, and calculates the spacecraft performance parameters for potential alternative propellants, which provides a reference for the design of NTP system.</p>

System Design for Ammonia Nuclear Thermal Propulsion

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

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