A conceptual design of a micro-propulsion device based on alpha particles

Area of Science:

• Space Propulsion
• Nuclear Power Sources
• Micro-propulsion

Background:

• Nuclear Power Sources (NPS) are crucial for long-duration, autonomous space missions due to their high energy density.
• Alpha particle micro-propulsion, combining NPS with micro-propulsion, utilizes alpha decay recoil for thrust, offering high specific impulse.
• Previous research calculated thrust for specific nuclides but lacked comprehensive analysis of temperature distribution and comparative performance.

Purpose of the Study:

• To investigate the performance of alpha-decaying films (Pu-238, Am-241, Po-210) on various substrates for micro-propulsion.
• To analyze thrust, energy deposition, and heat transfer, including temperature distribution across films and substrates.
• To compare the comprehensive performance of different nuclides and film configurations.

Main Methods:

• Utilized CERN's Geant4 Monte Carlo simulation for analyzing thrust, energy deposition, and heat transfer.
• Employed ANSYS's Fluent program and a simplified uniform temperature model to calculate temperature distributions.
• Investigated alpha-decaying films (Pu-238, Am-241, Po-210) on substrates like graphene and polyethylene.

Main Results:

• Thinner films resulted in lower temperatures, higher alpha particle escape rates, and increased specific impulse.
• Film shape was found to have no impact on the generated thrust.
• Pu-238 decay sails demonstrated potential to significantly reduce interplanetary travel times (e.g., 401-au journey reduced from 111.9 to 96.3 years).

Conclusions:

• Alpha particle micro-propulsion devices are suitable for precise, long-duration space missions due to their simplicity, high specific impulse, and modularity.
• Optimizing film thickness is key to enhancing performance by managing temperature and maximizing specific impulse.
• Future work will focus on thrust-atmospheric drag equilibrium for low Earth orbit satellite applications.