Exploring Aerogel's Attenuation for High-Energy Alpha Particles in Fission-Fusion Fragment Rocket Applications

There has been growing interest within the research community in exploring new nuclear propulsion methods for more efficient space travel beyond Earth’s orbit. One promising approach is the use of a Fission Fragment Rocket Engine (FFRE), which incorporates fissionable layers embedded in low-density aerogel. A key challenge in developing a functional FFRE prototype is understanding particle attenuation, ensuring that fission fragments escape the layers to generate thrust rather than being absorbed and producing waste heat. In this study, we developed an experiment to evaluate and analyze the attenuation of alpha particles emitted from 241Am sources within various aerogel materials. CR-39 Plastic Nuclear Track Detectors were used to estimate particle counts, while MCNP simulations were conducted on aerogels with varying densities and compositions to predict the intensity of alpha particles reaching a detector. Both experimental and simulation results provided valuable insights into aerogel’s attenuation properties, which are critical for assessing its potential as the core matrix for holding fuel materials in the FFRE.