Beam-Based Experimental Validation of FLUKA Predictions for Candidate Spacecraft Shielding Materials

Accurate prediction of radiation shielding performance is essential for selecting materials for future spacecraft and long-duration exploration missions. Monte Carlo radiation transport codes are widely used to simulate particle interactions, energy deposition, attenuation, and secondary radiation production; however, their reliability depends on validation against measurements obtained under controlled irradiation conditions. This study experimentally benchmarks FLUKA predictions for Aluminum 6061-T6, high-density polyethylene, a boron nitride nanotube composite, and boronated polyethylene exposed to a monoenergetic 150 MeV proton beam. Transmitted and secondary detector responses were measured using calibrated silicon detector instrumentation and compared with FLUKA models constructed from matched beam, material, and geometric definitions. Agreement was evaluated using normalized transmitted response, relative percent difference, root-mean-square error, spectral trend consistency, and combined experimental–simulation uncertainties. FLUKA reproduced the monotonic attenuation trends and identical material-performance ranking observed experimentally. Differences between predicted and measured transmitted responses remained within approximately ±5.1%, with an overall root-mean-square error of 0.035. Aluminum 6061-T6 produced the greatest downstream secondary response, whereas the hydrogen-rich and boron-containing materials produced lower integrated responses. The results provide a quantitative beam-based benchmark for FLUKA spacecraft shielding applications and identify material definition, detector response, secondary-particle transport, and geometric idealization as principal sources of residual discrepancy.