MCNP modelling of radiation effects of the Dragonfly mission's RTG on Titan II: Atmospheric ionization effects.

The Dragonfly mission to Titan represents the first use of a large-scale radioisotope power source in that environment; as such little is known of its potential effects on the surface or near-surface atmosphere. These effects represent backgrounds it will be necessary to subtract from the spacecraft's instrumentation data. Repurposing a Monte Carlo code model of the generator built for previous neutronic investigations with the addition of electron detectors allows for the determination of the degree to which the radiation fields from the generator may ionize the surrounding atmosphere and generate interference with the lander's conductivity measurements. Results showed good agreement with experimental data undertaken at the Idaho National Laboratory using the F-2 generator flown on the Perseverance Mars rover, and showed that the interference with readings taken in the daytime on Titan when atmospheric conductivity is expected to be low may be substantial. • MCNP Model of MMRTG, Dragonfly drone hull section & Titan/Earth atmospheres. • Ionization of dry Titan atmosphere greater than humid Earth atmosphere. • Conductivity within spacecraft hull significantly enhanced by backscatter. • Simulation results verified against empirical results taken at Idaho National Lab. • Open question of effect of methane humidity requires experimental work. [ABSTRACT FROM AUTHOR]