Radiation shielding mass saving for the magnet coils of the VISTA spacecraft

Radiation shielding structure of a design concept with inertial fusion energy propulsion for manned or heavy cargo deep space missions beyond earth orbit has been investigated. Fusion power deposited in the inertial confined fuel pellet debris delivers the rocket propulsion with the help of a magnetic nozzle. The nuclear heating in the super conducting magnet coils determines the radiation shielding mass of the spacecraft. It was possible to achieve con- siderable mass saving with respect to a recent design work, coupled with higher design limits for coil heating (up to 5mW/cm3). The neutron and -ray penetration into the coils is calcu- lated using the SN methods with a high angular resolution in (r±z) geometry in S16P3 approximation by dividing the solid space angle in 160 sectors. Total peak nuclear heat gen- eration density in the coils is calculated as 3.143mW/cm3 by a fusion power of 17 500MW. Peak neutron heating density is 1.469 mW/cm3 and peak -ray heating density is 1.674mW/ cm3. However, volume averaged heat generation in the coils is much lower, namely 74, 163 and 337 mW/cm3 for neutron, -ray and total nuclear heating, respectively. The net mass of the radiation shielding for the magnet coils is 200 tonne by a total mass of 6000 tonne of the space craft