Radiation Protection and Architecture Utilizing High Temperature Superconducting Magnets

The NIAC one year study evaluated multiple coil geometries including the Double Helix from AML and toroid designs. The Double Helix and other toroid concepts have a constant, no gap transverse field for turning ionized radiation, however significant loads on the habitat and between the coils result in significant structural design architecture and mass. Most toroid configurations result in a large field within the habitat requiring complex shielding from the magnetic field for the crew and electronics. The down-selected 6+1 solenoid coil array and compensator coil configuration minimizes both mass and in the cabin fringe field technical issues. The concept of coil expansion using the Lorentz force with high temperature superconductors enables very large coil diameters to increase the integral BdL of the system for improved dose efficiency while keeping to a reasonable launch mass and simplified assembly. Not only does the compensator coil tune to minimize fringe fields entering the habitat, but also simplifies the coil thermal management system by capturing the radiant heat from the habitat with cryocoolers. As a protection from SPE, analysis was completed for a 6m diameter by 10m length cylindrical habitat that resulted in 141 metric tons of 75 cm thick polyethylene providing similar protection as that from a 6+1 expanding coil array at 8 Tm with a simulated mass of 36 metric tons. The Blood Forming Organ (BFO) dose was ~50 mSv for a 180 hour SPE from October of 1989. This comparison maintained a constant habitable volume vice filling the volume with polyethylene for individual crew protection such as a storm shelter. Dose equivalent results for the 8 Tm configuration are comparable with annual dose equivalents for a spacecraft in LEO with barrel-only BFO results at 309 mSv and total results with nearly naked end caps with an empty habitable volume at 451 mSv. For comparison with the 150 mSv career limit, the body dose equivalent is 232 mSv for the 8 Tm barrel region only and up to 363 mSv if one includes the dose received through the end caps with missing architectural mass. Real GCR reduction has been achieved however, the reduction is not significant enough to provide significantly greater mission duration so more work is needed. Phase 2 intends to refine the vehicle configuration with added spacecraft architecture such as the propulsion system, logistics module, and a crew transfer capsule on the end caps of the habitat, all which is expected to contribute to the overall shielding efficiency of the 8 Tm 6+1 coil configuration. The technology will be considered along with the potential scalability of the 8 Tm coils. External fringe fields will be evaluated and the compensator coil integration with the solenoid array loads analyzed. The magnetic loads and structural design concept will also be considered for engineering feasibility and refinement of the system shielding mass.