Hi IsaacKuo, post 2: I agree, except future technology may be able to approximate miminal mass shielding at 10 or 20% of the mass based shielding, besides serving other functions. The Magsail calculations for a 50 kilometer super conducting loop used a 100megawatt nuclear power plant to charge the loop in two days, if I recal correctly. The 100 megawatts would be useful for other purposes between rare days it would be needed to charge the super conducting loop. Some energy is needed continously to reliquify oxygen. The loop can also perform minor station keeping and attitude adjustment for the colony. A better mid temperature superconductor may be available soon. Even at present, liquid oxygen could be used to cool the 50 kilometer mag sail loop. A large reserve of liquid oxygen would be a valuable commodity for the colony. That large a loop can likely direct nearly all the solar wind away from all of the colony and produce a small volume of reduced galactic cosmic rays. Colonists will likely have to accept slightly reduced life expectancy due to radiation exposure. Neil