The Limits of Space Radiation Magnetic Shielding: An Updated Analysis

A major problem of long-duration manned missions in the deep space is the flow of high energy charged particles of solar (SPE) and galactic (GCR) origin. SPE has short duration but can be extremely intense and can lead to acute, even lethal, effects. GCR flow is much less intense but is continuous, isotropic, and more energetic; it increases the risk of carcinogenesis and can affect the nervous and cardiovascular systems, restricting the endurance of missions to few months. It is commonly believed that the problem of space radiation can be solved by surrounding the spacecraft habitats with large superconducting magnets, even though a considerable technological effort would be required. However, magnetic shielding has several basic limitations, which restrict the reduction of the radiation dose: they range from the biological effect of the particles in the high region of the GCR spectrum, higher than the shield cutoff energy, to the generation of secondary particles due to the interaction of cosmic rays with magnet and spacecraft materials. The physical and technological constraints of space radiation magnetic shields are discussed in this paper. Despite such limitations, a superconducting magnet could completely eliminate the risk due to SPE. Moreover, it could reduce the GCR adsorbed dose enough to make acceptable the risk of developing long term diseases after a return trip to Mars.