Radiation shielding of spacecraft in manned interplanetary flights.

During the interplanetary flights the crewmembers will be exposed to cosmic ray radiation with great risk for their health. The absorbed dose due to CR depends on the galactic (GCR) or solar (SCR) origin. GCRs are isotropic and relatively high in energy and deliver a dose nearly constant with time that can be reduced only by means of "heavy" passive protection. The outer walls of the spacecraft usually shield the SCRs up to a few tens of MeV, but during some exceptional solar bursts, a great number of particles, mainly protons, are ejected at higher energies. In this case the dose delivered in a few hours by a solar burst can easily exceed 1 year cumulated dose by GCRS. The high-energy component of SCRs is quasi-directional so that a shielding system based on a superconductive magnetic lens can reduce the daily dose of SCRs to the level delivered by GCRS.