What we can learn from heavy ion therapy for radioprotection in space.

A major problem in manned space flight is the impact of cosmic radiation, especially that of heavy charged particles since they have an elevated biological efficiency (RBE). The RBE estimation determines the potential exposure for man. It is one of the limiting factors for space flight and should be known very precisely. The same is true for heavy-ion tumor therapy where beams of carbon ions are used to treat deep-seated tumors. There, RBE values determine the dose distribution and are estimated using the Local Effect Model (LEM). The clinical results confirm the correctness of LEM and suggest to use the same theoretical approach to assess the impact of cosmic rays.