interactions may cause space charge. The major interaction of concern is differential charging of various parts of a spacecraft, leading to high electric fields and arcing between spacecraft components. This can be resolved with well placed plasma contactor. However, there is no solution yet for when plasma contactors are turned off to allow maintenance work on the hull. Long term space flight at interstellar velocities causes erosion of the rocket's hull due to collision with particles, gas, dust and micrometeorites. At 0.2 for a 6 light year distance, erosion is estimated to be in the order of about 30 kg/m2 or about 1 cm of aluminum shielding. See also Nuclear photonic rocket References Antimatter Rocket propulsion