Abstract
We address the issue of radiation produced by post-operation radioactive actinides, daughter products, and fission product decay from an intact re-entered reactor. Specifically, we sought to identify orbits in which a nuclear powered spacecraft could be placed such that its orbital lifetime would be long enough to allow the radioactive inventory it carries to decay to acceptable levels. We also evaluated the infrastructure required for transferring the nuclear vehicles to the required operational orbit, and the space environment that would be encountered in that orbit. We found that for nuclear-thermal propulsion NERVA vehicles, the minimum required altitude for initial basing and Earth escape is 500 to 600 km; for final end-of-life storage, the required altitude is about 1000 km. For a 10-MWe nuclear-electric propulsion (NEP) vehicle, the basing node for initial operation is 800 km and the firal final end-of-life storage altitude is 1100 km; higher-power NEP vehicles require basing at even higher altitudes. The infrastructure required to transport nuclear vehicles to their initial operational orbits is a small fraction (less than 10 percent) of the total mass transferred. Finally, debris impacts may represent a serious risk to vehicles at altitudes on the order of 1000 km. For example, a vehicle the size of a NERVA or 10-MWe NEP vehicle could be expected to suffer one impact every ten days, with larger vehicles suffering proportionally more impacts. Thus, only short-term basing of vehicles at altitudes around 1000 km should be considered for active vehicles. although end-of-life storage of used vehicles should be acceptable. © 1991 American Institute of Aeronautics and Astronautics, Inc.