Use of Modular Heat Source Stack in RTGs

The use of stacked heat source modules in RTGs requires a structural support system which holds the stack together during launch, but allows it to disassemble when the generator housing melts during reentry. This is a much more difficult support problem than in the case of a monolithic heat source. A proposed, light-weight scheme for solving this problem is described, and illustrated with an actual RTG design for a specific mission. A detailed analytical model of the RTG and the spacecraft to which it is attached was constructed, and a NASTRAN analysis was carried out to assess the structural performance of the heat source support scheme under differential thermal expansion and dynamic launch loads, and to determine the system's characteristic frequencies, the loads transmitted to the RTG, and the resultant stresses and displacements. The analytical results presented confirm the structural feasibility of supporting a long heat source stack without intermediate support