Space Station ATCS Radiator Rotation Profiles in LVLH TEA/LVLH, Arrow and Gravity Gradient Mode

This study assessed Active Thermal Control System Central Thermal Bus radiator rotation profiles for the Space Station Freedom in Local Vertical/Local Horizontal, two Torque Equilibrium Attitudes (MB11 and MB17), Arrow and Gravity Gradient modes while maintaining radiator angular velocities and accelerations under 45 degree/minute and 0.01 degree/sec², respectively. To determine the thermal influence of the Flex Hose Coupler (FHC), cases ran with the ±105° radiator orientation restriction as imposed by the coupler.

The study used hot thermal environments and End-Of-Life panel properties. The model used was structured to produce radiator profiles that are as close as possible to an instantaneous and local minimum environment without violating the maximum angular rotation imposed.

The results from all the investigated cases indicate that the radiator should be allowed to rotate between -167° (Gravity Gradient mode) and 207° (Arrow mode). This envelope is needed in order to minimize the environmental incident fluxes on the radiators and maximize the radiator heat rejection capabilities. During Arrow and Gravity Gradient flight mode attitudes, the radiator profiles which could minimize the environmental impacts throughout the orbit were found to exceed the FHC ±105° envelope. Two of these profiles were then modified and used in a SINDA/FLUINT model to assess their thermal impact during transient conditions. They were found to reduce radiator heat rejection capabilities by at least 45.2%. However, considering the planned space station power down during arrow reboost, station requirements are still met.