Thermal Control

OMS thermal control is achieved by insulation on the interior surface of the pods that enclose the OMS hardware components and the use of strip heaters. Wrap around heaters and insulation condition the crossfeed lines. The heaters prevent propellant from freezing in the tanks and lines. The heater system is divided into two areas: the OMS/RCS pods and the aft fuselage crossfeed and bleed lines. Each heater system has two redundant heater systems, A and B, and is controlled by the RCS/OMS heaters switches on panel A14.

Each OMS/RCS pod is divided into eight heater areas. Each of the heater areas in the pods contains an A and B element, and each element has a thermostat that controls the temperature from 55 to 75 F. These heater elements are controlled by the left pod and right pod switches on panel A14. Sensors located throughout the pods supply temperature information to the propellant thermal CRT display and telemetry.

The crossfeed line thermal control in the aft fuselage is divided into 11 heater areas. Each area is heated in parallel by heater systems A and B, and each area has a control thermostat to maintain temperature at 55 F minimum to 75 F maximum. Each circuit also has an overtemperature thermostat to protect against a failed-on heater switch. These heater elements are controlled by the respective crsfd lines switch on panel A14. Temperature sensors near the control thermostats on the crossfeed and bleed lines supply temperature information on the propellant thermal CRT display and telemetry.