Diagram shows flow of heat through the Thermal Loop system.

This advanced temperature control system can transport large heat loads over long distances with small temperature differences and without external pumping power for circulation of liquid coolants. Key to this system is a loop heat pipe with multiple, small evaporators (with outer diameters of 9 mm), multiple condensers, and thermoelectric converters. The loop heat pipe collects heat generated within a spacecraft and transmits the heat to radiators for dissipation to space or to components that require additional heat. The thermoelectric converters control the system temperature within a tight range. The system can cool the "on" instruments and warm the "off" instruments simultaneously without using auxiliary electrical heaters, while maintaining all instruments at the same temperature.

The Thermal Loop retains all the operating characteristics and advantages of the state-of-the-art loop heat pipe (LHP) and offers many additional advantages:

1. The mass, volume and control heater power are reduced.

2. Multiple evaporators in a single LHP provide a single interface temperature to all instruments and allow the "off" instruments to receive heat from the "on" instruments, eliminating the need for supplemental heaters.

3. Multiple condensers allow the radiators to be placed at different locations and can be exposed to different heat sinks.

4. The flow regulator switches vapor flow between condensers and prevents unwanted heat from being transmitted back to the instruments.

5. Thermoelectric Coolers (TECs) enhance LHP start-up success and provide tight operating temperature control.

6. The coupling block allows the liquid returning from the condensers to the evaporators to absorb heat from the vapor leaving the evaporators, improving efficiency by reducing the control heater power required to maintain a constant operating temperature.

The Thermal Loop therefore enhances the functionality, versatility, and reliability of the state-of-the art LHPs, while offering the low mass, low power, and compactness necessary for future spacecraft.