Moveable Thermal Joints for Deployable or Steerable Spacecraft Radiator Systems

A possible solution to handle the heat dissipated by the batteries of the Columbus Polar Platform is to equip each battery ORU (Orbital Replacement Unit) with a dedicated heat pipe radiator. Such a radiator, being stowed during launch, has to be deployed in orbit and might be chosen to be steerable to achieve maximum radiator performance, hence minimum radiator size. In such radiator systems the coupling between battery and deployable or steerable radiator has to incorporate a rotatable or flexible thermal joint. Drivers for the design of such joints are a low thermal resistance, hence a limited temperature drop across the joint to optimize radiator size, and a small deployment/retraction torque or steering torque.

Different concepts for moveable thermal joints are described and quantitatively discussed.

Concepts identified as possible candidates for near-term application are:

• the flexible heat pipe;
• the braided conductor;
• the, hydraulically or mechanically, clamped joint;
• the low melting point alloy filled, grease filled or (low pressure) gas filled (finned) heat exchanger.

Concepts for non-near term applications turn out to be:

• the radial heat pipe (condenser rotatable with respect to evaporator);
• the oscillating hydrodynamic joint (flexible or rotatable);
• the rollable membrane radiator;
• the articulated or split heat pipe.