The objective is to develop a cryogenic Electro Hydrodynamic (EHD) driven and controlled cooling loop for a detector or for a focal plane assembly (FPA) cooling.

 

Focal plane assemblies for earth observation missions require cooling around 77K to 120K. The cooling is provided by radiators or redounded active coolers (e.g. Stirling or Pulse Tube Coolers). In most cases the component temperature should be stabilized in order to achieve the best performance. In addition, the detectors have to be mechanically decoupled from the rest of the structure and the cooling source to avoid thermo-elastic distortions and disturbances caused by micro vibrations e.g. from active coolers or reaction wheels. Typically this is achieved by coupling the detector to a cold source using a thermal strap. These thermal straps could be quite bulky and heavy to achieve the required performance. The temperature of the thermal interface is then controlled by a heater, which leads consequently to an over-design of the cooling system. For active cooling systems, an extra heat load coming from the redundant cooler has to be accounted for in the cryogenic budget.

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A controllable Electro Hydrodynamic driven loop could answer all of these needs. It will act as a heat switch between the cold interface and the detector while allowing the mechanical decoupling due to the flexibility of the tube and the absence of moving parts. Due to the controllability of the loop flow rate, the heat flux can be adapted to compensate for varying heat load and parasitic heat fluxes without the application of electrical heater power.

 

The overall size and mass is expected to be smaller compare to a thermal strap considering the same thermal conductance performance or vice versa an increase of the thermal conductance performance for the same mass as a conventional strap. An EHP driven loop would provide additional freedom due to the flexibility in piping routing and enable remote cooling. ?

The activity will focus on the development and the miniaturization of a cryogenic pumped (e.g. pumping Methane and/or Nitrogen) loop.

 

An Engineering Model (EM) will be built and will undergo performance testing in a relevant environment and configuration.