SWaP approach on Thales rotary cryocoolers leading to environmental impact improvements

Environment awareness and eco design principles are increasingly required during the development process of new products. Estimations of a products environmental impact will require a full life cycle analysis. Once the main environmental impacts have been identified, plans can be defined for potential reduction of these impacts. Alternative design concepts will need to be studied and decisions will need to take into account applicable legislation and potential environmental impact. For cryocoolers, besides considerations on used materials, supply chain and transportation aspects, the main influent topics that come to mind are related to the mass, size and power consumption of the final product. Here comes a paradox: further reduction of these characteristics on eco design approach is quite challenging as cryocoolers have been lately widely used in handheld sighting devices where size, mass and power have already been significantly pushed to the limit due to user requirements. Looking back in the recent and young history of cryocoolers, Stirling type mostly, the trend for mass, size and power reduction appears obvious when reviewing some landmark models from the last 40 years. Regarding the Thales range of rotary Stirling coolers, the evolution from the RM8 cooler developed in the eighties to the miniaturized RM2 from the nineties and to the recently released RMs1, is spectacular. These upgrades were possible due to improvements in detectors technologies (new detector materials, IDCA configuration, hot detectors, etc.) but also due to the continuous push to improve cryocooler performances. The combination of both cooler and detector developments enabled the SWaP progress seen in the past years. This paper will review the various environmental impact improvements made on these three generations of coolers: size and weight reduction, efficiency improvement, acoustic behavior, reliability, materials, etc. The analysis will reflect the cooler and its accessories, such as the electronic board.