Development of a Small Stirling Cycle Cooler for Spaceflight Applications

Abstract

This paper describes the development, from a previously proven design approach, of a robust and simple Stirling cycle cooler with long life potential. The need for a closed cycle refrigerator for use in a spacecraft borne infra-red radiometer is explained. The refrigerator is to supply 1 watt of cooling at 80 K for less than 80 watts of input power, be able to survive the launch environment and subsequently run for 26000 hours. Clearance seals achieved with a spring suspension developed from earlier space proven mechanisms have led to the production of a linear split Stirling cycle machine with no apparent life limiting features. A servo control system, in conjunction with moving coil motors and LVDT position sensors, permits running of balanced pairs of mechanisms. The working fluid, helium at a pressure of 1.2 MPa, is contained within titanium bodies having gold O-ring seals. A vacuum bakeout procedure, based upon experience and outgassing trials, reduces residual contaminant release to acceptable levels. A prototype refrigerator has been subjected to a vibration test and has subsequently run for 6000 hours with no detectable change in performance.

Experimental Demonstration of Cryogenic Cooler Disturbance Attenuation Using the Non-Linear Passive Isolation System

“…[1][2][3][4] The major advantage of cryocoolers in comparison with Stirling-type coolers is the omission of any moving part in the cold head, which results in a significantly increased mean time to failure (MTTF). Besides these advantages, a secondary benefit is the low vibration output, which is essential for highly sensitive detectors.…”

Development of high performance moving-coil linear compressors for space Stirling-type pulse tube cryocoolers

“…The clearance seal, which refers to the radial clearance between piston and cylinder is always maintained during operation, can effectively achieve the dynamic seal between the piston and cylinder while avoiding any contact of them, thus radically eliminating the source of rubbing wear and the necessity of oil lubrication [33,34,[40][41][42][43]. The clearance seal is maintained by the mechanical suspension system mainly constituted by flexure springs, which are then manufactured by the appropriate material and designed with the peak stress safely below its fatigue limit so that the mechanical suspension system has a theoretically infinite life.…”

“…clearance seal and flexure springs, were put forward by the researchers from the Oxford University at the time of the invention [40][41][42][43].…”

Low vibration microminiature split Stirling cryogenic cooler for infrared aerospace applications

“…The best available space cryocoolers rely primarily on the historical "Oxford" heritage [1][2][3], where the closed cycle Stirling refrigeration is achieved by a cyclic compression and expansion of a gaseous working agent produced by the almost sinusoidal reciprocation of compressor and expander pistons. Resulting from the imbalanced motion of the above mechanical components is the vibration export, the instantaneous magnitude of which is the product of moving mass and instantaneous acceleration [4].…”