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Cryocoolers for Aircraft Superconducting Generators and Motors



Ray Radebaugh


The proposal by NASA to use high temperature superconducting (HTS) generators and motors on future (2035) aircraft for turboelectric propulsion imposes difficult requirements for cryocoolers. Net refrigeration powers of about 5 kW to 10 kW at 50 K to 65 K are needed for this application. A 2010 survey by Ladner of published work between 1999 and 2009 on existing Stirling and Stirling-type pulse tube cryocoolers showed efficiencies in the range of 10 to 20 % of Carnot at 50 K, much less than the 30 % of Carnot needed to make the concept feasible. A cryocooler specific mass less than about 3 kg/kW of input power is required to keep the cryocooler mass somewhat less than the superconducting machinery. Current cryocoolers have specific masses about 3 to 10 times this desired value, even for those designed for airborne or space use. We discuss loss and mass sources and make suggestions where improvements can be made. For Stirling and Stirling-type pulse tube cryocoolers most of the mass occurs in the compressor. We show that higher frequency and pressure can have a major influence on reducing the compressor mass. Frequencies up to about 120 Hz and average pressures up to about 5 MPa may significantly reduce the overall cryocooler size and mass while maintaining high efficiency. Other suggestions for reduced mass are given.
Advances in Cryogenic Engineering


aircraft, cryocoolers, efficiency, machines, pulse tubes, regenerators, Stirling, superconductors, specific mass


Radebaugh, R. (2011), Cryocoolers for Aircraft Superconducting Generators and Motors, Advances in Cryogenic Engineering, [online], (Accessed June 22, 2024)


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Created June 13, 2011, Updated November 10, 2018