A High-Capacity Turboalternator for Turbo-Brayton Cryocoolers

Future DoD cryogenic cooling applications include space missions with relatively large cooling demands. These include space-based lasers, orbital transfer vehicles requiring cooling of stored fuels, and space-based platforms using large arrays of infrareddetectors. Loads for these applications will range from several watts to tens of watts. Temperatures of interest are between 10 and 100 K. Current reverse turbo-Brayton cryocoolers are optimized for a limited range of loads and temperatures,significantly below those of future high-capacity applications. In order to meet future needs for high-capacity cooling, additional research and development must be performed on the turboalternator, a key component in the system. This proposal addressesthe development of a high-capacity turboalternator. In Phase I, key turboalternator performance parameters and loss mechanisms were quantified. During Phase II, we propose to develop and test an advanced turboalternator optimized for a particularhigh-capacity, low-temperature application. The turboalternator will be installed in an existing Engineering Design Model cryocooler and the performance of the cryocooler will be quantified over a wide range of temperatures. The cryocooler test resultswill be used to set a baseline for scaling the system to other applications and to identify design features that require modification for other loads and temperatures.