An innovative cryocooler is under development that promises to provide high efficiency 4K-10K cooling for space-based focal plane arrays. It is based upon a novel modification of the Collins cycle, which is commonly used in large-scale high-efficiency terrestrial cryogenic machines. Cryogenic machines based on the conventional Collins or Brayton cycles routinely operate with input powers of about 740 Watts per Watt of refrigeration at 4K. Currently available
small-scale cryocoolers capable of about 1W of cooling at 4K typically require 5kW - 7.5kW per Watt of cooling. Microelectronic technology is employed in the modified cycle to enable a reduction in scale and mechanical complexity while retaining the high efficiency potential of the conventional Collins cycle. The modified Collins cycle is a continuous, or DC, flow device. This eliminates the need for the costly exotic alloys used in the regenerators of periodic, or AC, flow pulse-tube and Stirling type cryocoolers. It also permits separation of the cryocooler cold head from the load without a significant thermodynamic penalty, thereby enabling vibration isolation and the potential for improved system integration. An engineering prototype is currently undergoing development testing to demonstrate the potential of this concept to provide cooling at 10K and below. This paper will present the major design concepts employed in the engineering prototype, the results of initial engineering prototype development testing, as well as a discussion of the benefits of this approach and the anticipated space-based and terrestrial applications.