Our proposed cryocooler development effort will support NASA's long-term goal to increase aircraft efficiency and reduce aircraft emissions and noise. By providing a cryocooler capable of cooling MgB2 systems and optimized to meet the aggressive power density target required for aircraft, we will enable an alternative approach to HTS systems and allow a detailed evaluation of the relative advantages of HTS and MgB2 superconducting technologies. Such an evaluation is needed to clarify the road map for superconducting aircraft. While such aircraft are still two or three decades from production, supporting technology development needs to begin now if such aircraft are to become a viable alternative to the aircraft configurations in production today. The results of this SBIR project will support continuing NASA design trade studies, system demonstrations, and eventual superconducting aircraft demonstrations. Other NASA applications include space applications such as hydrogen cryogenic liquefaction and storage for planetary and extraterrestrial exploration missions, CEVs, extended-life orbital transfer vehicles, in-space propellant depots, and extraterrestrial bases. Terrestrial NASA applications include cooling for spaceport cryogen storage and transportation systems. The highly reliable and space-proven turbo-Brayton cryocooler is ideal for these applications. Superconducting materials have the potential to revolutionize the way we generate, transmit, and consume power. Transformational initiatives that rely on superconducting technologies include power conditioning and power transmission systems, large-scale offshore wind turbines, high efficiency data centers, Navy ship systems, and turboelectric aircraft. While the latter is the target application for the proposed cryocooler, the other applications represent potential near-term markets for the technology. Companies are currently pursuing approaches based on either HTS or MgB2 superconducting materials. The low-temperature cryocooler proposed here will support MgB2 systems, which offer a number of advantages over HTS systems including lower cost and reduced losses in varying magnetic fields. The 15 K operating temperature of these systems makes the cryocooler a critical component of any solution. There is also a large potential market beyond superconducting applications, including cooling for laboratory and industrial-scale gas separation, liquefaction, cryogen storage and cryogen transportation systems, liquid hydrogen fuel cell storage for the automotive industry, and commercial orbital transfer vehicles and satellites.