Aircraft Propulsion Motors With Cryogen-Free Superconducting Rotor

Hinetics is developing a cryogen-free superconducting electrical machine architecture that promises the efficiency and power density benefits enabled by superconducting technology, while greatly simplifying the cryogenic system and eliminating nearly all auxiliary overhead. The resulting architecture eases system integration for air-borne platforms, reduces heat rejection requirements, and, critically, opens the door to industrial applications that may provide an opportunity to collect long-term reliability data in the field and grow public confidence in superconducting machines prior to future flight demonstrations. The superconducting rotor is self-contained, with field coils conduction-cooled by a compact commercial-off-the-shelf (COTS) cryocooler and a permanently-sealed vacuum system. The slotless stator contains Litz wire made from resistive conductors and is cooled by either above-ambient fluid or a cryogenic fluid. Over the past three years, the team has worked to de-risk each sub-system in the multi-megawatt CRUISE and CHEETA machines. As a final, system integration de-risking step, the team built a sub-scale version of the machine architecture and demonstrated the world's first fully-integrated, cryogen-free superconducting motor in April 2025. This paper presents details on construction of the sub-scale motor and results from a long-duration test campaign to assess reliability and identify areas of improvements prior to final assembly of the full-scale CRUISE and CHEETA motors.