Cryogenic Vacuum Testing of Lunar Rover Drivetrain

In 2016, Ontario Drive & Gear Limited (ODG) and Canadensys Aerospace Corporation completed the design and fabrication of a pair of small to mid-size lunar rover prototypes funded by the Canadian Space Agency (CSA). These lunar rover prototypes were intended to demonstrate the compatibility of the CSA's rover architecture with higher technology readiness levels, with a target of achieving technology readiness level 6 (TRL-6) qualification for the driveline subsystem, including motors, gearboxes, structure, and a compliant, metallic wheel. To that end, a series of thermal vacuum (TVAC) tests was conducted at NASA Glenn Research Center (GRC) and NASA Langley Research Center (LaRC). The first test was conducted at NASA GRC in Cleveland, Ohio, in late 2015. The mid-size VF-13 vacuum chamber used at GRC allowed the equipment to be tested with a lunar simulant present under a variety of thermal scenarios. The drivetrain survived exposure to vacuum and temperature extremes from-175 degrees C to +130 degrees C and was driven approximately 30 km in a dusty environment at temperatures ranging from -70 degrees C to +130 degrees C. The design of the multi-stage non-contact dust seals was proven to be effective. During the first test campaign, one of the position sensor magnets in the motor was displaced after being subjected to -130 degrees C and then operated at +130 degrees C. A review of the motor design was conducted by the manufacturer and the design was subsequently improved to eliminate the failure mode. A subsequent vacuum test was conducted at NASA LaRC to ensure that the failure would not reoccur and that the motor would be able to withstand exposure to lunar night conditions. A motor module assembly, consisting of an updated motor, brake, and gearbox, was installed in the cryo-mechanisms chamber and connected to a dynamometer to apply load. A compliant metallic wheel was also installed in the chamber in a statically-loaded state. The motor was operated under load at temperatures ranging from -70 degrees C to +130 degrees C. Additionally, the motor was exposed to a minimum temperature of -242 degrees C overnight, after which it was again operated successfully at temperatures between -70 degrees C and +130 degrees C, with no degradation in performance observed. The wheel was subjected to temperatures ranging from -149 degrees C to +108 degrees C while under a load of approximately 647 N.