Design and Test of the VIPER Mobility Actuators

The Volatiles Investigating Polar Exploration Rover (VIPER) completed qualification in September 2024 for operation at the Lunar South Pole region with the capability to explore permanently shadowed regions (PSRs) and detect surficial and sub-surface volatiles. VIPER’s three mobility actuators integrate into a single “mobility module” assembly to provide actuated suspension, steering, and drive to each corner of the four wheeled, 450-kilogram scientific platform. These three unique actuators were developed in-house at NASA’s Johnson Space Center (JSC) and leverage commercial-off-the-shelf (COTS) elements. By critical design review (CDR) in September 2021, each mechanism engineering unit had demonstrated technology readiness level (TRL) 7 criteria. Four flight units were delivered for system integration after acceptance testing in May 2023 with a fifth qualification unit completing testing in parallel with flight vehicle integration. TRL 8 criteria was achieved through integrated system acceptance testing in September 2024. This paper focuses on a review of unique design elements for each actuator including drive train components, mechanism feedback sensors, hold-down and release methods, dust mitigation, thermal control and mitigation, and testing methodology. Additionally, this paper provides insights into the mobility architecture chosen for VIPER’s mission profile and its impacts on the mobility module requirements and design. Lessons learned from each stage of the development process are shared throughout.