Description: Develop an unheated magnetically-geared motor and an unheated piezoelectric motor that can operate continuously for a long duration at an ambient temperature of -240 ºC (33 K). Magnetically-geared and piezoelectric motors will utilize an inherently lubricant free gearbox at lower temperature for longer times (not including bearings). The rotational actuators will be evaluated in a controlled, reproducible, representative lunar dust environment. Conducting science in permanently shadowed and polar regions of the Moon, on bodies that may possess life, and in orbiting platforms that experience prolonged deep cold when shadowed requires rotational actuators that can operate reliably in extreme cold. Simply heating the actuators will be impractical or highly undesirable, because surface missions on these bodies are expected to be severely power constrained. To stay within mass and volume limits, these mechanisms currently require a mechanical gearbox to convert the low-torque, high-speed output of a small, lightweight motor into the higher-torque, lower-speed excitation demanded by rotational mechanisms (rover wheels, robot arms, drills, gimbals, etc.). Mechanical gearboxes currently require multi-stage dust seals and lubricant on the contacting surfaces of the gears and bearings. This lubricant is either (1) a dry film that causes reductions in life and efficiency or (2) a grease that must be heated to about -60 °C (213 K) or higher, which increases complexity and mass and significantly limits operational capability and the energy available for science. The penalties with dry films can be manageable in bearings but are often significant in gears. Consequently, rotational actuators that utilize non-contact, lubrication-free gearing (e.g., magnetically-geared motors) or eliminate the gearing (e.g., certain piezoelectric motors) can be game changing by enabling long duration missions in extremely cold environments. The overall goal of this project is to develop two complimentary motors to different TRL levels – one magnetically geared (TRL-5) and one piezoelectric (TRL-3) – that can operate for long durations in extremely cold (-240 °C to -60 °C [33 K to 213 K]) environments without supplementary heating. The magnetic motor will be fabricated and assembled along with integration to drive electronics, as well as conduction of performance testing in a relevant lunar surface environment. The piezoelectric motor will be fully designed but not assembled. To emphasize the permanently shadowed regions of the Moon, the project will also seek to improve lunar dust tolerance relative to conventional actuators. The developed motors will be ground tested as separate components and then as a system in a relevant lunar surface environment. The project will impact missions for many destinations and nearly every rotational mechanism.

Benefits: Magnetically-geared and piezoelectric motors will utilize an inherently lubricant free gearbox at lower temperature for longer times (not including bearings), therefore, reducing equipment power requirements, that would have been necessary to heat the gearbox. As an example, grease lubricant for gears & bearings requires heating to >-60ºC and uses 20% of Curiosity’s total energy production on Mars. In addition, the Magentically-geared and piezoelectric motors will have increased lifetimes compared to commercially off the shelf motors that utilize dry film lubricant, as dry film lubricant degrades actuator life. Another benefit is that the system weight (including actuator and wiring) will be reduced. Magnetically geared motor gear ratios will be designed to meet the typical space mechanisms needs, which are gear ratios between 100:1 and 1000:1 Piezoelectric motors will have lower gear ratios. Utilizing Magnetically-geared and piezoelectric motors in rovers, arms, and landers will allow for more power, space, and weight to be available for the science components on the mission