Future surface missions will require accessing new extreme environments which reach cryogenic temperatures. The Cold Operable Lunar Deployable Arm (COLDArm) system and component technologies can enable future missions in these extreme environments, including lunar night and Ocean Worlds. Here we report on the design, fabrication, and initial testing of the COLDArm system. The project is funded through the Lunar Surface Innovation Initiative (LSII) and managed by the NASA Space Technology Mission Directorate (STMD) Game Changing Development (GCD) program. The COLDArm system is developed with industrial partner, Motiv Space Systems, Inc (Pasadena, CA). The robotic arm leverages a design similar to the Mars Phoenix and Mars InSight robotic arms. The arm is four degrees of freedom (DOF), approximately two meters in length, and has a tip force greater than 40 newtons in the primary workspace. The significant innovation of the robotic arm is the ability to work in cryogenic environments without heaters. Eliminating heaters provides the benefits of reducing system energy needs and removing heat from mechanisms located near volatile sample collection locations. The robotic joints include a planetary gearmotor and strainwave gear which utilize bulk metallic glass (BMG) gears to eliminate the need for heaters. Both the BMG planetary gearmotor and BMG strainwave gear have been successfully demonstrated at cryogenic temperatures. Additionally, the Dual-Axis Controller for Extreme Environments (DACEE) motor controller also eliminates the reliance on a warm electronics box (WEB). The DACEE motor controllers have also been successfully demonstrated at cryogenic temperatures. A Robotic Avionics and Sensor Kit (RASK) is located on the baseplate in a WEB. The RASK leverages the avionics design used on the Ingenuity Mars Helicopter which has been successfully demonstrated on Mars. COLDArm specific functionality has been added, including a 4-k resolution stereo camera pair and a force torque sensor (FTS) interface. Flight software (FSW) was also developed which leverages the Ingenuity FSW utilizing the F prime framework. An end effector was designed in collaboration with Kennedy Space Center (KSC) and Glen Research Center (GRC) to collect geotechnical properties from the lunar regolith. End effector features include a scoop and geotechnical tool geometries to enable measurement of regolith properties such as bearing capacity, angle of repose, shear strength, and pressure-sinkage parameters. The geotechnical scoop tool was designed for Titanium additive manufacturing in collaboration with Marshall Space Flight Center (MSFC) following NASA-STD- 6030. A cryogenic capable FTS is located at the end effector to collect six-axis load information during the ground interactions. This FTS leverages the design from Mars 2020 and has been demonstrated at cryogenic temperatures. After fabrication and integration of the system, check-outs in the lab environment confirmed basic functionality of the system. Advanced functional testing was completed in the Jet Propulsion Laboratory (JPL) Lunar Advanced Robotics (LunAR) Lab, including ground interaction demonstrations with GRC-3b lunar regolith simulant. These ground interactions demonstrations included large surface pressure sinkage, angle of repose, and shear tests.
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