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Testbeds and technologies for potential Mars orbital sample capture and manipulation

Potential future Mars Sample Return (MSR) missions could collect planetary samples and launch them into Mars orbit; in a follow-on mission, a spacecraft could rendezvous with the orbital sample (OS) to return the samples to Earth. Due to planetary protection requirements and the need to position the OS in a preferred orientation for Earth re-entry, the rendezvous phase would present a number of technical challenges. To address these challenges, this paper presents a new end-to-end testbed elements demonstrating new technologies for 1. capture of the OS within the spacecraft, 2. orientation of the OS, and 3. stowage of the OS to a Primary Containment Vessel (PCV) and internal transfer of the PCV within the spacecraft to an Earth Return Module (ERM). The end-to-end testbed consists of a 3 DOF planar robotic arm, a capture cone volume, two interchangeable orientation mechanisms, and two interchangeable internal transfer mechanisms. To simulate zero gravity during the capture stage, a cyber-physical approach is used here that fuses simulation, hardware, and autonomy elements. During the capture stage, contact dynamics of the OS with the capture cone and robotic arm end-effector is simulated using high-fidelity multibody dynamics simulation software in-the-loop. The output of the simulation is used to control the state of the physical OS in real-time using a 3 DOF robotic gantry. Additionally, the end-effector of the robotic arm is equipped with a force-torque sensor and camera to detect contact and track the OS. In the second stage, two novel mechanisms demonstrate successful orientation of the OS. In the first orientation mechanism, wipers sweep the surface of a spherical OS to engage a positive feature, thereby manipulating the OS into a preferential orientation. In the second orientation mechanism, two sets of cups selectively engage and rotate a spherical OS about two orthogonal axes; the mechanism can be operated autonomously using computer vision or interactively with a human operator in-the-loop. Finally, in the third stage, two novel mechanisms demonstrate successful internal transfer of the OS within the spacecraft volume. The internal transfer motion requires 3 DOF (rotation, translation and release of the OS). In the first internal transfer mechanism, each DOF is independently controlled using three actuators. In the second internal transfer mechanism, the 3DOF are coupled mechanically using a single actuator.