Flux Pinning Concepts for On-orbit Capture and Orientation of an MSR Orbiting Sample Container

Concepts for on-orbit capture and orientation of a Mars orbiting sample container (OS) using flux pinning were developed as candidate technologies for potential Mars Sample Return (MSR). The systems consist of a set of type-II superconductors field cooled below their critical temperature using a cryocooler, and operate on an orbiting sample container with a series of permanent magnets spaced around the exterior, along with an integrated layer of shielding to preserve the magnetic properties of the returned samples. Benefits of the approaches include passive, non-contact capture and orientation, as well as a reduction in the number of actuators relative to various mechanical methods. System prototypes were developed, characterized, and tested in a microgravity environment to demonstrate feasibility. Flux pinning models were developed that accounts for magnet geometry, superconductor geometry, superconductor training geometry, superconductor temperature, superconductor material properties, and magnetic field shape, and output forces and torques the superconductors imparts on the OS via the magnets. Magnetic models of the OS were developed to evaluate magnetic shield effectiveness and demonstrate successful shielding of the sample. A vision system using AprilTag fiducials was used on a free-floating OS in a microgravity environment to estimate relative OS position and orientation while in motion. Integrated Capture, Containment, and Return System (CCRS) Capture and Orient Module (COM) payload concepts for an Earth Return Orbiter (ERO) using flux pinning were proposed and assessed based on relevant system evaluation criteria, such as mass, actuator count, and power consumption.

1. Introduction

Making significant progress towards Mars Sample Return (MSR) was highlighted as a high-priority goal for the decade 2013–2022 by the 2011 Planetary Decadal Survey [1]. A notional MSR campaign architecture, as shown in Fig. 1, consists of four elements: the Mars 2020 rover to acquire a set of samples and place them in a series of depots on the ground, a Sample Return Lander (SRL) with a fetch rover to recover the samples and launch them into Mars orbit in an Orbiting Sample (OS) container aboard a Mars Ascent Vehicle (MAV), an Earth Return Orbiter (ERO) to retrieve the OS from Mars orbit (see Fig. 2) and return it to Earth within an Earth Entry Vehicle (EEV), and a Sample Return and Science element consisting of a Mars Returned Sample Handling Facility to recover, receive, and curate the return samples. Figure 2.

Artist's concept of orbiting sample (OS) capture in Mars orbit (credit: D. Hinkle).