Magnetic Shielding of a Compact HTS Magnet for Deployment in Low-Earth Orbit

Magnets using high-temperature superconducting (HTS) tapes have been proposed for use in several space-borne applications. In particular they are well suited for use in applied-field magnetoplasmadynamic (MPD) thrusters for satellites as they can achieve a high magnetic field intensity in a suitable volume and mass range and can be cooled by commercial-off-the-shelf space-heritage Sterling cryocoolers. However, the stray fields produced by such magnets can be problematic, in that they can generate undesirable torque through interaction with the Earth's magnetic field and can interfere with other on-board systems and electronics. We present the design and initial mass optimization of a passive DC magnetic shield for a small HTS magnet that could fit within a 12U cubesat but will in the first instance be tested on board the International Space Station (ISS) in 2025. The magnet has a 62 mm diameter clear bore, compatible with a small MPD thruster, and will generate the target central field of at least 300 mT. The stray field from this magnet would be 1.7 mT at a distance of 220 mm from the center of the magnet and a magnetic shield is required to reduce this to 0.3 mT to comply with ISS specifications. We describe active and passive shield options, and choose ultimately to construct a passive shield from magnetic low-carbon steel and confirm that this is able to achieve the required stray-field level.