On-Orbit Simulations of a Superconducting Magnet for Space Propulsion on the International Space Station

Applied-field magnetoplasmadynamic (AF-MPD) thrusters represent a promising category of electric propulsion for satellites and spacecraft, boasting high-power, efficiency and specific impulse. These thrusters use electric fields and strong external magnetic fields to propel plasma to substantial velocities. The integration of high-temperature superconducting (HTS) electromagnets plays a pivotal role in minimising the mass, power, and volume requirements of AF-MPD thrusters, facilitating their application in space. To validate this critical technology, a collaborative effort led by the Paihau-Robinson Research Institute and Nanoracks LLC aims to send an HTS magnet to the International Space Station (ISS), titled the 'Hēki magnet mission.' Taking advantage of the Nanoracks External Platform (NREP), this technology demonstration will validate and mitigate risks associated with the use of miniaturised cryocoolers, HTS magnets and flux pumps in space. This endeavour marks a crucial advancement towards the in-space utilisation and potential commercialisation of HTS-powered thrusters. This paper presents on-orbit simulations of the thermal and electromagnetic performance of the Hēki payload. We developed thermal models to resolve the complex radiative thermal environment in space on-board the ISS to ensure that a 90 W miniaturised cryocooler can successfully cool an HTS magnet to a 75 K operating temperature, and we simulate the design of thermal radiators to prevent the cryocooler from overheating. We also investigate the time varying changes to the thermal environment in space as a function of ISS orbital changes throughout the year. Circuit and electromagnetic models of the HTS magnet and flux pump were developed to inform of the required performance to meet our mission goal of generating a central field of 0.3-0.5 T. Critical safety considerations are also simulated, such as a magnet quench because of a sudden loss of power, and the design of a rapid de-energisation system.