工学：ヨウ素を推進剤とした電気推進宇宙探査機の実証試験が地球周回軌道上で行われた

The performance of spacecraft that use electric propulsion systems may be enhanced by using iodine, rather than the more-expensive and difficult-to-store xenon, suggests a Nature paper. The findings demonstrate the advantages of using iodine as an alternative propellant within the space industry.

Electric propulsion uses electric power to create thrust from a propellant. Currently, xenon is the propellant of choice, but it is rare, requires pressurized storage and commercial production is expensive. For the long-term sustainability of the space industry, finding a replacement propellant is important. A possible alternative could be iodine, which is cheaper, more abundant and can be stored as a solid. Iodine has been shown to achieve higher efficiency than xenon in ground-based tests, but full in-orbit operation of a spacecraft entirely propelled by an iodine electric propulsion system has not yet been reported.

Dmytro Rafalskyi and colleagues report the successful in-orbit operation of a small satellite with a propulsion system based on iodine. The propulsion system was operated in space to guide a 20-kg CubeSat satellite, launched on 6 November 2020, with manoeuvres confirmed using satellite tracking data. Iodine is shown not only to be a viable propellant, but also to achieve higher ionization efficiency compared to xenon.

This demonstration could accelerate the adoption of alternative propellants within the space industry and shows the potential of iodine for a wide range of space missions, the authors suggest. For example, iodine enables substantial system miniaturization and simplification, which provides small satellites and satellite constellations with new capabilities for deployment, collision avoidance and end-of-life disposal.