Ane Aanesland and Dmytro Rafalskyi pioneered the use of iodine as a propellant for innovative satellite electric propulsion systems. Based on research work they originally performed at the Laboratoire de Physique des Plasmas at Ecole Polytechnique in France, they founded the company ThrustMe in 2017 to commercialize a new iodine propulsion technology. The system developed makes use of solid iodine propellant, which is then sublimated to form iodine gas. A plasma is then created using a radio-frequency inductive antenna, and positive iodine ions are extracted and accelerated with a set of high-voltage grids to produce thrust. After several years of development, the world’s first iodine electric propulsion system was launched into space on 6th November 2020 and subsequently successfully demonstrated in orbit. The results have recently been published in the leading scientific journal, Nature: less than a week after publication, the paper was already ranked within the top 5% of all articles ever tracked in terms of online media impact, and resulted in several hundred news articles and media interviews.
This new plasma-based technology is a major achievement for the space industry, and the impact of this work cannot be overstated: The electric propulsion system developed makes use of solid iodine propellant, which is sublimated to form iodine gas. A plasma is then created using a radio-frequency inductive antenna, and positive iodine ions are extracted and accelerated with a set of high-voltage grids to produce thrust. The use of iodine creates several complex challenges, which have required innovative solutions and fundamental physics investigations. Javier Martínez Martínez, as a senior engineer at ThrustMe, played a critical role by solving problems associated with corrosion, storage in space, and flow control. Within the space industry, high-performance electric propulsion systems have traditionally used xenon as the propellant. However, in contrast to iodine, xenon is very expensive, about €2500/kg; commercial production is limited; and it must be stored under very high pressure, typically one or two hundred times atmospheric pressure.
It is estimated that more than 24 000 satellites will be launched into space over the next ten years, and most will require propulsion systems. Space industry demand for xenon alone is anticipated to soon outpace supply, and it is critical that a viable replacement propellant be found. Iodine was identified over twenty years ago as a possible alternative to xenon but until now, despite being investigated by companies, space agencies, and universities around the world, no iodine propulsion system has ever been tested in space. Iodine is acknowledged as a transformative propellant. It is about a hundred times cheaper than xenon; it can be stored unpressurized as a solid, with a storage density almost three times higher than xenon; and is abundant, with global production around five hundred times higher than xenon. With growing space industry demand, and the rise of satellite mega-constellations, iodine will play a vital role in ensuring a sustainable space industry. In addition, because it can be stored as a solid, iodine enables substantial subsystem simplification and miniaturization. This allows a complete propulsion system to be provided to even very small satellites, and gives them a new capability for collision avoidance and for deorbiting to prevent space debris build-up. The high performance offered by an iodine plasma propulsion system will also enable advanced orbital manoeuvring for larger satellites, which will prove vital in the coming decades as humanity returns to the Moon and expands further into space.
It is impressive to see how Ane and Dmytro have taken their fundamental plasma research and, with the help of Javier, turned this into a product that is now available on the market and which has already gained significant commercial traction since its first demonstration in space.