The multipactor effect has been on the European Space Agency's (ESA) list of concerns for more than 40 years. It is an avalanche of electrons that occurs in vacuum, inside components such as antennas or waveguides, and can ultimately cause irreversible damage to equipment.
For decades, the standard solution has been to coat these parts with Alodine, a chromium-based compound that offers good protection but is harmful to the health of those who handle it and to the environment. European authorities have long been pushing for its ban, although none of the alternatives proposed so far has managed to match its technical performance.
