3 ms·

As an alternative, what's the heaviest element they could use that is safe for the environment?

• adrian_b 5y ago
  Xenon is easy to use for this purpose, but it is expensive and it requires much larger and much heavier containers for the same mass, because it must be compressed and liquefied. Iodine has almost the same atomic mass as xenon, but it is much easier to store than xenon (it is solid, but much less dense than mercury), even if it is corrosive. The elements with a closer atomic mass to mercury are difficult to vaporize. It would not be impossible to use any of them in an ionic thruster, but it would be extremely difficult to obtain a high enough ionic flux and a long enough lifetime of the engine.
  • somebodynew 5y ago
    Bismuth might be in a decent spot for optimizing price/density/boiling point/safety if the thruster can be made of molybdenum. I'm not sure if there are more delicate components required to withstand the boiling point of the mass source that can't be made of structural metal.
  • _joel 5y ago
    Krypton is cheaper.
    • adrian_b 5y ago
      It is also much lighter. The question was which are the heaviest usable elements, and those are iodine and xenon. Iodine is also cheap. However the fact that it is not an inert gas like krypton and xenon creates some difficulties, even if those are balanced by its easier storage.