It goes up to 1,344 °C with Li, I think—it's a very different engineering space from the stuff on Earth. The Soviet ones used K (or maybe NaK eutectic); there'

It goes up to 1,344 °C with Li, I think—it's a very different engineering space from the stuff on Earth. The Soviet ones used K (or maybe NaK eutectic); there's a ring of potassium metal dust around the Earth people track by radar (highly reflective)—a remnant from one of them exploding.