[Spaceships] Orion space drive: launch from underwater?

[Ulzgoroth]

Originally Posted by Fred Brackin

If you don't do something stupid that's pretty avoidable.

You probably do still want a dense metal for an outer casing just to help hold things together a little longer with inertia but even lead would do. Perhaps tungsten if you wanted to avoid chemical pollution.

Both have been used in modern thermonuclear bombs. You can gain more explosive power (50% more) by using even depleted uranium but that would be where the great majority of fallout from modern bombs comes from. Use lead for the outer casing (tamper) and you have what's called a "clean" bomb. Use uranium and it's called "dirty" but is twice as powerful.

I don't see how this avoids leaving the neutron-bombarded remains of the bomb.

Irradiated lead or irradiated tungsten still fit that description.