British Scientists think they are close to creating Metal Hydrogen.

Hydrogen, in it’s natural state (in Earth conditions) is a gas, oh course. Even cooled right down, you get liquid hydrogen; I guess if you get down further you get Hydrogen ice.

But by squashing hydrogen between two gems at a staggering pressure of 3.5 million atmospheres, they have forced the hydrogen molecules to rearrange into a lattice that is close to being a (presumably solid) metal.

Liquid hydrogen has the highest ISP of any rocket fuel (that is, it’s pound for pound the most efficient. But it has some drawbacks

•  It has to be stored under high pressure, and the storage and piping apparatus are therefore necessarily quite heavy, adding to the mass of the spacecraft
• It is difficult to store over long periods, as is any cryogenic fuel
• It’s prone to explode!

I haven’t read the exact properties of metal hydrogen, but if it easy to store, and either is easy to return back to it’s gaseous state or could react with an oxidiser directly, it could be a seriously good rocket fuel