Metallic Hydrogen

Metallic Hydrogen is an advanced future concept for rocket fuel with a very high specific impulse, with a theoretical specific impulse of 1700 s at a chamber pressure of 100 atm.

metallic hydrogen is not a typical metal as it requires the use of degeneracy pressure, a quantum mechanical quirk of matter under extreme conditions.

Metallic hydrogen has not yet been produced on Earth, but researchers may soon achieve this goal and determine its characteristics. If it proves to be usable as a rocket propellant with the anticipated specific energy, then engines and launch vehicles can be designed to use this propellant. The high specific energy creates chamber temperatures too high for currently available engine materials but diluting the propellant can reduce the chamber temperature.