Having long moved away from fossil fuels, the primary energy source for most planetary and interplanetary vessels and vehicles is Metallic Hydrogen. This element is an atomic form of hydrogen formed by super-compression in large celestial bodies such as gas giants. It has an exceptionally high energy density and remains liquid over a wide range of temperatures and pressures, enabling smaller vessels to easily attain interplanetary flight of hundreds of millions of kilometers on a single tank of gas. It is also environmentally safe, producing only water vapor in its combustion.
Metallic Hydrogen is extracted from certain classes of gas giants using unmanned ‘Metallic Hydrogen Rigs’, huge mechanical mammoths that float just above the molecular hydrogen layer, able to sustain the harsh atmospheric conditions that most gas giants expose them to.