A hydrogen G-cycle rotary vane internal combustion engine has a sodium vapor chamber transferring excess combustion heat into combustion chambers. An active water cooling system captures heat from the engine housing stator, rotor, and sliding vanes and transfers it back into the combustion cycle by premixing it with hydrogen to reduce peak combustion temperature and with an early an late stage combustion chamber injection to help transfer heat from the sodium vapor chamber, to control chamber temperature, and to increase chamber vapor pressure. A combustion chamber sealing system includes axial seals between the rotor and the stator, vane face seals, and toggling split vane seals between the outer perimeters of the sliding vanes and the stator. Sliding vanes reciprocate laterally in and out of the rotor assisted by a vane belting system. A thermal barrier coating minimizes heat transfer and thermal deformation. Solid lubricants provide high temperature lubrication and durability.