In an underwater vehicle, hydrogen and oxygen are fed into a combustion
chamber of a combustor of the underwater vehicle to initiate a combustion
reaction, which generates high-pressure steam. The high-pressure steam
can be cooled with the injection of seawater, and can be condensed into
high-pressure water by the addition of sufficient seawater. High-pressure
water is then ejected out of the combustor, generating thrust for the
underwater vehicle. Sensors that measure the combustor pressure and the
external pressure could be used to adjust the combustor pressure,
allowing for constant velocity as the depth of the underwater vehicle
changes. Alternatively, the sensors could adjust the area of an exit
nozzle of the combustor. Stored water can be converted back into hydrogen
and oxygen by using electrical power external to the system. After
regeneration of the water into hydrogen and oxygen, the propulsion system
would be ready for operation again.