An innovative new hybrid gas turbine and fuel cell submarine that can travel faster and further than conventional diesel electric and more quietly than nuclear submarines has been designed by BMT Defence Services in consultation with Rolls-Royce. The new concept, known as the SSGT, is superior to the capabilities of the SSK submarine class in many ways. It can travel at speeds of 20 knots for up to 6,000 nautical miles, with short ‘sprints’ of up to 30 knots. It is also quieter during stealth operations than nuclear powered submarines, which must operate pump machinery continuously.

The high speed, long endurance transit capability is made possible by an innovative propulsion design which uses twin, independent gas turbine alternator sets, housed in the ‘bulb’ on top of the fin. When operating in the fast transit mode, the boat operates as a semi-submersible with the bulb positioned above the surface. For more covert but slower transit requirements, fuel cell stacks provide the ship’s services and propulsion power. The stacks take in air from the atmosphere through a snort mast; this then reacts with hydrogen obtained from reformed kerosene, which is carried in external fuel bags mounted under the casing.

In-theatre, SSGT will operate fully submerged, in Air-Independent Propulsion (AIP) mode, for up to 25 days. The fuel cell stacks are fed by liquid oxygen (LOX) stored onboard to permit fully covert operations at up to 10 knots. The 30 knots sprints confer tactical advantage and are provided by power drawn from a large advanced ZEBRA battery, which also acts as a load leveller during operation of the fuel cells or the gas turbines.The design offers a flexible mix of vertical and horizontal weapon discharge tubes and unmanned underwater vehicle (UUV) stowage able to satisfy a range of mission profiles. The vessel’s systems are fully integrated making it highly capable, cost effective and environmentally sound.