Frigate of the future

Karl-Otto Sadler, the former programme manager of the ARGE F124 consortium of German shipyards (Blohm & Voss, HDW and Thyssen Nordseewerke), responsible for building the Sachsen-class air defence frigate published his ideas about advanced corvette and frigate designs in 1999, after his retirement. The publication formed the nucleus for a study to describe ? besides others ? a fully electrically powered vessel with pods and waterjets. Sadler succeeded in gathering nine well-known companies (naval equipment suppliers) for an “informal concept study”. They worked out what could be the FDZ 2020, the frigate of the future; a craft that would be realised between 2016 and 2020. Their main task was to define which technology would be available in the course of the next few years and what must be developed to meet the requirements of future naval vessels like corvettes and frigates. At this very early stage there is little to tell about the hull and the superstructure. It will be a 6,000t frigate of monohull design, with an igloo-type superstructure to minimise the signature. More interesting, in a general sense, is the propulsion and energy concept of the FDZ 2020. From informal discussions with officials in the German defence ministry it has emerged that a combined propulsion system with pods and waterjets should be integrated in the frigate and a new energy supply solution found. The specialists of the team for this task were HDW, MTU, Rolls-Royce, Siemens and Schottel. The result is a combined pod and waterjet drive (COPAW) that consists of two pods with an output of 7MW each and two twin waterjets with 14MW each. They are all electrically powered. The pods are Siemens/ Schottel SSP propulsors and the waterjets are of Bird Johnson twin-power AWJ-21 design. With only 7MW the pods stay within the commercial range of SSP drives up to 11 MW (as installed on TT Line?s Nils Holgersson. In this case they would be equipped with only one propeller. Contrary to standard use, the waterjets are not integrated in the hull but installed in pods outside the hull. This is similar to a solution Bird Johnson has developed for US Navy vessels. The propulsion concept also calls for new ideas for energy conversion and distribution on board. The general energy supply shall be taken over by two gas turbine-driven generating sets, each with an output of 14 MW. Discussions have focused on MTU LM1600 and the Rolls-Royce 1908-SM1C turbines. As a hybrid energy supply was requested, the next important point was to look at fuel cells. The maximum output of a fuel cell Siemens can offer today is 120kW. But 4.5MW is required from each of four units. The other problem is the amount of fuel to be stored on board. A diesel reformer produces a hydrogen-rich gas from the marine fuel. The hydrogen is needed as fodder for the fuel cell. HDW will focus on this feature. The company is very successfully working on methanol reformers, but again here, the output for the time being is not high enough. For both the fuel cell and the diesel reformer a lot of development work must be carried out in the coming years. It is intended to install two diesel reformer units on the frigate of the future, each of which must be able to supply the equivalent of 9MW of hydrogen-rich gas. A few distinguishing features of the FDZ 2020 are: a near zero emission vessel, high equipment flexibility, combined power supply as described, stealth technology and variable signature. More than 30 knots maximum speed is required and the operating endurance shall be in the order of 90 days. This means a high demand on comfort for a crew smaller than 100 persons. Standard accommodation will follow the comfort on cruise liners with two bed cabins. With his 1999 publication Sadler had already pointed out the importance of improved conditions for the living space onboard, especially for that part of the crew on duty in dark rooms, without daylight. He is convinced that crew accommodation must be located in the upper deck area with daylight cabins including worldwide TV and ISDN communication, which might also be used for open university courses. The necessary air-conditioning system for this accommodation and for the combined power supply system will be developed by Noske-Kaeser. This company is also the specialist for the permanent nuclear, biological and chemical (NBC) protection of the whole vessel.