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The paper reports on one aspect in the design of the extra-large unmanned underwater vehicle (XLUUV) MUM, referring to a large Modifiable Underwater Mothership. The vessel will be highly modular and has unique features, such as hydrogen fuel cell and lithium-ion batteries. Modules can be added and rearranged to fulfill different operations. The envisaged operation scenarios pose a challenge to the design of the propulsion and maneuvering system. Due to the limited power and energy storage, it must be efficient during submerged transit, capable of safe surfaced operation in public sea routes and of dynamic positioning. A design study is presented based on an initial design of two variants. The basic hull forms are compared in terms of required forces and moments for vessel motions. Simulations of hull forces are conducted using Reynolds-averaged Navier-Stokes (RANS) equations and vessel motions are determined with an actuator force model. Different arrangements of propulsors and thrusters are investigated and compared concerning their propulsion efficiency and their agility in translatory and rotary directions. The results are presented as tabulated data and in capability plots. A final design is presented and discussed and a conclusion is presented.

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This paper presents the joint research project “SMIS” with focus on the requirements and the design of the seabed station. A major issue for all autonomous subsea systems is the problem of limited battery capacity due to design boundary conditions. SMIS counteracts this by deploying an autonomous power-carrying vehicle, similar to a mobile petrol station, to extend the operation time for the AUVs. The demands of the autonomous seabed station include the unguided submerge through 6000 m water column, a safe landing on suitable ground without excessive power consumption and a reliable docking mechanism for power transmission to AUVs on the sea floor. Moreover, the communication between the SMIS vehicle fleet for georeference and path guidance during the AUV operation is essential. A modular design also allows operation in ROV mode, which expands the field of application.