to take some ribs out of the submarine fin to fit the new mast(s).”

Another important research topic concerned special forces. “MARIN was brought in to assist us with how Diver Propulsion Devices (DPD) should be fitted to the deck.” MARIN carried out research into the changes this makes to the hydrodynamics. “Submarine safety is reliant on being manoeuvrable. Therefore, MARIN conducted research into how to form the right shaped cradle for the DPDs and it modelled the cradle to see if this would have a negative influence. I think it is important to stress that this aspect needed to be solved at very short notice, within weeks and MARIN had the flexibility, was keen and capable to assist us.”

Shallow water As the Walrus Class was designed for the Cold War, patrolling the Greenland-Iceland-UK Gap, this would typically mean very deep diving and long periods under water without surfacing. But the work of the fleet has changed over the years, with coastal surveillance and special forces’ operations more likely tasks nowadays. “Our priority was to have a flexible vessel that could adapt to the post Cold War period.

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For example, we now operate a lot at periscope depth in shallow waters.”

Again, MARIN played a significant role addressing this issue, examining how sailing dived in shallow waters impacts manoeu- vrability, as well as the effects of the bottom on the submarine. MARIN built a simulation model to assist us in determining the manoeuvring envelope, which is also used to train officers and for the RNLN’s simulators. “I cannot say more but we are happy with the results. We needed data and modelling about this issue.”

Expeditionary diesel submarine Looking further into the future, Captain Ammerlaan believes that the basic tear- shaped hull will not change very much. “It is a good shape hydrodynamically speaking, but we will see a change when it comes to the introduction of larger Autonomous Underwater Vehicles (AUVs). There will be questions that need answering regarding the Launch & Recovery of these AUVs and how is manoeuvrability impacted when retrieving them. How will they be refuelled? Is a hatch going to open in the hull? Will drones be deployed…? This is all just speculation.

But I think it is certain that a submarine won’t stand alone so much in the future and will be involved in many more tasks. With regard to economic trade, the Netherlands will still need expeditionary diesel sub- marines, but will it be an evolution of the Walrus Class or one with a mix of unmanned and manned vehicles?”

Captain Ammerlaan adds: “We are learning from the current Walrus Class and MARIN is helping us as the MOD to remain ‘a smart specifier’. This means we still have the knowledge in-house to state our own requirements and continue to carry out the maintenance and overhauls etc. of the fleet for the coming years.”

Captain Hugo Ammerlaan will move on to a new role in April when he becomes the Netherlands Naval Attaché in Washington. He will be succeeded by Captain Herman de Groot, also a highly experienced submariner.

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