The German shipyard tkMS will propose a larger submarine than the current Walrus class in the Netherlands

In an interview with, thyssenkrupp Marine Systems (tkMS) gave more information about the plans they have for their proposal for the Netherlands. The German yard will consider an offer in the coming months, but the outlines of their plans are becoming increasingly clear.

Screenshot of Type 212CD E. (Image: tkMS/still YouTube)

tkMS is one of three yards in the race to build new Dutch submarines. We await the RFP that the Defense Materiel Organization (DMO) will send to Naval Group, Saab and tkMS in November.

In the meantime, shipyards are fine-tuning their plans based on the information they have received so far, although not all requirements and assessment criteria are known yet.

After a visit to the yard in Kiel in June, more details about tkMS’s plans for the Netherlands appeared on this page. With HDW-class 212CD E program manager and former submarine operator Holger Isbrecht, MarineShips spoke again about the design of the 212CD E. This design is derived from the 212CD being built for Norway and Germany. CD E has been adapted to the requirements, as far as they are known, from the Netherlands.

Basically, however, the boat tkMS has in mind for the Netherlands is the same as for Germany and Norway, says Isbrecht. “The number of crew members is larger, has longer range and more compartments. But it is based on the same core components: same diesel engines, electric motor, etc. That core has already been developed, other things like housing and fuel tanks around it have been made bigger.”

212CD E
212CD E compared to the Walrus. (Image: tkMS)

Longer and bigger
For the first time, tkMS provides some more information about the length of the boat. “The 212CD will be slightly larger than the Walrus class,” says Isbrecht. “The 212CD E gets even bigger.” And it is not without reason. With a bigger boat, tkMS wants to add things to meet the requirements in the Netherlands, making longer operations further away from home possible.

An illustration of the German yard shows that the design for the Netherlands will be longer than 80 meters. This makes the CD E significantly longer than the current Dutch walrus-class boats, which are more than 67 metres.

It can be disadvantageous to lengthen a submarine if it becomes relatively too thin. For example, the boat can then be more difficult to maneuver and it requires more energy to reach the speeds. The advantage of the 212CD as a basic design is that the outer diameter of 10 meters is already considerable. Isbrecht: “The length-to-diameter ratio is still good. Our way of changing the design is to lengthen the hull. As we increase the diameter, we have to modify the interior of the boat, including cables.”

Although the diameter of the pressure skin is slightly smaller than the Walrus at 7.2 to 7.8, the 212CD E will still have a significant displacement of more than 3,400 tons, based on the information in the above visualization.

212CD E
Click to enlarge. Accommodation on board 212CD E. Here you can mainly see the berths. (Image: tkMS)

212CD E
A seating area. (Image: tkMS)

New technologies
The Walrus is over 2800 tons, but does not have an outdoor air independent propulsion (AIP) that takes up much space. The 212CD E has it. According to tkMS, this is a new generation of AIP system which, like the previous German AIP systems, is based on fuel cells. tkMS (or better: HDW) also built these AIP systems earlier, but the fuel cells and support systems came from Siemens. This updated version is now entirely from tkMS. “We have improved the system,” says Isbrecht. “And it’s in our hands now. It’s important because it’s a core submarine technology that we want to have under our own control for future submarine development.”

The 212CD E is also suitable for lithium-ion batteries instead of the old lead-acid batteries. It is not yet certain whether these new batteries will be used in the new submarines. It is often said that lithium-ion batteries have a big impact on design because they are lighter. The lead-acid batteries are heavier and are ideal for adding weight and stability to the bottom of the boat.

According to tkMS, however, it is still possible to choose between the two versions at a relatively late stage, without having to redesign much. “We have chosen to follow two routes,” says Isbrecht. “Option A is lithium-ion on board, but at the same time we are also designing the boat with lead-acid batteries. There is a misunderstanding that lithium-ion batteries are much lighter than lead-acid batteries. This applies to the batteries themselves, but if you put the whole package together. If you compare it, you can see that it’s comparable. We’ve also added extra heavy-duty materials in the housing for the lithium-ion batteries.”

“Of course, you need different support systems if you choose lithium-ion. But it can be done. We have the experience, and our goal is to make the safest system for submarines. With lithium-ion, you have to look carefully at safety, because there is always a chance of fire. And these are things we focus on to achieve the safest possible system.”

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With a longer boat, the probability of a vertical launcher seems to increase. But that is not part of the design. But the 212CD E cruise missiles (maritime strike mentioned in the defense memorandum), says Isbrecht. “A vertical launch vehicle has too much impact on the design and cost, so it is not part of the design. We have offered the maritime strike option for some time, but it has now become more of a priority because it was mentioned in the Defense Memorandum. The technical requirements to launch such a weapon are comparable to launching a torpedo or an anti-ship missile.”

The weapons, whether cruise missiles or torpedoes, could also be American-made, says Isbrecht. The Mk48 torpedo carried by the Submarine Service is an American torpedo, and the Tomahawk may be added to it. Isbrecht: “We have experience integrating American technology. It is a question of working with interfaces. We have integrated American systems before. It is not about the design, but about how the secret data communication takes place between the torpedo and the other systems. is something Americans are particularly aware of’.

tkMS does not say for which countries and which weapons they have made the integration.

According to Isbrecht, the torpedo tubes are not a problem for these weapons: “We have our own design and construction department within tkMS that makes torpedo tubes that can fire all kinds of weapons.”

Construction in Germany
At the start of the tender, construction was still underway in Den Helder, but the navy and DMO did not want their own shipyard -DMI- to become a party to the tender. Are the boats built in Kiel? “In Germany”, replies Isbrecht. Because not only are additional buildings being built in Kiel for the construction of submarines, tkMS has also bought a new shipyard. “You know we recently took over a shipyard in Wismar. It gives us even more flexibility and capacity. We have the freedom to decide whether we can build in Kiel or Wismar. Although parts may be built in Holland.”

At least the maintenance of the boats takes place in the Netherlands. It is a requirement and a logical decision for tkMS. “It is quite normal. The Portuguese navy, which has two submarines, does not always sail the boats to Kiel, but carries out the maintenance itself. With the possibilities and capacity in the Netherlands, it is not a problem at all,” concludes Isbrecht.

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