More details proposal new Dutch submarine of Saab and Damen

The Swedish-Dutch combination Saab-Damen has presented the Netherlands with an ocean going submarine. The details were presented to during a visit to Saab Kockums earlier this week. 

Saab-Damen's proposal. (Image: Saab) 

Damen and Saab compete with the French Naval Group, the Spanish Navantia and the German TKMS to replace the Walrus class.  

Like the Naval Group , Saab and Damen Netherlands offer a submarine that is derived from a submarine that is currently under construction. The offer of Saab-Damen is based on the design of the A26 submarine that Saab Kockums is currently building in Karlskrona. 

The A26 is designed for the Swedish Navy and is therefore a boat intended for operations in the Baltic Sea. For the Netherlands Saab, with the design philosophy of the A26 in mind, has designed a boat that is not only bigger but also needs more. The new design has not yet received a name from both companies.

The designers wanted to design a boat that can be used worldwide (from arctic to tropical waters), in coastal waters and in the ocean, which has a large range without supply, can quickly switch between missions during a voyage (eg from submarine combat to dropping off special forces), a boat that has good accommodation, is reliable and often available. 

By opting for a relatively large globally deployable boat, not only the Naval Group, but also Saab-Damen has clearly chosen the line that the Navy deployed in the 1920s and is still the basis of the current Walrus class. submarines. The French and Swedish submarine designers, with their proposals, did not discuss the homeland security option, a small submarine for the waters close to home that was called an option by the sounding board group with the appearance of the A-letter. 
An example of the Homelandsecurity submarine is the A26, which in addition to some oceangoing properties, especially in the Baltic Sea, must protect the Swedish waters. In the case of a submarine that must be deployed globally, higher demands are placed on the temperature management, the accommodation, more goods must be stored and the boat must have a larger trim capacity to accommodate the differences in salinity in various sea areas. 

The design
With a water displacement of about 2900 tons the design is slightly larger than the current Walrus class submarines. The concept submarine is currently about 73 meters long and has a diameter of about 8 meters. 

In contrast to the volume, the number of target crew members has decreased compared to the current submarines. The exact number depends on the degree of automation that the navy wants but will be between 34 and 42 crew members.

The boat will have two decks. Because the periscopes have been replaced by up-and-coming masts, the command center no longer has to be placed under the sail. The Swedish designers have chosen to place the power station forward, above the bow tube room. By locating the power station at the end of the corridor, it is prevented that the crew has to walk through the power station to reach a space in the boat. 

In the Walrus and Swordfish class the plant is also placed at the end of the corridor. However, the bow tube room covers two decks there, which is therefore very high. In the Swedish-Dutch proposal, the bow tube room is just as high as the other rooms. 

The bow tube room is much more designed as a multifunctional space in the design. Of course torpedoes can be stored and there is space to temporarily place beds (torpedo beds), but in the middle there is room for a large desk with laptop connections where, for example, briefings can be given, or that can serve as a temporary command center for special operations. . All kinds of types and sizes of drones can also be placed under and above water. Seven tubes

A striking feature of the proposal is the number of (torpedo) tubes: six torpedo tubes and a Multi Mission Lock. The Walrus class has four tubes, but similar boats such as the Collins and Victoria class each have six tubes. 
The importance of many torpedo tubes has indeed decreased since torpedoes have become more accurate. Yet more tubes means that more targets can be attacked at the same time and that there is less disadvantage of long reload times. 

The seventh tube is special and comes from the A26 submarine. This is a tube with a diameter of 1.5 meters (torpedo tubes have a diameter of 0.53 meters). It is the Multi Mission Lock that allows divers, special units and drones to get off and on board while the submarine is under water or at the bottom.

For the larger equipment of special units, there is space under the casings on the deck at the top of the boat. That is already the case with the Walrus class. 

Behind the exchange is a module for accommodation of the crew. Following the concept on the OPVs and the Karel Doorman, the designers have opted for a joint dining room and four separate day quarters (for officers, non-commissioned officers, corporals and sailors). 

The beds can be turned into tables as required, so that more space is created to use a laptop for work or leisure time.
A lot of work was done with wood-like finish when decorating the concept designs. There are also no pipes visible. These are located under the decks, but are accessible for example for repairs. 

Sensors and weapon systems
The design is still a proposal, the designers have not made a choice for which brand of weapon systems and sensors. The most important weapon system is obviously the heavy weight torpedo. That can be the Mk 48 that the Netherlands now uses, but can also be another type. Also the brand sonar and cantonic mast is not fixed. The Dutch combat management system Guardion is also possible.

In addition, the designers offer extras such as a vertical launcher for missiles (the boat will be longer), masts with a machine gun or missiles against air targets. 

The design has batteries and diesels, plus the Stirling AIP engines that are also on other Swedish submarines. The Stirling engine uses ordinary diesel and liquid oxygen. Both are available in ports and also liquid oxygen can be loaded quickly. The engine is a combustion engine, but there are no explosions in place like a petrol or diesel engine. Instead, the engine works with a gas that expands by heat (the combustion) and shrinks again later by cooling. The engine is very quiet due to the absence of explosions. Moreover, the Stirling engine hardly vibrates. The writer has seen the Stirling engine in front of the A26 at the factory while a coin has been left on its side. 

Signature reduction
Saab Kockums, in their own words, pays a lot of attention to signature reduction; making it difficult to detect a submarine. This not only concerns a quieter submarine, but also a boat that emits little heat or electromagnetic radiation. 
Examples are the stealth sail of the design so that sonar signals do not reflect well, a special coating that has to absorb sonar signals, special type of shock absorbers (which are very different from those on the Walrus class) to absorb vibrations, cabinets around diesels and other engines, and the complete contents of the submarine in a module on rails with shock absorbers. 
If the Netherlands chooses to order submarines from Saab-Damen, construction will take place in both Sweden and the Netherlands. The work on the pressure skin (including sanding and cutting steel, bending, welding of the pressure skin and rafters) and the production of composite parts will then take place in Karlskrona. 

These parts are then shipped to Vlissingen and there the contents of the boat are assembled and placed in the boat.

The latter is a special method of the Swedish submarine builder. As for the A26, the contents of the boat are built in separate modules. These modules are complete, they are only placed on rails with cushions in the submarine when they are ready. 

Because they are built outside the boat, more people can be worked on and the modules (for example the command center or accommodation) are first fully tested outside the boat, before they are placed. 

Saab-Damen is the first of the four submarine builders to publicly present their customized design for the Netherlands. Comparison is therefore not possible now. The Defense Materiel Organization (DMO) will compare the builders and choose the two finalists at the end of this year. Before we know which design is chosen, it is 2021.