A26 Blekinge. The submarine of the future is being built at the Swedish shipyard

The first A26 submarine, Blekinge, is built at the Saab Kockums shipyard in Karlskrona. Many interesting technical solutions have been used in it, and the A26 is already sometimes called the most modern submarine with a conventional propulsion. We explain why it owes such an opinion and what is its connection with Poland.

If construction goes as planned, the Swedish Navy is holding the ship in 2027. A year later, a twin unit, the submarine Skåne, is to enter service. A26 is the latest generation of submarines, which is to provide the Swedish navy not only with a new quality, but also a long-term advantage over potential opponents. What are they offering? type A26 ships?

One of the key advantages of the new units, and at the same time the hallmark of modern Swedish submarines, is – apart from classic diesel and batteries – the AIP (Air Independent Propulsion) propulsion system. Thanks to the solution known as the Stirling engine, the Swedes will obtain ships that can stay under water for a very long time without the need to ascend.

Stirling engine – air independent drive

For decades, this was the main weakness of ships with conventional propulsion: under water they were powered by batteries, which, however, quickly discharged, and recharging them required surfacing (that is, revealing the ship’s position) and starting the diesel engines.

The Stirling engine (closed-loop external combustion reciprocating internal combustion engine) operates without the need for atmospheric oxygen, which solves the problem of frequent ascent. Although it is an internal combustion engine, it operates thanks to the resources of liquid oxygen stored in special tanks.

In practice, new ships gain an advantage that is usually assigned nuclear powered units, that is, the ability to stay immersed for a long time. How long? The currently estimated maximum immersion time of units without an AIP drive is – with the use of various technical solutions – up to about a week.

In the case of the AIP drive, this time can be increased many times – probably even up to 18 days. Another unique feature is associated with a long stay under the surface – the crew’s comfort, which is unusual for this type of weapon, which is reflected in, among others, individual berths in independent, closed cabins.

Modular design

The A26 is a ship built – literally – of bricks. At the design stage, the manufacturer provided nine different types of modules from which you can “assemble” a finished ship, completing its equipment and capabilities depending on your needs.

In practice, this means that, if necessary, the ship can be equipped, for example, with larger tanks for liquid oxygen and fuel, allowing for increased time spent under water. If the need arises (the ships under construction will not have such a module), the A26 can be retrofitted, e.g. with a module with vertical launch launchers for cruise missiles.

This solution facilitates the construction of ships, because the modules can be built and equipped independently of each other, and only at the final stage of construction to combine them together. A good example is the construction of the Blekinge ship – although it formally began on June 30, 2022, in practice the modules that the ship is now assembled from began to be built as early as 2015.

Thanks to the modules, there are also greater possibilities of modifying ships and adapting them to the specific needs of, e.g. a new, foreign user. At the same time, the modernization of already ordered units is significantly facilitated – in the future, if necessary, the appropriate module can be prepared in advance, which will shorten the modernization time and speed up the return of the ship to service.

In the configuration ordered by Sweden, the A26 ships will be 65 meters long, with a draft displacement of over 2,000 tons, and will be manned by a crew of 26. The ships will be armed with six torpedo tubes, allowing the use of “heavy” 533 mm and “light” 400 mm torpedoes.

Submarine A26 during construction
Photo source: © SAAB

Submarine A26 during construction

A sign of the times is a large lock, 6 meters long and 1.6 meters in diameter, placed between the launchers. It will allow you to work with underwater dronessoldiers of naval special forces, as well as for underwater loading and unloading of various objects.

A26 – “invisible” ship

A hole in the water – this is a short summary of the emissions from A26. One of the key features of the ship is its extreme silencing. The good results of the Swedes in this area are clearly demonstrated by the fate of the A26 predecessor, the A19 Gotland (ships of this type are to be modernized using the solutions applied on the A26).

This type of vessel was “loaned” by the United States to enable the US Navy to exercise detection and combat against super-silent ships. During the maneuvers, it turned out that the ship was so quiet that – to make the exercises possible at all – its acoustic signature was intentionally increased. During the exercises, the A19 was able to break through the cover American aircraft carrier and “sink” it in a simulated attack, then – still undetected – safely retreat.

In the case of the A26, the stealth features are to be further developed. One of the solutions to achieve this is to get rid of all equipment from the ship’s surface – devices and installations necessary, for example, during a stay in the port, have been hidden in special hull chambers.

One of the A26 modules
Photo source: © SAAB

One of the A26 modules

At the same time, the ship’s designers took care of its radar signature – especially the upper surface of the A26 and its kiosk were designed to minimize the so-called effective reflecting surface. It is a parameter that determines the “visibility” of various objects on the radars. In the case of the A26, this is to enable hidden operation of the unit, even when it is partially surfaced.

What do we care about A26 Blekinge?

There is also a Polish thread related to the A26 ships. Polish Navy from the turn of the century – after the withdrawal of the old, post-soviet submarines Foxtrot type – trying to find successors for them.

The time needed for this was to be “bought” by Poland, small Kobben-class submarines adopted from Norway. Time has passed, Kobbens – with half a century of operation behind them – after 20 years we have also withdrawn, ORP Orzel the open-air museum is constantly being repaired, and new units are not there any more.

The “Orka” program is supposed to provide them, but its implementation is in practice frozen. Over the years, various ideas appeared, such as ordering submarines in Germany or France. An alternative proposal was presented by the Swedes, who have been proposing A26 to Poland as the future pillar of our submarine fleet since 2016, but – despite the passage of time – decisions in this matter have still not been taken.

Łukasz Michalik, journalist of Wirtualna Polska

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