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From the swordfish to world-leading submarine technology

From the swordfish to world-leading submarine technology

14 min read

Today Saab is building the next generation of submarines with the working name A26. This is development work that has its roots in a tradition going back more than a hundred years. Kockums (now Saab) delivered its first submarine with the name Svärdfisken (Swordfish) in 1914. An important factor in its success has been its close collaboration with the Swedish Navy and the Swedish Defence Materiel Administration (FMV).

HMS Svärdfisken was launched on 30 August 1914 – the first submarine to be build at Kockums yard in Malmö. Unrest was in the air. The First World War had recently broken out between the major powers of Europe and nobody knew whether the Nordic countries would also be drawn into the war.

Many Swedes would certainly have been relieved to know that the Swedish Navy was in possession of these remarkable new submersibles – a means of strengthening national security in troubled times.

During a period of just over a century some 20 different classes of submarines have been designed in Sweden and more than 70 submarines of various types and sizes have been built in the country, with more than half being constructed at Kockums in Malmö.

Submarine pioneers

But submarines were not entirely new even in 1914. The first usable submarine was actually created in 1776, developed by the American David Bushnell and designed to be used against the British fleet during the American Civil War. But it was only with industrialisation and more sophisticated technology that really workable designs started to be developed in the late 1800s.

One of the submarine pioneers was in fact a Swede, Thorsten Nordenfeldt, who lived in England. He got to know the English clergyman and inventor George Garrett, who had a particular interest in diving and underwater technology. For his part Nordenfeldt was interested in the combination of submarines and torpedoes, and was one of the first to realise the potential of such a vessel for the countries’ navies.

Together Nordenfeldt and Garrett designed several steam-powered submarines. One submarine was built by Bolinders in Stockholm and was demonstrated in Öresund in 1885 to representatives of the Swedish Navy and nine foreign navies. Despite some shortcomings, the submarine met with interest and was sold to Greece. Two other submarines were built in England and sold to Turkey. A fourth submarine was bought by Russia, but sank on the way there. The submarine still had major stability and safety issues.

Sweden’s first submarine

Only after the development of electric motors and generators was it possible to start developing tactically usable submarines and then interest grew in earnest. The USA put its first modern submarine into operation in 1900. This design formed the basis of Sweden’s first submarine, Hajen, which was launched in 1904. Hajen was built at Stockholm’s Navy Yard on behalf of the Royal Swedish Naval Materiel Administration and was designed by marine engineer Carl Richson, who had experience of US submarine design. He would have a significant role for several decades as Sweden’s foremost submarine designer. Today Hajen is on display at the Naval Museum in Karlskrona.

The early submarines could only be operated at low speed and had a limited endurance. They are known as ‘dive boats’ and were quite small and fragile, but were still of strategic interest.

From the swordfish to world-leading submarine technology
Submarines were constructed even in the Karlskrona shipyard, including the Dragon series in the 1920s and 30s. Here is the launching in March 6, 1930 of HMS Ulven, which would be associated with disaster during World War II. Ulven was probably blown up because of a German mine and sank off the coast of Öckerö. The entire crew of 33 men perished. National Maritime Museums.

In 1909 the Italian Fiat shipyard delivered a more modern submarine to Sweden, named the Hvalen. But it was a hair-raising journey for the Swedish crew that had to sail the submarine home. The fuel used in the three petrol engines was flammable and the long journey was marred by cracked cylinders, leaking petrol tanks, petrol fumes and combustion gases.

The Kockums shipyard in Malmö was aware of the importance of keeping up with developments and in 1910 it acquired the licensing rights to build submarines in Sweden to the Fiat-Laurenti design. The Swedish Navy ordered two submarines and in 1912 Kockums started to build Svärdfisken and Tumlaren, which were completed two years later, just before World War I broke out. They were built to the Fiat-Laurenti design with a long narrow pressure hull and a well-designed outer hull. Both submarines were well-liked by their crews, which was demonstrated by the fact that they were only withdrawn from service more than 20 years later in 1936.

Sweden had now acquired a real taste for submarines. At the height of the World War I, in summer 1915, Kockums engineers brought new drawings home to Sweden from the Fiat shipyard and in the autumn the keels of Hajen, Sälen and Walrossen were laid down at the shipyard in Malmö. The Hajen II class (Shark) was larger than previous submarines so that it could house four torpedo tubes.

But submarines were not just built at Kockums. Submarines were also designed at the state-run Karlskrona shipyard and the country’s first minelaying submarine, which could carry a load of twenty mines, Valen, was built there in 1925. The Draken class (Dragon) was also built in Karlskrona in the 1920s and 1930s. This included the Ulven, which was tragically lost on the west coast of Sweden during World War II. The submarine was blown up, probably by a German mine, and sank outside Öckerö. The entire crew of 33 men perished. It was a disaster that cast gloom over Sweden and which many Swedes have long come to associate with submarines.

Full speed ahead for sub production

The 1930s and the war years marked an upturn in the construction of submarines. From 1936 to the end of the war, Sweden launched no less than 21 submarines. In 1936-37 Kockums delivered three Delfin II class (Dolphin) submarines, a further nine Sjölejon class (Sea Lion) submarines up to 1942 and in 1943 a further three Neptun class (Neptune) submarines.

In addition, Kockums and the Karlskrona Navy Yard also constructed what are known as the number subs in the U1–U9 series. Kockums benefited from the welding technology that the company had become a world leader in and produced the first fully welded submarine hulls. These coastal submarines formed the nucleus of the Swedish submarine fleet during World War II and at the start of the Cold War.

The development of various telecommunications aids such as radar, sonar and radio direction-finding equipment put strong pressure on submarine development at that time. The era of the diving boats which had been predominant had passed. Submarines that were capable of operating entirely underwater were now required.

One solution was the snorkel tube, which allowed the diesel engines to run when submerged (it requires air from outside). The Germans were conducting intensive research into ‘real’ submarines and new complex hydrogen peroxide systems which could give the submarines a considerably higher speed than previously. Fortunately for the allies, none of these submarines became operational before the end of World War II.

After the end of the war most submarine nations tried to utilise as much as possible of the new submarine technology. Sweden was extremely fortunate in that it more or less came across one of Germany’s most advanced submarines, the U 3503, as a ‘gift’ at the end of the war. It had been sunk in Swedish territorial waters at Vinga Sand by the Germans themselves on one of the very last days of the war and the Swedish Navy was able to salvage it.

As a result of this the project for Sweden’s first post-war boat was scrapped (A7 project) before construction had even started. All the older Swedish submarines were modernised into snorkel submarines. The streamlining of the hull was improved to obtain a higher speed when submerged and the guns were removed, since these were not relevant for a vessel that never operated on the surface.

Work also started at Kockums on a new series of submarines which were entirely based on the newly acquired knowledge: the Hajen III class (Shark class). They were designed with a snorkel from the outset. The innovations included an expanded hydraulic system for silent remote control of valves, and parts of the equipment had rubber suspension to increase impact protection and reduce the noise. It was a matter of ensuring that the submarine was capable of operating as silently and discreetly as possible.

With the Hajen III class Kockums also introduced sectional construction into the submarines and as a result the diesel engines were installed from the start. There were several advantages to the new method of construction: production time was reduced and the end result was better.

At the same time research into nuclear-powered submarines continued in the world and a milestone was achieved in 1954 when the USA launched the first nuclear-powered submarine in the world, USS Nautilus. Three different types of air-independent propulsion systems were being studied in Sweden: besides nuclear power (project Neptun), closed cycle diesel and fuel cells were also under consideration. Due to the high costs and limited tactical benefit, Sweden never acquired the nuclear propulsion system and neither was it appropriate for Kockums or the Karlskrona yard to pursue this route further.

However, the closed cycle diesel system and fuel cells were developed into functioning prototypes, but were ultimately considered to be too expensive. When producing the next submarine class, the Sjöorm class (Sea Serpent), the vessels were therefore built with a conventional battery-driven propulsion system for use when submerged and diesel operation when surfaced. Asea, Hedemora Verkstäder and Tudor were the main suppliers of components.

A new torpedo firing system had been developed in cooperation with the Naval Staff, the Naval Material Administration and Svenska AB Philips. The performance of the torpedoes had also been increased compared with previous generations.

But what was really new was the development of the X-rudder, which immediately revolutionised the submarine’s manoeuvrability when submerged. It was the Sjöormen that was first equipped with this design in 1968. As an amusing anecdote it can be mentioned that the tests were carried out on a scale model at Simhallsbadet swimming pool in Malmö, long after the normal swimmers had gone home!

There were five of these submarines, three of which were built at Kockums and two at the Karlskrona yard. They were launched between 1967 and 1968 and were in service for 30 years in the Swedish fleet until they were sold on to Singapore in 1997.

From the swordfish to world-leading submarine technology
HMS Vastergotland was the first ship in the Vastergotland-class and was launched in 1986. Kockums prominent technology and rational manufacturing methods led at about the same time until an order from the Royal Australian Navy. The picture from 1986. Naval Museum.

Old invention revolutionises submarine operation

The most significant breakthrough came with the Stirling system in the 1980s. Kockums succeeded in adapting the Stirling engine to a submarine propulsion system – a revolution for the entire submarine concept. And the engineers now benefited from an almost 200-year-old invention.

The Stirling engine was designed in the early 1800s by the Scotsman Robert Stirling as an alternative to the steam engine. The system had been forgotten. But the Stirling engine is well suited to submarine operation since it is extremely silent and can operate against a significant external pressure.

Kockums was privileged to be able to borrow one of the navy’s submarines, Näcken, to test the re-emerged technology. The submarine was converted by being cut off immediately behind the tower and extended by a new 8-metre section. The engineers housed an additional air-independent propulsion system there, based on the Stirling engine, which allowed the submarine to remain submerged for several weeks instead of just a few days.

It made the headlines when the modified Näcken was launched in 1988 and the president of Kockums Marine Paul Pålsson was relieved: “In doing so we’ve made a start in the race for new multi-billion orders for submarines around the world. We’re now seven or eight years ahead of our competitors.”

At roughly the same time the next generation Kockums submarine, known as the Västergötland class, was launched. This made the most of the main characteristics of Sjöormen and Näcken. Four submarines – Västergötland, Hälsingland, Södermanland and Östergötland – were built and launched between 1983 and 1988. The last two submarines underwent complete modernisation at Kockums in 2003-2004.

Major order for Australia

Sweden had become a world leader in the development of non-nuclear powered air-independent submarines, known as AIP (air-indepedent propulsion) submarines. There was also great interest from the rest of the world and a completely new strategic collaboration began with Australia in 1987 in that the Australian Submarine Corporation (ASC), in which Kockums was a shareholder, bought six submarines from the Malmö shipyard.

The submarines, known as Type 471, were a developed and larger version of the Swedish Västergötland class and were named the Collins class in Australia, after Australian Vice Admiral John Augustine Collins.

It was a lengthy evaluation attracting a great deal of attention that resulted in the next generation of submarines for the Royal Australian Navy being ordered from Kockums – against fierce international competition. The order was regarded by many as a sensation, not least in view of Australia’s close connection with the United Kingdom, and was viewed as an acknowledgement of Kockums’ high standards and of Swedish leading edge technology.

But it was not just the technology that attracted Australia – the methods of designing and constructing the submarine were also seen as crucial advantages. The Kockums Type 471 was the first submarine to be entirely drawn with the aid of CAD in 2D and 3D. Since the drawings were stored digitally, they could easily be saved in a database and sent to Australia where most of the construction took place.

Kockums had also continuously improved its production technology for the modular construction of submarines. This allowed the work to take place at different sites, independently, and as close to the subcontractors as possible. The sections were then joined together in ASC’s facility in Adelaide. Some 200 advanced technical specifications and around 15,000 manufacturing drawings were supplied.

A number of specialists from Kockums worked at ASC in Adelaide. Roger Sprimont, one of the key men behind the order, was the chairman of the board of directors at ASC. Olle Holmdahl headed the design team and was one of ASC’s two deputy managing directors. Through a special industrial programme Kockums undertook to promote technological collaboration between Sweden and Australia. This and all the other monitoring of Kockums’ interests in Australia was undertaken by a specific subsidiary company, Kockums Pacific, in Adelaide.

The submarine project meant a great deal for the South Australia region. It was Australia’s largest defence contract ever and a strategic industrial investment. In 2000, Kockums sold off its shareholding in ASC when the company was nationalised. The Collins submarines are still in service and are expected to be taken out of service in the 2020s.

Stealth technology widely discussed in the USA

In 1995-96 Kockums delivered three Gotland-class submarines, the Gotland, Halland and Uppland. The submarines can most easily be described as a further development of the Västergötland class. They were equipped from the start with a Stirling air-independent propulsion system and therefore have a longer hull than older submarines. They also have greater sensor capabilities and endurance and are even better adapted to concealment by using what is known as stealth technology.

From June 2005 to August 2007 the Gotland was leased to the U.S. Navy for joint exercises with the U.S. submarine fleet in San Diego. The exercises demonstrated that the Gotland was hard to locate due to the silent Stirling engines and the Swedish submarines were the subject of considerable international attention.

The world’s most modern submarine programme

A26 divers
The A26 submarine, also known as the Blekinge class submarine, currently in production at the shipyard in Karlskrona.

Work is now under way at Saab Kockums on developing the next generation of submarines with the working name A26. Two submarines are to be built for the Swedish Navy, with the first submarine being delivered in 2022. They will be a further development of the Gotland class.

4 September 2015 was a historical day for the shipyard in Karlskrona. That was when the steel for the first rib of the submarine’s hull was cut – almost 101 years after Kockums launched its first submarine.

The A26 is a next-generation submarine with the ability to perform in all oceans and across a broad spectrum of conflict environments. Along with its traditional load of mines and torpedoes, the submarine can be equipped with missiles. But the really major innovation is the large horizontal tube, the Multi Mission Portal, with its ability to launch and retrieve both manned and unmanned underwater vehicles.

The A26 will also be a crucial intelligence gathering platform in the defence network. The submarines are powered by conventional diesel engines and the Kockums Stirling AIP (air-independent propulsion) system. The Stirling system enhances the submarine’s stealth characteristics and makes it difficult to detect.