High Level of Ambition for Stealth Technology on Submarine A26
(Source: Swedish Matériel Agency, FMV; issued Oct 04, 2021)
(Unofficial translation by Defense-Aerospace.com)
Being able to appear hidden through a low and balanced signature, with the help of so-called stealth technology, is a basic characteristic of a submarine. Here, the new submarine A26 will be far ahead.

“A submarine is built so that it will not be visible from the surface. And if you have taken the trouble to build a boat that goes underwater, you do not want it to be easy to detect there either,” says Marcus Kylén, FMV underwater signature and marine measurement system.

A signature can be described as a deviation in what one can see, hear or measure. It is partly about optical signature such as color and shape, partly about things you can hear or measure with sensors, including noise, magnetism and pressure changes.

Everything that can be measured, which the submarine gives rise to, is a signature. If an operator wants to find a submarine, they put sensors in the water, for example, which can detect or in the worst case identify the submarine.

Because radar does not work underwater, a hydrophone, that is, an underwater microphone, is the classic sensor for detecting a submarine.

“Sound travels well in water, so reconnaissance with hydrophones is dangerous for submarines. Therefore, it is important to reduce the noise that leaves the submarine. If you have a high noise signature, there is no point in having a submarine,” says Marcus Kylén.

A submarine also distorts the earth's magnetic field a little. “During the Second World War, Germany, among other things, manufactured mines that could sense magnetism. These still exist, so we are working on technical systems that can reduce the submarine's magnetic signature. The A26 will be equipped with electrical coils, which act as a magnetic anti-roll bar.”

A high level of ambition

“When it comes to the A26 submarine, you have a high level of ambition to reduce signatures because you want to match the technical development on the sensor side. The A26 will therefore have a range of stealth technology solutions that are not available on previous submarine classes.”

“It is very exciting to work with this area. A submarine has a variety of technical systems on board that generate noise, including pumps and various pipe systems for hydraulic oil and water, ventilation systems and electric motors. There can be a lot of noise. How they should be designed to give low signatures is something we must think about early in the project, when we make the requirements. This is, among other things, where technology development takes place.”

Having a picture of what the enemy's sensors look like is also important, as building with a low signature is very costly. Therefore, it is important to set reasonable and realistic requirements before entering into a contract with the industry.

“We do not want to build too well in an area, so that we, for example, invest heavily in reducing noise and it turns out that the enemy is very good at detecting magnetic signatures. Then we have spent a lot of money unnecessarily. Therefore, the requirements need to be balanced and it is a time-consuming job.”

Kockums, which builds the submarine, then breaks down FMV's requirements into requirements for its subcontractors.

But adapting components to the requirements set by FMV can be both expensive and difficult.

“It requires a great relationship between us and Kockums. We must be able to trust that they make a good assessment of their subcontractors, of what is available to buy and how to solve problems.

Feeling privileged

For Marcus Kylén's, the first years with Project A26 were mostly about meeting demands, while in recent years it has been a lot about reviewing technical solutions and factory tests at Kockums and their subcontractors.

“It is fun to follow the various signature issues, from physical phenomena to real technical solutions that give low signatures. And I feel privileged to be the spider in the web and work with many talented specialists in the field,” he says.

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