Sweden and Finland have announced a joint procurement of torpedoes of the type New Lightweight Torpedo (NLT). This torpedo is produced by Saab Dynamics and is also known by the Swedish name of Torpedsystem 47 or Tp 47.
The hope is that the coordinated purchase will lower the costs of sustaining and further developing the torpedo system. It is also anticipated that this opens other possibilities for cooperation within anti-submarine warfare.
Finland is the first foreign country to buy Tp 47 which is still under development. The parties also signed an agreement that the Finnish Navy will rent older Tp 45 torpedoes from Sweden beginning in 2019 to cover the time until Tp 47 is ready. Both types can be fired from the same launchers so Finland can begin the shipboard installations right away. It is expected that Tp 47 will be delivered to Sweden in 2022 and to Finland in 2023-2025.
Torpedoes are a new weapon for Finnish navy
Tp 47 (and for a while Tp 45) will be the first torpedoes in the Finnish arsenal for more than 70 years. In fact, Finland gave up the right to own torpedoes in the Paris Peace Treaties in 1947, but later in 1990 announced that those limitations didn’t apply anymore.
The decision to reacquire torpedoes in Finland is connected with the increasing tensions in the Baltic and the persistent stories about Russian submarine activities on Swedish territory.
The torpedo launchers will be installed on the Hamina-class missile boats during their mid-life updates in 2018-2021 and on Finland’s new large multipurpose corvettes that are expected to be ready in 2024.
About the torpedo
Overall the Tp 47 (or NLT) is a versatile torpedo that can be used in many different scenarios. A signature mark of the torpedo, however, is that it has some advantages in littoral conditions. The topography, brackish water, and intensive traffic of the Baltic Sea make a difficult environment for torpedoes, and the Tp 47 is designed specifically to perform well under these conditions.
Tp 47 is a modernized version of the Tp 45. It has a caliber of 400 mm, is 2850 mm long, and weighs 340 kg. The speed range is 10-40 knots, and here the most noteworthy thing is how slowly it is able to move. Often torpedoes need to maintain a high speed to balance themselves, but the Tp 47 has a near neutral buoyancy that facilitates good maneuverability and slow speeds. This is an advantage when used against challenging targets or when navigating narrow passages where precise navigation is necessary.
The torpedoes can be launched from submarines, surface ships, and helicopters. It combines different control systems, so it can be used both as a fire-and-forget torpedo with active or passive sensors, or it can be guided by wire from the firing unit. The wire-guided option is an advantage when firing on targets in near vicinity of friendly units.
It uses a battery driven propulsion system, and is has a Lithium battery that can be recharged many times. The maximum range is over 20 kilometers, and it can be active in the water for more than an hour. The warhead can be detonated by contact sensors, proximity sensors or manually by the operator using the wire-guided controls. It can be used not only against traditional submarines but also against for example unmanned mini submarines.
Below is a short video from Saab’s introduction of Tp 47 at the Undersea Defence Technology (UDT) exhibition in 2017.