NRP Tridente Type 209PN - Design

The submarines are Type 209PN ocean-going submarines of high autonomy, are very identical to U214, taking operational requirements tailored to the needs of the Portuguese State.

Its most striking features are the extraordinary increase of its stealth capabilities and their autonomy in immersion, without need for charging batteries and thereby putting the Snort mast out of water, which makes it vulnerable to radar detection by aerial means of maritime surveillance. Snort is the technical term for the operation in which the submarine fully immersed but near the surface - 12 to 18 meters below the water-line - putting a tube out of water - the Snort mast - to feed air to the diesel internal combustion engines that recharge submarine batteries for a new period of deep immersion. The electrical powered propulsion is by two sets of high autonomy batteries which can be recharged by two processes:

• Via electric generator powered by diesel engines, which forces the submarine to go for a quota of approximately 18 meters, while remaining fully immersed but having to hoist the Snort mast for admission of fresh air to feed the internal combustion diesel engines. In this situation the boat will be more vulnerable to detection by passive acoustic means, or by speed cameras operated by air methods that can detect the snort mast tip out of water. However this mast was coated with radar radiation absorber material, which decreases the likelihood of detection by an opponent;
• Via a Fuel Cell system that basically is a device that combines hydrogen and oxygen through a porous membrane and that as a result produces electricity that charges the battery and water that is used on board. This system can be operated in deep immersion and allows keeping the submarine fully immersed for long periods (+17 days) without need to resort to Snort system to recharge the battery.

The reduced acoustic, electromagnetic and thermal signature makes it one of the more conventional Slinky world impossible to detect without recourse to high surface means, fitted with sophisticated state-of-the-art sensors, with very trained operators, in favorable environmental conditions and with much luck to the mix. The combination of all these factors in a given Ocean area at a given moment, taking into account the availability of existing surface, the enormous sophistication of sensors and weaponry needed and the large size of patrol areas that must be covered give the submarine an enormous tactical advantage, allowing an initiative making it the de facto Lord of the Seas, with the real capacity to disrupt and destroy much more numerous and powerful surface forces. The high level of automation of the ship is a crew of only 33 crew, which considerably reduces the costs of this operation, maintaining however a wide range of 60 days. All this high automatism has two nerve centers of information management and control, one facing the safety and conduct of platform, called EMCS (produced by Siemens) and the other facing the ISUS 90-combat-50 (produced by Atlas Elektronik GmbH). Also the introduction of better living standards, with more privacy in accommodation, which will enable the future inclusion of women in the crew. It is also a platform that meets all requirements in terms of environmental protection, being equipped with devices to prevent pollution by hydrocarbons, as well as material by the large number of systems of survival, escape and rescue.

It should be noted that the Government of Portugal caused increases in the price by specifying upgrades to the base 209 design, with features from the newer Class 214 submarines. Similarly, the Government of Portugal's choice of torpedoes to equip the submarines was problematic. While the six torpedo tubes in each sub could be armed with the U.S. Mark 48, the Government of Portugal purchased 24 Italian "Black Shark" torpedoes, considered less capable, less reliable and, at a cost of approximately US$2.8M per unit, 12 percent more expensive than the Mark 48. The Government of Portugal decision was almost certainly driven by EU pressure to buy European.