A26 Blekinge - Next Generation U-boat [NGU]

The A26 type submarine for the Swedish Navy is the world’s most modern submarine program. It is a next-generation submarine with a flexible design that is adaptable for both littoral operations and ocean-going capabilities. According to Per Nilson, program manager for A26, the next generation of submarines will be a step further yet again: “It will be much quieter, the sensors will be more advanced - detecting and documenting everything that goes on in the sea - and there will be a number of new capabilities such as the multi-mission portal in the bow that allows for the hosting of divers and small manned or unmanned vehicles. It will be a first-class intelligence-gathering platform” he said in June 2015.

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. Perhaps the most unique A26 design feature is its Multi Mission Portal, for the launch and retrieval of diverse mission payloads such as manned and unmanned vehicles. The A26 submarine will be a strong intelligence-gathering platform within the wider defense network.

A26 submarine for the Swedish Navy is the world’s most modern submarine program. The submarines will be powered by conventional diesel-electric propulsion machinery and equipped with the Kockums Stirling AIP (air-independent propulsion) system. The Stirling system makes the A26 very stealthy and difficult to detect. The A26 boosts all the traditional operational capabilities of a submarine and is also a strong intelligence-gathering platform within the wider defence network. Its proven modular design ensures availability, with efficient through-life upgrades and adaptations, and low life cycle costs.

The major design changes:

• Added stealth features in notably the hydrophone area
• Flexible load-up of number of crew (17-31) and equipment. (elint, special ops, traditional attack sub, information superiority, network based command center etc)
• Ocean longivity, faster speed, longer range.
• Reduced maintenance, less logistics. More hours at sea.
• Machine gun 25-30mm (optional, likely a RWS)
• Personell protection, rubber shock protection
• Autonomous underwater vehicles
• Latest version Sterling AIP propulsion.
• Requirement to move 1000's of nautical miles, stay in that area for weeks, and return. Transit speed ocean (sweden-usa and back) 9knots, normal operational speed submerged 20+, surfaced 10+.

Extreme stealth is at the heart of Saab submarines. They are designed to counter all known physical threats, surveillance methods and cyber warfare techniques. The new A26 submarines use advanced technology to make them effectively invisible – by balancing the complete range of signatures. This makes them impossible to detect, classify and localise, ensuring you operate undetected by the enemy. Sweden has a long history of designing silent submarines. The A26 features large, resiliently mounted platforms, using extensive flexible mountings and baffles to minimise structural borne and transient noise, as well as absorb shocks.

The signature characteristics of the submarine have been optimised and balanced from all perspectives; acoustic, heat, hydrodynamics, to mention a few. This will make the A26 submarines very hard to detect, nearly invisible. A capability that is crucial for a submarine. The construction of A26 is very rigid and shock resistant in order to withstand impacts from mines and other underwater weapons. Like all submarines built by Saab, A26 will be shock tested in real life before handed over to the customer, a quality assurance that increases the survivability of the submarine and its crew.

To further reduce sound, the space between the frames is filled with acoustic damping materials. This approach is used in unique combination with many other features and methods such as sound-isolated AIP Stirling and diesel engine modules; flexible hoses and compensators; specifying maximum flow speed in air ducts and pipes; minimum bending radius on pipes; and the special design of the hull, fin and casing. The Saab Gotland-class submarine was the first submarine class to have AIP installed during the building process. In a Stirling engine, the necessary heat is produced in a separate combustion chamber and transferred to the engine's working gas, operating in a completely closed system. The working gas forces the pistons in the engine to move, thus producing mechanical energy.

Since the 1980s, Stirling AIP has been proven to be a mature and robust technology. AIP mode enables the submarine to operate for an extended time, without breaking the surface for snorting and charging the batteries by the diesel engines. The AIP system has been delivered to several export customers and has attained over 30 years of operational service, as well as several tens of thousands of running hours on board submarines. Today, all Swedish submarines are equipped with Stirling AIP.

Compact, modular and manageable, Stirling AIP systems can be dimensioned for fully submerged missions up to 45 days. Thanks to the durability and low cost of operation, the technology is used continuously at patrol speed. Stirling AIP has an extremely low signature. The diesel engines are only used for long-distance transit at medium speed in either surfaced or snorting condition. The AIP system burns a mixture of gasified pure industrial liquid oxygen (LOX) and diesel fuel. The same fuel is used for both the diesel and Stirling engines, which enable cost-effective energy production and logistics.

In the bow of the A26 there is a lock with a diameter of 1.5 meters gives the ability to take in and out groups of divers, mini-boats or sensors. The universal lock is for many different types of strategic operations. The idea is to make an enemy unsure of what the submarine actually intends and how it is equipped. Kockums calls it "multimission portal". The idea is, among other things, that the submarine should be able to lie undetected on the bottom and track with the help of remote controlled underwater vehicles.

The lock can take in and out unmanned mini-boats or be used to send out up to eight divers with equipment on special assignments. Previously, divers have often gone on their missions by climbing out of the submarine's tower, but it forces the submarine to lie exposed in surface position. One reason why the gate is not on other submarines is the difficulty of technically handling a hole of 1.5 meters in the submarine's pressure hull.

The space can also be used for storage of cargo or for pressure equalization. The regulation takes place with air and guards in the lock retain the air bubble when the outer door is opened. The six-meter long lock is built in at the expense of the two light 400-millimeter torpedo cubes found on the vessels in the Gotland class. The four large 533 millimeter stubs remain on each side of the new lock. Per Nilson believes that the compromise is related to the use of future submarines.

Saab offers three A26 variants of different lengths and displacements, based on mission requirements. Each segment represents a technological achievement. By combining a unique range of capabilities, state-of-the-art stealth technology, Air-Independent Propulsion (AIP), high endurance, versatile combat system suite and various weapons, Saab has created a shock-resistant, modular submarine designed for maximum operational flexibility. Saab submarines are designed for operational interoperability with other organisations and stakeholders, both military and civilian.

The smallest is the 50-meter “Pelagic” version which has an AIP endurance of 20 days. Next is the “Oceanic” version which measures 65 meters in length with an endurance of over 30 days. The Oceanic segment encompasses submarines of similar size and capacity to the A26 submarine, ordered for the Royal Swedish Navy. The largest “Extended Range” model is over 80 meters long and has a range of over 10,000 nautical miles.

Saab’s Pelagic segment refers to the smaller submarines, adapted for long-range missions in narrow or littoral environments. Highly manoeuvrable with high speed and a large weapon load, these submarines represent a dangerous threat to any opponent. Pelagic submarines have a lower acquisition price and operating cost and can also be offered with the Stirling AIP technology for superior submerged endurance. In the Pelagic version, the A26 has a length of less than 50 meters and a displacement of 1,000 tons (on the surface). Its range is 4,000 nautical miles (7,408 kilometers) with a cruising speed of 10 knots (18.5 kilometers per hour). At the same speed the maximum time spent at sea is 20 days using the AIP (Air Independent Propulsion) system. Manning requirements are in the range of 17-25 people.

In the Oceanic version, the A26 has a length of 65 meters and a displacement of 2,000 tons (on the surface). Its range is 6,500 nautical miles (12,038 kilometers) with a cruising speed of 10 knots (18.5 kilometers per hour) or 30 days at sea using the AIP (Air Independent Propulsion) system. The manning requirements are in the range of 17-35 people. In the Oceanic ER version (Ocean, extended range) the submarine has a length of 80 meters and a displacement of 3,000 tons (on the surface). Its range is 10,000 nautical miles (18,520 kilometers) with a cruising speed of 10 knots (18.5 kilometers per hour). At the same speed the maximum time spent at sea is 50 days using the AIP (Air Independent Propulsion) system. Manning requirements are in the range of 20-50 people. Submarines in the Oceanic Extended Range (ER) segment are the largest in the series, designed for much longer missions, greater crew size and increased weapon payload capability. Oceanic ER submarines enable long-distance operations, suitable for any navy using forward deployment of their submarines on extended missions.Saab formed a partnership with the famous Dutch shipbuilder Damen in the tender for the replacement of the current Walrus-class submarines. Damen and Saab were confident the ER will be a good solution for international markets with similar requirements.

Both the Swedish Navy and the Polish Navy will take the standard Oceanic version while the Royal Netherlands Navy had been offered the extended range version. But all are tailored to the customer.

The design of the A26 is modular, on the one hand to be able to meet any customer requirement, on the other hand to be easy to maintain and support the submarine. In addition, great attention has been paid to the sound trail of the submarine, which is very low, while the whole design has obvious stealth characteristics, as well as the materials used for its construction. Internally the submarine uses rubber bases and bulkheads to reduce noise and absorb vibrations from the operation of mechanical parts. The rudder of the submarine is of "X" arrangement, with four (4) independent surfaces, which favor the best and quietest cruising of the submarine.

All versions of the A26 incorporate the AIP Stirling system and diesel engines, while they can sail in any sea of ??the world, without operating restrictions. In the Stirling system the necessary heat is produced in a separate space and transferred to the engines, through a closed circuit and thus the movement of the submarine is produced. Stirling was developed in the 1980s and is now a mature technology. With the Stirling system, the A26 operates in the safety of the seabed for a longer time. The use of Stirling is very quiet and does not produce a thermal trace. Consumes a mixture of industrial liquid oxygen, in the form of gas.