S-80-class submarine

The S-80 Class are AIP (air independent propulsion) submarines currently under construction for the Spanish Navy. Four boats have been ordered, three of which are under construction by the Spanish company Navantia at its yard in Cartagena. The submarines are being fitted with a new propulsion system designed for a high degree of autonomy under water. Their mission includes: projection of naval power onto land, naval special warfare, surveillance, protection of naval forces and deterrence. The first was planned to enter service in the Spanish Navy in 2015, with a second in 2016, but a weight imbalance issue has been identified which is to delay the project between 12 and 24 months. The construction of the third in the series began in 2009. The Indian Navy is considering this submarine for its next generation of submarines under Project 75I.

Capabilities
The submarines of the S-80 class are designed to better complete their mission in threat scenarios. Their operational mobility will allow them to operate in remote areas, traveling discreetly at high speeds. Their air independent propulsion (AIP) system, of new technological design, will ensure their ability to remain very long periods of time in an area without being detected and their ability to operate in possible conflict zones.

Their capabilities include:
 * A combat system for multiple target acquisition in different scenarios
 * The ability to transport personnel, including special operations forces
 * Low noise and magnetic signatures in order to minimize detection
 * Low radar and infrared signatures in order to minimize detection

Propulsion
The AIP (air independent propulsion) implemented on the S-80 is completely different from the French MESMA (Module Energie Sous-Marin Autonome) project. The S-80's AIP system is based on a bioethanol-processor (provided by Hynergreen from Abengoa) consisting of a reaction chamber and several intermediate Coprox reactors, that will transform the BioEtOH into high purity hydrogen. The output feeds a series of fuel cells from UTC Power company (which also supplied fuel cells for the Space Shuttle).

The Reformator is fed with bioethanol as fuel, and oxygen (stored as a liquid in a high pressure cryogenic tank), generating hydrogen and carbon dioxide as subproducts. The produced hydrogen and more oxygen is fed to the fuel cells.

The bioethanol-processor also produces a stream of highly concentrated carbon dioxide and other trace gases that are not burned completely during combustion. This gas flow is mixed with sea water in one or more ejector venturi scrubber and then through a new system called SECO2 (or CO2 Removal System), developed by Bionet, and whose purpose is to dissolve the "bubbles" of CO2 in water to undetectable levels.

The oxygen and fuel flow rates are directly determined by the demand for power. The AIP power in the S-80 submarine is at least 300kW. A permanent-magnet electric motor moves a fixed propeller of a special design, that doesn't create cavitations at high speed.

History
In the 1980s France began studies for the replacement of their S-60 Daphné class diesel submarines. The French shipyard DCNI came up with an all-new design called S-80, with a teardrop hull and new weapons and sensors, which their government decided not to fund. DCNI then proposed a cheaper option called the S-90B, an S-70 Agosta class submarine with limited improvements which was again rejected by the French but which was exported to Pakistan. Meanwhile Spain faced the same problem in replacing their Daphnés, known as the Delfín class in Spanish service, as part of Plan ALTAMAR. Bazán (later Izar, and then Navantia) started on a new design but when it started to look like the S-80, it was agreed to collaborate in a joint venture based on the French S-80. This joint design was shown at Le Bourget Navale in October 1990.

The end of the Cold War meant that funding dried up and the joint venture had to wait until 1997 for their first sale - to Chile - of the new design, which was designated the Scorpène class in export markets. The same year Spain started to look again at its requirements, and in 1998 they indicated that they would buy four Scorpènes, optionally with an air-independent propulsion (AIP) system for greater endurance when submerged. A staff requirement for the S-80 Scorpène variant was completed in October 2001. This was soon overtaken by events, as the Armada became more interested in using submarines for power projection than in a more static, defensive role. This shift was codified in guidance of January 2002 from the Chief of Naval Operations and in the strategic defence review of February 2003. The new requirement called for a larger submarine with better endurance and land-attack missiles, which became known as the S-80A design. This was an AIP submarine with a hull diameter of 7.3 m compared to 6.2 m for the Scorpène family, a submerged displacement of around 2,400 tonnes versus 1,740 tonnes, larger rudder surfaces and a different fin position.

The Spanish government approved the purchase of four S-80A submarines in September 2003 and signed a contract with Izar on 24 March 2004. The original deal was €1,756m to design and build four submarines, about US$550m per boat, but by 2010 this had increased to €2,212m (US$700m/boat). The plan envisaged the first boat to be delivered in 2011 but government dithering over who should supply the combat system pushed it back to 2013. In 2011 Spain's budget crisis further delayed the first delivery until 2015, with the remaining boats being delivered at one year intervals until 2018. Construction of S-81 began on 13 December 2007. In January 2012 the names were announced, honouring three engineers who made submarines and the first commander of Spain's submarine force respectively - Isaac Peral (S-81), Narciso Monturiol (S-82), Cosme García (S-83) and Mateo García de los Reyes (S-84).

In May 2013, Navantia announced that a serious weight imbalance design flaw had been identified which will delay the delivery of the first submarine to the Spanish Navy until possibly 2017. Excess weight of 75 - 100 tons has been added to the sub during construction and the current design is not able to resurface after diving. A former Spanish official says the problem can be traced to a miscalculation — someone apparently put a decimal point in the wrong place or by the addition of new technologic devices. Lengthening the submarine would create additional buoyancy, though at a cost of €7.5m per metre. With the project also suffering with an underperforming AIP system (which was to allow the submarine to stay underway for 28 days but was only managing 20 days) the Spanish Defence Ministry announced in June 2013 that Navantia has signed on the US company General Dynamics Electric Boat to help solve the excess weight.