A computer-generated image of the S-80 Plus submarine

Navantia was among the companies shortlisted for the Project 75I program. A Spanish shipbuilder has announced plans to hold an industry event on April 21 as part of its campaign to sell six advanced submarines to the Indian Navy

Navantia, which is regarded as the fifth-largest shipbuilder in Europe, is offering its S-80 Plus submarine design to the Indian Navy as part of the latter's Project-75I programme. In January, the ministry of defence shortlisted five foreign companies and two Indian shipyards for the Project 75I programme. Navantia was among the shortlisted foreign companies. Project 75I envisages the construction of six diesel-electric submarines that will be capable of extended underwater endurance and have the capability to fire land-attack missiles. The project has an estimated cost of about $7 billion.

Navantia has touted the S80 Plus as the only "3,000 ton AIP submarine currently under construction worldwide. This baseline is very close to the requirements of the Indian Navy, possibly the closest among all shortlisted competitors, and meets the Indian ambition with minimum risk". AIP refers to air-independent propulsion, which negates the need to charge the submarine's batteries by using its diesel engines that need atmospheric air to operate. Running diesel engines requires a submarine to surface or use a 'snorkel', a tube to suck in air. Both modes render a submarine on patrol vulnerable to detection and attack. Moreover, a submarine running on its batteries has an underwater endurance of only two-three days.

The S80 Plus submarine, designed by Navantia has an AIP system based on a fuel cell, which uses hydrogen produced via bioethanol and oxygen processing, to generate electricity to drive the submarine. The DRDO is developing a phosphoric acid fuel cell (PACF), which uses phosphoric acid as an electrolyte that reacts with hydrogen (generated from sodium borohydride) and liquid oxygen to generate electricity. Navantia claims the S80 Plus has an underwater endurance of up to three weeks.

In a press statement, Navantia claimed "More than 100 companies in India are already in contact with Navantia for the indigenisation of equipment and materials, and around 200 are expected to participate in the event (planned for April 21)". The industry event, which will be hosted from New Delhi, will be organised remotely given the novel coronavirus situation.

The Spanish Armada is buying four S80 Plus submarines, the first of which is scheduled to be delivered in 2022. However, the project, originally called the S80 class, had seen severe delays after an error in its design phase left the submarine over 100 tonnes heavy with respect to its length. In 2013, construction of the S80 submarines was halted and an American shipbuilder brought in to modify the design. The S80 design was lengthened by 10 metres to better distribute its weight and Navantia renamed the project S80 Plus.

Interestingly, Navantia was a partner with France's Naval Group in the production of the Scorpene submarines for the Indian Navy.