Building your own attack submarine from scratch is one of those things you either don’t do, or you do badly. The club of countries that can pull it off without foreign hand-holding is small, and Spain spent decades not really in it.<\/p>\n
For years the Spanish Navy rode French-designed hulls: Daphn\u00e9 boats, then Agostas. In the 1990s it went in with France on the Scorp\u00e8ne, a slick little export sub that sold to Chile, Malaysia, India and Brazil. Then Madrid walked away from that arrangement, bet the farm on a domestic design called the S-80, and proceeded to learn the hard way why this club stays small.<\/p>\n
And yet here we are. The second boat of the class is now in the water doing real work. Navantia has confirmed that the S-82 Narciso Monturiol<\/a>, the second-in-class of the S-80 program, has begun its first sea trials off Cartagena.<\/p>\n It’s a roughly 3,000-ton diesel-electric attack sub, built start to finish on Spanish soil. If these trials go the way Navantia hopes, it’s headed for the Spanish Navy before the year is out.<\/p>\n Key figures for the S-80 class, per Navantia. The three-week submerged endurance applies once the AIP system is fitted; the S-82 enters service without it for now.<\/p>\n “Sea trials” sounds like the moment a new boat tears off into the Atlantic at flank speed. It isn’t.<\/p>\n The first outing was on the surface, under the boat’s own power, and it kicks off a long testing campaign meant to validate performance and onboard systems before the handover later this year. Translation: they’re checking that the thing moves, steers and powers itself on top of the water before anyone gets clever about going deep.<\/p>\n Most of the hard part already happened pierside. Over the past few months, Navantia ran the boat through harbour trials covering battery charging, fuel loading, the diesel generators, electrical generation and the platform control system. The sea phase is where they confirm it all behaves once the lines are cast off.<\/p>\n The diving comes later. Navigation runs, diving evaluations and performance checks under real conditions are what ultimately clear the boat for delivery. You don’t take a brand-new submarine to maximum depth on day one. You do it after a few thousand hours of unglamorous box-ticking.<\/p>\n The S-80 exists because Spain stopped wanting to buy French. For decades the Navy made do with French Daphn\u00e9 boats, the Delf\u00edn class in Spanish service, and then the Agosta-based Galerna class.<\/p>\n In the 1990s, Navantia and France’s DCN, now Naval Group, jointly developed the Scorp\u00e8ne, first shown at Euronaval in 1990 and aimed squarely at the export market. It worked there. It did not survive Spain’s own requirements.<\/p>\n The Scorp\u00e8ne was simply too small for what the Spanish Navy wanted, so Madrid launched the bigger S-80, the two yards parted ways, and the S-80 became a wholly Spanish design. Spain ordered the boats into production in 2003. That’s roughly when the trouble started.<\/p>\n You can’t tell the S-80 story without the weight problem. The original hull was sized too small, the math didn’t add up, and the program had to be rescoped.<\/p>\n Errors in the design calculations left the boat roughly 70 tons overweight. That’s the polite way of saying they’d built one that might not have come back up. It was serious enough that Spain brought in America’s General Dynamics Electric Boat to help sort it out.<\/p>\n The fix lengthened the hull by about ten meters, added cost, and added years. The lead boat, S-81 Isaac Peral, didn’t enter service until November 30, 2023. So the S-82 starting trials now is the program’s second proof that Navantia’s redesign actually floats. Or rather, sinks on purpose and comes back.<\/p>\n The dimensions are useful context. Navantia puts the S-80 at around 80 meters long, with a hull about 7 meters across and a submerged displacement of roughly 3,000 tons.<\/p>\n That wider hull matters. At 7.3 meters across the pressure hull, against the Scorp\u00e8ne’s 6.2, it buys an extra deck level inside the same basic shape. This is a serious oceanic patrol boat, not a coastal interceptor, and it sits near the top of the non-nuclear weight class worldwide.<\/p>\n The weapons run through those six 533mm bow tubes: heavyweight DM2A4 torpedoes, UGM-84 Sub-Harpoon anti-ship missiles and SAES seabed mines.<\/p>\n There’s a headline capability on top of that. The S-80 was designed from the start to fire tactical land-attack cruise missiles from the same tubes, the Tomahawk among them. Navantia bills the class as the only conventional submarine in NATO or the EU built to do that. France manages the same trick, but on its nuclear Barracudas<\/a>, not a diesel boat.<\/p>\n Crewing is small, which is the whole point of a heavily automated modern sub. The S-80 runs with 32 sailors plus eight extra berths, courtesy of Navantia’s platform control system. For scale, even Russia’s far larger nuclear Yasen-M<\/a> takes 64. Fewer bunks, more sensors, longer patrols.<\/p>\n The signature piece of the S-80 is its air-independent propulsion, and it isn’t on this boat yet. The first two hulls, Isaac Peral and Narciso Monturiol, enter service without it and get it fitted during their first major overhaul.<\/p>\n The third boat, S-83 Cosme Garc\u00eda, is the first to carry it, with the fourth getting it during construction. Handy in theory, absent on the S-82 for now.<\/p>\n The chemistry is the unusual part. Navantia’s system, called BEST (Bio-Ethanol Stealth Technology), reforms bioethanol into hydrogen and feeds it to a fuel cell, which the company says lets the boat stay submerged for up to three weeks.<\/p>\n Most fuel-cell submarines carry hydrogen onboard in tanks. Navantia makes its own from bioethanol instead, which sidesteps the hydrogen-storage headache. Earlier this month it fired up that system for the first time, running the AIP module on the S-83<\/a> at a dedicated test hall in Cartagena.<\/p>\n Building a sovereign submarine industry is expensive, slow and politically annoying. Reporting has put the per-boat cost near a billion euros, closer to a nuclear sub than a normal diesel one. Spain decided it was worth it anyway, and the S-82 going to sea is the most visible payoff so far.<\/p>\n The clearest proof is the lead boat. In late 2025, Isaac Peral completed its first deployment under NATO operational control, in Operation Sea Guardian<\/a> in the Mediterranean: 46 days at sea, 840 hours submerged, more than 5,000 nautical miles. It even made a port call at Alexandria, the first Spanish submarine to tie up in Egypt in 91 years.<\/p>\n The class also lets the Navy finally retire the Agosta boats. That fleet is now down to a single hull, the S-71 Galerna, which has been in the water since 1983 and was kept alive largely because the S-80 ran so late.<\/p>\nWhat actually happens when “sea trials” start<\/h2>\n
The France divorce, briefly<\/h2>\n
The buoyancy mess they had to fix<\/h2>\n
What the boat brings to a fight<\/h2>\n
The AIP question (and the bioethanol thing)<\/h2>\n
Why Spain went through with it anyway<\/h2>\n