Sweden’s only submarine builder, SAAB, revealed in May that it had developed a variant of its new A26 diesel-electric submarine with an additional 10 meter, 500 ton section that contained three vertical cylinders containing each containing six VLS (Vertical Launch System) tubes for carrying Tomahawk cruise missiles. The A26 would be the first non-nuclear powered submarine equipped with this technology. Sweden would only say the VLS feature was developed for an unnamed export customer.
The Americans pioneered the development and use of VLS technology and in the 1980s began installing twelve VLS tubes in its last 31 (out of 62) Los Angeles class SSNs (nuclear powered attack submarines) and continued that in the subsequent Virginia class and in a late 1990s conversion of four older SSBN (nuclear powered ballistic missile sub) to replace the ballistic missiles with 154 Tomahawks. These submarine VLS launched Tomahawks have been used in combat regularly since then.
The A26 is a replacement for the Cold War era Gotland class boats and the only customer so far is Sweden, which ordered two of them in 2015. Two A26 subs will be in service by 2019 but all the new technology for them will not be ready until 2022.
The two A26s will eventually replace the three Gotlands that entered service in 1996. The basic A26 is a 1,900 ton boat that is 63 meters (207 feet) long and armed with a variable number of 533mm and 400mm torpedo tubes (similar fashion to the Gotlands but with about 20 percent more mines and torpedoes). It was revealed that the A26 can carry up to fifteen 533mm torpedoes, missiles or mines. The first two A26s will cost about $500 million each. Underwater endurance with an improved AIP (Air-Independent Propulsion) is the same as the Gotlands; 18 days with overall endurance of 45 days. The A26 crew is smaller (about 20 and accommodations for up to ten more)).
The A26 has better electronics and can dive a bit deeper (at least 200 meters/650 feet). Both designs were mainly intended for coastal waters and the relatively shallow Baltic Sea (average depth 55 meters and max depth 459 meters). The A26 is also equipped to carry naval commandos and has a special chamber for the commandos to leave and enter the submerged sub. The core stealth technology for the A26 is called GHOST (Genuine HOlistic STealth) and some of this may end up in one or more of the refurbished Gotlands. GHOST involves more tech for keeping machinery even quieter than it is now as well as designing the shape of the A26 to make it more difficult for sonar and other sensors to detect.
The new VLS variant enables the A26 to handle more underwater operations as well as UUVs (unmanned underwater vehicles). Sweden does not like to make public all details of their new A26 class in part because the design incorporates many clever design ideas and new technology. This was a feature of earlier Swedish submarine designs. It was revealed that the A26 will have a “ghost mode” that makes the sub virtually undetectable while submerged. This includes the ability to sit on the sea floor, as if it were inert wreckage, while divers from the sub can still move in and out to plant mines or perform other functions. In short the A26 will emphasize stealth and the ability to dominate shallow and “busy” (lots of inlets, rivers and islands) coastal waters.
What made the older diesel-electric Gotland unique was that it was the first submarine designed from the start to use AIP. With AIP it could remain submerged for 19 days. Gotlands were also among the quietest non-nuclear submarines in the world. The three Gotland class boats are highly automated, with a crew of 30. They displace 1,494 tons, are 60.4 meters (198 feet) long and have four 533mm torpedo tubes (with 12 torpedoes) and two 400mm tubes (with six torpedoes). They can also carry 48 mines externally.
Meanwhile the three Gotland boats are undergoing refurbishment and upgrades, which was always meant includes some of the new gear developed to the next class of subs. The refurbed Gotlands can serve into the late 2020s if need be. There are many nations who seek to buy second-hand Swedish subs and that’s what may happen to the Gotlands.
The U.S. Navy had a high opinion of the Gotlands as they leased one of them (along with Swedish crew) for two years (2006-7) to be a vital part of an anti-submarine warfare training program. The Gotland was something of a worst case in terms of what American surface ships and submarines might have to face in a future naval war. None of America's most likely naval opponents (China, North Korea or Iran), have many or any AIP boats, but they do have plenty of diesel-electric subs which, in the hands of skilled crews, can be pretty deadly. China is already putting AIP subs into service. Training against the Gotland enabled the U.S. Navy to improve its anti-submarine tactics and techniques, as well as getting much valuable data from inside the Gotland. All the results of this training is highly classified, but it was apparently successful enough to get the one year program extended for another year.