October 11, 2021: South Korea test fired a new ballistic missile today, one that was launched from the first of nine new 3,400-ton KSS-3 class submarines. The first KSS-3, the Dosan Ahn Changho, officially entered service in August and this missile test was planned some time ago. The Hyunmoo-2B ballistic missile has a range of 500 kilometers and is launched from one of the six VLS tubes the new sub is equipped with. The VLS tube can also launch Hyunmoo-3C cruise missiles (1,500-kilometer range). During its sea trials Changho broke the record for the time an AIP (air independent propulsion) equipped sub spent underwater. The duration of this feat was not released but since the current record is 18 days, the Changho had to stay under at least that long. It was implied that the South Korean sub remained submerged for over three weeks.

North Korea has been experimenting with building a Cold War era SBB (diesel-electric ballistic missile sub) that can launch a smaller ballistic missile North Korea already has. There have been successful test launches from underwater barges containing the launch tube but construction of an operational SBB has not yet happened.

Early Russian SBBs were soon replaced by SSBNs (nuclear powered ballistic missiles subs). The U.S. developed VLS technology in the 1970s and VLS tubes began showing up in destroyers and cruisers in the 1980s. Most NATO navies adopted it followed by China and Russia.

South Korea is building nine KSS-3 subs in batches of three. The second and third batches will each contain upgrades over the previous batch. All KSS 3 are high seas boats with endurance of 50 days, a 18,000 kilometers range and top speed of 37 kilometers an hour underwater and 22 kilometers on the surface. These boats are built to regularly operate throughout the Pacific. The KSS 3 boats are highly automated making it possible to get by with a crew of fifty. All are armed with eight 533mm torpedo tubes, four of them capable of launching Harpoon anti-ship missiles. KSS-3 Batch 1 has six VLS tubes for South Korean developed missiles while the last six subs will have ten VLS tubes.

VLS tubes on diesel electric submarines are rare. China built an experimental Type 32 class boat in 2012 that had nine VLS tubes, three for ballistic missiles and six for cruise missiles. So far there has been no further work in that by China. A few years later Sweden designed an optional VLS capability for their new A26 subs which requires an additional 10-meter, 500-ton section with three vertical cylinders each containing six VLS (Vertical Launch System) tubes for carrying Tomahawk cruise missiles. This option is meant to attract export sales. A26s built for Sweden do not include it. South Korea is the only country with diesel-electric subs equipped with VLS tubes as standard.

The U.S. Navy pioneered the development and use of VLS technology and in the 1980s began installing twelve VLS tubes in its last 31 Los Angeles class SSNs (nuclear powered attack submarines) and continued that in the subsequent Virginia class. All this followed the 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.

Future Virginias will carry more VLS tubes. The larger Block 5 Virginias will have VLS tubes for 33 cruise missiles or a smaller number of even larger missiles in the new VPM (Virginia Payload Module) section.

The Navy currently expects to build 66 Virginias but the importance of the large and more heavily armed Block 5s may increase that to over 70 subs with most of those based on the Block 5. Blocks 1-4 of Virginia are all armed the same way but eight of the ten Block 5s have additional space to store and launch missiles and can carry 65 missiles and torpedoes, 75 percent more than earlier Virginias. This is accomplished by adding a VPM to the current design. This adds 25.6 meters to the length of the sub and increases displacement from 7,800 to 10,400 tons. The VPM adds four more of the large launch tubes that can hold different sizes of missiles. For example, each of the VPM launch tubes can carry seven Tomahawk cruise missiles or a smaller number of new missile designs in development, like the hypersonic missile. Earlier Virginias already had older individual launch tubes forward of the sail (conning tower). The VPM is added behind the sail.