• US Navy sank ex-USS Klakring in a North Atlantic SINKEX using SM-6 and Mk 48
• UK frigate HMS Portland also fired a Naval Strike Missile during the exercise
• Drill underlined the US-UK capability gap, with no UK submarine involved

The US Navy conducted a SINKEX exercise off the UK coast in late-September which saw the test of an anti-surface variant Standard Missile 6 (SM-6) and a UK Naval Strike Missile (NSM) against a decommissioned Oliver Hazard Perry-class frigate.

According to a US Department of War release, US Navy assets involved in the exercise included the guided-missile destroyer USS Paul Ignatius (DDG 117) and the recently commissioned USS Massachusetts (SSN 798), a Virginia-class nuclear-powered attack submarine.

The test was carried out at the UK's Hebrides naval test range, off the northwest coast of Scotland around the islands and waters off South Uist, Benbecula, and St Kilda.

In addition, one of the UK’s few remaining surface combatants, the Type 23 frigate HMS Portland, also participated in the exercise.

Air assets including US Navy and Royal Air Force P-8 maritime patrol aircraft, a Royal Navy Wildcat helicopter, and US Air Force F-15E Strike Eagles were also present.

The USS Paul Ignatius struck the former USS Klakring with an SM-6 missile, while the USS Massachusetts sank the decommissioned frigate with a Mk 48 torpedo. The UK’s HMS Portland used its newly installed, canister-launched NSM to conduct its own strike.

Such exercises offer an opportunity for real-world tests of kinetic munitions against naval warships, with the US commonly using decommissioned warships for such serials.

The UK has not sunk one of its own warships for more than 20 years, as cost cuts prevent even the preparation of decommissioned vessels for use as live targets.

Instead, the UK Ministry of Defence prefers to sell out-of-service hulls for commercial recycling in Türkiye.

Contrasting contributions from US and UK navies

While the US Navy was able to provide a modern guided missile destroyer (USS Paul Ignatius was commissioned in 2019) and one of its latest Virginia-class SSNs, the UK was only able to commit a single Type 23 frigate, HMS Portland, which was commissioned in 2001.

No UK submarine was present, as all five of the Astute-class SSNs are currently languishing in port, amid a maintenance and readiness crisis. A sixth recently set off for a lengthy period of sea trials.

The Royal Navy has just five Type 23 frigates remaining operational, with the Type 26 and Type 31 replacements still years away from entering service.

In addition, there are significant differences in the surface attack capabilities used by the US and UK navies in the SINKEX of the former USS Klakring.

The US Navy’s SM-6 features a secondary anti-surface warfare (ASuW) mode to enable it to strike surface targets, augmenting its air and ballistic missile defence roles. The SM-6 is able to operate at ranges in excess of 200 nautical miles (370+ km), reaching speeds of over Mach 3.5, and is equipped with a 64 kg (140 lb) blast-fragmentation warhead.

The UK’s NSM, in contrast, is a subsonic ASuW munition, recently installed across some of the remaining Type 23 frigates. Unlike the SM-6, which is fired from a vertical launch system, the NSM is canister-launched, with each Type 23 frigate carrying a maximum of eight missiles.

The NSM is thought to have a range of around 250km and has a larger 125kg warhead.