The Sting Ray lightweight anti-submarine torpedo, the RN’s primary ASW weapon, is being upgraded to Mod 2 standard, Navy Lookout reports.
BAE Systems will undertake the design work for the upgraded torpedo at its facilities in Portsmouth and Fife, sustaining over 100 highly-skilled engineering and manufacturing roles as well as another 100 or so jobs in the supply chain across the UK.
In September 2024, the UK Ministry of Defence (MoD) announced a £60.1 million contract had been awarded to BAE Systems for the Assessment Phase of the Sting Ray lightweight torpedo Mod 2 upgrade. While the award had been made earlier in the year, it was not publicised due to election Purdah rules.
The Sting Ray torpedo (Mod 0) formally entered RN service in 1983 (early versions were rushed into service for the Falklands War). The Mod 1 version remains in service today and can be delivered from the Type 23 Frigates’ Magazine Torpedo Launch System (MTLS), or more likely dropped by a Merlin Mk2 or Wildcat helicopter. Mod 1 is officially capable of 45 knots and uses a mix of active and passive sonar guidance. The 45kg warhead is a shaped torpex charge designed to penetrate the tough pressure hull of the submarine.
Mod 1 entered service in 2001 and features a much-improved sonar, tactical control system and a new sea water-activated battery. The Mod 1 weapons were further modified from 2013 onwards with a new insensitive munition-compliant warhead which is a step change in handling safety.
Although Mod 1’s official out-of-service date is set for 2030, preliminary studies for its replacement began in 2019. The 2021 Defence Command Paper confirmed a new lightweight torpedo would be procured. BAE Systems had already begun self-funded work on what was provisionally called the ‘Future Lightweight Torpedo’ project and this development work will pull through into Sting Ray Mod 2, accelerating the assessment phase.
Sting Ray is regarded as an excellent weapon, likely superior in many respects to the US Mk 54 equivalent. It is optimised for open ocean operations against fast, deep-diving SSNs and SSBNs. Its use in shallower or more congested waters is rather limited as it takes time to arm and begin its search pattern. Mod 2 is likely to address this weakness with better littoral waters performance and improved target discrimination where there is high ambient noise or sophisticated decoys are deployed. It is also likely to have the ability to detect and target small, stealthy LUAV/XLUAVS which will increasingly be part of the underwater threat.
P-8A compatible
In November 2023 it was confirmed that Sting Ray Mod 1 will be integrated into the P-8A Poseidon. The software update will be globally available for all P-8A operators, allowing them to be armed with either Mk54 or Sting Ray. The UK initially acquired a stock of US-made Mk54s to provide an initial operating capability for the RAF’s aircraft but will now be able to take advantage of the larger UK Sting Ray inventory and eventually the Mod 2 upgrade. It will also provide a further degree of interoperability between RAF, RNoAF and US Navy Poseidon’s jointly operating from RAF Lossiemouth, Naval Air Station Keflavik and Evenes Air Station.
The US has developed a High Altitude Anti-Submarine Warfare Weapon Capability (HAAWC), a glider kit that allows the Poseidon to drop torpedoes from medium-high altitude, hugely extending the range from the aircraft to the drop location. It also avoids the need to descend to low-level for weapon release saving time, fuel and wear on the airframe. A Sting Ray compatible HAAWC would seem to be a sensible low-cost option for the RAF to pursue.
Delivering the punch
In June this year, the RN issued a Request for Information (RFI) notice for what it calls a future Long Range Anti-Submarine Warfare Weapon (LRAW). This is not a funded commitment and just a case of understanding what might be available and cost implications. Industry is expected to respond to proposals by April next year
LRAW can be described as a missile that will be fired from Mk 41 VLS cell capable of delivering an ASW torpedo beyond the range of existing submarine-launched heavyweight torpedoes. The weapon would be integrated with the ship’s combat and sonar systems and 500 missiles should be used as the costing assumption. LRAW would have little in common with the US ASROC system, demanding significantly improved range. LRAW will need to carry the ASW torpedo more than 50km to put the launch platform beyond the reach of the latest heavyweight torpedoes.
The LRAW RFI is only for the rocket and in practice, Sting Ray Mod 2 is the only viable payload of British origin. BAES are believed to have had informal talks with MBDA and Nammo about potentially supplying the rocket, while the LRAW requirement would have implications for the Mod 2 design. The forces placed on the torpedo when fired from a rocket are much more severe than the relatively gentle pneumatic launch from the MTLS or a parachute-retarted decent from a helicopter.
There are alternative ASW weapon delivery methods to MTLS, LRAW or a helicopter but the technical challenge is more complex than it might first appear. Other options under development are the Proteus Rotary Wing UAS, simpler heavy lift UAS or the Kingfisher gun-launched depth charge round. Finding a submarine will always be challenging but it is vital that the ASW operator also has a selection of reliable weapons available to prosecute the contact as quickly as possible.
