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Naval Warfare

HMS Onyx (S21)

Diesel-Electric Attack Submarine [ 1967 ]

HMS Onyx, part of the twenty-seven strong Oberon-class of diesel-electric attack boats, became a Falklands War veteran before her career ended in 1991.

Authored By: Staff Writer | Last Edited: 05/01/2018 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site.

The Oberon-class was a group of twenty-seven conventionally-powered (diesel-electric) attack submarines built at British shipyards during the middle-part of the Cold War period (1947-1991). The type was in active commission from 1960 until 2000 and went on to serve the nations of Britain, Australia, Brazil, Canada, and Chile for their parts in naval history. All of the boats have since been decommission with eight complete examples having been preserved.

The class was used to succeed the locally-designed and constructed "Porpoise-class" boats and, among their number, became HMS Onyx (S21) which served the storied British Royal Navy (RN) in the attack/ocean-patrol roles for her time at sea. The Oberon-class were more-or-less the same submarine as the earlier Porpoise boats save for new machinery, stronger steel, and other more subtle changes that warranted a new class name. HMS Onyx was laid down by Cammell Laird of Birkenhead on November 16th, 1964 and launched on August 18th, 1966. She was commissioned for service on November 20th, 1967 and would go on to see a twenty-four year career that included participation in the Falklands War (1982).

As designed, displacement ran 1,610 tons under standard load and over 2,000 tons under full load. Dimensions included a running length of 295 feet with a beam of 26.5 feet and a draught of 18 feet. Power was from 2 x Admiralty Standard Range 16 (SR16) VMS diesel-fueled generator units coupled with 2 x Electric motors offering 3,000 horsepower for undersea travel. All this drove 2 x Shafts at the stern. At the time of their arrival, the Oberon-class was considered one of the quietest diesel-electric forms ever built.©MilitaryFactory.com
The boat could make headway at speeds of 12 knots when surfaced and, more importantly, 17 knots when submerged. Due to the diesel-electric nature of the class, these boats were required to surface aft a period of time to recharge battery stores and expel dangerous, built-up CO2 gasses. Aboard was a crew complement of 68 that included six officers and Type 186 and Type 187 sonar systems were carried as was an I-band surface-search radar unit. Installed armament encompassed 8 x 530mm (21") torpedo tubes at the bow with twenty-four reloads carried. With this considerable war load, the boat could wreak havoc on enemy shipping and other surface threats all the while holding the initiative.

HMS Onyx was the only conventionally-powered Royal Navy submarine to participate in the Falklands War of 1982 against Argentina. In the conflict, the boat was used to insert special forces operatives ashore due to her relatively compact size when compared to her larger nuclear-powered cousins then in service. The war, which ended as a decisive British victory, showcased the importance of a powerful naval arm (and logistics) when attempting to reach far-off parts of the globe - and HMS Onyx certainly played her part as intended.

In the post-war period, she used her torpedoes against Sir Gallahad, a 1960s landing / logistical vessel heavily damaged during the Falklands War, to create a protected war grave - this became the last notable actions for the boat. For budgetary reasons at the close of the Cold War, HMS Onyx was decommissioned from Royal Navy service in 1991 and began her retirement as a preserved floating museum at Birkenhead, UK before being purchase for display at The Submarine Heritage Centre at Barrow-in-Furness (Cumbria). Despite additional efforts made to preserve her further, the boat was taken over from the museum in liquidation and scrapped to satisfy debt relief.

The Oberon-class was succeeded in RN service by the Upholder-class as British boat numbers began to shrink in the late-Cold War period (the dissolution of the Soviet Empire now negated the need for large military numbers). As such, the British focus was placed on fewer, though far more powerful, nuclear-driven types instead of quantitative diesel-electric forms favored by most European powers.©MilitaryFactory.com
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United Kingdom (retired)
Operators National flag of the United Kingdom
United Kingdom
National Origin
Decommissioned, Out-of-Service
Project Status
Hull Class


Submerged Attack
Traveling under the surface to search, track, and / or engage or reconnoiter areas.
Maritime Patrol
Active patroling of vital waterways and maritime areas; can also serve as local deterrence against airborne and seaborne threats.
Fleet Support
Serving in support (either firepower or material) of the main surface fleet in Blue Water environments.

295.2 feet
(89.98 meters)
26.5 feet
(8.08 meters)
18.0 feet
(5.49 meters)
Displacement (Submerged)

2 x Admiralty Standard Range 16 (SR16) VMS diesel generators with 2 x Electric motors outputting 3,000 horsepower to 2 x Shafts astern.
12.0 knots
(13.8 mph)
Surface Speed
17.0 knots
(19.6 mph)
Submerged Speed
10,341 nm
(11,900 miles | 19,151 km)
1 knot = 1.15 mph; 1 nm = 1.15 mile; 1 nm = 1.85 km

8 x 21" (533mm) torpedo tubes at the bow (all bow-facing).


Military lapel ribbon for the Cold War period
Military lapel ribbon for early warship designs
Military lapel ribbon for the Falklands War
Military lapel ribbon for the 1991 Gulf War
Military lapel ribbon for the Korean War
Military lapel ribbon representing modern aircraft
Military lapel ribbon for the Attack on Pearl Harbor
Military lapel ribbon for the Russian Invasion of Ukraine
Military lapel ribbon for the Vietnam War
Military lapel ribbon for the World War 1
Military lapel ribbon for the World War 2


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Image of the HMS Onyx (S21)
Image from the Public Domain.

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