French ‘Franken-Submarine’ Returns To Service Years After Fire

France’s Rubis class nuclear-powered attack submarine Perle has finally returned to active service after nearly four years. Perle had begun undergoing a routine maintenance and refit cycle in 2019, but then suffered a devastating fire in 2020 that required extensive repairs. This included grafting on a ‘new’ front half taken from a decommissioned Rubis class submarine, the ex-Saphir. The result is a unique submarine that is slightly longer than a standard Rubis.

The French Navy and shipbuilder Naval Group announced Perle‘s return to the “operational cycle” yesterday in separate press releases. The milestone had been formally reached on June 30. Perle, which was first commissioned in 1993, was the last Rubis class submarine built and is one of four currently in French service.

The Rubis class submarine Perle. Naval Group

Perle‘s saga began in 2019 when it arrived at French shipbuilder Naval Group’s yard in Toulon, along the country’s Mediterranean coast. This was for a scheduled “unavailability for maintenance and repairs,” which the French also refer to by the acronym IPER.

The submarine then suffered massive structural damage to its bow end in a fire that began on June 12, 2020, and that lasted for more than 14 hours. Hundreds of firefighters were needed to bring it under control. Fires onboard ships and submarines, especially those in port for maintenance with only skeleton crews onboard, can easily become disasterous. This was made particularly clear by the fire that raged for days aboard the U.S. Navy’s Wasp class amphibious assault ship USS Bonhomme Richard in 2020 and led to the vessel having to be scrapped. Submarines present particular complexities that make fires onboard even more dangerous, as you can read more about here. The nuclear reactor aspect is also a huge issue, clearly.

A picture of Perle‘s bow after the 2020 fire. BENOIT EMILE/MARINE NATIONALE/DÉFENSE

Perle was subsequently moved to Naval Group’s yard in Cherbourg, in the northern end of France on the English Channel, for what was originally described as a “nose job.” It then emerged that the decision had been made to combine the undamaged rear half of the submarine with the front section taken from the former Saphir. A ‘plug’ measuring 4 feet 6 inches wide was inserted between the two halves as part of the “hybridization” process.

In late 2021, the repaired Perle returned to Toulon to complete the rest of the scheduled IPER work. The submarine suffered another thankfully more minor fire there in September 2022. At the time of writing, there do not appear to be any official statements on the causes of either the 2020 or 2022 fires.

Perle finally left drydock there and began dockside testing in November 2022, which was followed by sea trials in May of this year. That included the submarine’s first test dive since its ordeal began.

Perle in drydock. Naval Group

In its press release about Perle’s return to service, Naval Group said that the repairs to the submarine following the 2020 fire required some 100,000 hours of engineering work that included the creation or updating of more than 2,000 plans and design documents. The company had previously highlighted the use of digital engineering tools, and the creation of a so-called “digital twin” of Perle, to help with this phase of the repair work.

Digital engineering has long been touted as being potentially revolutionary, especially when employed by defense contractors to help with complex projects like the repair of Perle. However, there has been growing skepticism about the true scope of the benefits of digital engineering, as you can read more about here.

Altogether, Naval Group says it then took another 250,000 hours of “industrial work,” to complete the “hybridization” of Perle. How much it ultimately cost to repair the submarine is unclear.

It’s worth noting that the idea of repairing a badly damaged submarine by cannibalizing half of another boat of the same class is rare, but not without precedent. The U.S. Navy’s Los Angeles class nuclear-powered attack submarine USS San Francisco went through a similar process after hitting an underwater seamount in the Pacific Ocean in 2005. The bow of the decommissioned USS Honolulu was subsequently grafted onto the San Francisco.

The US Navy’s Los Angeles class attack submarine USS San Francisco after its collision in 2005. USN

The U.S. Navy has more recently found itself in a similar situation following the Seawolf class submarine Connecticut‘s collision with an underwater seamount in 2021. Unfortunately, only three of the advanced Seawolf class boats were ever built, all of which are highly prized and in great demand, and there are no decommissioned examples to harvest components, let alone entire sections from. The repair bill for this submarine is expected to be very high.

For Perle, the scheduled IPER process then took more than one million hours to finish on top of the fire repairs. More specific details about that work are limited, but the French Navy has disclosed that it included the integration of the new F21 Artemis heavyweight torpedo onto the boat. Naval Group also makes the F21 and delivered the first of these torpedoes to the French Navy in 2019.

The French Navy’s newer Suffren class nuclear-powered attack and Le Triomphant class nuclear-powered ballistic missile submarines have been steadily armed with the F21, as well. Artemis is also expected to be the main torpedo armament for France’s future next-generation SNLE 3G ballistic missile submarines.

How long Perle or the rest of France’s remaining Rubis class submarines will stay in service now remains to be seen. The country has been in the process of replacing them with Suffrens since 2020. The French Navy and Naval Group say that Perle specifically at least has the potential to remain in service until 2028 thanks to the IPER and other repairs.

French Navy

Regardless, the time, effort, and likely high cost involved in getting Perle back into service shows that the French Navy places huge value on the boat and retaining a certain number of nuclear attack submarines on duty at any one time. Perle becoming operational again comes amid the ongoing fallout in Europe broadly from Russia launching its all-out invasion of Ukraine last year.

There is also the matter of rising concerns about China’s military posture and general influence in the Indo-Pacific region and beyond. In recent years, France has been expanding its military engagement in that part of the world, including through deployments of Rubis class submarines.

“I’m advocating to my European partners to engage with us, especially in the Indian Ocean – to fill the gaps and not let insecurity gain … because of what’s going on in Asia,” France’s Admiral Pierre Vandier, the French Navy’s Chief of Staff, said at a conference in London in May, according to a report from Naval News.

The newly returned to service Perle now looks set to be an important component of the French Navy’s future operations for years to come.

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Joseph Trevithick

Deputy Editor

Joseph has been a member of The War Zone team since early 2017. Prior to that, he was an Associate Editor at War Is Boring, and his byline has appeared in other publications, including Small Arms Review, Small Arms Defense Journal, Reuters, We Are the Mighty, and Task & Purpose.