Military

It's alive! French Navy takes delivery of nuclear 'Frankensub'

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SNA Perle and Saphir awaiting mating
Naval Group
SNA Perle and Saphir awaiting mating
Naval Group
SNA Perle and the Naval Group crew
Naval Group
SNA Perle after repairs
Naval Group
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In a move worthy of an old-school mad scientist, Naval Group has handed over to the French Navy a "Frankensub" made by stitching together the back half of one nuclear attack submarine with the front half of another.

On June 12, 2020, the French Navy suffered a major mishap when the Rubis-class nuclear attack submarine SNA Perle caught fire while in drydock in Toulon. The fire severely damaged the forward section to the point where it would have been reasonable to simply scrap the boat and call it a day. Instead, the French government decided on a course of action that was almost as ambitious as building a whole new submarine.

Under the eye of the Fleet Support Service, Naval Group was contracted to move the damaged sub to Cherbourg and continue refueling, repair, and modernization work on the undamaged aft section of the Perle, along with clearing out a lot of firefighting foam. They then took the decommissioned Rubis-class boat SNA Saphir and cut off its aft section.

SNA Perle after repairs
Naval Group

Now came the tricky bit. Naval Group then tried to fit the forward section of Saphir to the rear section of Perle. That's a very simple statement to write, but, in practice, it is a nightmare of engineering. Even though two submarines might be of the same class and design, each one is a unique creation as engineers and shipyard experts solve thousands of problems on the fly related to getting the boat to work.

Fitting the two sections together was like an organ transplant where the patient not only has to recover, but withstand the pressure of thousands of feet of seawater afterwards. This meant using highly advanced cutting and welding techniques and the precise alignment of the two hulls where even the smallest deviation could spell disaster.

Then came the fun part of reconstructing the interior decks as well as connecting hundreds of pipes, cables, wires, and various systems. According to Naval Group, this took 300 people, 100,000 engineering hours, 2,000 updated plans and design documents, 250,000 industrial hours, 2,000 electrical connections, and one million hours of maintenance and repairs.

Having completed sea trials, SNA Perle is expected to remain in service until 2028.

Source: Naval Group

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6 comments
pete-y
I guess it is similar to the stretching of ferries to add length and even breadth. Just more cables!!
Rick O
They said the other sub was decommissioned, but not why. I'm curious as to why they didn't just re-commission the sub, and use parts as needed from the damaged sub? I sure wouldn't want to be a sailor in this thing.
kwalispecial
Let me volunteer to be the last person to go on that sub.
CDE
Gee, did they really save any money as opposed to building it from scratch?
niio
@Rick A nuclear sub is not a sub with a reactor in it, it is a reactor shaped like a sub, at least the back half. These reactors are not rebuilt, they are replaced. This is what was done with Saphir.
Gregg Eshelman
The Saphir was the second Rubis class submarine built. Construction started in 1979. Perle started construction in 1987. The first four of the class had a very different forward structure, which was rebuilt with the Améthyste modifications to pretty much match the Améthyste and Perle. There was a very large amount of rework done to the first four for noise reduction and hydrodynamic improvements. It likely would have been far easier to piece together the Améthyste and Perle OR any combination of the Rubis, Saphir, Casabianca, and Émeraude. But since only the Rubis and Saphir have been decommissioned, one of them had to be the donor.

Another issue with the Rubis class is they have a single hull and the reactor and power system is tightly integrated into the boat so there's no removing and swapping the reactor by cutting a hole and taking it out. They'd have to take everything around it all the way to the exterior.

Now the French Navy has something akin to the SR-71C that was pieced together from a YF-12A and an SR-71. https://avgeekery.com/there-can-be-only-one-the-saga-of-the-only-sr-71c-blackbird-ever-built/