Gymnote (1964)

Conventional Ballistic Submarine (Built 1963-66). Service 1966-1986.

Gymnote (S655) was an experimental submarine of the French Navy, a conventional model which only purpose was to test submarine-launched ballistic missiles (SLBM), powered by diesel electric engines and had four tubes. Gymnote was previously the world’s first all-electric submarine, built in France in the late 19th century. She was built at Cherbourg between 1963 and 1966 (ordered in 1861) and once she fulfilled her role, helping to create the Redoutable class SSBNs, she was used for other tests until decommissioned in 1986.

Development

Development of nuclear power seen from France

In the history of submarines, January 1, 1955 was quite a date, when USS Nautilus crossed for the first time the Atlantic. France, which saw itsefl still occupying a prominent place in submarines, could not remain indifferent to this revolution of nuclear propulsion and its infinite possibilities. Nuclear as a weapon was known since 1945 and the development of a strategic submarine, could not be designed around any other propulsion than nuclear to really exploit its potential to the fullest. In 1956 France worked on the Q 244 pushed forward by PM Pierre Mendès France as early as 1954. This new project was around 4,500 tons, already well ahead of the 1920s Surcouf (3,500 tons). Q 244 combined a 8.50 meters wide pressure hull for 110 meters long and was only conceived as a SSN.
TYhe major issue was that of building a natural uranium reactor to fit in the space available. In 1958 this started to peter out, and prior to that, Washington had good relations wit the former government and follow with great interest these works, and even started proposals of help, with a great deal of scepticism however, notably from Rickover. The arrival of General de Gaulle however, which decided to withdraw from NATO’s integrated command stopped all discussions and offers. This killed Q 244 in the egg. Not having enriched uranium, the French meanwhile decided in 1957, to build an isotope separation plant at Pierrelatte. There was 440 kilos or uranium available, sufficient for a single propulsion installation. But due to severe supply restrictions it was strictly reserved for land-based projects.

In 1960, decision was taken, to build a prototype in Cadarache, since the French nuclear test center. Engineers worked with the General Delegate for Armament and took over what was already done in nuclear propulsion to concentrate only in military applications. At this site a reactor in 1964 achieved its maximum power. The facility was a veritable “submarine on land” and later enabled to fit in the new Redoutable class when started the same year. It was made in a hull placed in a swimming pool, surrounded by all control installations and very realistic for dissipation of power. Sailors started to be drilled in it, so it was used for training crews and prepare the Redoutable class.

Genesis: Q 244, the first French SSN (1954-58)

The French planned a nuclear propelled submarine in 1954, even laying down a hull, Q244 in 1955. However alongside it, France did not developed an uranium enrichment facility in time, and the planned power plant, a heavy water reactor, could only use utilize natural uranium. French engineers were could not produce a reactor small enough to fit into the submarine in 1957-58, and so the project was cancelled in 1959. What the Q 244 would look like.
Q 244 was an interesting project, and informations that survived showed a hull based on the large Narval class, stretched aft and with a modified fin. Her outer steel hull measured 113.75 m overall, beam 11.7 m, for a final displacement of estimated around 4,800t submerged and with a 44-53 MW reactor, capable of 23 knots and 90 days autonomy (food).
There was no way to obtain a US reactor of the PWR type in 1958 so the process was to take much, much longer, only relaunched as De Gaulle, which returned to power the same at the occasion of the Algerian War mess relaunched the project. Leaving NATO and forcing US troops out of the territory was not to please Washington obviously and ruined any chances of obtaining anything to built the French deterrence.
In 1960 the new French government started to develop an independent nuclear deterrent and create a SLBM from scratch and without help. Hull Q244, which was started and still available, was redesigned as a trials submarine with diesel-electric propulsion but four missile tubes in extended casing. It was the exact opposite of a SSN. Many in the Navy deplored De Gaulle’s decision as it placed France in a considerably more precarious situation. With a US reactor, Q 244 could have been as early as 1959 the first French SSN. Instead, France will have to wait until the commission of Le Redoutable in… 1971. Worst still, its first SSN, the Rubis class, was operational by …1983. This was the price for a complete autonomy, but was detrimental to France’s strategic posture in the could war. Until 1971, the Fre,ch deterrence rested of the Armée de l’Air’s Mirage IVs with conventional free-falling bombs (1964) and land-based sites SLBMs, notably at Albion in 1971 with 18 solids and S2 medium range missiles (capable of reaching only 3000 km or 1900 nmi). This was completed by a “last warning” tactical strike by Pluton missile vehicles (120 km (75 mi)).

Towards SSBNs

The birth of French nuclear ballistic submarines, which arrived before the first SSN (or nuclear attack submarines) were even built, a rare case in the restricted club of nuclear powers, was an interesting step, the Gymnote. This unique submarine was never truly “operational” but a test model to try ballistic missile tubes and launches. Technically, she was an SSB, conventionally propelled. Q244 was ordered in 1961 under De Gaulle’s plan for a French deterrence. The US opposed any help in that matter, unlike Britain, so France had to create its nuclear power from scratch. The maritime part of it was to comprise a class of SSBNs for which there was absolutely no experience at hand. It was decided to create that class without intermediate vessels, which was unprecedented, the exception being a test boat capable of launching nuclear ballistic missiles submerged, an evidence at the time. In 1960 indeed the Georges Washington class was in construction, with the first boat launched in 1959, based on the Skipjack class SSNs. The British would soon follow suite based on HMS Dreadnought, their first SSN.
The new French project was repurposing Q 244 as Q251, christened Gymnote, and re-ordered in 1961. The new test submarine was laid down again at Cherbourg on 17 March 1963 on plans already available, but reworked in depth, launched on 17 March 1964 and commissioned in 1966, roughly ten years after Q 244 was ordered. She fired her first M-1 missile in 1968, later deployed aboard the Redoutable-class submarines.

The five-year plan 1960-1964 played a very important role as it was prudent. In 1964 it was planned to finance a submarine, but decision was already made in 1963, by Ministerial Delegate for Armaments but only by 1964 the real decision to introduce a naval component of deterrence was taken. In 1963, confidence was restored with land-based prototype at Cadarache working remarkably well and Q 244, still on the slipways of the Cherbourg arsenal was cut out in two to inserted in its central part, 8.50 meters wide, a slice matched the missile launcher, 10.60 meters tall, so allowing to place 4 tubes for a true experimental missile-launching submarine. Thre were still a lot of discussions about the usefulness of taking such a date hull design. The French were well aware of the the USS Albacore, testing with success that a new hull design was not only possible, but recommended.

Design of the class

To gain time it was decided to keep the older hull and scrap the speed factor to concentrate exclusively in the integration and tests of SLBMs. Some still wanted to take other steps, notably politicians, but it was opposed by engineers due to planning issues. In 1962 Gymnote thus was restarted from the existing Q 244, on a brand new design, launched in 1964 and commissioned in 1966, launchign sucessively over 20 years, the M-1, the M-2, the M-20, the M-4 in very realistic conditions to the benefit of two generation of French SSBNs. An interesting perk is that the submarine had four tubes but only two ever were used. This was an option for salvoes that was simply never tested. All engineers however agreed that two tubes would have been enough for these tests anyway. Lainching two missiles in close succession would have given enough data to evaluate a launch of far more.

It was indeed a challenge and back in 1962 most believed it could have all virtues in terms of immersion, speed, autonomy, handling, and modern installations. But reistance among ingineers to respect tight delays meant, the first choice concentrating on choosing a suitable steel for construction. In France there was at the time still specialist that in 1940 could produce an armour steel that had already proven itself. French steelmakers behind the Marine Naitonale’s iconic Richelieu and Jean Bart, had kept producing a type of steel that could be incorporated by welding into much stronger hulls. They mnaged, after some investment, to produce a steel with average density equal to one. Thanks to this a brand new pressure hull unlike the one made for all previous classes was now to be built with a lower displacement, compared to all previous steels. 20% was the gain, and this enabled to even reduce ballast. Still a good reserve of it was kept, enabling additions later in the submarine’s life.

Hull and general design

Original cutaway plan showing the pressure hull

The Gymnote was designed by Armament engineer André Gempp, also designer of the bathyscaphe FNRS 3, Daphné class submarines and later Le Redoutable class SSBNs.
Redesigning the Gymnote was not an easy task as the nuclear reactor compartment was eliminated and internal spaces redistributed around the inclusion of four missile tubes, all in succession in a single file, and in a “shoulder” structure behind the fin that recalled soviet submarines such as the Yankee and Delta class. The hull in shape was still close to the previous French attack submarines, with the same keel, straight prow with top and bottom extensions for the sonars, two propeller shafts, and a “+” type stern tail arrangement with horizontal wings, inherited from Q 244. There were twodiving planes at the bow, which was also classic. There was a narrow bridge forward, no space alongside the launch tubes hump and so to access the aft deck, it was only possible via an aft hatch. This upper section was relatively high. All this made for a complicated and ungracious looking submarine, which masked its true purpose. Speed was not a factor and torpedo tubes were even absent from the design, just as USS Albacore.
Being cut down compared to Q 244 and loosing a great lenght, Gymnote ended with a displacement of 3,000 tons surfaced and 3,250 tons submerged. This was still twice as large as the Narval class, until then the largest cold war French submarines. Gymnote measured indeed 84 m (275.6 ft) overall for a beam of 10.6 m (35 ft) for the outer hull, same as Q 244, and same pressure hull. The Narval class indeed was not that shorter at 78.4 or 257 ft 3 in, showing the density achieved by the new design, twice as heavy for six meters of difference in lenght…
Its draught was 7.6 m (25 ft). This submersible and its new steel hull showed it was possible to study the resistance of special steels with high elastic limits to withstanding dives below 200 meters (650 ft). However the heavy hull had consequences and the new sub on trials showed that it had a tendency to roll almost like a battleship, in a predictable, gentle, but long motion.

Powerplant

Gymnote had a conventional powerplant related to other designs, composed of two electric diesels rated for 956 kW each, coupled with four Pielstick 12PA2 diesels rated for 620 kW each, and a comfortable battery with two sets of the latest Daphné type batteries for a grand total of 1300 HP. For 3000+ tonnes it was weak, but that was not the point. The powerplant took as little space as possible. Thuis as calculated she was capable only of 11 knots (20 km/h) surfaced, 10 submerged (19 km/h). While pushed up to 12 knots she was still able to reach 4,500 nm. Her crew comprised 8 officers, 38 petty officers, 45 crewmen. Accomodations were a mix of the Daphne class and former Q 244.

Armament

The core of Gymnote’s capability were her four ballistic tubes. They were quite tall as to take the entire hull with an extension above, and some room to spare for the M1 missile, first generation French SLBM. As said aboive, she had no torpedo tubes whatsoever, freeing a considerable space forward and aft, and greatly simplifying the design of the pressure hull. In french the missiles carried were called missile mer-sol balistique stratégique (MSBS). As said also above, she had four tubes but only the first two were used for testings.

The M1 is the French intermediate-range ballistic missile that was operated by Gymnote and later on the first two French nuclear-powered ballistic missile submarines of Le Redoutable class. This missile has two solid-propellant stages and carried a single MR 41 nuclear warhead rated for 500 kt TNT equivalent, range of 2,450 kilometers. It was Deployed from 1966 when fire tested but operationally from 1971, with 16 missiles carried on Le Redoutable class. Short ranged, it was quickly replaced by the M2 (range 3,000 kilometers) in 1974.
The M1 had a launched mass of 20 t for 10,67 m (35 ft) in height and 1,49 m (5 ft) of diameter. The range was a serious issue as the carrier needed to be positioned in the Norwegian Sea or in the Gulf of Genoa, busy, narrow seas too resticted to allow patrolling without being detected.

Sensors

The Gymnote was presumably equipped with the same sonar systems as the Daphne class, but downgraded. On one source, she had a Calypso II radar and DUUA-1 sonar only. The latter was installed on the upper dome at the top of her straight prow. In addition she had a very tall and peculiar instrumentation mast to keep tracks of the missiles launched. It was a permanent fixture, anchored on three points by steel cables and probably created a lot of drag while underwater. She was fitted with a prototype guidance and inertial navigation system intended for Le Redoutable class.

Author’s rendition for Helion’s a sword for peace and liberty vol 1 force de frappe FR

Career of Gymnote

From reddit, Gymnote at sea in the late 1970s.
A true laboratory, Gymnote, built in Cherbourg, sailed to Toulon on August 1, 1966 with 91 crew members on board. Soo she started her first campaign of experimental M1 missile firings. She was sent back to Lorient in 1968 for fixed and additions, and started two new firing campaigns in 1970 and 1971 in the Bay of Biscay.
Gymnote serve as a test platform for a new inertial navigation system and automatic immersion holding device to perfectly stabilize her when submerged at a given level. Her hull was a test of resistance of new special steels with a high elastic limit capable of withstanding deep dives. This will came in handy for the construction of the Redoutable class.
Unfortunately no detailed logs are available of her campaigns (so far).
In 1979 her M-1 tubes were replaced by larger M-4 SLBM (two M-4 missiles). Her extended casing was enlarged.
She was then adapted to M4 missiles in 1982 for tests at the Landes (Cadarache) Test Center.
Her last major refit was carried out in 1985 at Cherbourg and she returned there for a last campaign before being condemned in 1987.

In parallel with these tests, the SNLE (Nuclear Ballistic Missile Submarine) project was relaunched in 1964 and Le Redoutable cvonstruction started as the first French nuclear ballistic missile submarine, entering active service in 1971. She had a brand new, more stremlined hull, displaced 900 tons more, was able to dive down to 700m (2,297 ft) wuth a 90 days autonomy, 135 men crew. She was far more silent and had sixteen M1, then M2 missiles, then M4, giving France credible deterrent force.
In 1987 Gymnote, which had served her purpose; was condemned. She allowed to test 130 missile firings of all types between 1966 and 1986 and gather tons of useful data. She was brought back to Lorient but not preserved, instead, she was BU in Saint-Nazaire in 1990.

French Gymnote – Credits Rama – CC

Read More/Src

Books

Gardiner, Robert, ed. (1995). Conway’s All the World’s Fighting Ships 1947–1995.
Jean Moulin, Les sous-marins français en images, Marines Éditions, 2006
Claude Huan et Jean Moulin, Les sous-marins français 1945-2000, Rennes, Marines éditions 2010

Links

http://www.netmarine.net/bat/smarins/gymnote/index.htm
https://web.archive.org/web/20091014011143/http://www.stratisc.org/ihcc_nuc1_Gempp.html

Gymnote

https://www.la-flore.fr/fr/sous-marin-experimental-le-gymnote
https://fr.wikipedia.org/wiki/Gymnote_(S655)
https://en.wikipedia.org/wiki/French_submarine_Gymnote_(S655)

Un Sous-marin Français Construit aux Antipodes A French Submarine built in the Antipodes

Q244 on secretprojects.co.uk/
archive of Q244 on perso.orange.fr (not preserved)
https://www.sous-mama.org/blog/sous-marin-gymnotes-655-un-site-de-jean-paul-nadeau-de-la-section-minerve-billet-8086.html
https://www.seaforces.org/marint/French-Navy/Submarine/S-655-FS-Gymnote.htm

Videos

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