Military submarine: everything you need to know about the French naval forces' submersibles
The military submarine: the ultimate weapon of the ocean depths
The military submarine is undoubtedly the most formidable and mysterious weapon in the modern arsenal. Capable of moving completely stealthily at hundreds of meters depth, staying submerged for weeks or even months, and striking thousands of kilometers away, it embodies naval power at its most absolute.
France is among the very few nations — barely six in the world — capable of designing, building, and operating nuclear-powered submarines. It is Naval Group , the flagship of the French naval industry, which designed and built these technological marvels in Cherbourg and Brest. This comprehensive guide explains everything: the different types of military submarines, the French fleet, their staggering costs, and the exceptional lives of their crews.
The different types of military submarines
There are several major categories of military submarines, mainly classified by their propulsion type and primary mission.
The SSBN Nuclear Ballistic Missile Submarine
The SSBN is the pinnacle of underwater military power. Its unique and permanent mission: to ensure the oceanic component of French nuclear deterrence. At all times, one of the four French SSBNs of the Le Triomphant is patrolling somewhere in the world's oceans, ready to launch its M51 ballistic missiles capable of reaching any target on Earth. This is known as the FOST — Strategic Oceanic Force . This submarine is the ultimate guarantor of France's sovereignty and survival.
The SSN Nuclear Attack Submarine
Smaller and more agile than the SSBN, the SSN is the hunter of the depths. Its nuclear propulsion gives it almost unlimited endurance — only the crew's food supplies limit patrol duration. It can track and destroy enemy submarines, escort SSBNs, conduct precision strikes with cruise missiles, and gather intelligence discreetly. France currently operates the Rubis and is gradually introducing the new class Suffren (Barracuda program) , significantly more efficient.
The conventional diesel-electric submarine
Less expensive than nuclear submarines, diesel-electric submarines make up the vast majority of the world's fleets. France has abandoned them for its own navy but exports them successfully through the Scorpène from Naval Group — sold notably to Brazil, India, Chile, and Malaysia. Their endurance is more limited (a few weeks) but their acoustic stealth can be superior to that of nuclear submarines under certain conditions.
How many military submarines are there in France?
France has a fleet of military submarines that are 100% nuclear , placing it in a category of its own in Europe. Here is the detailed composition of the French submarine fleet in 2025.
| Type | Class | Number | Propulsion | Main role |
|---|---|---|---|---|
| SSBN | Le Triomphant | 4 | Nuclear | Nuclear deterrence |
| SSN | Rubis | 4 (in service) | Nuclear | Attack / Intelligence |
| SSN (future) | Suffren (Barracuda) | 6 (on order) | Nuclear | Replacement Rubis |
Source: French Navy — Ministry of the Armed Forces 2025.
In total, France has 8 nuclear military submarines in service or being delivered. The 4 SSBNs of the Le Triomphant class continuously ensure oceanic nuclear deterrence. The Rubis class SSNs are gradually being replaced by the much more capable Suffren from the Barracuda program—the first, Suffren , was delivered in 2022.
How much does a military submarine cost?
This is one of the most frequently asked questions—and understandably so, the figures are staggering. A military submarine is one of the most valuable objects ever built by humans, concentrating decades of technological research in a confined space subjected to extreme constraints.
| Submarine type | Country / Manufacturer | Estimated unit cost | Propulsion |
|---|---|---|---|
| Le Triomphant Class SSBN | France / Naval Group | 3 to 4 billion € | Nuclear |
| SNA Suffren Class (Barracuda) | France / Naval Group | 1.5 to 2 billion € | Nuclear |
| Scorpène (export) | Naval Group | 400 to 700 million euros | Diesel-electric |
| Virginia (United States) | General Dynamics | ~3.5 billion euros | Nuclear |
Sources: Naval Group — French Court of Auditors — publicly available estimates.
In addition to construction costs, maintenance and operational readiness (MCO) expenses over the submarine’s lifespan (30 to 40 years) often exceed the initial purchase price. An SSBN thus costs several tens of billions of euros over its entire life cycle.
Why such a cost?
The technological complexity of a nuclear submarine is comparable to that of a nuclear reactor embedded in a rocket capable of diving to 400 meters deep. The materials used (high yield strength steel, pressure-resistant equipment), underwater navigation systems without GPS, ultra-sensitive passive sonars, and integrated weapons systems each represent multi-year R&D programs. On average, it takes 7 to 10 years to build an SSBN.
Life on board a military submarine
Living and working on a military submarine is an extraordinary experience, reserved for elite sailors who are carefully selected and trained. A patrol on an SSBN typically lasts 70 days without ever surfacing, without communication with family, in a confined living space shared with about a hundred colleagues.
Living conditions on board
- Extremely limited living space: each sailor has a sleeping area 60 cm wide
- Shift work rhythm: 6 hours on watch, 12 hours rest, in continuous rotation
- Complete absence of natural light throughout the patrol
- Very limited and filtered communications with the outside world for security reasons
- Careful nutrition: the quality of food is a key factor in crew morale
- A military watch robust and precise watch is essential for managing shifts
Profile of submariner sailors
Becoming a submariner in the French Navy involves rigorous psychological and physical selection, specialized training lasting several months at the Brest Submarine School, and signing a specific voluntary commitment. In return, submariners benefit from a significant risk premium and a special consideration within the armed forces.
FAQ: The most frequently asked questions about military submarines
What is the maximum depth of a military submarine?
The maximum operational depth of military submarines is classified. However, it is estimated that modern SSBNs and SSNs can dive between 300 to 400 meters The absolute historical record is held by the Soviet experimental submarine K-278 Komsomolets, which reached 1,027 meters in 1985 — a feat not repeated since.
How long can a submarine stay submerged?
A nuclear submarine can theoretically remain submerged indefinitely thanks to its nuclear reactor, which produces electricity and continuously regenerates the air. In practice, the limit is human: food supplies and the psychological endurance of the crews set the maximum patrol duration at 70-90 days for the French SSBNs.
Which countries potentially have nuclear submarines?
Only six countries In the world, there are nuclear-powered submarines in six countries: the United States, Russia, France, the United Kingdom, China, and India. France is the only country in the European Union with this capability, giving it a unique strategic status on the continent.
Conclusion
The military submarine is much more than a weapon: it is a symbol of national sovereignty, a concentration of cutting-edge technology, and the setting for an extraordinary life for exceptional sailors. France, with its 4 SSBNs and next-generation SSNs, is one of the few nations in the world to fully master this technology from design at Naval Group to operation by the French Navy.
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