The M-20 was the third member of the MSBS (Mer-Sol-Balistique-Stratégique) family which comprised a number of submarine-launched, intermediate range missiles, similar in form to the US Polaris and Poseidon families. The force constitutes the second leg of the French nuclear deterrent force. The M-1 version went into service in 1971 and was phased out in favour of the M-2 in 1974, itself replaced by the M-20 in 1977. The new M-4 missile entered service in 1985 and has replaced the M-20. French nuclear-powered submarines (SNLE Sous-marines Nucleaire Lanceur d'Engins balistique), are able to carry 16 missiles each. The oldest boat, Le Redoutable, was not converted to carry the M-4 and was withdrawn from service in 1991. Logistical support for the MSBS fleet is provided by the Ile Longue Naval Base in Brest Bay where the assembly and storage facilities for maintenance of readiness are located. Three SSBNs are intended to be operational at any one time.
The M-20 system entered service in 1977. There were 100 missiles produced, and the M-20 ceased operational deployment in 1991.
The M-20 was a two stage, solid propellant, intermediate range ballistic missile, 10.4 m in length and 1.5 m in diameter. Launch weight was 20000 kg and the missile had a range of 3000 km. Control of the first stage was by four gimballed nozzles; the second stage by thrust vector control through a single fixed nozzle. The first stage propellant weighed 10000 kg and burns for 55 seconds, the second stage propellant weighs 6015 kg and burns for 58 seconds. Guidance was inertial. The payload was believed to include some penetration aids and the single re-entry vehicle had some hardening against nuclear effects. The TN-60 warhead was reported to be 1.2 MT.
|prime contractor||Aérospatiale, Space and Strategic Systems Division, Les Mureaux|
|Body diameter||1.5 m|
|Launch weight||20000 kg|
|Payload||Single warhead with penetration aids|
|Warhead||1.2 MT nuclear|
|Propulsion||2 stage solid|
|Accuracy||1000 m CEP|
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