This happened on March 12, 1974, when the Navy adopted for service the D-9 missile system with the R-29 ballistic missiles, said the Navy press service.
The development of a missile for submarines began way back in September 1964.
The technical goal intended a missile for hitting strategic facilities from afar in the World Ocean, where the potential enemy lacked an efficient antisubmarine defence, or from areas of the sea dependably covered by the Soviet Navy and aviation. In extreme cases, the missiles could be launched from the bases.
The two-stage R-29 with liquid propellant and the consequent arrangement of stages was 13.9 meters long and 1.8 meters in maximal diameter. The liquid-propellant cruise engines were built in the fuel tanks, making the missile shorter for lack of joining and intertank sections. The upper bottom of the fuel tank in the second stage was cone-shaped, housing an inverted warhead containing a nuclear charge. Fuel tanks were fuelled by the manufacturer, after which the missile was sealed.
The tight layout of the missile made it possible to place engines with a high nozzle coefficient, largely increasing the specific impulse, fuel reserve and, consequently, the range of fire. The R-29 had a mono-block warhead with an explosive payload of 1 megaton.
To penetrate the probable enemy's antimissile defence the missile carried light decoy targets, jettisoned from special containers at the moment when the nose cone separated. Computerised ship-borne weapon control system in combination with the stellar monitoring system, automatic pre-launch and blast-off preparation processes ensured a high combat readiness of the missile system.
The D-9 missile system was installed on strategic missile cruiser submarines 667B Murena (12 PU). Launch was possible from submerged position and straight from submarine basing points. Adopted in 1978, the R-29 modification with a lighter mono-block warhead could hit targets up to 9,000 kilometres away. The size of the missile was the same but the accuracy of fire was higher. The missile system D-9D (the number of missile launchers was increased to 16) was also updated.