Missile R-29R (SS-N-18 Stingray)

The R-29R traces to a July 1968 decision to begin advance design of the D-9M complex, completed in December 1970 as part of a wider programme for a single missile fitted with one, three or eight warheads. That project was shelved in favour of solid-propellant work, but the immaturity of Soviet solid-fuel technology and the American move to multiple warheads led to a July 1972 order for a preliminary design of the D-9R complex, and a Council of Ministers decree of 13 February 1973 authorised full development. The design reuses the two main stages of the R-29 Vysota, the first Soviet submarine-launched missile with intercontinental range, with uprated engines and slightly greater stage length; the multiple-warhead front end was new. Compressed timescales forced the abandonment of a new propellant, an encapsulated pop-up launcher and the conversion of earlier hulls; launchers, servicing systems and ground equipment were carried over from the D-9 system. Ground launches at Nyonoksa numbered 18, of which 7 were successful; submarine trials from K-441 began in November 1976 and ran to 10 launches, including two-missile and four-missile salvos. The complex was accepted into service in August 1977, the first Soviet submarine-launched missile to combine intercontinental range with independently targetable warheads.

The missile is a two-stage liquid-propellant design with a post-boost bus, burning unsymmetrical dimethylhydrazine and nitrogen tetroxide. The 3D40 first stage combines a staged-combustion sustainer housed inside the fuel tank with two open-cycle vernier chambers; the single-chamber 3D41 second stage is gimballed in two planes, with roll control by nozzles fed from turbopump exhaust gas. Propellants are ampulised, the missile being delivered fully fuelled and without its warhead section. Launch is "wet", from a flooded tube using a dynamic gas bubble, with the verniers igniting first and the sustainer starting while the missile is still in the tube; firing is possible submerged or surfaced, from depths down to 50 m, at boat speeds up to 5 knots and in sea states up to 6. Guidance is autonomous inertial, with a three-axis gyro-stabilised platform, a Sokol stellar sensor under a jettisonable dome and a triple-redundant TsVM-6T digital computer. Full azimuthal stellar correction, performed after first-stage separation, compensates carrier navigation errors of up to 10 km in position and one degree in heading; CEP is about 900 m. Three warhead fits exist: a single 450 kt unit, three 200 kt independently targetable warheads, and, from the R-29RL, seven 100 kt warheads. Decoys for penetrating missile defences can be carried, and the warhead sections are interchangeable and replaceable without unloading the missile from its tube.

The R-29RL was accepted in July 1979; the R-29RK followed in September 1982 with a high-speed re-entry vehicle originally developed for the R-39 programme, which widened the deployment footprint and improved accuracy. The R-29RKU of October 1987 added a re-entry vehicle designed as a counterpart to the American W76 and the ability to fire from latitudes up to 89° north; the R-29RKU-01 was accepted in March 1990 and the R-29RKU-02 in 2006. The seven-warhead fit was dropped in service, the bus proving unequal to it, and the missile served in its three-warhead configuration.

Only the Soviet and Russian navies operated the missile, aboard Project 667BDR Kalmar submarines — the Delta III class — which carried sixteen rounds each. Fourteen boats entered service between 1976 and 1984, most of them with the Pacific Fleet at Rybachiy and the rest with the Northern Fleet; under-ice Arctic patrols began in 1980. About 180 launches were conducted in service up to 2007, 140 of them successful. During the Grom-2019 exercise on 17 October 2019 the submarine Ryazan attempted a two-missile salvo and one round failed to leave its tube; Ryazan, the last carrier, was withdrawn from service after 2021, ending the type's deployment. The Volna space launch vehicle, derived from the missile and fired from submarine tubes, flew five times between 1995 and 2005. Development of the R-29R fed directly into the R-29RM Shtil, the three-stage weapon that armed the Project 667BDRM Delta IV boats from 1986.