RK-55 Granat (SS-N-21)

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The RK-55 Granat (NATO: SS-N-21 “Sampson”) is a submarine and ground-launched intermediate range cruise missile produced by the Soviet Union since 1976.

Granat (SS-N-21 “Sampson”) at a Glance

Originated from
Possessed by
Alternate Names
RK-55, Sampson, 3M10, Granat, SSC-X-4, Slingshot, 3K10
Subsonic cruise missile
Road-mobile, submarine-launched
8.09 m
0.51 m
Launch weight
1,700 kg
Single warhead
Nuclear 200 kT (ground/submarine), HE 410 kg (submarine)
Turbofan, solid booster
2,400 km (submarine), 3,000 (ground)
In service

RK-55 Development

The RK-55 is the submarine/ground-launched component of the “55” series of cruise missiles which also included the Kh-55 air-launched missile. This family of cruise missiles was the Soviet Union’s response to the U.S. Tomahawk series. 1 The ground-launched variant was dismantled and destroyed due to the signing of the 1987 INF Treaty.

Both the ground and submarine-launched missiles have a length of 8.09 m, a diameter of 0.51, and a launch weight of 1,700 kg. Both missiles were capable of carrying a 200 kT nuclear warhead, although the submarine variant had a 410 kg HE option. The RK-55 utilized a booster motor that was jettisoned after launch. The range of the ground variant was 3,000 km, while the submarine variant was capable of 2,400 km. The accuracy of the submarine version is 150 m CEP. The accuracy of the ground-launched version is uncertain, but it is likely similar.

The ground-launched RK-55 is a road-mobile system, capable of carrying six missiles per TEL vehicle. The submarine version is carried on a number of Russian vessels including Victor 3 (Project 671RTM), Akula 1/2 (Project 971), Sierra 1/2 (Project 945), Yankee Notch (Project 667AR/AT), and possibly Delta 1/2/3 class submarines. The maximum number of missiles carried per ship varies from 20 to 35, although actual numbers are likely much lower.

The RK-55 ground-launched missiles were destroyed three years after the INF Treaty was signed. The submarine-launched version is still in use, and current estimates suggest 150 to 180 operational missiles on board Russia’s Akula-class submarines. As part of the START 2 agreement, the nuclear-armed RK-55 have been removed from service, or converted to conventional systems. Some have suggested that given the expansive use of U.S. Tomahawk missiles, many nuclear-armed RK-55 missiles were converted to conventional weapons. 2


    1. “Soviet/Russian Cruise Missiles.” Air Power Australia, April 2012, http://www.ausairpower.net/APA-Rus-Cruise-Missiles.html#mozTocId888341.
    2. “RK-55 Granat (SS-N-21 ‘Sampson’/3M10),” and “RK-55 Granat (3M10),” in IHS Jane’s Weapons: Strategic 2015-2016, ed. James C. O’Halloran (United Kingdom: IHS, 2015), 200-201.
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Missile Defense Project, "RK-55 Granat (SS-N-21)," Missile Threat, Center for Strategic and International Studies, August 10, 2016, last modified April 23, 2024, https://missilethreat.csis.org/missile/ss-n-21/.