R-27 Zyb

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Simple scheme of an R-27 missile
Place of origin	USSR
Service history
In service	1968 - 1988
Used by	Soviet Navy
Production history
Designer	Makeyev Rocket Design Bureau
Designed	1962 - 1968
Manufacturer	Zlatoust Machine-Building Plant Krasnoyarsk Machine-Building Plant[1]
No. built	~1800 produced
Variants	R-27 R-27U R-27K
Specifications
Mass	R-27/R27-U: 14,200 kg (31,300 lb) R-27K: 13,250 kg (29,210 lb)
Length	R-27/R27-U: 8.890 m (29.17 ft) R-27K: 9.000 m (29.528 ft)
Diameter	R-27/R27-U/R-27K: 1.500 m (4.92 ft)
Main armament	R-27: Single warhead, 1 MT yield R-27U: Single warhead, 1 MT yield or 3x 0.2 MT Warheads
Payload capacity	R-27: 650 kg (1,430 lb) Single Warhead[1] R-27U: 650 kg (1,430 lb) Single Warhead or 3x 0.2 MT Warheads 170 kg (370 lb) each[1]
Propellant	N2O4/UDMH
Operational range	R-27: 2,400 km (1,500 mi)[1] R-27U: 3,000 km (1,900 mi)[1]
Flight ceiling	R-27: 620 km (390 mi)
Boost time	R-27: 128.5 Seconds
Accuracy	R-27: CEP 1.9 km (1.2 mi)[1] R-27U: CEP 1.3–1.8 km (0.81–1.12 mi)[1] R-27K: CEP 0.37 km (0.23 mi)
Launch platform	Yankee-class submarine

The R-27 Zyb (

Total production was 1800 missiles.

The R-27

.

Technical details

The missile's body is an all-welded construction made of hard-worked AMg6 (АМг6) aluminium-magnesium-alloy panels, which underwent a two-step process of deep industrial etching and mechanical milling, reducing the plate thickness to one-fifth and one-ninth of the thickness of the original plate.^[4]: 87

The outer surface of the missile was covered with a protective heat- and moisture-resistant Asbestos-based coating. In order to fit the R-27 into the corresponding launch tube, the missile was built without

to keep the missile's skin from scratching along the side of the launch tube when fired.

The missile's tip featured a single, 650-kg detachable warhead with a yield of 1 MT. A high-explosive linear-shaped charge was used to separate the warhead from the missile.^[5]

Directly beneath the warhead, the instrumentation necessary for guidance of the missile was housed inside of a hemispherical compartment formed by the upper bulkhead of the oxidiser tank. This design decision allowed the easy removal of the guidance system from the missile for maintenance and removed the need for a service hatch.

To maximize the volume of propellant available inside the missile, the upper oxidiser tank and the lower fuel tank shared one common bulkhead instead of one bulkhead each as it was absolutely necessary to use every bit of volume available to be able to fit the missile into a submarine.

Another novelty was factory fueling with the subsequent "ampulization" of the tanks by welding filling and drain valves.^[4]: 89 In conjunction with efforts to improve the corrosion resistance of materials as well as the tightness of seams and joints, these fabrication methods allowed the missile to have a lifetime of 5 years, which was later extended to 15 years.^[4]: 89

The missile was powered by an 4D10

. The 4D10's main chamber operates on a highly-efficient oxidiser-rich staged combustion cycle to maximize fuel efficiency, while the two smaller chambers use the more ordinary gas-generator cycle. Both the larger chamber and the smaller chambers could be throttled by either regulating the single propellant line leading to the main chamber or a shared oxidiser line leading to the smaller chambers.

One of the most important novelties on this missile is that the main chamber of this rocket motor was integrated into the missile by permanently

inside the missile.

When the R-27 was fired underwater, the container housing them was first overpressurized before the container was flooded and the pressure was equalized. To reduce the effect of water hammer when igniting the rocket engine, the nozzles were housed inside of a watertight air-filled adapter connecting the bottom of the missile with its container. The two smaller chambers are ignited first, before finally igniting the main chamber. The missiles were fired from a depth of 40 to 50 meters under the sea. Preparations for launch would take 10 minutes, and a salvo could be fired with an interval of 8 seconds between each launch.

Variants

R-27

• Total Mass: 14,200 kg
• Diameter: 1.50 m
• Total Length: 8.89 m
• Span: 1.50 m
• Payload: 650 kg
• Warhead: single nuclear: 1.0 Mt
• Maximum range: 2400 km
• CEP: 1.9 km
• Launch platform: project 667A submarines

R-27U (RSM-25)

• Total Mass: 14,200 kg
• Diameter: 1.50 m
• Total Length: 8.89 m
• Span: 1.50 m
• Payload: 650 kg
• Warhead: 3 : 200 kt
• Maximum range: 3,000 km
• CEP: 1.3 km
• Launch platform: project 667AU submarines

R-27K

The 4K18 was a Soviet medium-range anti-ship ballistic missile (also known as R-27K, where "K" stands for Korabelnaya which means "ship-related") NATO SS-NX-13. The missile was a two-stage development of the single-stage R-27, the second stage containing the warhead as well as propulsion and terminal guidance.^[6] Initial submarine testing began on 9 December 1972 on board the K-102, a project 605 class submarine, a modified Project 629/ NATO Golf class lengthened 17.1m (formerly B-121), to accommodate four launch tubes as well as the Rekord-2 fire control system, the Kasatka B-605 Target acquisition system and various improvements to the navigation and communications systems. Initial trials ended on 18 December 1972 because the Rekord-2 fire control system hadn't been delivered yet. After a number of delays caused by several malfunctions, test firings were finally carried out between 11 September and 4 December 1973. Following the initial trials, the K-102 continued making trial launches with both the R-27 and the R-27K, until it was accepted for service on 15 August 1975.^[6]

Using external targeting data, the R-27K/SS-NX-13 would have been launched underwater to a range of between 350 and 400 nm (650–740 km), covering a "footprint" of 27 nm (50 km). The Maneuvering Re-Entry vehicle (MaRV) would then home in on the target with a CEP of 400 yards (370 m). Warhead yield was between 0.5-1 Mt.^[6]

The missile system never became operational, since every launch tube used for the R-27K counted as a strategic missile in the SALT agreement, and they were considered more important.^[6]

Although the R-27K could fit in the launch tubes of the Project 667A (NATO Yankee class), the subs lacked the necessary equipment to target and fire the missile.^[6]

Zyb (Suborbital Launch Vehicle)

In 1992, there was an ongoing effort to convert surplus

Launch Date	Payload	Description
1. December 1991	Sprint Module	Research on superconductivity.
9. Dezember 1992	Efir Module	Biotechnological research regarding electrophoresis. The 650 kg re-entry capsule was recovered intact, but the experiment had failed to perform.
1. Dezember 1993	Efir Module	Biotechnological research regarding electrophoresis. The 650 kg re-entry capsule was recovered intact, experiment successful.

Derived missiles

In 1992, the

It is suspected that a modified subvariant of this missile was then sold to the Iranian Military in 2005 under the designation BM-25 "Khorramshahr".^[9]

Operators

 Soviet Union

The Soviet Navy was the only operator of the R-27.

Iran

Operates the Khorramshahr, a heavily modified design based on the R-27.

North Korea

possibly operates the Hwasong-10, a modified variant of the R-27, some sources suggest North Korea might have abandoned development of the design due to its complexity.^[10]

See also

• Hwasong-10, based on the R-27
• Khorramshahr based on the Hwasong-10

References

External links

• R-27 (Globalsecurity.org)