Kh-55 (missile family)

The Kh-55 (Х-55; NATO:AS-15 'Kent'; RKV-500;) is a Soviet/Russian air-launched cruise missile, designed by MKB Raduga. It has a range of up to 3000 km and can carry conventional or nuclear warheads. Kh-55 is launched exclusively from bomber aircraft and has spawned a number of conventionally armed variants mainly for tactical use, such as the Kh-65SE and Kh-SD, but only the Kh-101 and Kh-555 appear to have made it into service. Contrary to popular belief, the Kh-55 was not the basis of the submarine- and ground-launched RK-55 Granat (SS-N-21 'Sampson' and SSC-X-4 'Slingshot').

A Kh-55 production unit was delivered to Shanghai in 1995 and appears to have been used to produce a similar weapon for China.

Development
In the late 1960s, the "Ekho" study conducted by the GosNIIAS institute concluded that it would be more effective to deploy lots of small, subsonic cruise missiles than the much more expensive supersonic missiles then in favour. Work started at the Raduga bureau on an air-launched cruise missile in 1971, with a first test flight in 1976. The appearance of the US Air Force's AGM-86 ALCM in that year gave further impetus to the programme, with the Soviet Air Force issuing a formal requirement for a new air-launched cruise missile in December 1976. The longer-range Kh-55SM was developed a few years after the original went into service. In the late 1980s work began on a replacement missile with either conventional (Kh-101) or nuclear (Kh-102) warheads and greater stealth. It was designed by Igor Seleznyev of Raduga. The importance of advanced missiles as "force multipliers" increased as Russia's fleet of available cruise-missile bombers declined in the early 1990s. The cancellation of the ambitious Kh-90 ramjet missile due to INF treaty in 1987 led to a renewed emphasis on improving the Kh-55, in particular to achieve the <20 m accuracy required to hit infrastructure targets with conventional - as opposed to nuclear - warheads. First flight of the Kh-101 was in 1998, and evaluation trials started in 2000.

After the end of the Cold War and anti-proliferation treaties restricting the deployment of long-range nuclear missiles, the Russians made efforts to develop tactical versions of the Kh-55 with conventional warheads. First came the 600 km-range Kh-65SE (derived from the Kh-55) announced in 1992, then the 300 km-range Kh-SD tactical version of the Kh-101 for export, and finally the Kh-555. In 2001 the Russian Air Force are believed to have selected the Kh-101 and Kh-555 for development.

A 1995 Russian document suggested a complete production facility had been transferred to Shanghai, for the development of a nuclear-armed cruise missile. Originally it was thought that this was based on the 300 km-range Raduga Kh-15 (AS-16 'Kickback'), but it now appears that it was the Kh-55 that was transferred to China.

Design
It is powered by a single R95-300 turbofan engine, with pop-out wings for cruising efficiency. It can be launched from both high and low altitudes, and flies at subsonic speeds at low levels (under 110 m/300 ft altitude). After launch, the missile's folded wings, tail surfaces and engine deploy. It is guided through a combination of an inertial guidance system plus a terrain contour-matching guidance system which uses radar and images stored in the memory of an onboard computer to find its target. This allows the missile to guide itself to the target with a high degree of accuracy, with a reported CEP of 15 meters.

The original Kh-55 had a drop-down engine; the Kh-65SE had a fixed external turbojet engine, whilst the Kh-SD had its engine inside the body of the missile.

Operational history
The original Kh-55 entered service in 1984. The Kh-55SM followed in 1987. The conventionally armed Kh-55SE was flight tested on 13 January 2000, and first used in exercises over the Black Sea 17–22 April 2000. The Kh-555 is thought to have entered service in 2004, the first pictures of the Kh-101 appeared in 2007.

The Kh-55 can be carried by the Tupolev Tu-95MS ('Bear-H') and Tu-142M ('Bear-F'), and the Kh-55SM is carried by the Tupolev Tu-160 ('Blackjack'). Sixteen Kh-55's can be carried by the Tu-95MS16 (Tu-95MSM) variant, ten on underwing pylons and six on a MKU-5-6 rotary launcher.

The Kh-55 was also tested on the Tu-22M ('Backfire'). The Kh-SD tactical version was to have been carried by the Tu-95MS (fourteen missiles) and the Tu-22M (eight missiles); the Kh-101 is expected to be carried by the Tu-160 (twelve missiles), Tu-95MS16 (eight missiles), Tu-22M3/5 (four missiles) and Su-34 (two missiles).

The end of the Cold War left Ukraine with 1,612 Kh-55's, part of the armament of the 19 Tu-160's of the 184th Heavy Bomber Regiment at Priluki and the 25 Tu-95MS of the 182nd Heavy Bomber Regiment at Uzin-Shepelovka. It was reported that Ukraine demanded US$3bn for the return of the planes and their missiles to Russia. In October 1999 a compromise was reached that saw Russia pay US$285m for 11 aircraft and 575 missiles, whilst the rest were meant to be destroyed under a US-funded disarmament programme. However, in March 2005 Ukraine's prosecutor-general Svyatoslav Piskun said that in 2001, 12 Kh-55's had been exported to Iran in a deal allegedly worth US$49.5 million and six to China. It has also been reported that Iran has started producing the missiles locally and is working on a longer range version.

Variants

 * Kh-55 (NATO 'Kent-A', RKV-500A, Izdeliye 120) - original model with 2,500 km range.
 * Kh-55-OK - development name of Kh-55SM
 * Kh-55SM (NATO 'Kent-B', RKV-500B, Izdeliye 121) - with TERCOM (Terrain Contour Matching) navigation and extra fuel tanks to extend range to 3000 km.
 * Kh-101/102 (Izdeliye 111) - developed as a very stealthy replacement for the Kh-55SM in the late 1980s, the Kh-101 has a conventional warhead and the Kh-102 is nuclear. A propfan version with 5000 km range was cancelled in 2000. Accuracy is reportedly 6–9 m. Speeds reach over 800km per her hour. Estimates range that it will outnumber the Russian nuclear missile fleet by 5:1, making them some of the most numerous and effective cruise missiles in the world. They are expected to be in service in those numbers by 2023.
 * Kh-65SE - tactical version announced in 1992 with 410 kg conventional warhead and restricted to the 600 km range limit of the INF treaty.
 * Kh-SD (средней дальности Srednei Dalnosti - 'Medium Range') - 300 km range conventional version announced in 1995, possibly for export. Shared components with the Kh-101, range reportedly increased to 600 km with a high-altitude approach, but the Kh-SD was apparently shelved in 2001. An alternative active radar seeker was proposed for anti-shipping use.
 * Kh-555 (NATO 'Kent-C', Kh-55SE, Kh-55Sh) - conventionally armed version with an improved guidance system and warhead developed in response to the lessons of the NATO air offensive against Yugoslavia in 1999. It became operational in 2000.

It was believed originally that the RK-55 (SSC-X-4 'Slingshot' and SS-N-21 'Sampson') were land- and submarine-launched derivatives of the Kh-55, but it is now known that the Kh-55 is different from the other two as its motor drops down below the missile during flight.

Current

 * 🇷🇺: The Russian Air Force uses the Kh-55 series.
 * 🇨🇳: 6
 * 🇮🇷: 12

Former

 * : the Soviet Air Force deployed the Kh-55 as its original operator.
 * 🇺🇦: ~487 scrapped, ~587 returned to Russia

Similar weapons

 * RK-55 - so similar to the Kh-55 it was long believed in the West to be merely a sub-/surface-launched version
 * AGM-86 Air-Launched Cruise Missile - 1430 kg missile with 2400+ km range, Mach 0.73
 * AGM-129 ACM (Advanced Cruise Missile - stealthy 1330 kg missile with 3700 km range)
 * BGM-109 Tomahawk - surface/sub- launched, but otherwise similar to the Kh-55
 * Babur missile (Pakistan)
 * Nirbhay(India) - Nirbhay will be an all-weather low-cost medium-range cruise missile with stealth and high accuracy. The missile will have a range of 1000 km, which will be increased later
 * CJ-10 - Chinese land-attack cruise missile, believed to have incorporated elements from the Kh-55