Chevaline

Chevaline. It was a top-secret British project to improve the Polaris missile system, ensuring its ability to penetrate advanced Soviet ABM defenses around Moscow. Developed during the Cold War by the Atomic Weapons Research Establishment at Aldermaston, the program significantly enhanced the Royal Navy's nuclear deterrent credibility. The costly and complex upgrade involved new penetration aids and a sophisticated maneuvering re-entry vehicle, entering service aboard the Resolution-class SSBNs in the early 1980s.

History

The impetus for the project stemmed from intelligence assessments in the late 1960s indicating the Soviet Union was deploying the Galosh anti-ballistic missile system around Moscow. This development threatened to negate the effectiveness of the United Kingdom's Polaris A3TK missiles, which formed the core of its independent strategic deterrent. Following the cancellation of a proposed Anglo-French collaboration and the decision not to purchase the American Poseidon missile, the Heath government authorized initial development studies in 1973. The program, codenamed Chevaline, was conducted under extreme secrecy, with its existence and enormous cost concealed from Parliament and even much of the Cabinet for years, a fact later revealed in the 1980 Statement on the Defence Estimates.

Design and development

The primary objective was to develop a new front-end for the existing Polaris A3 missile, creating the A3TK (Chevaline) configuration. The system was designed to counter the Moscow ABM defense system by using sophisticated penetration aids and a complex maneuvering bus. Key elements included two hardened warheads, multiple decoys, and chaff dispensers, all contained within a larger, heavier nose cone. The heart of the system was the Advanced Inertial Reference Sphere, a British-developed guidance package of exceptional accuracy. Major contractors included the British Aircraft Corporation for systems integration and Marconi for electronics, with overall management by the Atomic Weapons Research Establishment at Aldermaston.

Technical specifications

The upgrade modified the existing Polaris A3 missile, which was launched from submerged Resolution-class submarines. The new front-end, or Penetration Aid Carrier (PAC), contained two British-designed thermonuclear warheads, each with a yield in the sub-megaton range. It also carried numerous lightweight decoys, known as "gravel," and chaff to saturate enemy radar and confuse Anti-ballistic missile interceptors like the Gazelle. The maneuvering re-entry vehicle, or "bus," was propelled by a liquid-fueled engine, allowing it to deploy its payload along a complex trajectory after the main rocket motor burnout, a concept sometimes described as a "partial orbital" approach.

Operational history

After extensive and reportedly troubled testing, including launches from the Eastern Test Range at Cape Canaveral and the Pacific Missile Range Facility, the system achieved initial operational capability in 1982. It was deployed exclusively aboard the four Royal Navy Resolution-class submarines: HMS *Resolution*, HMS *Repulse*, HMS *Renown*, and HMS *Revenge*. Each submarine carried 16 Polaris A3TK (Chevaline) missiles. The system remained the United Kingdom's sea-based nuclear deterrent throughout the 1980s, providing a guaranteed second-strike capability against key Soviet targets despite the ongoing modernization of the Soviet Air Defence Forces.

Decommissioning and legacy

The Chevaline system was withdrawn from service between 1992 and 1996, as the Royal Navy transitioned to the new Trident II D5 missile system aboard the Vanguard-class submarine. The program's total cost, estimated at over £1 billion, sparked significant political controversy when finally disclosed. While criticized for its expense and development challenges, Chevaline is credited with maintaining the credibility of the British nuclear deterrent during a critical period of the Cold War. Its technology and experience directly informed the development of the successor Trident warhead, and the project remains a notable example of a clandestine, nationally-executed strategic weapons program.

Category:Nuclear weapons of the United Kingdom Category:Cold War missiles of the United Kingdom Category:Anti-ballistic missile countermeasures