Father of Soviet submarines dead at 91

A towering figure in the secret world of strategic arsenals, Kovalyov is credited with designing 92 types of submarines at a time when Moscow and Washington fought a bitter war for supremacy of the world's seas.

He began his career in 1948, working at first on the design of a revolutionary S-99 model that became the fastest submarine in the Soviet Union's nascent naval forces. Kovalyov began designing his first nuclear-powered ballistic missile submarine in 1958, the same year he was appointed in charge of the Soviet Union's entire strategic naval forces programme.

In a congratulatory message issued on Kovalyov's 90th birthday, President Dmitry Medvedev called him "a designer who has made an outstanding contribution to the development of the national ship building industry."

Most recently, Kovalyov was involved in designing off-shore oil and natural gas production platforms, an industry vital to Russia's efforts to develop the energy reserves trapped off its Pacific coast.