A technical plan was prepared to modify a Project 667A strategic missile submarine cruiser into a Project 09780 sub (‘Akson-2’) for sea trials of sonar systems for the new generation of submarines. Chief Designers were O.Ya. Margolin and E.A. Gorigledjan from 1987. Later, Rubin's suggestion was accepted that the Project 667AK submarine (Akson-1) was to be refitted to Project 09780 after completion of its testing program to reduce the cost and duration of refitting. The revised technical plan for refitting that submarine to Project 09780 was developed in 1988. The scope of works within Project 09780 was considerably wider as compared to 667AK not only because antennas became much larger and the equipment amount increased, but also because of the very strict requirements from the sonar to interference, power supply and cooling. In the process of refitting, a number of engineering problems found their solutions crucial both for the production of a new generation prototype submarine and serial boats. The works on the submarine refitting and repair were completed in August 1995. After successful Harbour Tests, Shipyard Sea Trials and State Acceptance Trials the submarine was commissioned by the Navy in 1996.