The new vessels are the next generation of Russia's Project 955 Borei-class ballistic missile submarine and Project 855M Yasen-class guided-missile submarines, which are late-Soviet-era designs, reported international affairs magazine the National Interest.
The Sierra-class replacement is being designed as an "interceptor" that would protect the Russian nuclear ballistic missile submarine fleet, while the Oscar-class replacement would be a guided-missile submarine that would hunt US carrier strike groups like their predecessors.
Anatoly Shlemov, a senior executive with United Shipbuilding Corporation, in an interview with the Russian news outlet Lenta.ru earlier this year, said:
"As part of the ongoing work on the design of fifth-generation of nuclear submarines, two models of the submarine will be created. The main purpose of the first: to ensure the sustainability of strategic missile submarine cruiser combat groups, and fighting enemy submarines. The second boat will carry cruise missiles to hit shore and surface targets."
While the two submarines will be based on a common hull design, the interceptor variant will not feature tubes to carry long-range anti-ship or cruise missiles, according to Shlemov.
Russia expects the new submarines to enter production sometime between 2017 and 2018, with the interceptor variant entering service in the 2020s.
Russia is already upgrading 12 existing nuclear submarines, Oscars and Akulas, at the Zvezda shipyard in Bolshoy Kamen in the Russian Far East. The comprehensive upgrade includes new combat systems, countermeasures, and weapons.
