OSCAR-II Class SSGN
The Russian Navy is modernizing two of its Project 949A OSCAR-II Class cruise missile submarines (SSGNs) to carry the latest generation of missiles. These boats, designated Pr.949AM will have their P-700 Granit (SS-N-19 SHIPWRECK) missiles replaced by a combination of Kalibr land-attack cruise missiles (SS-N-30A SIZZLER) and P-800 Oniks (SS-N-26 STROBILE) dual-putpose anti-ship and land attack cruise missiles. This also implies the possibilities that it will in the future also be able to carry the 3M22 Zircon hypersonic anti-ship missile. The number of missiles carried in the new fit has not been released but it is expected to use the SM-315 triple launcher so the number could be 72 missiles compared to 24 in the original fit.
Original artwork - CLICK for HIGH-RESOLUTION image. 
The OSCAR-I / II classes of large Cruise Missile submarine (SSGN) were designed during the Cold War to take out the US Navy’s Carrier Battle Groups. These are massive and expensive boats, each costing around half an Aircraft Carrier. They are the second largest submarines ever built, behind only the Project 971 TYPHOON Class SSBN.
As built, the OSCAR-II Class carry a formidable battery of 24 x P-700 GRANIT (SS-N-19 SHIPWRECK) supersonic anti-ship missiles. These have a range of 340 nm and can carry a 500kt thermonuclear warhead or 750 kg (1,653 lb) conventional one.
The immense size of the submarine is apparent in these shots. Note that the walkway along the inside of the missile hatch outer doors when they are fully opened, visible on the left, is almost lost in the right hand image. The hull has five decks in some compartments.
Russian SSGN History
Since the 1960s Russia has designed a series of dedicated cruise missile submarines (SSGN) directly to counter American aircraft carrier battle groups. Although the US Navy does use the term SSGN for its own submarines, these were either designed to attack land targets with strategic nuclear weapons (e.g. USS Halibut - SSGN-587) or tactical weapons (e.g. Ohio Class SSGN modification). Russia (/Soviet Union) is the only Navy to have operationalized such dedicated anti-ship missile submarines.
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The first generation of Soviet SSGN was the Pr.659/675 ECHO Class. These entered service in 1960 as part of the first generation of Soviet nuclear-powered submarines, the so-called HEN trio: HOTEL Class SSBN with ballistic missiles, ECHO Class SSGN and NOVEMBER Class attack submarine. Initially, the early ECHO-I boats were used for nuclear strike similar to the contemporary US Navy USS Halibut due to the inaccuracy of their six P-5 Pyatyorka (SS-N-3C SHADDOCK) missiles. This deficiency was reminded with the follow-on ECHO-II Class with eight improved P-6 (SS-N-3A SHADDOCK) anti-ship cruise missiles.
ECHO-II Class SSGN
The ECHO Class had the major tactical disadvantage of having to surface before they could fire their missiles. In May 1964 the first of the next generation Pr.670 CHARLIE Class SSGN was laid down. These boats carried eight P-70 Ametist (SS-N-7 STARBRIGHT) missiles which could be launched while the boat was submerged. These are later replaced by the more capable P-120 Malakhit (SS-N-9 SIREN) missile which had a longer range. Unlike on the ECHO, the CHARLIE-I and enlarged CHARLIE-II classes carried their missiles down the sides of the hull slanted forward. This configuration continues to the current OSCAR-II to class.
CHARLIE-I/III Class SSGN. The third picture has an OSCAR-II Class SSGN in the background for scale.
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The CHARLIE Class was built in some numbers (11 CHARLIE-I and 6 CHARLIE-II) and served as a frontline type until the mid-1990s. Its replacement in operational terms was the OSCAR-I Class but between the two was a unique boat, the Pr.661 PAPA Class. This boat was somewhat larger than the CHARLIE class and had twin screws, but its defining characteristic was that the hull was constructed out of titanium. Although it was not publicized until years later, the ultra-light hulled PAPA Class was the fastest submarine in the world reaching a record-breaking 44.7 knots and was even faster unofficially. >The incredibly expensive design was not put into series production however.
PAPA Class SSGN.
The follow-on to the OSCAR-II would have been the Pr.881 Merkuriy but that was cancelled in 1989. The design of Pr.881 was more similar to ballistic missile submarines (SSBNs) and would have been around 170 to 180 meters (558 ft to 591 ft) in length. The submerged displacement would have been even greater than the OSCAR-IIs at around 25,000 tons. Despite the SSBN appearance, the Bolide missiles would have been in inclined launchers like the OSCAR however.
Pr.881 SSGN.
New Cruise Missiles
The upgraded Pr.949AM boats will carry the 320 nautical mile ranged P-800 (3M55) Oniks (SS-N-26 STROBILE) which is mainly viewed as an anti-ship missile but has a proven land attack capability and has been used in Syria. In the land-attack role it carries the 1,600 nautical mile ranged SS-N-30A SIZZLER (3M14K) Kalibr missiles. With these systems the submarines could target East Coast US cities from the mid-Atlantic.
Oniks (left) and Kalibr (right)
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