Supercavitating Torpedoes
Trying to go fast under water induces a lot of “parasitic” drag—the effect of the passage of fluid over the surface of a submerged vehicle. How much develops is a function of the fluid’s density and the square of a vessel’s speed.
Supercavitation can improve under-water speed by replacing dense water with air. Gas is released through a nozzle at a vessel’s front to continuously generate a bubble around the vehicle. This allows the drag effects to depend on air, which is tens to hundreds of times less dense than the surrounding water.
The Soviet Union deployed the VA-111 Shkval supercavitating torpedo in the 1970s (though unbeknownst to Western navies until the early 1990s). According to Norman Friedman (Naval Institute Guide to World Naval Weapon Systems, Naval Institute Press, 2006), the 8.2-meter-long torpedo could travel up to 200 knots with a range of about 6 nautical miles. The Shkval (“squall”) had a fairly primitive guidance system, depending on a fast, straight run and a nuclear warhead to take care of its target.
A variety of recent reports suggest Russia has designed a new supercavitator: Business Insider reported in 2017 that the Khishchnik (“predator”) is in advanced development. Friedman suggests the new Russian torpedo might have a top speed up to 300 knots, though maneuverability will remain a challenge. Keeping the entire torpedo inside a gas bubble is difficult even in a straight line, and “the forces resisting any change in . . . course would be enormous,” Friedman writes.
The U.S. Navy on the Threat
Admiral James G. Foggo III, commander, U.S. Naval Forces Europe–Africa and Allied Joint Force Command–Naples, has a podcast (“On the Horizon”) and has given interviews where he has spoken extensively about the undersea threat posed by the Russian Navy.
On the podcast in September 2018, he said, “I think Russian submarines today are perhaps some of the most silent and lethal in the world, with the exception of our own. . . . We still . . . hold the edge.”
He added, “Russia has renewed its capabilities in the North Atlantic and the Arctic, in places not seen since the Cold War. For example, Russian forces have recently reoccupied seven for their former Soviet Union bases in the Arctic Circle.”
Around the same time, he told Pentagon reporters, “Russia is not 10-feet tall but they do have [undersea] assets that keep me vigilant, concerned. The new Dolgorukiy [Borei]-class submarine, . . . the Severodvinsk-class submarine. They’ve produced the new Kilo hybrid-class submarines that are very capable.”
USNI News reported Foggo declined to say whether the U.S. Navy believes it tracks all Russian subs at sea, saying only, “I can tell you that we hold an acoustic advantage, and we will continue to do that. Our boats are the best in the world.”
SS-N-30 Kalibr Missiles
(in service since 2015)
990-lb high-explosive or thermonuclear warhead
Length
20.5 ft
Propulsion
Turbojet, booster
Range
900–1,500 mi (upgrade to 2,700 mi)
Flight altitude
150 ft over land,
66 ft over water
Ceiling
3,300 ft
Speed
Mach 0.8
Guidance
Inertial guidance, terminal active-radar homing
Accuracy
10 ft
Sources: Jane’s “Game Changer” 2017; NATO Russian Studies, “Russian Weapons,” May 2018; The National Interest, “Russia’s Dangerous ‘Kalibr,’” January 2019; Missile Threat CSIS, “Kalibr at a Glance,” June 2018; Office of Naval Intelligence, The Russian Navy (p. 16); Interview with Norman Polmar; list of active Russian Navy ships (Wikipedia); Russian Navy 2019: List of Active Russian Navy Ships and Submarines (russianships.info).