One of the most innovative underwater weapons developed by the Soviet Union was the VA-111 Shkval (“Squall”) supercavitating torpedo, a weapon that is coming back into view as US-Russia tensions ramp up in a new competitive age.
Forget the Red October, first strike Soviet submarine from the movie of the same name — this was a torpedo that could suddenly go six times faster than its predecessors.
Powered by a rocket engine, it is capable of astonishing speeds of up to 200 knots an hour and boasts a maximum range of 7,500 yards.
In a world where physics ensured most ships and underwater weapons topped out at 50 knots, how did Russian engineers accomplish this?
Traditionally, torpedoes use propellers or pumpjets for propulsion. Shkval, on the other hand, uses a rocket engine. That alone is enough to make it fast, but traveling through water creates major drag problems, the report said.
The solution: get the water out of the path of the torpedo. But how exactly does one do that in the middle of an ocean? The answer: vaporize liquid water into a gas.
Shkval solves this problem by diverting hot rocket exhaust out of its nose, which turns the water in front of it into steam.
As the torpedo moves forward, it continues vaporizing the water in front of it, creating a thin bubble of gas that drastically reduces drag.
This process is known as “supercavitation.”
With conventional torpedoes, steering is simple — just adjust the flaps.
But with supercavitation torpedoes not only the fins of the torpedo have to be moved, but also the bubble sheath surrounding the torpedo.
The rotation distorts the bubble surrounding the torpedo and can cause the torpedo to come into high-speed contact with water.
To avoid this problem, more of the bubble-forming gas must be moved to the side of the torpedo facing the bend, the report said.
This makes turning maneuvers tricky, as a change of heading will force a portion of the torpedo outside the bubble, causing sudden drag.
Early versions of Shkval apparently had a very primitive guidance system, and attacks would have been fairly straight torpedo runs.
Originally designed in the 1960s as a means of quickly attacking NATO nuclear missile submarines, Shkval could deliver a nuclear warhead at unheard-of speeds.
It began mass production in 1978 and entered service with the Soviet Navy that year.
Like any weapon, there are drawbacks.
For one, the gas bubble and rocket engine are very noisy. Any submarine that launches a supercavitating torpedo will instantly give away its approximate position, the report said.
Another drawback to a supercavitating torpedo is the inability to use traditional guidance systems.
The gas bubble and rocket engine produce enough noise to deafen the torpedo’s built-in active and passive sonar guidance systems.
Also, controlling the torpedo is limited. Basic gentle turns would work, but no sharp turns.
And with so much effort going into speed and control, SC torpedoes often carry a smaller warhead about 2/3 the size of conventional heavy-weight torpedoes.
The SC torpedo can communicate to the launching platform via a thin wire trailing from the torpedo to the launching submarine.
This can allow the submarine to guide the “blind” torpedo to its target.
If the wire would be broken, however, an uncontrolled torpedo with a speed of more than 200 knots is a problem.
Controlling depth is also no walk in the park.
The deeper a torpedo dives, the more pressure it is subjected to by the ocean — and the smaller the bubble envelope gets. In order to compensate for this, additional gas needs to be injected inside the bubble to help the torpedo rise.
Sources say Russia has been developing a new SC torpedo named Khishchnik (“Predator”), which is possibly a remedy for the weaknesses of the Shkval.
Unlike various supposed superweapons which they boast about publicly, the Russians are keeping very quiet about Predator because the project is highly classified.
It is only known that it is being developed by the Elektropribor design bureau, which specializes in aviation technology.
However, experts say Khishchnik may also be significantly faster than the 1970s Shkval. Very high speeds underwater are certainly possible.
Georgiy Savchenko of the Institute of Hydromechanics at Ukraine’s National Academy of Sciences works on supercavitating designs, also says that improved fuel will make a dramatic difference – he estimates that the range could be improved by a factor of ten.
Western analysts have tended to be scathing about the Shkval, calling it a suicide weapon because of its short range.
American efforts to copy Russian supercavitating technology have not so far been successful. There have been great successes in the lab, but these have not translated into deployed hardware.
DARPA had an ambitious plan for a 100 mph+ supercavitating submarine called the Underwater Express. They had a three-year contact with sub makers Electric Boat from 2006-2009, but it came to nothing.
The US Navy’s supercavitating torpedo project has been on hold since 2012; a spokesman says that improved understanding of the basic physics of supercavitation is needed.
Sources: National Interest, FuturoProssimo, NavalPost.com, Yahoo! News, We Are The Mighty