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The Supercavitating Torpedo: The One Weapon the U.S. Navy Can’t Match

Russian Submarines
Pictured is a Kilo-Class Russian Submarine in the English Channel. The image was taken from Royal Navy Wildcat HMA2 Helicopter of 815 Naval Air Squadron. Kilo class is the NATO reporting name for the diesel-electric attack submarine.

In the 2000s, a German firm developed a torpedo that was faster than high-speed trains. Here are the details.

Torpedos

Submarines are the ultimate underwater weapon—silent and hard to detect hundreds of feet under the ocean surface. Submarines’ main armament, torpedoes, come in two sizes generally, 533-millimeter and 650-millimeter heavyweight torpedos. In general, they are tipped with high explosives.

Though there are a startlingly wide variety of propulsion systems used by torpedos, some, like the United States’ Mark 48 and Mark 46 torpedos, use a piston engine and specially formulated propellant. They are faster than the majority of surface ships and submarines, but cannot travel faster than 50 miles per hour.

But there is a different design—that is orders of magnitude faster.

Supercavitating torpedos

Supercavitating torpedos on the other hand travel extremely fast—hundreds of kilometers an hour. Torpedos of all types are slowed down by drag caused by friction with water. One way to overcome this drag is with bubbles.

Supercavitating torpedos travel through the water in a large bubble that encapsulates most or all of the torpedo. Compressed gas stored inside the torpedo is ejected out of the nose, and the torpedo “glides” through the water inside the bubble, remaining relatively dry.

Control surfaces, generally fins, pierce the bubble and maintain contact with the water, allowing the torpedo to steer.

One of the design challenges is target acquisition. Torpedo homing technology limits target acquisition. Since supercavitating torpedos are propelled by a rocket engine, they are loud—very loud. They would likely be unable to home in on a target using acoustics.

Gas envelope problem

With conventional torpedos, steering is as simple as adjusting fins. But with supercavitating torpedos, not only do fins need to be shifted, but the bubble sheath that surrounds the torpedo must also be maintained.

Turning distorts the bubble surrounding the torpedo, and can cause the torpedo body to come into contact with the ocean. To compensate for this, more of the bubble-forming gas needs to be shifted to the side of the torpedo that is facing the turn. This is not easy.

Superkavitierender Unterwasserlaufkörper

In the early 2000s, a Germany company worked in tandem with the German Navy (Deutsche Marine) to develop the Superkavitierender Unterwasserlaufkörper, or Supercavitating Underwater body.

The German torpedo had a unique cone nose that projected forward of the torpedo body. The torpedo’s velocity was allegedly 400 kilometers per hour, or about 250 miles per hour. The Superkavitierender Unterwasserlaufkörper can also control for depth by injecting more gas into the bubble to offset compression that happens as depth increases.

Several other countries produces supercavitating torpedos as well. The Soviet Union made one in the 1970s, and Iran claims to have developed a torpedo that nothing in the ocean can avoid. The United States may also have developed a similar torpedo, but details are scant.

Next Big Thing?

Supercavitation could revolutionize naval warfare—if the technology can be mastered. Simply going straight ahead is simple enough—maneuvering is the challenge. If reliable—and steerable—supercavitating torpedos ever enter serial production, they will dominate the seas.

Caleb Larson is a Defense Writer based in Europe. He holds a Master of Public Policy and covers U.S. and Russian security, European defense issues, and German politics and culture.

Image: Reuters.

Written By

Caleb Larson, a defense journalist based in Europe and holds a Master of Public Policy degree from the Willy Brandt School of Public Policy. He lives in Berlin and writes on U.S. and Russian foreign and defense policy, German politics and culture.

6 Comments

6 Comments

  1. Duane

    September 22, 2021 at 7:40 am

    Another tiresome article about the gee-whiz supercavitating torpedo, written by someone with no knowledge of how torpedoes actually work.

    First of all, a supercavitating torpedo supercavitates. The loudest possible sound that any vessel or waterborne weapon can make underwater is cavitation. Cavitation is what happens when a gas or vapor collapses due to water pressure – what you have lots of with subs – and can be detected easily by any decent sonar from tens of miles away.

    That is why the modern navies, especially the US Navy, developed anti-cavitation shrouded screws and propulsors for their subs – to eliminate cavitation. In the world of subsea combat, if you cavitate you’re dead.

    Also, for the same reason, the supercavitating torpedo cannot use its own internal sonar sensors to find and lock on to the target. That would be like trying to detect the sound of a mosquito from miles away while a four engine jet is revving its engines only a few yards from you. Think about that.

    Because of these two factors, the only way a supercavitating torpedo can find and home in on a target is if it is wire guided from a mother sub that is very near by. And that means its range will be measured in thousands of yards, not tens of miles as a Mk 48 ADCAP torpedo is capable of. A Mk 48 can be wire guided close in, but it can also be fired at long distances and use its onboard sonar sensor to lock onto a target.

    This short range problem for the supercavitators also means that the attacking sub has to get very close to the target. Any decent ASW capability would eliminate such a sub long before it got to within firing range.

    The supercavitating torpedo, also because of its extremely loud noise due to cavitation, becomes the easiest of all targets to find and destroy by anti-torpedo weapons, which we have.

    The supercavitating torpedo is yet another of those headline grabbing “super duper stuper weapons” that the Rooskies brag about to scare civilians who don’t know any better, like their super sized nuke torpedoes. But I’ll take a Mk 48 ADCAP any day of the week over any such all sizzle but no steak weapons.

  2. Duane

    September 22, 2021 at 7:47 am

    Oh, and I forgot to mention .. any sub that fires a supercavitator also gives away its own position, extremely loudly, making it easy peasy for ASW targeting against the attacker. The sub will only get one salvo in before getting killed in attacking any ASW-equipped naval target or any escorted transport vessel target.

  3. Icepilot

    September 22, 2021 at 12:56 pm

    I wholeheartedly endorse Duane’s comments.
    Submarine warfare is entirely a question of who gets detected first.
    The U.S. dominates undersea warfare because our subs are the quietest & have the best acoustic sensors. While you can make an argument for a diesel boat operating on her battery, no SSN is going to rush into those waters without sniffing around for a couple of days. And when that diesel boat snorkels, she’s toast.

  4. Rufus

    September 22, 2021 at 3:01 pm

    If a torpedo can move that fast perhaps it is what we have seen in the water by military forces claiming to be from space aliens.

  5. Doug Mayfield

    September 22, 2021 at 4:42 pm

    I enjoyed the article and the comments and admit up front, other than reading, that I know almost nothing about undersea warfare. In that context, I will ask a question. Given that the trend in warfare seems to be more and more unmanned, what about small cheap unmanned subs to get close and launch fast supercavitating torpedoes against large high value targets. (For example, consider https://nationalinterest.org/blog/buzz/war-games-swedish-stealth-submarine-sank-us-aircraft-carrier-116216)
    Such an attack would take advantage of the torpedo’s speed and given unmanned and cheap, it may not matter that the defenders destroy such a sub after damage is done. Thoughts?

  6. Rob

    October 1, 2021 at 11:33 am

    Supercavitating torpedoes wouldn’t work with US Navy submarine doctrine. While speed is sexy, silence is deadly. Of course the Russian played around with the idea because for years their subs sacrificed silence for speed. Having a super fast torpedo does you know good if your adversary is so quite that you can’t find them.

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