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Science

Supersonic Submarines 20

Posted by michael from the build-a-better-jet-ski dept.
Daktaklakpak writes "Not really new stuff, but it's too cool to pass up. Researchers are developing a method called supercavitation which may one day allow submarines to break the sound barrier. It works by placing the entire vessel in a gas bubble except for the tip, thus reducing the total drag." We've run an article about this before, but this is a bit more informative, with a lot of speculation about possible uses... Update: 03/07 03:24 PM EST by michael : Note that space.com does not use permanent URLs for these "breaking news" stories, so the link above is wrong, but should be findable, for a time at least, on the space.com site.
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Supersonic Submarines More

Supersonic Submarines

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  • actually, it seems to be 14 (13 is the phone, page 12 looks like something from battlebots, if only it were larger).

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  • according to a Russian Admiral, a nearby Russian warship fired a drone missile at the Kursk which failed to break up like it was supposed to, and the resulting explosion knocked the Kursk hard enough to detonate a torpedo. It was on ananova somehwere, but I don't have a hard link, or info on how reliable ananova is.
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    Peace,
    Lord Omlette
    ICQ# 77863057
  • Well here is a question. How are they planning on keeping it in the bubble/bubbles? I mean buoyancy would make it pretty difficult to keep the sub from falling out of the bubble and lawn darting the bottom of the ocean. Now they are going to speed of sound, with a bubble of air around the sub, how does the sonar work? Then again, what do I know about sonar. If a jet is going mak 1 and hits a pigeon, it could go through the cockpit and kill the pilot bringing the jet down. So what happens when a sub hits a shark or a school of tuna at mak 1? The big sky theory really seems to fall apart in water. Lastly, don't we have plains for that?

  • Cool ... before you'd start rocketing around, you'd have to make 'the appropriate calculations', like in Star Wars, so that you wouldn't hit any asteroids, planets, or whales or anything.

    -Christian

  • It may be that any Sub that may do something like this may end up being very large. Such a sub may be best used for shipping. Very fast speed, very high volume. We may be able to ship equipment and people faster and cheaper then by air. There may be the possibility to go under the North Pole as the short cut from the Atlantic to the pacific.
  • Currently, the quietest sub in existance, the SSN-21 Seawolf class boats, is still limited to operating below 10 knots at depths of 200ft or less because the resulting cavitation from any faster velocity sounds like a flat knocking noise when listening to the target via passive sonar. As a sub, you DON'T want cavitation because it gives your position away.

    I'd say the only benefit of being able to supercavitate is to travel fast enough to evade an incoming torpedo; however a torpedo with that kind of technology will basically still be able to out run the boat (simply, it takes less effort to accelerate something that is 1/100 the mass of the boat). Thus, the best strategic is STILL going to remain staying slow, deep, and using a towed array to listen in the baffles in order to stay undetected.
  • uh no. you seem to be confusing detection and tracking mechanisms. A plane's noise signature doesn't mean anything, because you don't use a sound-wave vector to detect it. However, a plane's *radar* signature is what makes it detectable. Thus, you have development of the F-117A "stealth fighter", the B-2 "stealth bomber", and the F-22 Raptor. This is because you want to minimize the aircraft's radar signature. Suppose there was some sort of scramjet engine, that when retrofitted onto the F-117A that allowed it to cruise at Mach 5. Sure, it's fast, but what if the new engine causes it to appear bright and green on a radar screen, and the enemy has a SAM that travels at Mach 6?

    The same principle applies to a submarine. Passive sonar is used to listen to mechanical sounds traveling through the water. Preferably, you want a silent boat, one which makes NO noise, so it will be undetectable, but since all mechanical movement creates friction, this energy is converted to sound. Unless you have stopped your engines and are at 0 speed, you will hear the boat using hydrophones. Thus, you hear the rumbling of a propellor 200 feet under the ocean.

    Furthermore, cavitation causes a feedback interference into the boat's own hydrophones, which decrease the ability of the sonar operator to hear the surrounding area for other boats. So when cavitating, a sub is deaf and at the same time loudly transmitting its location to every other sub or surface warship in its vicinity.
  • It would likely be the speed of sound in air, because the speed of sound is water is much higher then that of the speed of sound in air. So the sonar would still travel fast enough, you just might have a hard time catching the signal.
  • Ananova links:
    http://www.ananova.com/news/story/sm_220365.html
    http://www.ananova.com/news/story/sm_227556.html
    http://www.ananova.com/news/story/sm_228258.html
    --
    If the good lord had meant me to live in Los Angeles
  • As a sub, you DON'T want cavitation because it gives your position away.

    That is kind of old school thinking. Just like the jet engine and hot air balloon. If you would have shown a jet engine to a 1900s ballonest I'm sure he would have said it was useless for ballooning.

    The military doesn't care too much about the noise that modern day jets generate. (Well they do, and they work on quieter engines, which I'm sure will happen with super cavitation as well)


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  • A plane's noise signature doesn't mean anything, because you don't use a sound-wave vector to detect it.

    Well, it did mean something before radar (I should have done prop vs. balloon), but that didn't stop the development of faster and louder planes.

    Passive sonar is used to listen to mechanical sounds traveling through the water.

    This is true, how ever "passive" sonar does take a while (5 to 10 minutes, heading on the same course in good conditions), this is how US subs can hit relatively large fishing boats in good weather. If a super fast sub was used, it could be out of the area before any body could start the long procedure of getting fix.

    I've very sure that this technology will catch on regardless. I'm sure the cavitation could also be turned off and on pretty fast making it even harder to locate than a normal sub.

    So when cavitating, a sub is deaf and at the same time loudly transmitting its location to every other sub or surface warship in its vicinity.

    So, in that case why wouldn't the cavitating sub use an active sonar (selected Freq. to avoid cavitating side effects). Anybody listening already knows it's in the area, so why not have a look, it wouldn't compromise you more that cavitating does. When cavitation is off it could return to a passive sonar.

    What I'm hope is that the sub's uses wouldn't be kept to just the military. Imagine a super fast rescue craft that could save lifes at sea. Or large ocean traveling cargo subs that aren't affected by weather and travel as fast as a jet.

    We've got water, let's use it!


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  • Wow, that would be cool to see a sub blow all it's tanks and come shooting out of the water at supersonic speeds! That would be a rough landing for the crew though. And watch out all ye Japanese fishing boats!
  • As I understand it, the bubble is constantly generated by the low pressure zone surrounding the sub as its tip pushes through the water. The bubble doesn't really contain air, but water vapor.
  • If the sub is travelling at the speed of sound, how do they use their sonar equipment? Surely the cavitation alone would be that noisy that the sonar would be ineffective?
  • http://www.space.com/businesstechnology/technology /space_gear_13.html

    that one's for a phone of some sort
  • The theory is that the Russian submarine Kursk was testing this technology (in the form of a torpedo) when it suffered its fatal explosion.

    That's why there was a US Sub nearby, cuz we were snooping on the test.
  • Here's [http] the link (or http://www.space.com/businesstechnology/technology /space_gear_13.html) - the previous link didn't work for some reason...
  • Dangit! my work account won't let me access those sites!

    So is this the speed of sound measured in air or water? From what I know, the speed of sound in water is a lot more than the speed of sound in air.

    If it's the speed of sound in water, I wonder what sort of wave effects this would have, especially on the surface of the water, a sonic boom in water instead of air might be cool to see!

  • Supercavitation (Score:3)

    by K-Man ( 4117 ) on Wednesday March 07, 2001 @01:47PM (#380859)
    The ultimate weapon: a torpedo that makes your teeth fall out.

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