# If an object can go faster than sound underwater - Is there an aquatic "sonic boom"? **URL:** \ **Category:** Factual Questions\ **Created:** [March 27, 2003, 12:02am UTC](https://boards.straightdope.com/t/if-an-object-can-go-faster-than-sound-underwater-is-there-an-aquatic-sonic-boom/164410 "2003-03-27T00:02:12Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [March 27, 2003, 12:02am UTC](https://boards.straightdope.com/t/if-an-object-can-go-faster-than-sound-underwater-is-there-an-aquatic-sonic-boom/164410/1 "2003-03-27T00:02:12Z")
If you had a torpedo (or whatever) that could go faster than speed of sound _in water_ what would happen at the point the torpedo exceeded the speed of sound in water? Aqua sonic boom of some kind, or nothing… or what? According to [this site](http://arts.ucsc.edu/EMS/Music/tech_background/TE-01/soundSpeed.html) the speed of sound in water is 1480 m/s or 4856 ft/s or more than 3000 miles per hour. ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [March 27, 2003, 12:12am UTC](https://boards.straightdope.com/t/if-an-object-can-go-faster-than-sound-underwater-is-there-an-aquatic-sonic-boom/164410/2 "2003-03-27T00:12:06Z")
Of course there would be a sonic boom, it’s exactly the same principle. When it reaches the speed of sound, all it’ssound waves essientally bunch up together as the sound producer is travelling at the same speed as them and via constructive interference make one big sound wave. ---
**Author:** ![BrandonR](https://avatars.discourse-cdn.com/v4/letter/b/779978/32.png) [@BrandonR](https://boards.straightdope.com/u/BrandonR)\ **Post date:** [March 27, 2003, 12:12am UTC](https://boards.straightdope.com/t/if-an-object-can-go-faster-than-sound-underwater-is-there-an-aquatic-sonic-boom/164410/3 "2003-03-27T00:12:58Z")
Would it make a large wave of water or something special? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [March 27, 2003, 12:15am UTC](https://boards.straightdope.com/t/if-an-object-can-go-faster-than-sound-underwater-is-there-an-aquatic-sonic-boom/164410/4 "2003-03-27T00:15:09Z")
But water is a LOT less compressible than air. I’m thinking that would make a big difference in the ability to even approach the speed of sound underwater. ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [March 27, 2003, 12:19am UTC](https://boards.straightdope.com/t/if-an-object-can-go-faster-than-sound-underwater-is-there-an-aquatic-sonic-boom/164410/5 "2003-03-27T00:19:55Z")
Yes QED, it’s not really feasible at all to have a torpedo travel that fast, water resistance exerts a much larger force than air resistance. I imagine it would have the same effect on surface waves as throwing a stick of dynamite underwater, in otherwords no massive waves. ---
**Author:** ![World\_Eater](https://avatars.discourse-cdn.com/v4/letter/w/f04885/32.png) [@World\_Eater](https://boards.straightdope.com/u/World_Eater)\ **Post date:** [March 27, 2003, 12:25am UTC](https://boards.straightdope.com/t/if-an-object-can-go-faster-than-sound-underwater-is-there-an-aquatic-sonic-boom/164410/6 "2003-03-27T00:25:17Z")
A tsunami? ---
**Author:** ![Yossarian](https://avatars.discourse-cdn.com/v4/letter/y/9de0a6/32.png) [@Yossarian](https://boards.straightdope.com/u/Yossarian)\ **Post date:** [March 27, 2003, 12:37am UTC](https://boards.straightdope.com/t/if-an-object-can-go-faster-than-sound-underwater-is-there-an-aquatic-sonic-boom/164410/7 "2003-03-27T00:37:15Z")
Tsunamis are fast, but at 200 m/s (in 4 km of water), not even close: [http://www.eng.vt.edu/fluids/msc/my\_pages/ocean/tsunami.htm](http://www.eng.vt.edu/fluids/msc/my_pages/ocean/tsunami.htm) ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [March 27, 2003, 1:01am UTC](https://boards.straightdope.com/t/if-an-object-can-go-faster-than-sound-underwater-is-there-an-aquatic-sonic-boom/164410/8 "2003-03-27T01:01:36Z")
[Faster than a speeding bullet (supersonic submarine)](http://www.freerepublic.com/forum/a397c938f46bc.htm) > [@](#): > > According to Mark Galeotti, a defence expert at Keele University in Staffordshire, prototypes of the torpedo appeared in the 1980s, but there was still plenty of work to be done. “It was only in the early 1990s that the Russians were in a position to produce a proper working torpedo,” says Galeotti. Called Shkval, meaning squall, it is said to be capable of speeds as high as 500 kilometres an hour. It is fired like an arrow from the submarine, possibly with a mechanical catapult. That gets it moving fast enough for the cavity to form, so that its rocket can be lit. > > The Russians had built themselves a formidable weapon. Shkval leaves enemy torpedoes standing, and can knock out an opposing sub before it has time to react. It could even be used defensively to intercept enemy torpedoes. > > But Shkval is a slowcoach compared with what was to follow. By the time it had appeared in the early 1990s, the US had established its own supercavitation programme. To begin with, it concentrated on unpowered projectiles–underwater bullets. When conventional projectiles are fired into water, they are dragged to a halt before they have penetrated more than a metre or so. Researchers at the NUWC knew that supercavitating munitions ought to be able to go a lot further, and at very high speed too. > > In 1997, they proved it. Just a few years after Shkval’s debut, NUWC researchers announced they had gone supersonic. An unpowered projectile, with a carefully designed flat nose and fired from an underwater gun, broke the sound barrier in water. That’s nearly 5400 kilometres per hour–or 1.5 kilometres per second. > > Lacking any onboard power to sustain its motion, the shell slowed rapidly, but this was still a vivid demonstration of the speeds that supercavitation makes possible. Already they aren’t very far off the 2.5 kilometre-per-second speed record for conventional munitions in air, and NUWC scientists have calculated that their supercavitating projectiles should be able to match or even surpass this. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [March 27, 2003, 6:34pm UTC](https://boards.straightdope.com/t/if-an-object-can-go-faster-than-sound-underwater-is-there-an-aquatic-sonic-boom/164410/9 "2003-03-27T18:34:15Z")
Things do move faster than sound in water all the time, but it doesn’t produce a “boom”. **Desmostylus** ’s quote almost mentions the right term: “cavitation”. A “hole” opens in the water that will collapse back on itself once the fast moving object goes on. The tips of propeller blades do this if turned fast enough. This is not good: the cavitation can damage the blades, engine efficiency is lost, and (most imp. for navy purposes) the noise of the collapsing bubbles is easily picked up on sonar. ---
**Author:** ![Hail\_Ants](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@Hail\_Ants](https://boards.straightdope.com/u/Hail_Ants)\ **Post date:** [March 28, 2003, 12:18am UTC](https://boards.straightdope.com/t/if-an-object-can-go-faster-than-sound-underwater-is-there-an-aquatic-sonic-boom/164410/10 "2003-03-28T00:18:35Z")
For awhile rumors were flying that a (malfunctioning) prototype supercavitating torpedo is what sank the Russian sub Kursk. I believe it was generally discounted later. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [March 28, 2003, 12:37am UTC](https://boards.straightdope.com/t/if-an-object-can-go-faster-than-sound-underwater-is-there-an-aquatic-sonic-boom/164410/11 "2003-03-28T00:37:02Z")
> [@](#): > > \*Originally posted by ftg \* > \*\*Things do move faster than sound in water all the time, but it doesn’t produce a “boom”. **Desmostylus** ’s quote almost mentions the right term: “cavitation”. A “hole” opens in the water that will collapse back on itself once the fast moving object goes on. > > The tips of propeller blades do this if turned fast enough. This is not good: the cavitation can damage the blades, engine efficiency is lost, and (most imp. for navy purposes) the noise of the collapsing bubbles is easily picked up on sonar. \*\* That just isn’t right. Cavitation is “cold boiling” of the water. The pressure on the forward side of the propellor becomes so low that the water boils. ---
**Author:** ![hobbes730](https://avatars.discourse-cdn.com/v4/letter/h/97f17d/32.png) [@hobbes730](https://boards.straightdope.com/u/hobbes730)\ **Post date:** [March 28, 2003, 1:53am UTC](https://boards.straightdope.com/t/if-an-object-can-go-faster-than-sound-underwater-is-there-an-aquatic-sonic-boom/164410/12 "2003-03-28T01:53:16Z")
Cavitation can also cause dam spillways to corrode in much the same way as they might a propeller, causing catastrophic failures in very short amounts of time.