China developing supersonic submarine powered by a rocket motor.

[rtxoff]

Seriously??

http://www.scmp.com/news/china/article/1580226/shanghai-san-francisco-100-minutes-chinese-supersonic-submarine

[Kermunist]

My guess? They want to build one of these

http://en.wikipedia.org/wiki/VA-111_Shkval

And somewhere between the scientists doing the work and the south china morning post publishing the story, someone decided to try and think of a nice, non-military use for the research. And this is what they came up with.

[Tommygun]

Is supercavitating what happens when you hit 100kg of Yellowfin tuna at 370km/h?

[Godot]

While it sounds interesting, the big question is, whether it is less environmentally damaging (and uses less fuel) than a supersonic passenger plane

(and with "environmentally damaging" I don´t even mean chemical byproducts of the engine, but also the underwater noise that the supercavitation most likely produces ... since decades we have cases of whales stranding on beaches ... many scientists are thinking that underwater noise may be the culprit)

[Scotius]

OK, i can see sense in military use of supercavitating vessels. But in civilian transport? It's not like we've ran out of space in the air and ocean's surface. IMO it's just a gimmick to get funding

[xenomorph555]

What would something underwater look and sound like, I find it very hard to imagine...

Anyway it sounds epic and I say they should do it!

[NASAFanboy]

Congress, take notes here.

Now give America tons of science subsides or else.

[ZedNova]

Sounds like KSP submarines.

[jfull]

This only makes sense for a military craft... there's no reason to use this technology for any kind of civilian transport, because its far easier to hit those high speeds with an aircraft.

Also, I can't imagine that it would be able to carry enough rocket fuel and compressed air for more than a few minutes.

[Seret]

Congress, take notes here.

Now give America tons of science subsides or else.

Or else what? The Chinese will develop a capability the Soviets had decades ago? Supercavitating torpedoes are a bit unusual, but not new.

[lajoswinkler]

This won't happen. It's far more viable to fly planes.

The noise would also be dreadful for whales etc.

[SolNG]

Is supercavitating what happens when you hit 100kg of Yellowfin tuna at 370km/h?

Exactly, haha! Or a pod of whales.

[Godot]

Or else what? The Chinese will develop a capability the Soviets had decades ago? Supercavitating torpedoes are a bit unusual, but not new.

Exactly ... and for Torpedoes it actually makes sense

[Vanamonde]

I have a hard time visualizing how masses of ocean water could be shoved out of the way of something the size of a submarine at speeds like those being discussed here. But then, I would have said that the 370km/h torpedo is impossible. Is that for real? Has it been verified?

[Kryten]

It's very much verified; we're not talking about some exotic testbed, this has been mass-produced for decades and exported to multiple countries.

[Alshain]

I have a hard time visualizing how masses of ocean water could be shoved out of the way of something the size of a submarine at speeds like those being discussed here. But then, I would have said that the 370km/h torpedo is impossible. Is that for real? Has it been verified?

Same way masses of air can be shoved out of the way really. At those speeds air and water behave surprisingly similarly.

[JDCollie]

I have a hard time visualizing how masses of ocean water could be shoved out of the way of something the size of a submarine at speeds like those being discussed here. But then, I would have said that the 370km/h torpedo is impossible. Is that for real? Has it been verified?

Absolutely, cavitation is an observable phenomenon where bubbles form in fluids that encounter swift pressure changes such as when a bullet or torpedo passes through water at high speed. It doesn't just occur with projectiles either; propellers can have cavitation around their blades, pipes can have it where they narrow (which can cause serious damage btw, and is a topic of much concern for engineers), and the Pistol Shrimp uses cavitation bubbles created by it's claw as a weapon.

Someone (I.E., the Russians) figured out how to consistently produce and exploit those bubbles to reduce drag, and viola!, cavitation torpedos.

[TrooperCooper]

What happens when your passenger submarine hits a whale under water at supersonic speed?

[Skyler4856]

Why can't they use systems similar to RCS for steering?

[JDCollie]

What happens when your passenger submarine hits a whale under water at supersonic speed?

The same thing that happens to everything else.

Edited August 25, 2014 by JDCollie

[Herr Doktor Strangemember]

Why can't they use systems similar to RCS for steering?

From my limited reading on the subject the super-cavitating object has to stay in the bubble created otherwise you find out just how unforgiving water can be at high speeds.

Regards.

[vger]

I have a hard time visualizing how masses of ocean water could be shoved out of the way of something the size of a submarine at speeds like those being discussed here. But then, I would have said that the 370km/h torpedo is impossible. Is that for real? Has it been verified?

What kind of pressure would that put on a sub? It's a lot easier to displace air than water, and to think of how many aircraft got torn apart in those tests. Maybe I'm overestimating the power of water, but I'm thinking that building a sub that can safely explore the bottom of the Mariana trench would be EASIER than building one that could withstand Mach 1 underwater.

Not really sure what the point would be if they want to use it for military purposes though. Sonar would hear that coming from half way across the globe. I'd love to see the surface chop from such a thing though. It would probably look like Godzilla taking a swim.

[JDCollie]

From my limited reading on the subject the super-cavitating object has to stay in the bubble created otherwise you find out just how unforgiving water can be at high speeds.

Regards.

Given how fast water slows down a bullet, I imagine the failure of a cavitation envelope around a submarine would be . . . slimy for those involved.

[tater]

Given how fast water slows down a bullet, I imagine the failure of a cavitation envelope around a submarine would be . . . slimy for those involved.

Yep. This is why you can't take anything seriously that involves, well, any specialty at all, in the news. Reporters cannot manage to even write well (they require copy editors), much less actually understanding what they are writing about. I have heard the following attributed to Murray Gell-Mann, but that may be apocryphal (paraphrased by me, might be BS, all disclaimers apply): He was supposedly interviewed about physics, unsurprisingly, and went to read the article in the paper (a highly thought of paper). They not only got the gist of what he said wrong, but pretty much exactly wrong, the opposite of his explanation. He said that he was annoyed, then went on to read the paper, and believed what he read on other pages since he was not in expert in those subject areas. Obviously upon further thought, he realized he should not take any of it as any more accurate than his own story was.

[Vanamonde]

I get that cavitation can push water out of the way. What I'm saying is, the transverse cross-section of a submarine would be quite large, and the vehicle would have to push that area-times-the-speed volume of water out of the way, with sea water being many times more massive, viscous, and under far higher pressure than air at the same speed. What I'm meaning is, one can't get around the conservation laws, and no matter which means is used, a tremendous amount of energy is going to be needed to move that mass of water out of the sub's way.

But I don't think I'm expressing myself well, without the technical background and terminology to say what I mean.