Faster Than Supersonic Travel - Underwater

waimate writes "This fascinating article describes a scheme devised by the Soviet Union for superfast underwater travel - faster than Concorde. The idea is to use Cavitation - an effect usually the enemy of marine architects, and turn it to an advantage, creating vessels (initially torpedoes) encased in a bubble of vacuum and powered by rockets. All under the water. Watch out for that mullet !"

Comments

Re:It'll never happen

[Chris Johnson]

Oh, by all means. Nobody seems to be taking into consideration how efficient water is for wave transmission. Ever heard of the Yangtze River Dolphin? It's an endangered species (not sure of its current status) in a very busy river. Douglas Adams wrote a book about endangered creatures called 'Last Chance To See', one of which was the Yangtze River Dolphin. One problem of the dolphin's was the amount of background noise in the river from just plain old outboard motors- lots of them- interfering with the dolphin's echolocation, its sonar. Douglas Adams tried to check out what noises were in the river, and put a hydrophone into the water (a waterproof mike), expecting to hear something like New York City rush hour, only with outboard motors...

Water is a very efficient transmitter of soundwaves. Adams heard no outboard motors, no dolphins- nothing but a continuous, ceaseless, raging white noise so intense no information could be heard from it at all. All those outboard motors echoed and echoed until the river was one unbearable shriek of sound...

Now. How much louder than a cheap outboard motor is a rocketpowered submarine creating a cavitation bubble so great that a _ship_ fits inside it?

This might work as a military weapon where you don't give much of a damn what else you hit, but use as sea transportation will, surprisingly quickly, leave _no_ form of sonar available for anybody. Not whales, not fish, not oil tankers. I'm not sure how many of these subs it would take but you have to understand how incredibly 'live' water is- sound does not propagate like it does in air. The ambient noise level will simply rise and rise until you can't use sonar for anything anymore- by which time of course, huge amounts of the sea's ecosystem will be hosed, which could also be considered a Bad Thing. That _is_ where the earth gets most of its oxygen y'know ;P

250 GigaWatts: Time Travel?

[IntelliTubbie]

Combining the two results gives us 250 GW of power required to move our submarine.

Wow, and it only takes 1.28 GW to travel through time! That is, if you can find an engine powerful enough to accelerate you to 88 mph. Doc, look out!

Cheers,
IT

US Navy Too!

[superid]

The US Navy has been researching this technology for quite a while as well. See this article from 1998.

Quick calculation

[jmv]

Consider a "small" submarine with a radius of 2m, going at a speed of 340 m/s (Mach 1 at sea level). The amount of water this submarine has to push aside is pi*(2m)^2*340m/s = 4300 m3/s

That's 4300 tons of water per seconds. Now this water has to be pushed at around 340 m/s too, which corresponds to a kinetic energy of 58000 kJ/ton of water. Combining the two results gives us 250 GW of power required to move our submarine.

This calculation is very approximate, but it still gives an order of magnitude. Even if I'm 100 times over, it still means thousands of megawatts, the power of a big nuclear plant. This is why I doubt we'll see a supersonic submarine soon.

Screw Underwater

[cybercuzco]

The real question is can this be done in air? One of the big problems supersonic vehicles have is shockwaves and heating on leading edges, now while getting my Aerospace engineering degree i had to take a fluid dynamics course or two, and the gist of it is that fluids are fluids and both air and water are fluids. If you can create a blunt nosed craft that can reach high speeds with low drag, this can be an amazing breakthrough for air and spaceflight. it certainly has piques my curiosity and ill be following devlopments closely.

Stealth this is not -- more like murder

[Morgaine]

Any living organism caught by the shock front from this thing is going to be jelly. A megawatts drive underwater would translate directly into millions or billions of fish dead on each trip, and probably several boats and human lives lost as well for good measure.

Someone's got to be kidding.

Somebody has way too much time on their hands...

[CyberPup]

Sheesh, give a little techno-babble to a reporter and he has everyone dreaming about daily bullet trips across the Atlantic. Gimme a break.

This technology is fairly reasonable for what it's being used for (blind, dumb, fast, small things).

It won't scale to large vehicles, and most reasonable humans have an aversion to travelling in blind, dumb, fast things anyway.

Here's a short list of "strikes against it" that immediately come to mind:

(1) Hello, it's blind. How the heck is it going to see where it's going? Navy ships' passive sonar capability is seriously reduced at speed because of the noise being produced by the ship going through the water (and the increased noise of the ship's machinery). Active sonar? Well, that *might* help a little, but echo from active sonar has to be heard too (see above).

(2) Most of the marine life (including seaweed, etc) stays relatively close to the surface. Great, you say -- make the thing travel deeper to avoid skewering whales, etc. Well, that'd be nice, but it's a *lot* harder to cavitate at depth due to the increased pressure (and reduced temperature) -- and the relationship is not a proportional one. Besides being harder to cavitate in the first place, it'd be harder to maintain the bubble around the vehicle (because sea pressure would be trying to collapse it).

(3) Even if you could see where you were going, how would you turn? Control surfaces on the vessel wouldn't do anything because they're in a bubble. Change the direction of the rocket? Kill the bubble.

(4) Rockets aren't exactly green machines either. Pump our oceans full of chemicals? I don't think so.

(5) The speed required to maintain a cava-bubble (tm) around a large commercial vessel would be MUCH greater than that required to create/maintain a bubble around a small object like a bullet or a torpedo.

(6) Revisiting the "can't see" issue a bit -- assuming they *could* get active sonar to work from within a noisy bubble, what kind of range/warning is it going to give at those speeds? Ever drive really fast at night? Headlights don't give you a whole lot of reaction time, do they? This situation would be much worse.

(7) This is currently being used for non-manned things that we don't care about. They either run into something or blow up or whatever. Great. Ever wonder what the stopping experience is going to be like for humans? Think about it -- the speed creates the "bubble" which eliminates the drag. Okay, we reach our destination, start to slow down -- bubble collapses -- but guess what, we're still going pretty fast -- now we have a ton of drag slammed onto us. And people whine about a airliner slowing down after a landing. :o)

(8) Cost? Well, I dare say it'd be a heck of a lot more costly than the Concorde.

(9) If people are interested in travelling on submarines, why don't we have commercial submarines now?

-- CP (Who, by the way, spent several years on submarines; and spent three years teaching Heat Transfer & Fluid Flow)

It'll never happen

[John Jorsett]

Environmentalists have conniptions over sonar discombobulating whales migration patterns and maybe even deafening them. They also accuse the supersonic Concorde of contributing to the degradation of the ozone layer. Now combine the two in the form of supersonic underwater travel and you may as well just paint the target on your back for Greenpeace. Had this emerged before environmentalism took such a hold, maybe it would continue to be used, but attempting to introduce it today just isn't going to fly. And I hate to say it, but just maybe that would be a good thing for once.