300knt torpedo

To keep it in context, my complete comment was "A dumb as **** statement. How does launching conventional torpedos not do the same thing?"

 

Franklin,
don't make me do a third edit!!

But seriously, sorry about the misquote, you are correct of course, I was rushing a bit to try to get in before another few posts occurred.

Referring also to your comment on conventional torpedoes doing the same thing, I absolutely agree.

But, even though I am logicallyh and naturally inclined to your position, this aint really my argument, and certainly not in my expertise.

 

Can you explain why its that much different? You do realize that both are fluids and things moving through each are affected by the same principles. The only difference is that water is much more dense which creates a few more problems.

My question.. is what problems does it cause that prevents the navy from doing this? I'm sure they could get around the increased resistance/drag and current/sea state issues. I must be overlooking something more critical though...

 

The Ocean

You're overlooking pretty much everything.

Radar doesn't work underwater.

Active (pinging) sonar (unless you're a dolphin) has no where near the precision required for a weapons fire control system.

The ocean is full of sound.

The ocean has multiple layers that can reflect or channel sound.

 

Just doing a quick search,
there seems to be a lot out there regarding 'development' of anti-torpedo weapons. Nets, sound waves etc.

http://www.pittsburghlive.com/x/pittsburghtrib/s_291277.html
is one link where the second tests of an anti-torpedo torpedo is supposed to be happening this year.

The point is though, that this technology is still in development. Also, what ever technology is developed that can help torpedo B track and hit torpedo A, can also be used to help torpedo A track and avoid torpedo B. The technology at present seems to be all about conventional torpedo's.
If supercavitating torpedo's (ST's) get developed past traveling in a straight line, and can track and avoid, then of course due to their heightened speed they would need to be defended by something like a supercavitating-anti-supercavitating-torpedo-torpedo. (theres a tongetwister.)
How a plain straight line travelling ST would fair against a conventional anti-torpedo torpedo (which is yet to exist) is another question. It would obviously have alot to do with timing, angles, etc etc..

 

Heres another link,
http://www.airshow.ru/expo/587/prod_570.htm
where a defensive "300 mm diverting Rocket Projectiles (diverting and barrage depth-charge)." will supposadly detect incoming torpedoes where "The system reaction time from the moment of the torpedo detection is 15 s" and lay several drifting curtains of projectiles. They claim a 0.9 kill probability to a straight running torpedo, and a 0.76 kill probability for a homing torpedo.

I am not so sure how effective this would be against ST's, at 300 knots 15 seconds is a long time.

 

Right, I figured the super-cavitating would propose a whole different problem. Great point about torpedo a tracking b and b avoiding a. I forgot about the flip side. I just figured all the passive and active systems that a carrier and its battle group have they should be able to figure out where a torpedo is, and where its going. I'm specifically mentioning a carrier battle group because its probably not feasable to have an anti-torpedo system on anything much smaller. What kind of naval ships have torpedo capablilties? (besides subs) I know aircraft also have anti-sub weapons and tracking devices but they probably arent the best platform because they'd have to be in flight and in close proximity to the ship.

 

Speed

At 300 knots 15 seconds is over 6,000 feet distance traveled.

Even faster speeds may be possible.

http://www.ctechdefense.com/speed.html

2509 West 19th Street, Port Angeles, WA 98363
PHONE (360) 452-2275 * FAX (360) 452-2297 * info@ctech.esdcorp.com

Underwater Speed Limits
(Following is the full text submitted to Scientific American. The published version was shortened for editorial reasons.)

"There appear to be two conceptual ways of approaching supercavitation. The generally accepted one derives from propeller cavitation theory and holds that the water is essentially boiled by dropping its pressure via abrupt acceleration. This creates a source of gaseous water vapor which creates the cavitation bubble. It is generally assumed that the cavitation bubble is filled with this water vapor. Indeed, in low speed (say torpedoes) supercavitation applications the cavity size is usually enhanced with ventilation gases. This fits well with the understanding that gas creates the bubble in the first place and appears to work well within that context. It also fits comfortably in the general framework of marine engineering.

Last September, at an ONR sponsored Supercavitation Conference, Dr. Kirschner (of Anteon Corporation) and I were discussing the idea of a theoretical speed limit for supercavitating objects, assuming material strength issues could be overcome. As previously mentioned, conventional wisdom holds that the cavity is created by the water vapor and therefore, at some speed, the volumetric rate at which vapor can be generated will become insufficient to support the formation of a cavitation bubble which will clear the body. In other words, at some velocity the rate at which the water boils will become insufficient to fill the volume of the "hole" in the water created by the passage of the projectile and the cavity will collapse.

For whatever reason, I have a different mental picture of how the bubble is created, perhaps due to my background in hypersonics in graduate school. In that field discontinuities and rarified flows are encountered in the course of normal business. I do not know if anyone else shares this view but Dr. Kirschner and I have discussed it at some length. In any case, I believe the process is fundamentally one of momentum transfer. The cavitator, be it a disk or cone or whatever, imparts a significant radial velocity (relative to the axis of flight) to the water it comes in contact with. In effect the water is thrown violently to the side. It therefore has a high radial momentum that is resisted by the pressure of the water around it. This pressure serves to slow its radial velocity and will bring it to a stop over a finite time. The accepted definition of cavitation number is compatible with this idea. In the meantime, assuming a circularly symmetric cavitator, a round "hole" has been created in the water. What is in this hole, other than the projectile? I believe it is a vacuum, at least initially. Of course the water on the interior face of the bubble begins to boil, but it can only boil so fast, even in a hard vacuum. At slow velocities the rate of boiling can create a fairly decent partial pressure of water vapor in the cavity. In the limit case, as velocity increases, the pressure inside the cavity in the vicinity of the projectile will go to zero. Eventually the pressure acting on the water will reverse its radial velocity and cause the cavity to close. However, the projectile will be long gone by that point. If this approach is correct then, except for finding a material to withstand the steady state stagnation pressure, there may be no hydrodynamic upper limit to the velocity of a supercavitating body.

In any case, perhaps there is room for both viewpoints. In fact, they may very well be opposite sides of the same theoretical coin. I would certainly be interested to know what other people in the field thought of this approach. Perhaps it would provide an interesting topic of discussion within the article?"

 

Actually, the do have underwater radar.

 

ok, good point,
but
"The system has been designed to be a low-weight and rugged imaging device suitable to operate at medium range (approximately 10 m) in clear seawater."

maybe this can all be upscaled, but at present wouldn't do much to help dodge or destroy a torpedo, let alone one traveling at 300 knots.
if it can be upscaled then the 'clear water' requirement may also be a problem.

 

Radar isn't just radar

And once more you grossly oversimplify.

There are many types of radar.

Long range tracking radars use much different wavelengths (and resulting frequencies) than do short range fire control radars.

 

I agree in the conventional torpedo scenario, but the ST is another matter. Because you have to have the cavitation generator on the front of the torpedo, it cannot hear anything infront of it - the cavitation would block everything else. I don't see how it could hear effectively from the sides, either - the dang thing is rocket powered. The entire cavitation chamber is going to be full of rocket sound. I don't know how physics could get around that particular problem.

As I said earlier, the interceptor doesn't have to be faster than the ST. The quintesential example is a baseball catcher - the ball is moving near 100 mph, yet the catcher doesn't move his glove nearly as fast because he only has to intercept the pitch's path - it's not necessary to match the pitch's speed.

Another option, and the one I think is most practical, is a system similar to the current CWIS turrets, only optimized to shoot into the water. If your rate of fire is fast enough, your first few bullets will be used to dig a hole in the water down to the intercept depth. I got that idea from a sci-fi book describing how a futuristic tank would fire a stream of projectiles at near lightspeed. Seems like it would be fairly easy in water, as I can splash my hand down several inches before the water rushes in to cover it; at the current 6000 rounds per minute of the CWIS system, I doubt it would have much trouble holding the hole open until it ran out of ammo.

 

Actually, that statement was more to prove that more things are possible than some people seem to think, than to claim it can be used for military purposes.

Actually, current fire control systems using sonar will work just fine within the intercept ranges we are discussing. How far out will you realistically intercept a torpedo? The CWIS system, which does exactly what we are discussing except above water, generally operates at ranges of less than a mile. I would think, with the much slower speeds of the ST's, that that range would be greatly reduced.

 

Now I will have to get a bit theoretical.
Let us say that (as might be the case) the ST has too much 'rocket noise' to detect an oncoming torpedo.
So long as it can still succesfull communicate with something (ie a third party) then it could still track. I am assuming here that there would be some range of frequency that could be communicated on.
One solution may be that once a target is chosen the sub would fire out some stealth superquite tracking and targeting drones which would reach a certain positions along the trajectory before the sub would fire the ST. Now the drones would update the targeting and 'radio control' the ST, and the drones would also do the detecting for anti-ST torpedos.
This could mean that the ST can react and change course like something that is capable of carrying all the sensitive equipment that the stealth targeting drones can.

Once a ST is able to navigate, target or dodge, this would also mean that your second point, about the speed of the interceptor not having to match the intercepted, no longer stands. Sure a catcher can catch a baseball when it goes straight to him, but what if it goes straight to him down really low, and he gets in position, but then 2 feet from the pitcher the ball does a ninety degree vertical turn up above his head, another ninety degree turn back to its original trajectory and then straight over the plate. Sure the catcher may see this happen, but once he has committed to the lower catch, he simply cannot move fast enough to intercept the ball on its new trajectory. Speed has everything to do with it.

Unless of course the interceptor is a ST as well. But then we are back to your first problem. Without third party targetting, this would be hard. Maybe a ship would have automatic targetting set up that would instantly detect an incoming ST and route this information to outgoing anti-ST's,
But it is always going to be easier to target something like a ship that something like a torpedo.

 

Nonexistent technology

There are no fire control systems based on active sonar.

Torpedos use passive sonar to home in on the noise of the target.