Pulling Iran's Fangs
Just thought I would post this to clear up confusion on the supposed capabilities of Iran's new weapons. As I suspected, Iran exaggerated a lot of it's claims.
This post is just in reference to their new torpedo design...which as it turns out is not quite as new as we were led to believe. This article discusses the capabilities of the Soviet made Shkval (entering service in 1977). Which, presumably, is what the Iran version is based on.
First, regarding their stealth capabilities:
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Among errors of fact that one might have read in a newspaper or on-line news digest, or even seen in a TV documentary, is that Shkval-type weapons move faster than their own noise. This makes them totally undetectable to their victim -- a Virginia-class sub is sometimes mentioned in this context as a choice target -- until the rocket torpedo detonates and the American sub is destroyed.
There's just one serious problem with this, not for the Virginia-class sub but for the enemy. The speed of sound in seawater varies subtly with local conditions, but is typically just under one statute mile per second -- five times the speed of sound in air, for comparison.
This makes the speed of sound in seawater about 3,000 knots. A supercavitating weapon doing 300 knots is barely making Mach 0.1 in the medium in which both it and its target are located. And rocket engines are terribly noisy. That noise signature will travel on ahead of the Shkval to be heard by a submarine's passive sonars well before weapon impact. As detailed below, (and despite bellicose Iranian claims to the contrary), American submariners have an ample toolkit for swiftly throwing off the Shkval's aim, and then fighting back.
http://www.military.com/soldiertech/0,14632,
Soldiertech_060420_shkval,,00.html
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This covers passive sonar, but Iran is claiming it's torpedos will evade active sonar as well. A little more on that:
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Iran isn't about to give up easily in their war of words (and associated psy-ops) about their new wonder-torpedo. They allege it's “sonar evading.” If you know very much about sonar, you have to be scratching your head and asking, What the heck is that supposed to mean?
[...] Sonar evasion per se, by any weapon or vessel, is achieved in one of two ways. The first is to be very quiet, so your target's passive sonars can't detect your presence nearby. Scratch that, since supercavitating rockets are deafeningly loud -- the vacuum bubble collapses in the turbulence of their engine exhaust, providing scant sound isolation if any at all.
The second is the old, familiar use of sonar layers and other underwater noise propogation effects to mask your acoustic signature from the target as you approach. But no one understands these effects better than the U.S. Navy, and not just subs but surface ships and aircraft are equipped to leave no room for a roaring rocket motor to hide.
(Surface combatants can stream variable-depth sonar towed arrays, and their supporting anti-submarine helicopters can use variable-depth dipping sonar and also drop optimized patterns of sonobuoys.)
Purists will note there is a third way to achieve low observability against active pinging sonar, namely the use of anechoic -- sound absorbing -- coatings on the hull. But modern U.S. submarine passive sonars are able to derive the range to any high-decibel sound source instantly, obviating the need to ever go active against an inbound torpedo. The implied analogy to radar-absorbent materials on cruise missiles fails underwater.
http://www.military.com/soldiertech/0,14632,
Soldiertech_060420_shkval,,00.html
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So much for their claims of stealth. Now on to it's speed.
As noted before, saying it moves at the speed of sound isnt that big a deal necessarily, since the speed of sound underwater is much much lower than the speed of sound in the air. But he has more to add:
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Previously in thie piece I stated that the Shkval isn't, as claimed, completely immune to friendly defensive weaponry. This is because, for years, the U.S. Navy has been investing in, developing, and testing undersea weapons that really do move at Mach 1 or faster in seawater.
[...] So what are the true Mach 1 weapons America is working on?
One of these devices is an anti-torpedo dart, fired underwater by an sonar-aimed gun in a streamlined turret. In a proof-of-concept experiment several years ago, the Naval Undersea Weapons Center Newport Division was able to shoot a dart in a tank at greater than the speed of sound in the surrounding water. Though the dart is not self-propelled, and thus loses velocity (and accuracy) with range, as a close-in defense system against fast (and not so fast) enemy torpedoes it holds great promise.
The other device that's been discussed for a while in the unclassified literature is a hull-mounted pressure-wave generator. (Think of something like an active sonar array that sends out a tremendously strong burst of noise.) The pressure-wave generator transmits an intense underwater focused shock wave in the direction of an inbound torpedo. Since shock waves automatically move at the speed of sound, this provides a genuine Mach 1 countermeasure against any Shkval. If the pressure wave is aimed well and the timing is just right, a “hellacious” wall of acoustic energy will smash the Shkval to pieces. (The Shkval's higher speed makes the collision all the more violent!) This device is ideal for mounting on the hulls of all-electric surface ships, such as the DD(X)/CC(X) fleet of the future, and maybe LCSs and even subs too.
If you're really feeling the need for speed, think about these developmental supersonic underwater weapon systems. They outclass the Shkval by a factor of ten.
http://www.military.com/soldiertech/0,14632,
Soldiertech_060420_shkval,,00.html
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So that appears to be one fang pulled. I am not really surprised...Iran does not have the resources to compete with major world powers when it comes to military technology. So I kind of assumed they were pulling their claims out of their aѕses. But it is nice to get the actual data with which to argue specifics in the future.
He ends with this:
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Some urgency is called for regarding such advanced defensive measures, as supercavitation technology is quickly proliferating among America's actual and potential foes. But at the same time it's crucial to recognize that the Shkvals of the world have been surrounded in a fog of plain untruths and insidious rhetoric. What concerns me most is not the supercavitating weapons themselves -- as I say, they've existed for decades. Their sensationalized treatment in pockets of the media give domestic nay-sayers further ammo to press their case in the most absurd and self-destructive claim of all, that America's current nuclear submarines are nothing but Cold War relics -- now, because they're supposedly hopelessly vulnerable to Shkvals. This essay has attempted to show that it's the Shkvals that are the real Cold War relics. So long as they're deprived of their nuclear warheads, against a properly trained and equipped U.S. Navy their speed is their own greatest weakness.
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