Iran recently announced the successful test of a new, high-speed torpedo, one that could move through the water at speeds of up to 100 meters a second. This is four times as fast as conventional torpedoes, and is thus nearly "unavoidable" by its intended target.
The new Iranian weapon is apparently based upon Russia's VA-111 Shkval (Squall) torpedo. The Shkval is a high-speed supercavitating rocket-propelled torpedo originally designed to be a rapid-reaction defense against US submarines. Basically an underwater missile, the solid-rocket propelled torpedo achieves its speed by producing an envelope of supercavitating bubbles from its nose and skin, which coat the entire weapon surface in a thin layer of gas. This drastically reduces metal-to-water friction. The torpedo leaves the tube at nearly a hundred kilometers an hour, then lights its rocket motor. In tests in the 1990s the Shkval reportedly had an 80 percent kill probability at a range about seven kilometers, although steerability was reportedly limited.
The reliability of such rocket-propelled torpedoes remains uncertain. The much publicized loss of the Russian submarine "Kursk" was, according to some sources, likely due to an accidental rocket motor start of such a torpedo while still aboard the boat. News of this new Iranian weapon was accompanied by the announcement that Iran had also tested a new ballistic missile, the Fajr-3, which employs some stealth technology and carries several warheads.
Iran's possession and successful testing of this weapon is troublesome for several reasons. One is Iran's increasing belligerence, especially towards nuclear-armed Israel (which is estimated to have at least 200 nuclear weapons and the missiles and submarines to deliver them) as well as an almost equal antipathy towards the US. Another reason to worry is Russia's apparent intent to continue close economic ties with Iran and the resulting transfer of its technology to this Islamic state run by fanatics and others who are apparently just plain nuts.
Iran is believed to have three late-model Kilo class SSKs bought from Russia, eight mini-subs purchased from North Korea, and several older boats of unknown type. The navy has several dozen fast attack boats that might carry the new torpedo but whose capabilities are in other ways modest. Its small fleet of P-3K "Orion" aircraft could conceivably also carry such a torpedo although it is unknown if Iran plans to arm its Orions with the new torpedo. Iran's navy is the smallest of its armed forces.
However, there is also the matter of credibility and capability. For decades, Iran has continually boasted of new, Iranian designed and manufactured weapons, only to have the rather more somber truth leak out later. Iran's weapons design capabilities are primitive, but the government has some excellent publicists, who always manage to grab some headlines initially, before anyone can question the basic facts behind these amazing new weapons. Take, for example, the new wonder torpedo. The Russians have not had any success convincing the world's navy that their rocket propelled torpedo is a real threat. For one thing, the attacking sub has to get relatively close (within seven kilometers) to use it. Modern anti-submarine tactics focus on preventing subs from getting that close. For that reason, the Russians themselves tout the VA-111 Shkval torpedo as a specialized anti-submarine weapon for Russian subs being stalked by other subs. This is also questionable, because Shkval is essentially unguided. You have to turn the firing sub and line it up so that the Shkval, on leaving the torpedo tube and lighting off its rocket motor, will be aimed directly at the distant target. Do the math, and you will see that there is little margin for error, or chance of success, with such a weapon. If the Iranians bought the Shkval technology from Russia, they got the bad end of the deal.