By David Hambling
May 29, 2021
Last week, Iran’s Defense Ministry showed off examples of weapons developed by their Defense Industries Organization. One sharp-eyed analyst spotted something curious in the background – what looks like a copy of the Russian SPP-1, a handgun for use underwater. Submarine warfare expert HI Sutton confirmed the identification on his website CovertShores. While this sort of exotic hardware might look to be of interest only to SEALs and 007 enthusiasts, it highlights an aspect in Iranian research which may be ahead of anything known in the West and matched only by Russia and China.
The Soviet-made SPP-1 came into service in 1971 as a weapon for special forces frogmen. Normal bullets do not travel far underwater due to the huge drag. As Mythbusters confirmed with the aid of a .50 Cal rifle, even a few feet of water provide bulletproof protection against supersonic rounds.
The SPP-1 fires a special bullet, a long, blunt projectile which the designers called a ‘flying nail.’ This uses the principle of supercavitation: the shockwave from the blunt nose produces a large underwater cavity, so that apart from the tip, the projectile experiences virtually no drag. The SPP-1’s supercavitating bullets have an effective range of at least 50 feet underwater. The bullets are less effective in air than other handguns and the range is similar to underwater.
Later developments included the APS underwater assault rifle with a range of at least 100 feet – the practical limit of visibility underwater – which was superseded by the ASM-DT dual medium or amphibious rifle which is as effective as the APS underwater and has a similar range to a normal rifle in air.
Although there has been some U.S. Navy research in this area, there is no American equivalent to these underwater weapons. The most advanced U.S. project in this area was the RAMICS, a helicopter-mounted 30mm cannon firing supercavitating ammunition to reach underwater with enough remaining velocity to destroy mines, but this never reached service.
The Russians also went on to develop a range of Shkval supercavitating torpedoes with speeds of over 200 knots. The next generation reportedly have much greater ranges, and target-seeking sonar. While the U.S. has ambitions in this area – including DARPA’s proposed Underwater Express, an ultra-high-speed mini-sub proposed in the early 2000s– nothing has ever been fielded. German company Diel attempted to develop a supercavitating torpedo called Barracuda, also in the early 2000s, but the project was shelved.
While the U.S. Navy has now effectively abandoned research on supercavitation (perhaps barring super-secret black projects) , other countries have pushed ahead. Iran acquired and test-fired a Shkval torpedo in 2004 and two years later they test-fired their own prototype supercavitating torpedo, the Hoot or al-Houth (‘Whale’), releasing video of it hitting a target ship.
The firing may have been mainly a publicity stunt , but the Iranian military clearly saw the potential of the technology. There were further launches of a presumably more advanced version in 2015 and 2017.
A slew of open-source academic papers from several institutions dating back at least to 2008 — some of them military — suggests that Iran has continued to push forward the science of supercavitation, developing a pool of expertise in this area. Papers reveal they have tested new shapes and configurations – such as a stepped cylindrical cone – traveling both through water and from air to water, geared to practical applications as well as theoretical understanding. The only other nation which produces a similar number of papers on the topic is China. Interestingly, China has also developed its own supercavitating underwater weapons resembling Russian designs.
The Iranian underwater pistol is not of itself too important. But it suggests an interest in, and the capability to develop, a whole range of other weapons, from mine-busters like RAMICS to anti-torpedo defenses, novel anti-submarine weapons, as well as high-speed torpedoes and underwater rockets.
If this is what Iran puts on show, we can only guess that what other developments are being kept under wraps following years of development.