Shortly after President Donald Trump's controversial meeting with Russian president Vladimir Putin, the Russian government published several videos that appear to show off a host of new nuclear weapons systems.
One particular video stands out: an alleged prototype of a giant torpedo that one expert dubbed a "doomsday machine."
Putin first publicly described that nuclear-powered device on March 1 during an address to the Russian Federal Assembly. He said the autonomous drone would quietly travel to "great depths," move faster than a submarine or boat, "have hardly any vulnerabilities for the enemy to exploit," and "carry massive nuclear ordnance," according to a Kremlin translation of Putin's remarks.
"Unmanned underwater vehicles can carry either conventional or nuclear warheads, which enables them to engage various targets, including aircraft groups, coastal fortifications, and infrastructure," Putin said.
The videos the Russian president presented in March were primarily computer renderings, though Putin claimed Russia had finished testing a nuclear-powered engine for the torpedo in December. However, on July 19, the Russian Ministry of Defense uploaded several new clips to its YouTube account that may show real-world hardware — including one of a torpedo-shaped device called "Poseidon."
Defense analyst H.I. Sutton wrote in a blog post that the prototype in the new video is "generally consistent" with Russia's prior depictions of a giant, autonomous, nuclear-powered, nuclear-weapon-armed submarine. The device also goes by the code names Oceanic Multipurpose System Status-6, Skif, and Kanyon.
Based on still images from the video, Sutton said he figures Poseidon could be about 2 meters (6.5 feet) wide and 20 meters (66 feet) long, with room for a nuclear reactor in the center and a large thermonuclear warhead toward the front.
"It is really fantastic," Putin said of the device in March, adding, "there is simply nothing in the world capable of withstanding them."
Why the Russian 'doomsday' device could be terrifying
The Russian government reportedly leaked a diagram of a Poseidon-like weapon in 2015 that suggested it would carry a 50-megaton nuclear bomb about as powerful as Tsar Bomba, the largest nuclear device ever detonated.
In a 2015 article in Foreign Policy, Jeffrey Lewis, an expert on nuclear policy at the Middlebury Institute of International Studies, dubbed the hypothetical weapon "Putin's doomsday machine."
Nuclear physicists say such a weapon detonated below the ocean's surface could trigger a local tsunami, causing great devastation. US nuclear tests of the 1940s, '50s, and '60s, including the underwater operations Crossroads Baker and Hardtack I Wahoo, demonstrated why.
These underwater fireballs were roughly as energetic as the bombs dropped on Hiroshima or Nagasaki in August 1945. In the tests, they burst through the surface, ejecting pillars of seawater more than a mile high while rippling out powerful shockwaves.
Some warships staged near the explosions were vaporized. Others were tossed like toys in a bathtub and sank, while a few sustained cracked hulls and crippled engines. Notably, the explosions roughly doubled the height of waves to nearby islands, flooding inland areas.
"A well-placed nuclear weapon of yield in the range 20 MT to 50 MT near a sea coast could certainly couple enough energy to equal the 2011 tsunami, and perhaps much more," Rex Richardson, a physicist who researches nuclear weapons, told Business Insider in March, referring to the Tohoku earthquake and tsunami that killed more than 15,000 people in Japan.
"Taking advantage of the rising-sea-floor amplification effect, tsunami waves reaching 100 meters in height" — about 330 feet — "are possible," he said.
Richardson and other experts have also pointed out that a near-shore blast from this type of weapon could suck up tons of ocean sediment, irradiate it, and rain it upon nearby areas — generating catastrophic radioactive fallout.
"Los Angeles or San Diego would be particularly vulnerable to fallout due to the prevailing onshore winds," Richardson said, adding that he lives in San Diego.
The problem with blowing up nukes underwater
Some experts question the purpose and effectiveness of Putin's potential new weapon, given the far more terrible destruction that nuclear explosions can inflict when detonated aboveground.
Greg Spriggs, a nuclear-weapons physicist at Lawrence Livermore National Laboratory, said a 50-megaton weapon "could possibly induce a tsunami" and hit a shoreline with the energy equivalent to a 650-kiloton blast.
But he also suggested that it "would be a stupid waste of a perfectly good nuclear weapon."
That's because Spriggs believes it's unlikely that even the most powerful nuclear bombs could unleash a significant tsunami after detonating underwater, especially miles from shore.
"The energy in a large nuclear weapon is but a drop in the bucket compared to the energy of a [naturally] occurring tsunami," Spriggs told Business Insider last year. "So any tsunami created by a nuclear weapon couldn't be very large."
For example, the 2011 tsunami in Japan released about 9.3 million megatons of TNT energy. That's hundreds of millions of times as much as the bomb dropped on Hiroshima in 1945 and roughly 163,000 times as much as the Soviet Union's test of Tsar Bomba on October 30, 1961.
Plus, Spriggs said, the energy of a blast wouldn't all be directed toward shore — it would radiate outward in all directions, so most of it "would be wasted going back out to sea."
A detonation several miles from a coastline would deposit only about 1% of its energy as waves hitting the shore. That scenario may be more likely than an attack closer to shore, assuming US systems could detect an incoming Poseidon torpedo.
But even if such a weapon exploded on the doorstep of a coastal city or base, its purpose would be questionable, Spriggs said.
"This would produce a fraction of the damage the same 50 MT weapon could do if it were detonated above a large city," Spriggs said. "If there is some country out there that is angry enough at the United States to use a nuclear weapon against us, why would they opt to reduce the amount of damage they impose in an attack?"
Why would Putin develop a 'doomsday machine'?
It's still unknown whether Russia has really developed this underwater weapon, though the Trump administration addressed its possible existence in the US' most recent nuclear posture review.
If realized, the "doomsday machine" would join thousands of nuclear weapons in Russia's arsenal.
In Lewis' 2015 article, he wrote that there was speculation that the underwater weapon might be "salted," or surrounded with metals like cobalt, which would dramatically extend fatal radiation levels from fallout for at least several months, or possibly even decades. That's because the burst of neutrons emitted in a nuclear blast could transform those metals into long-lived, highly radioactive chemicals and sprinkle them all over.
"What sort of sick bastards dream up this kind of weapon?" Lewis wrote, noting that such salted weapons were featured in the 1964 science-fiction Cold War parody film "Dr. Strangelove."
But Spriggs said the fallout — also called "source term" — from an underwater explosion would be dramatically reduced.
"In reality, the vast majority of the source term will never escape from the ocean as air-borne particles," Spriggs told Business Insider via email in April. "Most of the fission products and activation products that are thrown into the air during the explosion will be trapped in the water droplets in the water spout and will fall back to the ocean within just a few 1000 feet from the detonation point."
But if a nuclear bomb were dropped from the air, "almost 100% of the source term [...] ends up on the land," Spriggs said. So the fallout from a "salted" weapon blown up above a target could "be many, many orders of magnitude worse than the fallout produced by an underwater detonation."
To Lewis, it doesn't necessarily matter whether the nuclear torpedo will be completed or if the descriptions and videos are Russian posturing designed to prevent the US from attacking Russia or its allies.
"Simply announcing to the world that you find this to be a reasonable approach to [nuclear] deterrence should be enough to mark you out as a dangerous creep," Lewis said.
This story was originally published on April 24, 2018. It has been updated with new information.
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