|Fig. 1: An inactive mk-8 torpedo in an English park. (Source: Wikimedia Commons)|
On Febraury 3, 2018, articles appeared across the internet, for instance, on CNN, describing a Russian developed nuclear submarine, referenced as "Status-6", purported to carry a 100-megaton thermonuclear weapon. [1,2] This device, according to Mizokami, could travel upwards of 100 knots, down to a maximum depth of 3,280 feet, and would be designed to target coastal cities and naval bases.  To put the explosive power of this weapon in perspective, the largest thermonuclear weapon ever detonated, Tsar Bomba, yielded a 50 Megaton blast, merely half the capacity of this torpedo, and broke windows hundreds of kilometers away.  Yet, reports of the weapon are still conflictive, and existence of the bomb is debated. [1,2] There is indeed a nonzero chance that the leaking of the report of this weapon is merely a political tactic, designed to scare or intimidate US leaders. However, the concepts and deadliness of such a bomb can be put into perspective using weapons and events from history. From reports of salting the warhead to the fuel of the torpedo itself, this new concept presents new and unique takes and perspectives on existing nuclear weaponry.
According to Mizokami, the nuclear warhead attached to Status-6 could be encased in Cobalt-60, long lasting radioactive isotope designed to produce maximum radioactive fallout lasting anywhere from months to years.  The nomenclature of salting comes from the various texts describing how Romans sprinkled salt over the lands of Carthage after sacking it, rendering cropland infertile and useless. In the radioactive version of this scorched earth strategy, radioactive fallout is enhanced as compared to a non-salted nuclear detonation, therefore maximizing the fallout hazard from the weapon. As a side note, this salted bomb concept differs from a dirty bomb, where radioactive material is planted in a predominantly non-nuclear explosive device.  A salted bomb, with a larger radioactive fallout content, is thus able to contaminate a larger geographical area.  The idea of the Cobalt salted bomb originated with Nuclear Scientist Leo Szilard in 1950, not for the purposes of constructing such a weapon, but to prove the destructive effects of nuclear weaponry.  As far as is known, no special purpose salted bomb has ever been built, save for one 1 kiloton bomb detonated by Britain in 1957.  However, because the half life of Cobalt-60 is only about 5 years, and due to the limited mass of Cobalt that would be able to be packed in this warhead, this threat is probably negligible.
While torpedoes, similar to the one in Fig. 1, have been weaponized with nuclear warheads since the onset of the cold war, nuclear powered torpedoes are something new. The United States deployed its Mk-45 torpedo in 1963, but it too, lacked nuclear thrust. Even its successor, the Mk-48, lacked nuclear power. Using piston technology popular during the time, its range would have been capped around several miles. However, per the BBC, the range of the status-6 would be upwards of 6,200 miles. 
In regards to the destructive power of the proposed nuclear weapon, even if the nuclear blast of the torpedo doesn't destroy the target area, the detonation of the purported Status-6 could produce a tsunami of up to 500 m in height (BBC).  However, looking at examples from history, no tsunamis have been reported from even 10 MT blasts, like the "Ivy Mike" test blast in 1952.  Thus, while numbers thrown around in sensationalist reports do inspire fear and wariness, their validity should be questioned with healthy skepticism. While these feats are technically possible, the idea that enormous sums of money would be sunk into pursuing these metrics is economically implausible.
The rumors around this weapon have allowed for interesting exploratory analyses of the nuclear components of such a bomb. However, it should be noted that there might be easier ways for a nation intent on way to achieve such deleterious effects. For instance, instead of having a sub that can travel at over 100 knots, it would be significantly easier to simply launch a missile from a bit further away. Per Professor Laughlin, this might come down to the infeasibility of the economics for such scientific war goals.
© Sean O'Bannon. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 B. Starr and Z. Cohen, "US Says Russia 'Developing' Undersea Nuclear-Armed Torpedo," CNN, 3 Feb 18.
 K. Mizokami, "Pentagon Document Confirms Existence of Russian Doomsday Torpedo," Popular Mechanics, 16 Jan 18.
 S Narayanan, "The Tsar Bomba," Physics 241, Stanford University, Winter 2015
 K. Bhushan and G. Katyal, Nuclear, Biological and Chemical Warfare (Ashish, 2002), p. 75
 "Russia Reveals Giant Nuclear Torpedo in State TV 'Leak'," BBC News, 12 Nov 15.
 A, Singh, "Ivy Mike: How to Wipe Out an Island," Physics 241, Stanford University, Winter 2015