It sounds like a Bond movie plot device: a nuclear-tipped torpedo is on its way to destroy New York City with a radioactive tsunami. Now, the Bulletin of the Atomic Scientists (BOAS) – the group behind the infamous Doomsday Clock – warns that Russia’s rogue President Vladimir Putin wants 30 of them. And while the concept sounds far-fetched, some military analysts believe the idea has potential. Conventional intercontinental ballistic missiles (ICBMs) can be tracked from the moment they are launched. And many nations have demonstrated the ability to intercept their deadly warheads on the edge of space – well before...