Submarines couldn't always launch airborne missiles from under the sea, Launching a missile from a submarine isn't as easy as pressing a big red button. It uses lot's of engineering and rocket science to ensure a missile gets from an underwater launch tube to streaking through low-Earth orbit at more than 13,000 mph.

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According to popularmechanics the physics of launch ade by Lockheed Martin, the current Trident II D-5 missile is a squat, blunt-nosed, 44-foot-long cylinder weighing nearly 120,000 pounds. It's fired by a steam cannon. First, an explosive charge flash-vaporizes a tank of water into steam.

Launching a missile from a submarine is harder than you think https://t.co/UNuVxWfa1X pic.twitter.com/nS84lCe5tF

— Popular Mechanics (@PopMech) February 13, 2017

As the pressure of the expanding steam drives the missile out of its launch tube, it provides enough momentum for the weapon to clear the water's surface. This cocktail of high pressure and dangerous explosives is a crucial phase of every launch. Multiple safety mechanisms are in place to deactivate the missile if it fails to get away from the sub.

North Korea Fires Missile, US Decides Not To Escalate https://t.co/nlb4RKDQaV pic.twitter.com/GVqhZWMgiJ — Popular Mechanics (@PopMech) February 14, 2017

News.vice says that North Korea has long been capable of launching ballistic missiles from land, but the added ability to fire from underwater would make defending against possible attacks much more difficult for South Korea, Japan, and the US, which has a number of military facilities in the region. There have also been reports that North Korea is attempting to "miniaturize" a nuclear warhead to fit on a ballistic missile.

For this kind of research it take's more time, It takes years to develop an operating SLBM system and the submarine to carry it. This is not something that happens overnight.