The headlines all say that North Korea's successful missile launch today brings them one step closer to a nuclear missile, but there are plenty — plenty — more steps to take before they get there. The DPRK launched a two-stage rocket that traveled about 1,600 miles before deploying what its official state news agency enthusiastically called a "satellite" that "successfully entered its preset orbit." That's a significant step for a country dreaming of frightening the globe with a fleet of ballistic missiles — even the South Koreans haven't put anything in orbit by themselves yet — but it's still a far cry from being able to deliver a working nuclear weapon to enemy territory like, say, the West Coast of the United States. There are still a lot of very complex technical hurdles to overcome.
For starters, the missile they launched today might have technically reached space (although Secretary of Defense Leon Panetta is disputing that), but it certainly didn't come back. In order to threaten the U.S. (or most other parts of the world), North Korea's projectile needs to be able to survive re-entry intact, David Sanger explains in The New York Times — and that's a trick the North Koreans have yet to even attempt. It also had no target. Every missile they've fired has either exploded or fallen randomly into the sea. There's no indication that they have the guidance capabilities to hit any specific place with any amount of accuracy. Not that they would need much to hit South Korea or Japan, but that's the other point: North Korea already has weapons that can reach their two biggest rivals, so on that score, today's test doesn't change anything.
Despite the fears of swapping out a harmless payload for a weapon of mass destruction, it's unlikely that the Unha-3 rocket they fired today could even carry one. The satellite that was launched into space weighed only 220 pounds, according to The Times, one-tenth the size of an average nuclear warhead.
Yet even if they solve those problems and graduate to a true intercontinental ballistic missile with real range and deadly accuracy, they still have to a put a nuclear bomb on it, which is of course no small feat in itself. North Korea has only conducted two nuclear weapons tests in its history. The first, in 2006, produced a 0.2 -kiloton explosion, a far cry from the 15-kiloton bomb that had to be dropped from a plane on Hiroshima — and would itself be considered puny by today's weapons standards. They tested a second one in 2009, but it wasn't much larger. There is speculation that North Korea will perform a nuke test again soon, but their nuclear program is still not as advanced as it needs to be.
They've only just begun to master the technology behind nuclear weapons, and there's a big leap from setting off an explosion underground to a working bomb that can be hurled halfway around the globe and exploded on target. They have the uranium to build bombs and the know-how to set them off, but making them small enough to put on a rocket and control them from afar just isn't in the cards right now.
Pretty much every expert agrees that North Korea doesn't have a weapon capable of being placed on a missile, and they still don't have a missile that can be fired across an ocean. When and if they do, they need the sophistication and tools to putting all the pieces together and make it work as one cohesive weapon delivery system. For a nation with North Korea's size and limited resources, that remains a pretty tall order.