The New York Times reports: North Korea’s threat to launch four intermediate-range ballistic missiles into the ocean near Guam could mark the first combat test of the sophisticated missile defense systems of the United States and its Asian allies.

The launches might not happen for any number of reasons. North Korea’s Hwasong-12 missiles might fail, or the United States or its allies could destroy them on the launchpad. Japan and the United States might also decide to do nothing and let the missiles splash harmlessly into the sea.

But if the four Hwasong-12s do make it off the ground, the options for stopping them mostly rely on hitting them on the way down — in their “terminal” phase.

On the Way Up

The Hwasong-12, a domestically developed liquid-fueled missile, has a maximum range of 3,000 miles, and hits an altitude of about 470 miles on the way to its destination. The velocities needed for those numbers mean that by the time the missile has been in the air one minute, it is already traveling several times the speed of sound.

At those speeds, a missile trying to chase and hit it from behind would have no chance during this part of the flight, called the “boost phase.” The Terminal High Altitude Area Defense system, or Thaad, several of which are now stationed in South Korea, could use its radar to track the launches of the North Korean missiles. But it is not designed to hit them as they climb into space.

At one point, the United States Air Force poured billions of dollars into a huge laser mounted on a Boeing 747 that was designed to destroy enemy ballistic missiles during the boost phase — and it worked. But it was so expensive, and required the laser-equipped aircraft to fly so close to enemy territory, that it was abandoned. [Continue reading…]