美国有线新闻 CNN 美在韩部署萨德遭中方强烈反对 详解萨德反导系统（在线收听）

The Terminal High Altitude Area Defense or THAAD is a missile defense system. It uses missile to stop missiles.

And the U.S. has deployed the first components of a THAAD system to South Korea. Why? Because North Korea, which is a rival of both the South and the U.S., has been test-launching missiles of its own lately and the THAAD system could potentially be used in self-defense.

In a clear example of how tensions have been rising in the Korean Peninsula and abroad, China is getting involved in this. It's North Korea's only real ally in the world and it's telling North Korea to suspend its nuclear weapons program which other countries consider illegal. The Chinese officials are also strongly opposed to the U.S. sending a THAAD system to South Korea. They believe it could be used to monitor potential missile launches from China as well.

How exactly does a THAAD system work and could it be effective against ICBMs, intercontinental ballistic missiles?

TOM FOREMAN, CNN CORRESPONDENT: This missile defense system is a state of the art array of vehicles, typically nine of them, most of them are launchers, but they also a couple of command centers and they have an advanced radar system, which both acquires the targets and helps guide these missile-killing missiles toward that target.

About 70 missiles would be with all of these trucks out here and which one would be about like this, about 20 feet long, weigh about 2,000 pounds.

This is the booster down here. That gets it going.

And once it gets closer to the target, this part will break away, leaving only the front. Up here, you have some advanced electronics and infrared system that will unshroud in flight so it can seek out the target very specifically and the control system that helps guide it in.

Collectively, all of this is called the "kill vehicle" and the range on it, not too bad. Across the ground, it can go about 125 miles away and about 16 miles high.

Now, does it explode when it get there? No, not at all. What it does is simply intercept and ram into the target.

Look at this video from the military. Bear in mind, when this thing takes off and it's meeting with an incoming missile, a threat out there, the incoming missile may very well be traveling close to 4,000 miles an hour. So, when they hit, that's the result.

Military analysts say you can't really use this so effectively against great, big ICBMs. But for short range and middle range missiles, the kind that South Korea might be worried about from North Korea, yes, it's got a pretty good record.