How do anti-missile defense systems work?

It is likely that you know that the United States has a missile defense system, and only knowing it may, if you live in the country feel a little security and comfort. But do you know how these systems work or how effective they are? Actually they are not the impenetrable shield you could believe.

North Korea recently launched another missile and this convinced experts that the entire territory of the contiguous United States is in the range of its intercontinental ballistic missiles (ICBM), as long as the missiles do not carry a very heavy load. heavy. That has caused many more to wonder about the missile defense system of the United States and if it really works. After an alleged failed defense attempt in Saudi Arabia using a US Patriot missile system, many wonder if they are safe in the country. But before talking about how effective the system is or not, let's see how it works.

How an anti-missile defense system works

The most basic functions of a missile defense system are simple: use a ballistic missile to shoot down other missiles. But during this process other things happen. Here you will find a step-by-step description of how an anti-missile defense is developed, as well as the US Airborne Defense System (GMD) and the Aegis ballistic missile defense system of the Navy, and how they are supposed to stop an intercontinental ballistic missile like the ones North Korea has been testing.

The threatening missile is launched.

The satellites detect the launch and track their trajectory using infrared technology and radars.

The enemy missile releases a warhead and decoys (known as "the threat cloud").

The radars on land and at sea continue to monitor the cloud of threats, trying to identify which is the warhead (which is the explosive charge).

The missile defense system launches an interceptor missile.

The load of the interceptor, "the murderous vehicle", is separated from the body of the missile.

The killer vehicle locates the threat cloud and tries to intercept the warhead at the top of the atmosphere.

If everything goes according to plan, the warhead is destroyed in space, before it can reach its target on dry land.

However, these systems are different from Patriot, Arrow and Iron Dome missile defense systems in terminal case within the atmosphere (tiny complicated names). These systems work similarly but are designed to intercept short and medium-range missiles that move slower and at lower altitudes than ICBMs. These only cover areas with a size of up to a few dozen kilometers, so although it is good to have them as a backup for mid-air anti-missile (GMD) systems, these are more useful in regions such as South Korea and Japan than in the United States. (as long as the launch comes from North Korea).

The US Army's high-altitude defense system (THAAD) is also a defensive final-phase system, but it has some tricks up its sleeve. The THAAD works more like a defense system in mid-flight and can destroy objectives through direct collusion both in the upper part of the atmosphere and over it.

So, how effective are they?

As far as ICBM defense systems are concerned, we have no idea. Maybe it works, maybe not. Why? George N. Lewis, physicist and associate researcher at the Judith Reppy Institute for the Study of Peace and Conflict at Cornell University, explains in his study about the effectiveness of ballistic missile defense systems, there is no real experience so far using these systems. The GMD have been tested and have been successful, but these tests are not developed constantly and are usually a fully planned demonstration that only make us clear the reliability of these systems, but not their effectiveness.

It must be taken into account that it is very likely that attackers use "countermeasures" when launching their missiles. These countermeasures include mechanisms such as decoys or a cooling cover designed to confuse or alter the anti-missile system so that it fails. The United States has not tested the systems in this way, even when the technology to develop these countermeasures is well known. The US GMD system is very effective in detecting missile launches and tracking several long-range objectives, but it is not very easy to identify which is the warhead and which are the decoys. The primary discrimination sensor found in Honolulu, called the SBX radar, has very important operational limitations.

That said, the book "Making Sense of Ballistic Missile Defense" of the National Academy of Sciences of the United States suggests that these countermeasures are difficult to deploy, as demonstrated when the United States and England tried to develop this type of systems during the Cold War. . There is also a high probability that these countermeasures reduce the load, range and reliability of a missile.

Although the United States GMD defense system is, in theory, able to protect its entire territory from ICBM missile attacks, it has never been tested against a real threat, and the results of its tests are not completely comforting:

As you can see, the GMD system succeeds only half the time, and it does not seem to be improving. The Aegis BMD system of the Navy has better results:

Not only do they have higher success rates, but they have also been tested during the day and night, against short, medium and long distance objectives. They have also been tested against complete missiles as with separate warheads, and even against two targets simultaneously. Unfortunately, Lewis says that by being slower they can not cover so much territory as to be the defense system of the whole country, but in 2018 the United States hopes to deploy the new SM-3 Block IIA interceptor systems to do this work ( although they failed a test in June).

So, is the United States sure of a missile attack? It's hard to say, but maybe not as much as you could imagine. The US military usually announces success rates that are greater than reality. During the Gulf War the army claimed that they had succeeded 96% of times against the modified missiles in Iraq, but then changed that figure to 61%. Further analysis determined that the number was actually much lower, and could even be 0%. After the recent missile attack in Saudi Arabia, President Trump said:

"Our system shot down that missile in mid-flight. That's how good we are. Nobody does what we do, and now we are selling it all over the world. "

But later evidence suggests that the Patriot missile system failed and that the warhead almost hit its target (an airport), and that some people heard an explosion. Regarding the GMD defense systems in the United States, Lewis says that the officers have also exaggerated their results:

Statements by US officials suggest that a system designed to counteract nuclear missiles could be considered "effective" if its predicted effectiveness exceeds 90%. On June 16, 2019, barely a week after Defense Secretary Robert M. Gates told Congress that the GMD system is "adequate to protect the nation from the North Korean threat," General James Cartwright told a Senate committee that determined that the effectiveness of the GMD system was "90% or more".

A year later, after many official statements about his confidence in the GMD system, Lt. Gen. Patrick O'Reilly, director of the missile defense agency, told a committee that there was "more than 90% chance" that the system could counteract an ICBM launched by Iran.

Here's the problem: even if the GMD or Aegis BMD systems achieve success rates of 80% or 90%, it is not enough. After all, a failure rate of 10% to 20% is not acceptable against a bombardment of nuclear missiles. As the United States has shown in the past, one need only fall to devastate a region completely.

Improving these anti-missile systems requires many more tests (including realistic scenarios), which translates into time and money. These tests are not cheap (the one that the country carried out in May cost 244 million dollars), but they are necessary if a country is going to depend on these systems. However, perhaps the best thing would be to try to avoid any conflict in which we need it.