The GMD Finally Intercepts an ICBM (kinda)

On May 30th the Ground Based Mid-Course Missile Defense system (GMD) successfully intercepted it’s first ICBM. Authorized in 1999 by the Missile Defense Act and offically deployed over a decade ago, the GMD has been plagued with problems. The test on May 30th was the first time the system was successfully tested against the threat it was designed to defeat.

How it Works

The GMD aims to intercept ICBMs during their mid-course phase. This is the stage at which the missile has left the atmosphere but is not yet in its terminal descent. This phase is optimal because the missile is still going slowly enough that there is a reasonable chance of interception. Once it reaches terminal phase an ICBM (or in this case the reentry vehicle) can hit speeds of up to Mach 25; far too fast to reliably track and intercept.(although we did try once)

How it Works

The interception starts with a ground, sea, and/or space based sensors detecting and tracking the flight path of the enemy ICBM. A fire solution is then calculated and the Ground Based Interceptor (GBI) is fired. The GBI blasts through the atmosphere into the predicted path of the ICBM with the sensors keep it updated as to the status of the enemy missile.

Once the Interceptor has finished boosting into space the Exo-Atmospheric Kill Vehicle (EKV) mounted at on the tip of the GBI is released. Using its own infrared sensors and series of small boosters the kill vehicle positions itself directly in front of the enemy missile’s path. The 120 lb EKV then collides directly with the enemy warhead. The result should be the destruction of the warhead without a nuclear detonation.

EKV-and-Shroud
An EKV sitting inside it’s shroud.

 

The May Test

Although the missile intercepted by the GMD in late May was meant to be a simulation of an ICBM, is was not quite a realistic test. With only a 3600 mile range the”ICBM” was slower than any actual missile the GMD might face in war. Such a test does not indicate the missile defense system is complete yet. Only a full-bore test with against a target with standard defenses would prove that the United States has the capability to shoot down an ICBM.

Still, the test shows significant technical prowess and proves that the GMD concept does work, at least in concept. While more tests will be necessary to refine the system and prove its capability for the purposes of deterrence, this test shows that it does indeed have the potential to defend against an ICBM.

What it isn’t.

The GMD is not a panacea for missile defense and will never be one. The interceptors it uses are complicated and expensive. The cost is due not only to the complexity of the interceptors but their size and infrastructure requirements. Each GBI is several stories tall and requires its own silo equipped with a control room.

Total program costs total about 41 billion dollars with the May 30th test alone running the Missile Defense Agency about 244 million dollars. To add the 14 additional missiles planned to roll out this year would cost an addition billion dollars.

The cost of the system has prohibitive effect on deployment.Because of their expense and size of the GBI only 36 Interceptors are currently fielded; split between Vandenberg Air Force Base in California and Fort Greely in Alaska.

ABM_GMI_Missile_Setup_lg
A GBI being lowered into it’s silo with a crane.

 

The size and expense of the GMD means that even fully functional, the system would only be capable of protecting the western United States from a limited nuclear attack by a nation like North Korea, whose ability to saturate the system would be limited.

Even well-tried systems like the Patriot tend to fire missiles in salvos to ensure hits. A new capability like the GMD would likely do the same; meaning those 36 interceptors will go quick. A high-end threat like a rogue Topol ICBM with 10 warheads and penetration aides would certainly overwhelm the system and in a general nuclear exchange the GMD would be worthless.

This has long been the problem with ABMs going back to the Nike series. It is usually cheaper to build more missiles to than to field more interceptors. Therefore the GMD will always be a niche tool in the American arsenal, tailored for a specific threat rather than general use against all ICBMs.

The GMD’s niche role is also due to its inflexibility. Unlike the MIM-104 Patriot or the THAAD which can counter a series of low to mid range threats, the GMD can only take out ICBMs in their mid-course phase outside the Earth’s atmosphere. The system cannot defend itself against other threats like IRBMs and MRBMs like the THAAD and cannot perform air short or range missile defense like the Patriot.

Politics

Politically, there is a price for such a capability. China, with its bare bones nuclear deterrent is unlikely to take this development well. Russia, which has always viewed missile defense as a destabilizing force is also unlikely to be happy about a limited American ABM capability even if it could overwhelm it with just two missiles. The fact that the interceptor is itself a three stage missile will also give them fodder for their crusade against the INF.

The system could also generate strategic instability and spur nations like China to press on with systems like the hypersonic glide vehicle in order to counter the threat to its limited deterrent, a trend that will only accelerate if more GBIs are fielded and the new KVs are introduced.

As for North Korea, a functional GMD might box them into a corner, but will not remove the threat. With no political solution in sight, Kim is getting closer to an ICBM. As the North Korean missile program advances so does the nuclear program. By 2020 Kim’s regime could have enough material for 50 to 100 weapons in addition to an ICBM capability.

Even if only 12 or 24 of those warheads are mounted on ICBMs the U.S would have to expand it’s GBI deployments considerably to counter them. The only other option would be to glass North Korea in a massive nuclear counter force strike.

All in all the GMD is technically impressive but its usefulness is limited by both it’s cost and the missiles it will face. The capability it provides will encourage adversaries to explore new missile technologies and require constant updates for the system to retain its capability to defeat limited ICBM attacks; a costly proposal for a threat that is likely to last indefinitely.

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