Intercepting intercontinental missiles

Intercepting an intercontinental ballistic missile (ICBM) in flight has often been described as hitting a bullet with a bullet, and it makes for a pretty accurate analogy. Dr Gareth Evans asks whether it can be done.


Hitting a bullet with a bullet sounds like the sort of trick shot that the Wild West’s legendary Annie Oakley might have gone in for, but if that ‘bullet’ was flying 10 times faster than any ammunition she ever used, perhaps even she would have thought twice about it.

The task facing all ICBM interceptor systems is shooting down a projectile travelling at a staggering 6,000 m/s – roughly 13,500 mph – before it hits its target, and it is one which has taken on a whole new dimension since the recent spate of North Korean missile tests.

With Kim Jong Un’s tally of launches now running at 14 in the first seven months of 2017 alone – only two short of the total his father achieved in the entire period of his leadership – more than a few countries have begun to look again at just how feasible missile defence is, and whether some fast acquisitions might be in order.

There are already a number of ballistic missile defence (BMD) systems operating in the region. Notably, the US recently delivered the Terminal High Altitude Area Defense (THAAD) anti-ballistic missile system to South Korea, while various incarnations of the Patriot, including the latest PAC-3, are in use and the ship-borne Aegis is deployed aboard US and Japanese warships.

However, all of these have been designed to provide theatre ballistic missile defence, to deal with the threat of short to intermediate-range weapons, and while Aegis’ use to bring down a faulty spy satellite suggests it could conceivably target a true ICBM, it has never been put to the test. None of these were ever intended for the job; the US Ground-based Midcourse Defense (GMD) system, however, is an entirely different kettle of fish.

GMD success

The world’s only conventional ballistic missile defence system specifically designed to intercept ICBMs, GMD passed an important milestone at the end of May with its first ever successful intercept of an ICBM-class target.

The GMD system consists of state of the art ground detection and tracking technology, a three-stage solid rocket booster capable of flying at near-hypersonic speeds to exit the atmosphere and an exo-atmospheric kill vehicle (EKV). Once released from the interceptor missile, the EKV’s on-board computer steers the vehicle using tracking data from multi-colour sensors and its own rocket motor onto an intercept trajectory, enabling the kinetic force of the collision to destroy the threat without the need for a conventional warhead.

"GMD has only been tested once against an ICBM – and it did succeed – but has failed quite a few times against slower, shorter range ballistic missiles."

The recent test is undoubtedly a major fillip for ballistic missile defence but, as James Dwyer, Politics and International Relations Teaching Fellow at the University of Tasmania points out, despite their enormous lead in the technology, the US still struggles to achieve consistent success. “GMD has only been tested once against an ICBM – and it did succeed – but has failed quite a few times against slower, shorter range ballistic missiles,” he says.

It is a fair point; according to the US Missile Defense Agency’s own ‘Ballistic Missile Defense Intercept Flight Test Record’ to 30th May 2017, since 1999 GMD has achieved just 10 successful intercepts out of 18 attempts. Even taken as a whole, across all the Aegis, GMD, THAAD and Patriot PAC-3 programmes combined and against ballistic missiles in general, not ICBMs, the success rate runs at just under 80% since 2001. Given the huge inherent difficulties involved, are we ever likely to see a system that can better that and get anywhere near to providing total reliability?

A ‘Star Wars’ revival?

Dwyer, who has made an extensive study of the effects of ballistic missile defence on nuclear deterrence and regional security, thinks not. “I hesitate to say never, but there is nothing foreseeable that could provide a reliable defence against an ICBM attack, let alone approach a 100% success rate.”

He says that the advantage always favours the attacker, who simply has to launch more ICBMs or make use of multiple, independently targetable re-entry vehicles (MIRVs) to overwhelm the defence. There is another factor too; this approach is cheaper for the attacker than it is for the defender, and even for militaries with very deep pockets, that could be significant.

“Even if the US attempted another defence program on the scale of the Strategic Defence Initiative, often referred to as ‘Star Wars’, it is difficult to say it would be truly effective, and would certainly not approach a 100% certainty of defence,” Dwyer says.

Aside from the cost, technological constraints and the small matter of violating several global treaties and agreements covering the weaponisation of space, Dwyer explains that there are other problems with any notions of revisiting President Reagan’s ‘Star Wars’ project. Today’s submarine launched ballistic missiles (SLBMs) fired on a depressed trajectory shot, travelling on a lower arc which trades range and accuracy for surprise and shorter flight times, could already prove a major challenge for such a system, and the next generation of in-atmosphere hypersonic glide vehicles are waiting in the wings. It appears that for the foreseeable future at least, 100% effective orbiting laser defence systems are definitely still more Darth Vader than Donald Trump.

MAD world

It is perhaps not such a bad thing; if missile defence becomes too good, it could bring its own problems. “Nuclear deterrence will continue to be the main defence against nuclear attack,” says Dwyer “and the risk posed by BMD may renew a nuclear arms race between the US, Russia, and China as they seek to maintain the credibility of their nuclear deterrents against the possibility of a more reliable US BMD system.”

However, while a return to the deterrence value encapsulated in the Cold War-style concept of mutual assured destruction – with its wonderfully ironic acronym, MAD – may be the only practical defence against nuclear attack, how does that play in the context of North Korea?

"It is perhaps not such a bad thing; if missile defence becomes too good, it could bring its own problems."

While BMD involving the kinds of anti-ballistic missile systems already deployed in the region can provide defence for states such as South Korea and Japan against shorter range ballistic missiles, ICBMs remain a problem. However, Dwyer believes that deterrence will continue to prove effective in preventing North Korea from engaging in a nuclear attack on another country.

Bellicose posturing aside, he says that the leadership in Pyongyang know that if they were to use a nuclear weapon in an offensive manner, especially against the US or one of its allies, it would be suicide. In practical terms too, Dwyer also doubts that North Korea will be able to develop a large, reliable arsenal of ICBMs and nuclear warheads, but he does see one potential nightmare scenario.

“The issue here is if North Korea is attacked first. Then I think deterrence may not be effective, and could easily envisage North Korea adopting a position of ‘if we are going down, we’re taking you with us’.”

“Certainly not a pleasant situation to be in,” he says.