A Sociology of Ballistic Missile Defence

Principal Investigator:

Dr Graham Spinardi

Research Team:

Dr Graham Spinardi and Professor Donald MacKenzie


This project was funded by a grant from the Economic and Social Research Council.


Ballistic Missile Defence (BMD) is one of the most challenging and controversial technologies ever developed. Over the last fifty years the United States has spent billions of dollars on its development, but has only deployed a national defensive system on two occasions. The first of these, known as the Safeguard system, was declared operational in 1975, but deactivated only months later. The second the Ground-based Midcourse Defence was deployed by the administration of G. W. Bush, with interceptor missiles based in Alaska and California.

Two key concerns have plagued BMD development throughout its whole history:

  • Is BMD technically feasible?
  • Is BMD deployment desirable?

This project has focused primarily on the first issue, investigating how knowledge about the technical performance of BMD has been constructed, placed in the context of shifting political and international developments.

The Challenge

Ballistic Missile Defence

An attack by nuclear-armed Intercontinental Ballistic Missiles (ICBMs) is difficult to defend against because:

  • the warheads from such missiles travel very quickly – around 7 km/sec in the mid-course – allowing limited time for the defence to operate
  • each ICBM can carry multiple warheads
  • lightweight decoys can be made to look very similar to the warheads
  • chaff (metal foil) can be used to obscure the warheads from radar
  • if the attacker predetonates a nuclear warhead then this may obscure or confuse the view of defensives radars and other sensors
  • the consequences of even one nuclear warhead penetrating the defence would be devastating.

Interception can in principle be carried out at three stages of the missile’s flight, each of which has advantages (+) and disadvantages (-).

Boost phase

  • + The missile has just taken off and presents a large, vulnerable target because the booster rockets have not yet been discarded
  • + It is a very valuable target because the missile has typically not released it multiple warheads and any decoys or other countermeasures.
  • - The boost-phase is short, lasting only about 3-5 minutes, and it may be difficult to deploy land or sea-based interceptor missiles within range
  • - Space-based interceptors that could potentially carry out boost phase interception anywhere would be very expensive to deploy

Mid-course phase

  • + This phase is relatively long – about 20 minutes – and the warhead trajectories are predictable
  • - Multiple warheads may have been released and could be accompanied by countermeasures such as decoys and chaff, and there is no atmospheric drag to slow down and help distinguish these countermeasures

Terminal phase

  • + Atmospheric drag strips away light-weight objects and so the warheads are easy to distinguish
  • - Atmospheric drag also can make it hard for infra-red homing interceptors to work
  • - There is very little time – maybe a minute – until the warheads will detonate

Key Issues

Technological controversy

Many opponents of BMD argue that the technology will not work against a determined enemy employing countermeasures, and even BMD supporters are divided over the best approach. Some support ground-based interceptors such as the current Ground-based Midcourse Defence, while others argue that only space-based boost phase defence can be effective. Because there is no operational experience of BMD against nuclear missile attack, these claims about technical feasibility rely heavily on in-principle arguments about what is theoretically possible.

The testing issue

Flight-testing is a contested arena for BMD development because it provides the main source of empirical evidence to support claims about performance. Critics of BMD argue that flight-tests are unrealistic because the defence has prior knowledge of the nature, timing and direction of the attack, and because only a narrow range of intercept trajectories have been used. Although flight tests can certainly be made more demanding, such criticism is hard to counter in principle because tests are inevitably different from the real thing. Whether those differences are significant is a matter of judgement, and such judgements are likely to be coloured by political preferences, and in particular, how likely a nuclear attack is thought to be.

The lessons of Patriot

The only operational use of BMD was the US short-range Patriot missile in the two Gulf conflicts in 1991 and 2003. Although official reports initially claimed that Patriot had performed well in 1991, later analysis suggested that very few Iraqi Scud missiles had been intercepted. It seems that the Scud missiles, modified by the Iraqis to provide longer range, were so unstable in flight that they tended to break up, thus producing a number of targets that confused the radar-controlled Patriot. Critics point to this as an example of how real life operations can present unexpected challenges not revealed in testing. BMD supporters counter by arguing that this version of the Patriot had only recently been adapted from its original anti-aircraft role, and that subsequent models are greatly improved.

Does technical performance matter?

A further lesson that BMD supporters draw from the first Gulf conflict is that technical effectiveness is not necessarily critical so long as BMD deployment is politically effective. It is argued that the deployment of Patriot in that conflict helped persuade Israel not to take military action, and thus enabled the US to build a coalition involving Middle Eastern states. The contemporary implication of this argument is that it does not matter if the currently deployed GMD system is not technically very effective so long as it has the political effect of creating uncertainty in the minds of potential aggressors.

A New Arms Race?

As well as doubts about its technical effectiveness, the other main argument against BMD has always centred on the risk that one sides defensive developments would provoke the other side to increase its offensive capability. Some now worry that current US BMD developments might spur nations such as Russia or China to increase their offensive nuclear forces. Others argue that US BMD systems are only capable (if anything) of defending against a small nuclear attack such might be fielded by North Korea and Iran, and so should not provoke concerns by larger nuclear powers.


Further Information


US Ballistic Missile Defence History

Anti-Ballistic Missile (ABM) technology

From the mid-1950s to the mid-1970s US missile defence work focussed on ground-based, radar-guided interceptor missiles armed with nuclear warheads. The use of nuclear warheads on the defensive missiles compensated for the limited accuracy of using ground-based radars to guide the ABM missiles towards their targets. These technologies were deployed in the Safeguard system, of which only site was completed, with the mission of protecting a Minuteman intercontinental ballistic missile field in North Dakota. However, within days of being declared operational in October 1975, Congress voted to close down Safeguard and it was deactivated a few months later. One reason was doubts about its effectiveness; for example, the Safeguard contractor, Bell Labs had the belief that the system, as it is being built, cannot adequately perform the missions assigned to it. Another reason was that the USA and Soviet Union had signed the ABM Treaty in 1972 and in its 1974 revision this limited each side to only one ABM site, in effect agreeing that both sides should remain mutually vulnerable to nuclear attack.

The Strategic Defence Initiative

Popularly known as Star Wars, SDI was set up after President Ronald Reagan made his famous speech of March 23rd, 1983 when he called upon the US scientific community to make nuclear weapons impotent and obsolete. Unlike earlier US missile defence efforts, SDI proclaimed a rhetoric of a near-perfect shield, based on a layered defence that would gain particular leverage from the use of boost-phase interception (before Soviet missiles could release their warheads and decoys), and proposing the use of futuristic technologies such as lasers and particle beams based in space. However, no missile defence systems were deployed by SDI, and the practicality of space-based boost-phase interception remains highly controversial.

National Missile Defence

The use of the short-range Patriot missile in the first Gulf conflict in 1991 had a significant impact on US domestic politics as regards BMD development. Although widely considered ineffective in intercepting Iraqi Scud missiles, the Patriot experience led many in Congress to conclude that any defence was better than none, and that deterrence could not be relied upon against rogue state leaders such as Saddam Hussein. This led to a revival in BMD technology based on ground-based interceptor missiles, but this time using hit-to-kill interception in which an infra-red sensor guides the kill vehicle into a direct collision with the target warhead. With the end of the Cold War, and concern about the emergence of nuclear-armed states such as North Korea and Iran, the mission of BMD changed. Rather than thousands of Soviet nuclear warheads, the challenge is now interception of a few warheads. Doubts still remain about the effectiveness of the system deployed by the administration of G. W. Bush known as the Ground-based Midcourse Defence but others also question whether it is necessary, arguing that the threat of US nuclear retaliation will deter these states from attacking the USA.