Chinks in the armour

Why the NMD is a fundamentally flawed and unworkable concept.

R. RAMACHANDRAN

AS the Pentagon, the U.S. Department of Defence's strategic arm, prepares to conduct the Deployment Readiness Review (DRR) of the grandiose National Missile Defence (NMD) system, the proposed protective shield over the U.S. territory to annul missile att acks during their flight in space, two things are likely to militate against a positive outcome of the review. The first is the fact that two out of the three missile interceptor tests carried out so far have failed. The second is more basic, although th e Pentagon has been dismissive of it. It is the overwhelming scientific opinion that an NMD is a fundamentally flawed and unworkable concept.

The reasoning of the scientists and the arms control experts is simple. Irrespective of how elaborate and sophisticated, the defence shield design is, the countermeasures at the adversary's disposal would overwhelm any such system and render the shield p orous. Besides, the deployment of an NMD would undermine the various arms control measures that are in place and lead to increased vertical proliferation by the adversarial missile powers.

From a public policy point of view, this opinion of the scientific community assumes importance and could influence President Clinton's pending decision on deployment. For this, the conclusion of the DRR with regard to technological feasibility, even if favourable, is only one of the criteria to be met.

With the presidential elections approaching, political calculations may, however, lead him to ignore the opposition and give the green signal to the NMD.

On July 6, the day before the failed interceptor test, 50 Nobel laureates wrote to the President urging him to reconsider his decision on deploying an NMD. In fact, scientists have been arguing against the feasibility of an NMD right from the 1960s when a nuclear shield had been proposed against Soviet missiles. Called Safeguard, the nuclear shield involved interceptors that would rely on the blast from nuclear explosions to destroy incoming warheads. The large kill radius of a nuclear blast was used to overcome the limitations of defence. This system was operational only for a few months in 1976. In 1968, writing in Scientific American, physicists Richard Garwin and Hans Bethe described how China or the Soviet Union could easily elude the missi le shield.

Rapid advances in missile, computer and sensor technologies have led to alternative defence technologies to destroy a target, the high point of which was the directed energy laser beams of the Strategic Defence Initiative (SDI). The descendants of these chemical lasers are being developed for today's ballistic missile defence (BMD) systems in the form of Air-Borne Laser (ABL) and Space-Borne Laser (SBL). But the bulk of the technologies in the BMD today, including the NMD, have focussed on hit-to-kill c oncepts that use the large kinetic energy of objects moving towards each other at a speed of several kilometres a second, to destroy the target.

But at such speeds hitting a target is no easy task because the kill vehicle is essentially a heavy object such as a rod or a disc that is only tens of centimetres in diameter and it must hit a target that would be a metre or so across. Hit-to-kill missi le defence is similar to hitting a bullet with a bullet but at a speed 25 times higher. A system based on hit-to-kill interceptors is more easily defeated by simple countermeasures than by nuclear-tipped missiles. The argument that any NMD would be techn ologically ineffective was an important reason behind the U.S. and the Soviet Union signing the ABM Treaty in 1972. The fear that such a system would escalate the arms race also contributed to the conclusion of the Treaty. The Treaty prohibits both count ries from deploying a nationwide missile defence system.

The general architecture of the NMD that the U.S. is planning to deploy during the next century and how the various key components are meant to operate are pretty much clear. The NMD would be a fixed, land-based non-nuclear missile defence system aided b y a space-based detection system. Broadly, it comprises five elements:

* Ground-based Interceptors (GBIs);

* Battle Management, Command, Control and Communications (BMC3), which includes: (a) Battle Management, Command and Control (BMC2), and (b) In-Flight Interceptor Communications System (IFICS);

* X-Band Radars (XBRs);* Upgraded Early Warning Radars (UEWRs);

* Defence Support Programme Satellites/Space-based Infra-red System (SBIRS).

An Inter-Continental Ballistic (ICBM) fired at the U.S. would be first detected by infra-red early warning satellites and then by one or more of the large phased-array early warning radars which are positioned at Massachusetts, California, Alaska, Britai n and Greenland. Their range and resolution are not very high but they can provide trajectory data on a small number of well separated ballistic targets.

Flight path data from infra-red satellites and early-warning radars is beamed to the primary sensor of the NMD, the ground-based X-band radar. Based on this data the radar focusses its missile search over a smaller area. This phased-array radar has the c apability for long-range detection and tracking. A prototype is in use at the U.S. Army's Kwajalein Atoll Missile Range in the Pacific. The high-resolution radar and sensor data thus collected are then transmitted to the battle management centre which wo uld determine possible intercept points and issue launch and guidance commands to a ground-based interceptor missile. Each interceptor consists of a rocket booster and what has been termed an Exo-atmospheric Kill Vehicle (EKV), which does the interceptio n in outer space once it separates from the booster. (ICBMs would be launched from too far away a distance to be targeted earlier by ground-based interceptors.) (In the July 7 Integrated Flight Test (IFT-5) the Kwajalein radar apparently performed well b ut the interceptor booster failed. At present, the reworked Payload Launch Vehicle (PLV), which is actually a two-stage Minuteman II missile, is being used as the booster for the tests. In the operational mode, the NMD will use a specially configured thr ee-stage booster rocket which will be put to use from IFT-8 onwards.)

In order to maximise the exent of the defended area and the number of hit attempts at the incoming missile, the interceptor would have to be launched soon after an attack is detected. The interceptor, travelling in excess of 7 km a second, will receive c ontinuous guidance updates based on data from various sensors. In order to increase the probability of kill, several interceptors could be fired at a missile: the shoot-look-shoot scenario. The first phase of the NMD envisages 20 interceptors at a single site, and the number is to be subsequently enhanced to 100 interceptors.

Using its own on-board infra-red seeker and data from ground-based radar and other sensors, the EKV will attempt to differentiate between an attacking warhead and any missile debris or decoys used to confuse it. Weighing about 50 kg, the EKV would then u se its on-board thrusters to manoeuvre itself into a high- speed (25,000 km/hr) collision with the target. In an ideal situation, the intercept would destroy the kill vehicle and the target.

In an expanded NMD system, several improved sensors are planned. Existing early warning radars will be enhanced so they can track targets and guide interceptors better. New X-band phased array radars, similar to the main ground-based radar, will be insta lled, some of them in conjunction with the early-warning radars. A space-based missile tracking system called SBIRS-LEO (space-based infra-red system Low Earth Orbit), formerly called Brilliant Eyes, is also under development. This system is designed to track missiles and their warheads from the early stages of flight using short, medium and long-wave-length infra-red sensors as well as visible light sensors.

Critics argue that given the very low success rate (four out of 17) in high altitude hit-to-kill tests so far, the technology is not ready for use. Even if all the tests had been successful, scientists point out that there is no guarantee that in real-li fe situations the concept would work. They cite the case of the Patriot missile in the Gulf war in 1991, the only instance of a missile defence system used in combat.

Patriot, a theatre missile defence system, had a perfect test record before the war: 17 successes in 17 interceptor tests. Yet it failed in most or all of the 44 of its attempts to destroy the Iraqi Scud missiles, which behaved in a manner that was diffe rent from test targets. Therefore, assuming that the basic components of the NMD are workable, the real-world effectiveness of the system will depend on its ability to cope with such unpredictable behaviour of incoming warheads, in particular the counter measures adopted by the adversary to beat the system.

In April, the Union of Concerned Scientists (UCS) at the Massachusetts Institute of Technology, United States, consolidated all the arguments that they have been voicing at various forums and in journals on the technological infeasibility of an NMD, to p roduce a report titled "Countermeasures". The report, the contributors to which were mainly physicists and engineers, called for a shelving of the current NMD plans as unworkable and counterproductive. Their analysis, the report said, was based on an und erstanding of basic physics and technology and used only information available in open literature. "We do not believe that access to classified information would in any significant way alter our study or its conclusions," said the report.

An obvious way to foil the system would be to launch enough ICBMs to overwhelm it. But this option may be affordable only to a missile power like Russia, not even China and even less to emerging missile states like North Korea. An affordable and feasible option would be to devote some of each missile's payload to lightweight countermeasures designed to confound the interceptor. The 1999 U.S. National Intelligence Estimate (NIE) on the ballistic missile threat to the U.S. stated that countermeasures woul d be available to the emerging missile states.

This is not surprising because these are low technology measures and any country capable of producing or obtaining ICBMs and weapons of mass destruction (WMD) would be able to produce or acquire effective countermeasures, the report points out. Thus, sci entists say, that if the U.S. deploys the NMD, it must expect that any ICBM launched against it to be equipped with countermeasures.

The report is also critical of the approach to the DRR and the deployment decision, for saying that the Pentagon's assessment would consider only whether the first phase of the system would be effective against a threat with no credible countermeasures; it will not consider whether the full system would be effective against realistic countermeasures.

According to the study, the Pentagon has underestimated the effectiveness of countermeasures that an emerging missile state could deploy and thus inaccurately describes the actual threat against which the NMD has been designed. The system will, therefore , fail in the real world, says the report.

In space, where the system is designed to intercept missiles, it is a state of free fall and all objects would travel on identical trajectories regardless of their weight, shape and so on. So a variety of countermeasures could be used. For example, an IC BM could be designed to disperse a lightweight decoy warhead alongside the real one and the kill vehicle would have to differentiate between the two. Once they enter the atmosphere, the lighter one would travel more slowly and the kill vehicle sensor cou ld tell a decoy from a warhead. But by then it would be too late for an intercept.

To drive home the point of the ineffectiveness of the system against even simple countermeasures, the report examined three potential countermeasures in detail: submunitions with biological or chemical weapons; nuclear warheads with anti-simulation decoy s and nuclear warheads with cooled shrouds. According to the study, since these use readily available materials and straightforward technologies, any emerging missile state could construct and employ them.

An attacker could pack an ICBM with dozens or even hundreds of small submunitions containing deadly gases or biological agents. Each submunition could be designed to withstand the heat during re-entry into the atmosphere - the analysis demonstrates the f easibility of this, and in combination they would thwart the defence by simply overwhelming it. Moreover, because the submunitions would distribute the chemical/biological agents over a large area and disperse it at low speeds, they would be more effecti ve than packing them in a single warhead.

If a missile is made to release dozens of lightweight decoys, it could overwhelm the missile defence. Decoys resembling warheads could make differentiation by radars difficult, if not impossible. But anti-simulation - making warheads look like decoys - i s far easier and more effective. Warheads wrapped in aluminium coated Mylar balloons, for example, could be launched along with numbers of empty balloons.

The thin metallic layer covering each balloon would reflect radar beams, preventing detection of warheads, and each balloon could carry a heater to prevent discrimination by infra-red sensors. Alternatively, balloons of different sizes and shapes equippe d with heaters of different strengths could be used.

Defence systems sensors and radars would find it extremely difficult to decide which is the real one among the large number of different targets, none of which would look like a warhead.

The ICBM warhead could be covered with a shroud cooled by liquid nitrogen. The cooled shroud would reduce the infrared radiation emitted by the warhead by a factor at least one million, making it effectively invisible to the sensor. Such a shroud, the re port points out, could be made of aluminium alloy and thermally isolated from the warhead by a multilayered insulator.

Any of the above countermeasures could defeat the NMD system. But many more exist: radar jammers or other electronic countermeasures, warhead manoeuvres, chaff or the use of shaping and radar absorbing materials to reduce the visibility of the warhead to the defence's radars. And such countermeasures could be used singly or in combination with others.

In addition, many operational and technical factors make the job of the defence more difficult than that of the attacker. For instance, the defence system has to firm up a specific technology and architecture before the attacker does. This permits the at tacker to tailor countermeasures to the specific defence system. One effective countermeasure will suffice to defeat the defence mechanism, whereas the system must be designed to defeat every possible combination of countermeasures. In the case of hit-to -kill kind interceptors there is little margin for error; the defence must work the first time it is used. The proposed system does not appear to be even close to being capable of meeting these goals, says the report.

However, the director of the Ballistic Missile Defence Organisation (BMDO), Lt. Gen. Ronald Kadish, testifying before the U.S. Senate Appropriations Committee on April 12, a day after the UCS study was released, said that such scenarios would come true o nly if an enemy launched a high number of incoming warheads combined with countermeasures - in which case you can overload the system. In the scenario that the system is designed for, namely to protect against tens of warheads, he claimed that the organi sation had devised ways to get into the countermeasures issue which he believed would be very effective.

More pertinently, the UCS study points out that long-range missiles would neither be the only ones nor the optimum means of delivery of the WMD for an emerging missile state attacking the U.S. Other delivery options available would be less expensive, mor e reliable and more accurate than long-range missiles. These alternatives include cruise missiles or short-range missiles launched from ships off the U.S. coast, nuclear weapons detonated in a U.S. port while still in a shipping container and cars or tru cks dispersing chemical or biological agents as they are driven through a city.

* * *R. RAMACHANDRAN

ON May 11, 2000 Theodore A. Postol, a Professor of Science, Technology and National Security Policy at the Massachusetts Institute of Technology (MIT), made a disclosure. He accused the Pentagon of scientific fraud in tests of technologies for the Nation al Missile Defence system. According to him, the Pentagon had covered up the failure of a crucial technology test pertaining to NMD's Exo-atmospheric Kill Vehicle (EKV) of the missile interceptor. In a letter to John Podesta, the White House Chief of Sta ff, he said that his analysis of Ballistic Missile Defence Organisation (BMDO) published data from the first Integrated Flight Test (IFT-1A) showed that the EKV could be defeated by the simplest of balloon decoys.

He also contended that the BMDO had colluded with its contractors in order to hide the fact by tampering with the data from and analysis of the IFT-1A test. He made this allegation on the basis of documentary evidence in his possession. His investigation s also revealed that the BMDO had modified the configurations of the IFT-2, 3 and 4 follow-on flight tests in order to hide the programme stopping facts from IFT-1A. However, the BMDO has claimed that a successful intercept in IFT-3, which was carried ou t on October 2, 1999, had proven the basic feasibility of the seek and hit-to-kill concept that underlies the interceptor-based defence against ICBMs.

The basic point Postol made was that the EKV sees both decoys and warheads as unresolved points of light and attempts to identify warheads by examining how each point of light fluctuates in time. The data from IFT-1A showed that the changing spatial orie ntation of the decoys and warheads as they fall through the near vacuum of space was almost the same, each resulting in a signal that fluctuated in a varied and totally unpredictable way, he pointed out. Consequently, he said, there was no fluctuating fe ature in the signals from decoys and warheads that could be used to distinguish one object from the other.

According to Postol, the post-flight analysis of telemetry data from the IFT-1A showed that the defence system was always wrongly identifying partially inflated balloon as the mock warhead. This failure was dealt with simply by removing the balloon from the data, as if it was never there, Postol wrote. Even after removing the balloon, the post-flight data still showed that two other benign objects were brighter than the warhead and, therefore, were being identified as mock warheads. The BMDO analysis de alt with this by simply rejecting the data, he said.

This elaborate hoax was then screened by describing this tampering with the data and analysis in misleading, confusing and self-contradictory language to create the false impression that the results were supported by established scientific methods, Posto l said. In truth, he remarked, the procedures followed by the BMDO were similar to rolling a pair of dice and throwing away all outcomes that did not give snake eyes and then fraudulently making a claim that they have scientific evidence to show that the y could reliably predict when a roll of the dice will be a snake eyes. Such a fraudulent analysis became necessary because the IFT-1A data showed that signals from decoys and mock warheads were indistinguishable, observed Postol.

In the light of these unsettling results of IFT-1A that could undermine the programme, the BMDO reconfigured the follow-up tests by changing the number of objects planned to fly from ten to four. In addition, the fidelity of the experiments was further u ndermined by the careful choice of the time of day to have the sun in a convenient position in the sky.

Postol stated that his analysis supported similar allegations by Nira Schwarz, a former engineer working with the company - a consortium of Boeing, TRW and NRC - contracted to develop the differentiation technology for EKV. Schwarz had alleged that the c ompany was doctoring the data and had taken the matter to court. Her charge had led to an investigation by the Defence Crime Investigation Service.

Besides an initial off-the-cuff denial, the BMDO has so far not responded to these charges in detail. The interesting thing is that despite this, IFT-3 is being held as a demonstrator of the technological feasibility of the system and the NMD Deployment Readiness Review (DRR) is going on as if none of this happened.