v1.1.2 / chapter 1 of 3 / 01 mar 08 / greg goebel / public domain
* The history of missile defense is long and convoluted. This chapter provides a short overview of the history and issues of missile defense, followed by descriptions of early missile-defense programs.
* Interest in missile defense systems, originally called "anti-ballistic missile (ABM)" systems, began even before ICBMs were deployed. The German V-2 short-range ballistic missile, launched against London and Antwerp by the Germans in the last year of World War II, made it clear that long range missiles were a future threat. In the mid-1950s, the threat became tangible as the technology became available to develop long-range missiles with accurate guidance systems and nuclear warheads. There was a logical desire to develop weapons to intercept these missiles.
As ICBM development proceeded through the 1950s, ABM systems began to move from "paper projects" to actual research and development programs. By the early 1960s the US and the USSR were testing elements of ABM systems, based on long-range ABM interceptor missiles armed with nuclear warheads and directed by elaborate radar networks.
The technical challenge and pricetag of fielding ABM systems proved enormous. An incoming missile "re-entry vehicle (RV)" carrying a nuclear warhead moves very fast, and getting an interceptor missile close enough to disable it is a difficult task, compared by some to "hitting a bullet with another bullet". The radar systems had to be powerful and sophisticated, and the missile defense network had to be linked together by a software and data communications system that is a challenge now, and was a nightmarish prospect with 1960s technology.
The task of hitting an incoming warhead is complicated by the possible use of "multiple independently targeted reentry vehicles (MIRVs)", in which an ICBM carries several RVs that can hit widely-spread targets, confounding and possibly saturating a defense. Even an ICBM carrying a single RV can make life more difficult for the defender by deploying "penetration aids", such as a clouds of metallic radar-reflective strips, known as "chaff", or various kinds of decoys. Decoys can be dummy re-entry vehicles, or simple metallized balloons inflated in space, with the real RV concealed inside a balloon to make it difficult to distinguish from the decoys. To be sure, the RV quickly leaves balloon decoys and chaff behind as it re-enters the atmosphere, but by that time there are only moments left for a defender to stop the warhead.
A particular problem of 1960s ABM systems was the reliance of the ABM interceptors on nuclear warheads. The electromagnetic pulse (EMP) caused by explosions of interceptor warheads would likely disrupt the defender's ABM radar network, disable satellites, and interfere with national communications and electronic systems. Another problem was the remote possibility that an ABM interceptor warhead might cause accidentally cause "collateral damage" to the defender's country or a neighboring country, in the case of the US this being read as "Canada". There was also the prospect that use of nuclear warheads on ABM interceptors would extend the nuclear arms race into space.
* By the late 1960s, the difficulties and expense of ABM defense had led to a bitter debate that continues to this day, fading and regaining strength in step with the fall and rise of missile defense schemes.
Advocates of ABM defense admitted that there was no way to build a leakproof defense against ICBMs, but maintained that even a partial defense could save tens of millions of lives; would complicate the plans of any adversary scheming to perform a nuclear sneak attack, or "first strike"; and would more than pay for itself if a single enemy ICBM were launched by accident, or as a "potshot" by a lesser power with a limited offensive capability. In the 1960s, this "lesser power" was usually identified as Red China. The advocates also objected to the established policy of nuclear deterrence, in which both sides maintained the capability to perform a massive nuclear strike on an enemy even if the enemy struck first. The concept was known as "mutual assured destruction (MAD)". The advocates felt, with plenty of justification, that MAD had a highly arguable moral basis, and more to the point was a situation that was "spring-loaded to the accident position".
In response, the critics felt that building an effective ABM system was impossible given the technical challenges, massive expense, and effectiveness of relatively simple countermeasures. They also felt that an ABM system might actually disrupt the balance of power. An effective ABM system, so the thinking went, might let one superpower destroy the other while blocking a counterstrike; or at least an adversary might worry that was the intent, and be tempted to strike first.
The theory behind the nuclear arms chessgame of the 1960s became increasingly baroque, convoluted, and not very credible, but in the end the ABM advocates were not able to sell their agenda. In fact, a useful ABM system was almost certainly beyond the technology of the time. Both the US and USSR sought security in arms-limitation treaties, including an "ABM Treaty (ABMT)" signed in 1972 that all but killed active ABM development.
* ABM research continued in a quiet fashion, however, with work on new "kinetic kill" or "hit to kill (HTK)" interceptor technology that was extremely accurate, destroying an incoming RV by simply ramming it. An HTK interceptor would carry no nuclear warhead, not even a conventional explosive warhead, and so was referred to, somewhat as a joke, as a "smart rock".
The missile defense controversy flared back up again in the early 1980s, when US President Ronald Reagan began a program, known as the "Strategic Defense Initiative (SDI)", to develop a missile defense system to protect America from nuclear attack. SDI, also known "Star Wars", focused not only on HTK interceptor missiles, but on exotic technologies such as high-power conventional lasers, other types of energy weapons, and ultimately an orbiting constellation of automatic battle stations carrying downscaled HTK interceptors, known as "Brilliant Pebbles", derived the older term "smart rocks".
Like the 1960s ABM effort, the public debate was bitter, with the critics hammering on the technical difficulties and also worrying about overturning the 1972 ABM treaty. Also as with the 1960s effort, the technological challenges turned out to be too great. The collapse of the Soviet Union in the late 1980s and early 1990s greatly reduced the chances of an all-out nuclear exchange, and so also reduced the perceived need for a missile defense system to protect America from a Soviet nuclear strike. Star Wars as such faded out.
* American work on HTK interceptor missiles continued on a low level. The concept was given a new lease on life by the Persian Gulf War in 1990:1991, in which Iraqi dictator Saddam Hussein launched Soviet-designed Scud tactical ballistic missiles (TBMs) at forces of the American-led Coalition fighting to evict him from his occupation of Kuwait, also launching Scuds at Israel to create political complications for the Coalition.
Saddam Hussein's Scuds proved very troublesome to the coalition. Although the Scuds were extremely inaccurate and hadn't the least chance of actually slowing down Coalition military operations, bringing Israel into the war might have driven a wedge between the US and its Arab friends. The Scuds also did inflict some casualties, with a Scud killing 28 US military personnel in Dhahran on 25 February 1991. As a result, the war led to a general consensus among American defense officials that since many countries had TBMs such as Scuds, American forces in the field needed a "tactical ballistic missile defense (TMD)" system.
America was also motivated to develop a TMD system because it seemed technically feasible, as demonstrated during the war when US Patriot surface to air missiles (SAMs) scored hits on Scuds. Postwar analysis indicated that the effectiveness of the Patriots was exaggerated at the very least, but the technology was still felt to be within reach, and a TMD system seemed like a realistic objective. Exotic technologies, such as high power lasers, that had been too ambitious in the 1980s, also began to seem much more practical, if farther out than HTK technology.
* American work towards a TMD system inevitably and quickly resurrected the debate on a US "national missile defense (NMD)" system. A TMD system designed to protect US forces in a battle theater could just as easily protect small countries that were threatened with TBMs. Israel was at such a risk from countries such as Iraq and Iran; Japan and South Korean faced possible missile attacks from North Korea; and Taiwan was confronted with a similar missile threat from mainland China.
It was then just a small logical step to propose the implementation of a limited NMD system for the United States, all the more so because the rationale was no longer to protect America from an overwhelming nuclear strike by the Soviet Union, which had ceased to exist, but to stop a limited missile attack by countries such as North Korea, which was assessed by American intelligence to be developing missiles with enough range to hit the continental US.
* The US is now fielding TMD and NMD systems, though the debate continues. In the 1960s debate, a US NMD system was conceived as a defense against a massive Soviet nuclear strike, though in practice advocates had to scale down the goals to stopping small-scale accidental or potshot attacks. After the fall of the Soviet Union, the security of the old Soviet nuclear arsenal became a matter of serious doubt, and the attempts by countries such as North Korea to develop an ICBM capability meant that the main threat faced by the US was in fact a small-scale attack, not a massive nuclear strike.
This change in goals made an NMD system more plausible. Advocates argue that the rationale for ICBM development by the smaller powers is to give them the means of intimidating the US, allowing the smaller powers to engage in aggression against American allies and then daring the US to respond. The advocates believe that an NMD system would prevent the smaller powers from playing such a "blackmail" game.
The critics reply with traditional arguments. An attempt by a smaller power to attack the continental US, they say, would be suicidal, and the response would be massive retaliation. They point out as an example that Saddam Hussein had chemical and biological munitions available for use against Coalition forces, but did not use them in combat because of the fear of nuclear retaliation. They also point out that the smaller powers could smuggle "weapons of mass destruction (WMD)" such as nuclear, chemical, or biological weapons, into the United States to play the blackmail game even if they didn't have ICBMs.
The critics also point out that the possible use of a chemical or biological weapon payload on an ICBM complicates defense, since a chemical or biological weapon payload would likely be implemented as a "cluster munition", carrying not a single large munition but a set of many "submunitions" that would be dispersed over the target area. A dispersed swarm of cluster submunitions flying towards a target makes a poor target for an HTK interceptor.
Finally, the critics say that HTK interceptors can be defeated by simple countermeasures, including traditional chaff and decoys, or by cooling the RV, since HTK terminal guidance is generally with a passive infrared "seeker" system. Work on missile defense systems, and the debate, continues.
* After World War II, the US Army sponsored the first studies on how to intercept ballistic missiles such as the German V-2s that had been fired on London. The studies, codenamed THUMPER and WIZARD, concluded that interceptor missiles or, more speculatively, "directed-energy" weapons such as particle or microwave beams, might be able to shoot down an incoming missile.
In 1956, the US Army initiated development of an ABM system that would become known as "Nike-Zeus". Bell Laboratories was in charge of design and development, while Bell's Western Electric was the prime contractor for the Army. Douglas designed the missile element of the system, the two-stage "Zeus" missile, derived from the Nike Hercules anti-aircraft missile then going into Army service.
The Zeus missile was only part of a very complex system. As envisioned in the plan, the first line of defense in the Nike-Zeus system was the long-range "Zeus Acquisition Radar (ZAR)", which picked up incoming ICBM warheads from a range of 2,400 kilometers (1,500 miles). ZAR provided advance warning and location of the region under attack. Following acquisition by ZAR, the incoming warheads were then targeted by "Discrimination Radars (DRs)" at the missile launch sites, which sorted out which of the targets were really RVs and which were decoys or junk left over from the booster. Once the real RVs were identified, "Target Tracking Radars (TTRs)" then locked onto them, and the Zeus missiles were launched from underground silos.
The Zeus missiles were guided to their targets by "Missile Track Radars (MTRs)", with course corrections transmitted by radio. The Zeus missile released what would now be called a "kill vehicle" as it approached a target RV at an altitude of 320 to 400 kilometers (220 to 250 miles). The kill vehicle was a maneuverable nuclear warhead with a yield in the megatonne range that detonated when it came near to the incoming RV, or on command from the ground. The Zeus kill vehicle only had to come within a few kilometers of an incoming warhead to "kill" it with its own warhead.
Nike-Zeus was designed to protect large urban areas, not military targets. The initial system, which was to provide cover for a limited number of cities, was projected to consist of 69 batteries with 50 missiles each, at a total cost of $10 billion USD in contemporary dollar values. An expanded system with 120 batteries was expected to cost $15 billion USD.
* Elements of the Nike-Zeus were completed and performed impressive feats in tests, with an initial successful interception of an Atlas ICBM reentry vehicle in July 1962, subsequent interceptions of other Atlas and Titan I reentry vehicles, and a successful interception of a satellite in October 1963. However, the tests clearly showed that Nike-Zeus was not a practical system. The radars were all mechanically directed, and so tracking a large number of separate targets was impractical. The ability to discriminate between decoys and an actual RV was very poor. The Zeus missile could only engage RVs before they entered the atmosphere.
Work on a new system named "Nike-X" was begun in the 1960s in hopes of resolving these difficulties. This involved new fast-scanning, electronically-steered "phased array" radars, including the long-range "Multifunction Array Radar (MAR)" and the short-range "Missile Site Radar (MSR)". Development work was begun by Martin in 1962 for a short-range missile named "Sprint", and in 1965 Douglas was awarded a contract to update the Zeus.
The Zeus was given a third stage and updated subsystems, and renamed "Spartan". Spartan was a solid-fuel missile, 16.8 meters (55 feet) long, with a launch weight of 13,015 kilograms (28,700 pounds) and a range of about 750 kilometers (465 miles). It had a warhead with megatonne yield plus enhanced X-ray production, improving its ability to "fry" RVs moving through space.
The short-range Sprint was a single-stage solid-fuel missile, in the form of a tall narrow cone, with a length of 8.23 meters (27 feet), a launch weight of 3,400 kilograms (7,500 pounds), and a range of 40 kilometers (25 miles). The missile had a fast-burn propellant that gave it an astounding acceleration of 100 gees, and had a skin covered with a silica phenolic matrix ablative materials to withstand intense friction. Sprint's control electronics were radiation-hardened to function through a nuclear explosion, and the communications link had to be able to penetrate the envelope of ionized gases that surrounded the streaking missile in flight. The Sprint was armed with a nuclear warhead in the low kilotonne range. The first Sprint firing took place in 1965, with the first successful intercept of an RV, launched by a Minuteman ICBM, in December 1970. The missile was directed by an MSR, which also commanded the Sprint to detonate its warhead.
* In 1967, faced with Soviet refusal to discuss arms limitations on ABM systems, US President Lyndon Johnson decided to go ahead with deployment of the Sprint-Spartan system, which was given the overall name of "Sentinel". Sentinel was regarded as a limited defensive system, able to defend against attacks from a relatively unsophisticated adversary such as Red China, but not an all-out attack by the Soviet Union.
In 1969, US President Richard Nixon refocused Sentinel to protect US ballistic missile sites from a Soviet pre-emptive strike. The system was renamed "Safeguard". In principle, Safeguard could be expanded to provide a defense from Red Chinese missiles, though again no one seriously considered that it could stop an all-out attack by the USSR.
Technology development continued on a relatively straight path during these changes in mission definition. The first Spartan missile was delivered in 1968, and performed its first successful intercept of a re-entry vehicle, launched by a Minuteman ICBM, in August 1970. A double intercept was performed in January 1971, and later in that year a Spartan successfully intercepted a warhead launched by a Polaris missile along with decoys and other penetration aids.
* The Soviets had not been idle during this time, and indeed may have performed the first successful intercept of an RV in 1961. By the mid-1960s, they were deploying an ABM system that was codenamed "Galosh" by the Americans.
By the 1970s, however, both sides were tiring of the game. The expense was clearly enormous and the effectiveness of the ABM systems highly uncertain. These efforts to build an ABM system were terminated by the 1972 Anti-Ballistic Missile Treaty (ABMT), which was half of the first Strategic Arms Limitation Treaty (SALT I). The ABMT limited each side to two land-based fixed ABM sites, with no more than 100 ABM weapons at each site. A 1974 revision of the treaty reduced the number of sites to one. The US deployed a Safeguard site in 1976 and shut it down a few months later. The US Army scaled back ABM development efforts, focusing on studies of hit-to-kill interceptors.
* Missile defense was revived in the 1980s by US President Ronald Reagan. While Mr. Reagan was campaigning for the presidency in 1979, he was shocked during a visit to NORAD headquarters inside Cheyenne Mountain in Colorado to find out that the US had absolutely no defense against a ballistic missile attack. Mr. Reagan was also morally opposed to the concept of MAD.
After lobbying by missile-defense advocates, in 1983 President Reagan announced that the US would start a major research program to determine if missile defense was practical. The effort was begun with a two-part feasibility study, the first part being the "Defensive Technologies Study / Fletcher Report", and the second part being the "Future Security Strategy Study / Hoffman Report". The two reports concluded that missile defense was in fact possible, though the Hoffman Report suggested that a tactical ballistic missile defense capability be acquired first as a stepping stone to a system to protect America against ICBMs. The reports also detailed the general architecture and funding for a ABM research and development program.
The reports led to the formation of the Strategic Defense Initiative (SDI) or "Star Wars" in January 1984. The research and development effort was conducted by the Strategic Defense Initiative Organization (SDIO). SDI was heavily promoted by Lawrence Livermore National Laboratories (LLNL), particularly by LLNL's "godfather", the late Dr. Edward Teller, and his protege, Dr. Lowell Wood, a highly assertive LLNL staffer.
* With new funding, the US Army was able to finally test the HTK concept the service had been tinkering with since the mid-1970s. In June 1984, after two failed tests, the first apparently successful intercept of a missile with an HTK vehicle was accomplished.
In the test, codenamed "Homing Overlay", a Minuteman missile was launched from Vandenberg Air Force Base on the California coast to toss a dummy RV over the Pacific Ocean. A few minutes later, another Minuteman launched an interceptor from Kwajalein Atoll in the Pacific. Once in space, the interceptor located the RV and fired a kill vehicle at it. The kill vehicle deployed a structure that resembled an umbrella frame studded with weights to improve the probability of a hit, and struck the target. A fourth Homing Overlay test failed. The Homing Overlay kill vehicle was strictly a proof-of-concept demonstrator: it weighed almost a tonne and its infrared seeker took 24 hours to cool down to operating temperature.
While work on HTK weapons proceeded, LLNL also investigated a number of speculative technologies, such as particle beam weapons, high-power conventional lasers, and orbiting X-ray lasers that were "pumped" by nuclear explosions. Although tests were performed on high-power lasers that showed some promise, these schemes proved impractical over the short term. In particular, much was made of X-ray lasers in the early days of SDI, but in practice X-ray lasers never amounted to more than a few tests that provided ambiguous results, producing nothing that remotely resembled a working weapon.
* In 1988, LLNL came up with the less ambitious "Brilliant Pebbles" scheme. Brilliant Pebbles envisioned a large constellation of orbiting HTK interceptors. This was not an entirely new idea, since a similar concept had been investigated in late 1950s and early 1960s under the name "Ballistic Missile Boost Intercept (BAMBI)", which featured HTK interceptors somewhat resembling those tested in Homing Overlay. Although paper studies of BAMBI painted an optimistic vision of its potential, in hindsight it was beyond the leading edge of the technology of the time, Even if it had been realistic, it would have been wildly expensive, and it was cancelled during the Kennedy Administration.
Brilliant Pebbles updated BAMBI by adding the concept of a "distributed network", borrowed from computing. Instead of building a defensive system around high-value centralized assets, the Brilliant Pebbles plan envisioned an orbiting network of thousands, or even tens of thousands, of small, cheap, mostly autonomous battle stations. Each of the Brilliant Pebble battle stations would have an on-board sensor and a processor to allow it to spot the exhaust of an ascending ICBM. The battle station would then fire an HTK interceptor to destroy the missile. Prototype interceptors were developed and tested in lab environments. Government studies proclaimed Brilliant Pebbles workable and affordable, with an ultimate price tag of $25 billion USD for deploying the entire network.
However, the critics had come out of the woodwork with the announcement of SDI, and the debate was bitter even by the standards of ABM politics. Estimates that a Brilliant Pebble battle station would cost no more than $100,000 USD were dismissed with contempt, with critics persuasively replying that a Sidewinder air to air missile, a very mature and comparatively simple weapon system, cost $50,000 USD a unit when purchased in quantity. Sidewinders also didn't need to be put into Earth orbit, an expensive prospect in itself.
The critics also believed that the Brilliant Pebble stations were much too vulnerable to attack and countermeasures, and pointed out that to be truly effective, the Brilliant Pebbles network would have to be activated at all times. Ensuring that a semi-autonomous Brilliant Pebble didn't lose a bit and attack a Soviet cosmonaut launch or even the US space shuttle might prove difficult, and military brass take a dim view of deploying weapons that aren't under well-defined control.
This was only one aspect of the development issues that faced the project, with the critics hammering on the challenge of developing the complicated software needed for Brilliant Pebbles, in particular the difficulty of testing and debugging that software to the level needed to ensure that Brilliant Pebbles would work reliably. In fact, as each Star Wars concept was investigated in more detail, the difficulties mounted and the likelihood of operational deployment faded. British intelligence, obtaining information through "moles" in the Soviet government, found that the leadership of the USSR had been thoroughly panicked by the announcement of SDI, believing from the program and Reagan's noisy anti-Soviet rhetoric that the US was preparing to attack the Soviet Union. By the late 1980s, Soviet intelligence had convinced the leadership that SDI was unworkable.
The collapse of the Soviet Union in the early 1990s finally eliminated most of the rationale for SDI. With the end of the USSR, American defense budgets were cut, and the US military was forced to focus its constrained resources on more immediate requirements. A Brilliant Pebbles network was no longer realistic, and in 1993 the name of SDIO was accordingly changed to the more modest title of the "Ballistic Missile Defense Organization (BMDO)". Brilliant Pebbles was officially dead, but research on missile defense technologies continued on a limited basis. The emphasis was mainly on TMD systems, which became fashionable after the Gulf War in 1991.
