Nuclear weapons will remain of central importance in international affairs for the foreseeable future, even though the size of the main nuclear arsenals will be reduced. Although the military budgets of the major industrialized countries will probably decrease in the coming years, the resources devoted by both the USA and possibly the Commonwealth of Independent States to research into and the development of nuclear weapons and their delivery systems is unlikely to decrease.
Many Russians, particularly the military and defence bureaucrats, believe that the superpower status of Russia depends mainly on the maintenance of a strategic nuclear force and the continual modernization of this force. The USA believes fundamentally that its national security depends on maintaining its position as world leader in military technology, including its leadership in nuclear-weapon technology.
We can, therefore, expect the east west nuclear arms race to go on for a while, in spite of the break-up of the former Soviet Union and detente. Even though the risk of a deliberate global nuclear war may, in the words of Mikhail Gorbachev, have 'practically disappeared', the risk of nuclear war by accident will still be with us.
But perhaps the most serious nuclear threat arises from the spread of nuclear weapons to countries that do not now have them. Most believe that the more nuclear-weapon powers there are the greater the risk of nuclear war. A future war in an unstable region, such as the Middle East, which includes one or more countries with a nuclear force may escalate to a nuclear war involving nuclear-weapon powers outside the region. Such a war may begin with conventional weapons and then escalate to a local nuclear war in which the nuclear weapons of local powers are used. This local nuclear war may then spread, say, to Europe. There is then an obvious link between the proliferation of nuclear forces and world security.
A third nuclear threat is nuclear terrorism, to be dealt with in detail in Chapter 7. There is a considerable risk that sub-national groups,
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including terrorists and even small groups of criminals, will in the future acquire fissile material particularly plutonium and construct a nuclear explosive. Nuclear terrorism has considerable ramifications for world, as well as regional, security. Any use of nuclear explosives could escalate to a nuclear world war.
To understand the extent of these nuclear threats to world security it is useful to begin by briefly considering the nature of nuclear explosives.
The design of a 'first generation' nuclear weapon, such as the bomb that destroyed Nagasaki in 1945, is no longer secret. Amory B. Lovins, for example, in an article in the scientific journal Nature, summarized the bulk of the necessary physics data showing that a component nuclear physicist can find the relevant information in the open literature (Lovins 1980).
The basic nuclear weapon is the fission weapon, or A-bomb (A for atomic) as it was first called. A fission chain reaction is used to produce a very large amount of energy in a very short time roughly a millionth of a second and therefore a very powerful explosion.
The fission occurs in an isotope of a heavy element either uranium or plutonium. Specifically, the fission bombs built so far have used the isotopes uranium-235 or plutonium-239 as the fissile material. A fission occurs when a neutron (one of nature's elementary particles) enters the nucleus of an atom of one of these materials, which then breaks up or 'fissions'.
When a fission occurs a large amount of energy is released; the original nucleus is split into two radioactive nuclei, the fission products; and two or three neutrons are released. These neutrons can be used to produce a self-sustaining chain reaction. A chain reaction will take place if at least one of the neutrons released in each fission event goes on to produce the fission of another uranium or plutonium nucleus.
There exists a critical mass for uranium-235 and plutonium-239 the smallest amount of the material in which a self-sustaining chain reaction is just sustained. The critical mass is that from which just as many neutrons escape per unit time as are released by fission, If this mass of material is increased, the number of neutrons produced by fission builds up, and considerably more fissions occur in each successive
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generation. A 'super-critical' mass is created and a nuclear explosion takes place.
The critical mass depends on a number of factors. First, the nuclear properties of the material used for the fission, whether it is uranium235 or plutonium-239. Second, the shape of the material a sphere is the optimum shape because for a given mass the surface area is minimized which, in turn, minimizes the number of neutrons escaping through the surface per unit time and thereby lost to the fission process. Third, the density of the material (the higher the density, the shorter the average distance travelled by a neutron before causing another fission and therefore the smaller the critical mass). Fourth, the purity of the material (if materials other than the one used for fission are present, some neutrons may be captured by their nuclei instead of causing fission). Fifth, the physical surrounding of the material used for fission (if the material is surrounded by a medium like beryllium, which reflects neutrons back into the material, some of the reflected neutrons may be used for fission which would otherwise have been lost, thus reducing the critical mass).
The critical mass of, for example, a sphere of pure plutonium-239 metal in its densest form (alpha-phase, density 19.8 grams per cubic centimetre) is about 10 kilograms. The radius of the sphere is about 5 centimetres. If the plutonium sphere is surrounded by a natural uranium neutron reflector, about 10 centimetres thick, the critical mass is reduced to about 4.4 kilograms, a sphere of a radius of about 3.6 centimetres. A 32-centimetre-thick beryllium reflector reduces the critical mass to about 2.5 kilograms, a sphere of a radius of 3.1 centimetres.
Using a cunning technique called implosion, in which conventional chemical explosives are used to produce a shock wave which uniformly compresses the plutonium sphere, the volume of the plutonium sphere can be slightly reduced and its density increased. If the original mass of the plutonium is just less than critical, it will, after compression, become super-critical and a nuclear explosion will take place.
Using implosion, a nuclear explosion could, with a good modern design including an effective, but practicable, reflector, be achieved with about 2.5 kilograms of plutonium. The trick is to obtain very uniform compression of the sphere.
In an implosion design, the plutonium would be surrounded by a spherical shell, made from a heavy metal, like natural uranium, which acts as the tamper. The conventional explosive used to compress the plutonium sphere is placed outside the tamper.
The tamper has two functions. First, because the tamper is made of heavy metal, its inertia helps hold together the plutonium during the explosion to prevent the premature disintegration of the fissioning material and thereby obtain a greater efficiency. Second, the tamper
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converts the divergent detonation wave into a convergent shock wave to compress the plutonium sphere.
The plutonium may also be surrounded by another spherical shell, situated between the plutonium and the tamper. Its purpose is to reflect back into the plutonium some of the neutrons which escaped through the surface of the plutonium core to minimize the mass of plutonium needed. Beryllium is a good neutron-reflecting material.
In a nuclear explosion exceedingly high temperatures (hundreds of millions of degrees centigrade) and exceedingly high pressures (millions of atmospheres) build up very rapidly (in about half a millionth of a second, the time taken for about fifty-five generations of fission). The mass of the material used for fission expands at very high speeds initially at a speed of about 1,000 kilometres a second. In much less than a millionth of a second the size and density of the material have changed so that it becomes less than critical and the chain reaction stops. The designer of a nuclear weapon aims at keeping the fissionable material together, against its tendency to fly apart, long enough to produce an explosion powerful enough for his purpose.
The complete fission of 1 kilogram of plutonium-239 would produce an explosion equivalent to that of 18,000 tons (18 kilotons, or kt) of TNT. Modern fission bombs have efficiencies approaching 40 per cent, giving yields of 7 kilotons or so per kilogram of plutonium present. It is this high yield-to-weight ratio that makes nuclear weapons so special.
A major problem in designing implosion fission weapons for maximum efficiency is to prevent the chain reaction from being started before the maximum achievable super-criticality is reached an eventuality called pre-detonation. Pre-detonation is most likely to be caused by a neutron from spontaneous fission fission that occurs naturally without the stimulation of an external neutron in the material used for fission. In 6 kilograms of plutonium-239, for example, the average time between spontaneous fissions is only about three-millionths of a second. To prevent pre-detonation and loss of efficiency, the assembly of a plutonium bomb must be very rapid. Implosion is necessary.
The timing of the detonations of the chemical explosives to produce the shock wave to compress the plutonium sphere is crucial for the efficient operation of an implosion atomic bomb. Microsecond (a millionth of a second) precision is essential. The shapes of the explosive lenses are rather complex and must be carefully calculated. The high explosive must be chemically extremely pure and of constant constituency throughout its volume.
The Nagasaki bomb used high-explosive charges of Composition B, a mixture of cyclotrimethylene-trinitramine (RDX) and trinitrotoluene (TNT), a fast-burning explosive more effective than TNT on its own.
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More modern implosion charges use diaminotrinitrobenzene (DATB) or triaminotrinitrobenzine (TATB). The amount of high explosive used in a fission weapon has decreased considerably since 1945 from about 500 kilograms to about 15 kilograms or less (Hansen 1988).
Normally, the more explosive charges there are, the more perfect is the spherical symmetry of the shock wave. Forty or so detonations would be typical. Getting the timing of the detonation sequence milli-microsecond (a thousandth of a millionth of a second) precision is essential and the chemistry and geometrical shapes of the explosive lenses right is the most difficult problem in designing an efficient implosion-type nuclear fission weapon.
A typical circuit to fire the detonators uses Krytrons to generate short high-current pulses with amplitudes of about 4,000 volts and rise-and-fall times of a few milli-microseconds. The Krytron is a cold-cathode gas-filled switch using an are discharge to conduct high peak currents for short times.
The energy in the current pulse used to fire the detonators in a nuclear weapon is normally produced by charged capacitors. Because the rate of change of current is very large, the capacitors must have a very low self-inductance. This is why the manufacture of such capacitors, rugged enough for military use, requires special attention.
For maximum efficiency, the chain reaction in an atomic bomb must be initiated at precisely the right moment the moment of maximum super-criticality. The initiation is achieved by a pulse of neutrons. In today's nuclear weapons, the neutron pulse is produced by a small electronic device called a neutron 'gun'. The problem of getting the timing of the shaped-charge detonations and the injection of the neutron pulse right is mainly theoretical, in calculating the timing sequence for optimum efficiency. The practical problems of manufacturing the electronic components and building the circuits to produce the calculated sequence of triggering pulses are much less difficult.
The alternative to plutonium-239 as the fissile material in a nuclear weapon is uranium-235, although some of the most advanced types of nuclear weapon contain both materials arranged in thin concentric shells, rather than a solid sphere. Plutonium undergoes fission faster than uranium, and placing it inside a shell of enriched uranium makes more efficient use of its fission neutrons. In this way a greater explosive power can be achieved for a given mass of fissile material.
The amount of highly enriched uranium in, for example, the American nuclear arsenal is about 500 tons, five times the amount of plutonium in the arsenal. But the more modern nuclear weapons tend to use relatively more plutonium than earlier models.
Natural uranium contains the isotopes uranium-235 and uranium-238. As dug out of the ground, uranium is mostly uranium-238 out
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of a thousand atoms of natural uranium, only seven are uranium-235. The problem with uranium-238 is that a neutron can only cause fission in it if its velocity exceeds a certain value. But too few of the neutrons available from the fission process have more than this critical velocity to sustain a chain reaction, A chain reaction is, therefore, not possible using uranium-238. But a nucleus of uranium-235, like a nucleus of plutonium-239, will undergo fission when any neutron, even one moving very slowly, collides with it. And so a chain reaction is possible using uranium-235.
To obtain uranium that can be used to construct a nuclear weapon, the amount of uranium-235 in natural uranium is increased by a process called enrichment. The proportion of uranium-235 is normally enriched from its natural value of 0.7 per cent to more than 40 per cent, preferably to over 95 per cent. The greater the amount of uranium-235 in the uranium, the less will be the critical mass.
In uranium-235, the average time between spontaneous fissions is much greater than it is in plutonium-239, and the so-called 'gun' method can be used to assemble a critical mass of uranium-235 in a nuclear weapon. In the Hiroshima bomb, for example, a less than critical mass of uranium-235 was fired down a 'cannon barrel' (the barrel from a naval gun) into another less than critical mass of uranium-235 placed in front of the 'muzzle'. When the two masses came together they formed a super-critical mass which exploded.
About 60 kilograms of uranium-235 were used in the Hiroshima bomb. About 700 grams were fissioned. The average time between spontaneous fissions was about one-fiftieth of a second quite adequate for the gun technique. The yield of the Hiroshima bomb was about 12.5 kt.
A fission weapon using uranium-235 can, however, also be made using the implosion technique. If surrounded by a reflector made from natural uranium 15 centimetres thick, 100 per cent pure uranium-235 has a critical mass of 15 kilograms (compared with 4.4 kilograms for plutonium-239). With uranium enriched to 40 per cent uranium-235, the critical mass increases to 75 kilograms; with 20 per cent uranium235, it is 250 kilograms. High concentrations of uranium-235 are, therefore, very desirable if the material is to be used to produce nuclear weapons.
Designs based on the Hiroshima and Nagasaki bombs are likely to be used by countries beginning a nuclear-weapon programme. But even the first weapons now produced by a country would probably be more sophisticated than these early, primitive weapons. The Nagasaki bomb, for example, was about 3 metres long, 1.5 metres wide, and weighed about 4.5 tons. A modern fission weapon, even the first
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produced in a nuclear-weapon programme, should weigh no more than a few hundred kilograms.
The difficulty of designing and fabricating a nuclear weapon from earlier plutonium-239 or uranium-235 is often exaggerated. A competent group of nuclear physicists, and electronics and explosives engineers, given adequate resources and access to the literature, would have little difficulty in designing and constructing such a weapon from scratch. They would not need access to any classified literature.
Although very large explosions equivalent to the explosion of 100 or 200 kt of TNT can be obtained from nuclear weapons based on pure fission, there is a limit to the explosive power that can be obtained from an operational one. The maximum explosive power of a militarily usable fission weapon is 50 kt. Higher explosive power than can be achieved by a pure fission nuclear device can be obtained by 'boosting'.
In a boosted weapon, some fusion material is placed at the centre of the plutonium sphere in a fission weapon. When the fission weapon explodes, nuclear fusion takes place. The neutrons produced during the fusion process produce additional fissions in the plutonium in the weapon, increasing its efficiency. The fusion is used mainly as an additional source of neutrons to help the fission process, rather than as a direct source of energy.
Boosted weapons are essentially sophisticated fission weapons. Using boosting, a much higher explosive power is obtained from a given amount of plutonium. Militarily usable boosted weapons have explosive powers of 500 kt, i.e., about ten times the power of non-boosted operational weapons. The yields of the most powerful boosted weapons are equal to those of low-yield thermonuclear weapons.
In a typical boosted weapon a mixture of deuterium and tritium gases (heavy isotopes of hydrogen) is used as the fusion material. A pressurized deuterium tritium mixture is injected from a reservoir, placed outside the fission-weapon core, into a space at the centre of the plutonium sphere after the fission process has begun. Because the centre of the sphere is needed for the fusion mixture, a boosted weapon must be initiated by an external neutron gun.
The pressure in the boosting system is typically about 20 million N per m³, and about 5 grams of the deuterium tritium gas mixture are injected into the centre of the plutonium sphere. The timing of the injection is crucial for maximum efficiency.
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If explosions in the range of 1,000 kt, or 1 megaton (mt), are required, extra energy must be obtained from fusion. The fusion process is the opposite of fission. In fission, heavy nuclei are split into lighter ones. In fusion, light nuclei are formed (i.e., fused) into heavier nuclei.
In nuclear weapons, the heavier isotopes of hydrogen deuterium and tritium are fused to form helium. The fusion process, like the fission process, produces energy and is accompanied by the emission of neutrons. There is no critical mass for the fusion process; and, therefore, in theory, there is no limit to the explosive yield of fusion weapons or H-bombs (H for hydrogen) as they are often called.
Fission is relatively easy to initiate one neutron will start a chain reaction going in a critical mass of fissionable material, such as plutonium-239 or uranium-235. But fusion is possible only if the nuclei to be fused together are given a high enough energy to overcome the repulsive electric force between them due to their positive electric charges. In H-bombs, this energy is provided by raising the temperature of the fusion material. Because H-bombs depend on heat they are also called thermonuclear weapons.
In a typical thermonuclear weapon, deuterium and tritium are fused together. But to get this fusion reaction to work the deuterium tritium mixture must be raised to a temperature of a hundred million degrees Centigrade or so. This can be provided only by a pure fission nuclear weapon (atomic bomb) in which such a temperature occurs at the moment of the explosion. An H-bomb, therefore, consists of a fission stage, which is an atomic bomb acting as a trigger, and a fusion stage, in which hydrogen isotopes (tritium and deuterium) are fused by the heat produced by the trigger.
Normally, the fusion material is in the form of a cylinder. The cylinder is made out of lithium deuteride. When neutrons from the fission explosion bombard lithium nuclei in the lithium deuteride, tritium nuclei are produced. The tritium nuclei fuse with deuterium nuclei in the lithium deuteride to produce fusion energy.
It is very advantageous to use lithium deuteride as the fusion material because it is a solid at normal temperatures whereas tritium and deuterium, the fusion materials used in boosted weapons, are gases at normal temperatures. It is, of course, much easier to construct nuclear weapons from solid materials than from gases.
The energy released from such a thermonuclear weapon comes from the fission trigger and the fusion material. But, if the fusion device is surrounded by a shell of uranium metal, the high-energy neutrons produced in the fusion process will cause additional fissions in the uranium shell. This technique can be used to enhance considerably
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the explosive power of a thermonuclear weapon. Such a weapon is called a fission fusion fission device. On average, about half of the yield from a typical thermonuclear weapon will come from fission and the other half from fusion.
H-bombs are much more difficult to design than fission nuclear weapons, The problem is to prevent the fission trigger from blowing the whole weapon apart before enough fusion material has been ignited to give the required explosive yield. Sufficient energy has to be delivered to the fusion material to start the thermonuclear reaction in a time much shorter than the time it takes for the explosion to occur. This means that the energy must be delivered with a speed approaching the speed of light.
Rotblat has described the technique used:
The solution to the problem lies in the fact that at the very high temperature of the fission trigger most of the energy is emitted in the form of X-rays. These X-rays, travelling with the speed of light, radiate out from the centre and on reaching the tamper (surrounding the fusion material) are absorbed in it and then immediately re-emitted in the form of softer X-rays. By an appropriate configuration of the trigger and the fusion material it is possible to ensure that the X-rays reach the latter almost instantaneously. If the fusion material is sub-divided into small portions, each surrounded with a thin absorber made of a heavy metal, the bulk of the fusion material will simultaneously receive enough energy to start the thermonuclear reaction before the explosion disperses the whole assembly.
(Rotblat 1981)
Although essentially weightless, X-rays can exert great pressure. In an H-bomb, the pressure (several million pounds per square inch) is exerted uniformly on the fusion material and long enough for the fusion process to work before the material is blown apart. Because the radiation travels at the speed of light, it arrives at the fusion material about a millionth of a second before the much slower moving shock wave from the trigger explosion. When the shock wave arrives, and blows the assembly apart, the fusion explosion has occurred.
The fusion process in a thermonuclear weapon is initiated by a so-called 'sparkplug', a thin sub-critical cylindrical rod of weapons-grade uranium-235 or plutonium-239 placed at the centre of the cylinder of fusion fuel (Hansen 1988). When the fusion fuel has been compressed, by radiation from the explosion of the fission trigger, neutrons from the trigger penetrate into the sparkplug. The sparkplug begins to fission; and the fission reaction, in the middle of the highly compressed fusion fuel, initiates the main fusion explosion.
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Very large explosive yields have been obtained with thermonuclear weapons. Typically, each stage of a thermonuclear explosion explodes with a power roughly ten times that of the preceding stage. If the fission trigger explodes with an explosive yield of a few tens of kilo-tons, the first fusion stage would explode with a yield of several hundred kilotons, and the second fusion stage, if present, would yield several megatons. For example, the Soviet Union exploded an H-bomb in 1962 with a yield equal to that of 58 million tons of TNT equivalent to about 3,000 Nagasaki bombs. This was probably a three-stage device, with a fission trigger which exploded with a power of several hundred kilotons, and two fusion stages. Even higher yields could be obtained.
The target assigned to a nuclear warhead is determined by the combination of its explosive yield and the accuracy with which it can be delivered. Recent technological advances have considerably increased the accuracy of the delivery of nuclear warheads. Modern American nuclear weapons illustrate the accuracies now possible.
The accuracy of a nuclear warhead is normally measured by its circular error probability, or CEP, defined as the radius of the circle centred on the target within which a half of a large number of warheads of the same type fired at the target will fall. The Americans have continually improved the guidance system of their intercontinental ballistic missiles so that the CEP has been considerably reduced. For example, the CEP of a Minuteman II warhead, first deployed in 1966, is about 370 metres; the new American intercontinental ballistic missile the MX has a CEP of about 100 metres. The latest Russian intercontinental ballistic missile, the SS-25 Sickle, has a CEP of about 200 metres (International Institute for Strategic Studies 1991).
Similar developments are taking place in submarine-launched ballistic missiles. The new American Trident D-5 submarine-launched ballistic missile, for example, has a CEP of about 120 metres whereas the CEP of the older Trident C-4 is 450 metres, Warheads with CEPs of about 100 metres or less are war-fighting weapons.
Trident-2 and MX warheads may eventually be fitted with terminal guidance, in which a laser or radar set in the nose of the warhead scans the ground around the target as the warhead travels towards it through the earth's atmosphere. The laser or radar locks on to a distinctive feature in the area, such as a tall building or hill, and guides the warhead with great accuracy on to its target. With terminal guidance, Trident-2 and MX warheads will have CEPs of 40 metres or so.
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Now that the Cold War is over, the Iron Curtain has gone, Germany is reunited, and the Soviet military threat has evaporated, what nuclear policies are being evolved to suit the new international order? The evolution of these policies may be determined more by the technological advances incorporated into nuclear weapons than by foreign-policy considerations.
Over the years, the nuclear arms race has acquired a technological momentum which has caused, and is causing, changes in Russian and American nuclear strategies. It seems likely that the authorities in Moscow will continue to control the former Soviet nuclear forces and determine nuclear strategies.
The formation of large teams of nuclear scientists and technologists to operate military nuclear reactors and other nuclear-weapon facilities, and to design, develop, test and produce nuclear weapons eventually results in the emergence of powerful lobbies of professionals, who want to design and produce increasingly sophisticated nuclear weapons just to convince themselves that they can do so and for the satisfaction of it.
These lobbies become part of the political process, which together with the other elements of the defence establishment generate inputs into the decision-making process, in favour of the continual modernization of nuclear weapons and their supporting technologies; inputs so strong as to be very difficult for political leaders to overcome. Nuclear strategies are then mainly determined not by the requirements of rational foreign-policy considerations but by the technological characteristics of nuclear weapons and their supporting technologies. (This argument applies to the small nuclear powers including, for example, Israel as well as to the two big ones.)
The American administration has made it clear that it intends to continue to modernize its nuclear weapons and their supporting technologies, even though there is no obvious enemy at which to aim a sophisticated nuclear force. Research and development in anti-submar-ine warfare and anti-ballistic missile systems will continue. These developments will have consequences for nuclear policies.
The targets at which nuclear weapons are aimed, no matter which country owns them, are generally determined by the accuracy with which the weapons can be delivered. Inaccurate nuclear weapons are seen to be useful for nuclear deterrence, by threatening an enemy with unacceptable death and destruction; accurate nuclear weapons
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are seen as more useful for fighting a nuclear war than for deterring one by assured destruction.
The policy of nuclear deterrence by assured destruction rests on four tenets. First, the nuclear forces of the deterrer must be fashioned exclusively for retaliation in response to an attack by the other side's weapons of mass destruction or in response to a threat of annihilation. Second, the nuclear forces including their command and control systems must be capable of prompt action. Third, the threat on which the deterrence rests must be the killing of a large fraction of the enemy population and the destruction of much of its economy. Fourth, the enemy must be aware of the threat in time to deter it from making the actions that will provoke the massive retaliation.
The commonly held view that the very destructiveness of nuclear weapons precludes the outbreak of nuclear war is false. Even if 'rational' behaviour is assumed, nuclear war is unlikely to occur only if it is believed that neither side can win. If one power perceives a chance of winning, then there is a risk that it will decide to strike while it has the advantage. Moreover, in a serious crisis, the side which perceives that it is at a disadvantage may, if it believes that the use of weapons of mass destruction is very likely, attack first, and perhaps prematurely, in the hope of reducing the damage it thinks it is almost bound to suffer.
A relatively small number of nuclear weapons are needed for assured destruction. All that is needed is the number of nuclear weapons required to target the enemy's significant cities. Even in both the USA and the Commonwealth of Independent States, for example, there are at most 200 cities with populations greater than about 100,000 people. If the relations between states, even hostile ones, are being determined rationally, a very small number of nuclear weapons which can be reliably delivered on to their targets are enough for a minimum nuclear deterrent. For the USA and the former Soviet Union, this number is certainly much less than a hundred.
A paradox of the nuclear age is that nuclear deterrence based on mutual assured destruction (MAD), if it works at all, only does so with inaccurate nuclear weapons. As more accurate nuclear weapons are deployed the enemy may assume that your nuclear weapons are targeted on his nuclear forces and not on his cities. The cities then cease to be effective hostages. In other words, accurate nuclear weapons weaken and eventually kill nuclear deterrence based on assured destruction.
With nuclear weapons accurate enough to destroy even very hardened military targets, nuclear war-fighting based on the destruction of hostile military forces becomes the preferred policy. Accurate nuclear weapons change nuclear strategy from nuclear deterrence to nuclear
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war-fighting, whether or not the political leadership wants to make the change.
Unless military nuclear technology is brought under control, a nuclear war-fighting strategy will give way to a nuclear war-winning one, which is seen to give a nuclear strategic superiority, A range of military technologies is being developed that will strengthen military and political perceptions about the possibility of fighting and winning a nuclear war. The most important of these technologies are those related to anti-submarine warfare and anti-ballistic missile systems.
If one side could severely limit the damage that the other side's strategic nuclear submarines could create in a retaliatory strike, and it believed it could destroy, by anti-ballistic missiles, the enemy missile warheads which survived a surprise attack, then the temptation to make an all-out first strike might become strong.
Developments in anti-submarine warfare are particularly disturbing. Now that land-based ballistic missiles are vulnerable to a first (preemptive) nuclear strike by hostile land-based missiles, nuclear deterrence depends mainly on the continuing invulnerability of nuclear strategic submarines. If strategic nuclear submarines do become vulnerable, a first nuclear strike may be seen as desirable and even essential to prevent the other side from itself acquiring a first-strike capability. Moreover, moves to nuclear war-fighting and war-winning strategies considerably increase the risk of nuclear war by accident.
All the declared nuclear-weapon powers are improving the quality of the nuclear weapons an activity usually referred to as 'modernization'. And Israel seems to be following the same path. Political leaders seem unable to control the momentum of nuclear-weapon technology. New nuclear policies are adopted to justify the deployment of new nuclear weapons.
The move from nuclear deterrence by mutual assured destruction (MAD) to nuclear war-fighting is virtually certain if large numbers of accurate nuclear weapons are deployed. These are, in military jargon, 'counter-force' rather than 'counter-city'. A nuclear war-fighting policy can justify the deployment of a large number of nuclear weapons.
'War-fighting deterrence', as the present policy has been called, will give way to war-winning strategies, in which it is argued that victory is possible in a nuclear war. A range of military technologies is being developed that will strengthen military and political perceptions about the possibility of fighting and winning a nuclear war. The most important of these technologies are those related to anti-submarine warfare
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(ASW), anti-ballistic missile (ABM) systems, and anti-satellite warfare systems.
If one side could severely limit the damage that the other side's strategic nuclear submarines could create in a retaliatory strike, and it believed it could destroy, by anti-ballistic missiles, the enemy missile warheads which survived a surprise attack, then the temptation to make an all-out first strike might become virtually irresistible, particularly during a period of international crisis. Hence the importance of developments in ASW and in ABM systems.
Now that land-based ballistic missiles are vulnerable to a first (preemptive) nuclear strike by hostile land-based missiles, east west nuclear deterrence depends mainly on the continuing invulnerability of strategic nuclear submarines. If strategic nuclear submarines become vulnerable, a first nuclear strike may be seen as desirable and even essential to prevent the enemy from himself acquiring a first-strike capability.
ASW systems are designed to detect, identify and destroy enemy submarines. Modern submarines are very effective if they get within range of enemy warships. The best way of dealing with them is to engage them before they get within range.
To attack enemy submarines at long range, the American navy, for example, relies mainly on long-range maritime patrol aircraft, particularly the P-3 Orion, and on its own attack submarines. The Long Range ASW Aircraft (LRAACA), a land-based four-engine ASW patrol aircraft, a derivative of the P-3 design, is under development to supplement the P-3.
Any enemy submarines that evade detection at long range will be attacked by the surface warships. An American carrier battle group, for example, will use formations of surface ships carrying passive and active sonar systems to detect hostile submarines and torpedo-armed helicopters to attack them.
In ASW, detection is the critical element. Detection methods are being improved by increasing the sensitivity of detectors, improving the integration between various sensing systems, and improving the computer processing of the data collected by sensors.
The main categories of ASW sensors are electronic, based on radar, infra-red or lasers; optical; acoustic, particularly active and passive sonar; and magnetic, particularly the Magnetic Anomaly Detector (MAD), in which the disturbance to the earth's magnetic field caused by the presence of the submarine is measured. Sensors may be carried
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on aircraft and ships, deployed on satellites in space, or fixed to the bottom of the ocean.
Sonar devices rely on sound to detect objects in the ocean. Although light doesn't travel well through water, sound does. During the Second World War, the development of underwater acoustic technology accelerated rapidly, spurred on by the needs of anti-submarine warfare. The technology led to the development of Sound Navigation And Ranging or sonar.
In an active sonar device, a pulse of sound is transmitted from the sonar transmitter. If, in its passage through the ocean, it hits an object like a submarine, some of the sound will be reflected back and some of the 'echo' will be collected by the sonar receiver. The time taken for the sound to travel to the object a submarine, for example and back to the sonar receiver is measured. From this time and the known velocity of sound, the distance to the submarine is calculated, If a number of sonars are used, the directions the echoes come from give the position of the submarine. A typical sonar system, which may, for example, be towed behind a ship, is an array of acoustic transducers. A transducer acts as both a transmitter and a receiver, emitting short pulses (bursts) of sound waves at regular intervals and listening for echoes between the pulses.
The ASW activities of the USA are global and continuous, involving a total system of great technological complexity, including the use of a network of foreign bases. In American ASW activities, fixed undersea surveillance systems, based on arrays of hydrophones and monitoring a large area of ocean, play a key role. (A hydrophone is an electro-acoustic transducer used to detect sounds transmitted through water.) Mobile and air-dropped systems supplement the fixed sea-bottom sensors.
The US navy operates special ships, called Tagos Ocean Surveillance Ships, which are platforms for the Surveillance Tower-Array Sensor System (SURTASS), with long-range surveillance capabilities to extend ASW coverage to those parts of the world's oceans not covered by the fixed ocean-bottom systems. P-3 Orion aircraft, which operate from a number of bases throughout the world, are provided with information about the general location of Russian submarines. The aircraft then use large numbers of sonobuoys, and sophisticated computers to process the data and pinpoint the submarines. A sonobuoy is dropped and floats on the sea to pick up noise from any submarine and transmit a bearing of it to the aircraft. Three such bearings enable the aircraft to fix the position of the submarine.
ASW systems are also carried on surface warships, particularly cruisers and destroyers. American warships, for example, carry the Tactical Towed Array Sonar (TACTAS) system in which a network of sono-
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buoys is towed behind a ship to detect any submarine in the vicinity. ASW helicopters are carried on the ships and used to attack any submarines detected with torpedoes or depth charges. An example of such a helicopter is the American SH-60B Seahawk Light Airborne Multipurpose System (LAMPS) Mk III, a computer-integrated ship helicopter system which deploys sonobuoys and processes information from them. It is also a platform for radar and electronic warfare support measures. The SH-60F is a derivation of the SH-60B, providing quick-reaction inner-zone protection for a carrier battle group using an improved tethered sonar.
The most effective weapon system for detecting and attacking enemy submarines is another submarine the hunter-killer submarine. A hunter-killer is usually a nuclear-powered submarine equipped with ASW sensors, underwater communications equipment, computers for data analysis, and computers to fire and control ASW weapons, particularly torpedoes and ASW missiles. Once detected, enemy submarines can be destroyed with torpedoes, missiles or depth charges. The Americans are now developing two new long-range ASW missiles that will be able to attack enemy submarines at distances beyond torpedo range.
The Pentagon is planning the Phase One Strategic Defense System as the initial deployment of an ABM system. It argues that Phase One known as Global Protection Against Limited Strikes (GPALS) is technically achievable and could be deployed by the year 2000. It is a layered defensive system consisting of ground- and space-based interceptors, their support systems and a command centre.
There is now no pretence that an ABM system could protect the whole of the USA against a full-scale Russian strategic attack. The rationale for GPALS is to defend against an accidental attack involving one or a small number of missiles, a limited attack launched by a mad military commander, and a future attack by a Third World country involving a few long-range missiles. The system is supposed to defend against a ballistic-missile attack of up to 200 nuclear warheads.
In the space-based layer, Brilliant Pebbles missiles, now under development, are designed to destroy enemy ICBMs in their boost phase, before they release their warheads and decoys. The ground-based interceptor missile, the High-altitude Endoatmospheric Defense Interceptor (HEDI), will attack enemy warheads which survive the Brilliant Pebbles shortly after they re-enter the earth's atmosphere. HEDI is in an advanced stage of development.
The Boost Surveillance and Tracking System (BSTS) will detect
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enemy missile-launches, acquire and track the boosters, and assess the number of missiles destroyed. The Space Surveillance and Tracking System (SSTS) will acquire and track post-boost vehicles and re-entry vehicles, satellites and anti-satellite weapons, and assess the destruction of enemy warheads. The Airborne Optical Adjunct (AOA), an infra-red radiation sensor system carried on a Boeing-767 aircraft to track warheads in their mid-course and terminal stages, is in an advanced stage of development.
The Ground-based Surveillance and Tracking System (GSTS) will discriminate between re-entry warheads and decoys, track re-entry vehicles and decoys, and assess the destruction of enemy warheads. GSTS will probably be complemented by a railway-deployed Ground-Based Radar (GBR) system. The command centre will link all these systems and control the space battle.
Each Brilliant Pebble is a self-contained system, consisting of a lightweight missile including integrated sensors, guidance and control. Current plans for GPALS involve the deployment of Brilliant Pebbles, encased in protective bullet-shaped cases, on a thousand or so satellites orbiting at altitudes of about 960 kilometres. Each missile is about 1 metre long, 0.3 metres wide, and weighs about 45 kilograms; each will be provided with a solar cell to keep its systems charged. In addition, the deployment of between 750 and 1,000 HEDI anti-ballistic missiles is called for.
When the satellites are commanded, by coded signal, to release the Brilliant Pebbles, the protective cases open and the missiles are released. Each Brilliant Pebble carries sensors to detect ultra-violet and infra-red radiation. These can pick up the radiations from the exhaust flames of the rockets of enemy ballistic missiles as they are launched from their silos. The Brilliant Pebble's computer would then calculate the speed and trajectory of the enemy missile and programme itself on to an interception course. The Pebble's rocket motor would fire and direct it on a collision course with the missile. The Pebble would depend on the kinetic energy of impact to destroy its target missile.
If the current thaw in international relations continues, funding applications for GPALS, including Brilliant Pebbles, will have a rough ride in the US Congress. But research and development of more advanced Star Wars concepts, including high-powered free-electron and chemical lasers and neutral particle beam weapons, continues in the hope of a deployment option in several years' time.
The perceived success of the US Patriot surface-to-air missile against Iraqi SCUD surface-to-surface missile attacks against Israel and Saudi Arabia gave a considerable boost to theatre anti-ballistic missiles to defend against attacks by tactical ballistic missiles. The plan is to deploy anti-tactical ballistic missiles with American forces stationed
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around the world. Current American research and development pro-grammes include improvements for the Patriot system; the Extended Range Interceptor (ERINT); the Arrow missile, a joint American Israeli programme to develop 'a high-altitude interceptor; and the Theater High Altitude Area Defence (THAAD) system.
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