Nuclear Technology: Arms Control in Prespective
Wilson, A. H., Contemporary Review
LAST month George W. Bush and Vladimir Putin provided some much needed welcome news by agreeing to slash more than two thirds of America's and Russia's nuclear weapons. President Bush said that this will 'liquidate the legacy of the Cold War'.
Contemporary International Relations (IR) text books note that, at the height of the 'second Cold War' between 1985 and 1990, the (then) Soviet Union (USSR) and the United States of America (USA) held between them a total of some 21,200 intercontinental, strategic, nuclear weapons, despite a previous series of arms 'limitation' treaties. Numbers subsequently fell as both sides implemented the first stage of the Strategic Arms Reduction Treaty in 1991. In addition, the text books note that the largest nuclear device ever exploded in a test explosion achieved a yield of 50-52 megatons (being the equivalent of 50-52 million tons of 'conventional' explosive -- Tri Nitro Toluene -- T.N.T.). This device was some 4000 times more powerful than either of the two 12.5 kiloton atomic bombs (equivalent to twelve thousand five hundred tons of T.N.T.) which totally destroyed first Hiroshima, then Nagasaki in Japan at the end of the Second World War. These facts raise the following questions:
1. Why were so many weapons required?
2. If one 12,500 kiloton weapon could totally destroy a city, why was such an increase in power subsequently needed?
3. What has actually been given up in the various arms control and limitation treaties?
Contemporary IR literature tackles these questions from various perspectives and interpretations; this article will address them at the more pragmatic levels of the mechanical and operational. In order to do so, it first establishes the histories both of nuclear weapons and their delivery systems, and then makes relevant technical points. Together these will provide answers to the first two questions above. The article then looks at how developments in delivery systems underpinned each of the 'limitation' and 'reduction' treaties to show what has been 'given up'.
Starting then with nuclear weapons, they first appeared in 1945 when a single US aircraft dropped a single atomic bomb on the Japanese city of Hiroshima on 6 August 1945. The city was destroyed. A second bomb was dropped on Nagasaki on the 9th of August, with similar results. Japan surrendered on 14 August.
The USA remained the only atomic power until 1949, when the USSR acquired an atomic capability. Other countries followed in due course, some publicly (UK 1952, France 1960, China 1964), others covertly, despite the 1968 'Non-Proliferation Treaty'. Of these some have subsequently admitted possession of nuclear weapons (South Africa 1991, India and Pakistan 1998), possession by others remain speculative, but may include Israel, North Korea, Brazil. Following the breakup of the USSR into its component states, Ukraine was left with some ex-Soviet weapons, but in return for economic aid is currently working to dismantle its stockpile.
Both the USA and the USSR developed and tested thermonuclear (hydrogen) bombs, the USA in 1953, the USSR in 1954. A hydrogen bomb is triggered by an atomic bomb, and so could only be developed by countries that already had an atomic weapon capability. (Although in theory they might be triggered by other means, no country has apparently yet achieved this.) A hydrogen bomb produces a vastly increased explosive effect, hence the 50+ megaton explosion noted in the introduction. It is however, relatively simple to 'progress' from atomic weapons to hydrogen bombs, and it is likely that the UK, France and China also now have this capability, although not yet tested.
The first single bombs used were dropped on Japan by aircraft, flying at virtually the limit of their range. In the early 'Cold War' possible targets initially were cities. Because the range capability of the available aircraft could be calculated, observed, or found by espionage, in the early days defence planners could calculate possible approach routes from any given airfield to any given target. This enabled defences (predominantly fighter aircraft initially) to be concentrated along likely approach routes. The ability to provide a defence, led attack planners to require more aircraft (to saturate defences), of longer range (to give more flexibility in approach routes), and of greater load carrying ability. Thus more than one weapon could be carried, to allow for the possibility that any single weapon may not work (see below) and for 'multiple targets' to further confuse defences. Thus the first level in the escalation of numbers of atomic weapons was simply to fill the increased capacity of the new aircr aft, not to wreak more damage on the opponent, but to wreak the same level of damage that had been possible before the defences were built up.
Airports then became 'first strike' targets, on the basis that, if they could be 'knocked out' then the opponent's nuclear attack forces would be neutralised. Allies were sought to provide new airports, in new locations to enable more attack routes, and so circumvent defences. Because airports became targets, more airports were needed to maintain attack capacity if the initial airports were 'knocked out'; the new airports then needed more aircraft and more nuclear weapons to stock them. The new enemy airports in turn became targets, needing more aircraft (and weapons) to knock them out. The numbers of nuclear weapons began to spiral upwards.
Intercontinental Ballistic Missiles (ICBMs) were first deployed by the USSR in 1958, and then by the USA in 1959. Their capacity to follow a ballistic trajectory from the launch site, through the stratosphere and then via an almost vertical descent to their target gave them (in theory) the ability to avoid the massed fighter defences, and become virtually unstoppable. Initially however, they were both inherently unreliable and inaccurate. The inaccuracy was due to the limitations of the available navigation and control systems, the unreliability to the complexity of the various systems within the missile, all of which had to work perfectly to achieve an on-target explosion when required. The following paragraphs explain these problems more fully.
The first ICBMs used liquid fuel. In the US models this consisted of a mixture of 'kerosene' (one of the family of 'paraffin' light oils) and hydrogen peroxide, a chemical oxidising agent. If mixed together and stored they formed a highly explosive and unstable combination. Thus, to be used as a fuel, they had to be precisely mixed at the point of ignition in the engines. A minimum of four engines were needed on each missile to enable navigation (up/down, left/right). Kerosene is volatile, flammable and leaks very easily from containers. Hydrogen peroxide is unstable and breaks down in sunlight or if too warm to form oxygen and water. Thus US missiles were prone to fires (from leaking kerosene) and engine failure due to the deterioration of the hydrogen peroxide. Missiles had to be routinely de-fuelled (to remove the deteriorated peroxide), cleaned, to remove the leaking kerosene, and then re-fuelled. Any deteriorated fuel, any malfunction of the mixer mechanisms, or any failure to start up the gyro navigation systems (see below) would prevent launch.
In flight, imprecise mixing of the fuel in any engine caused erratic burning, and uneven pressure from the engines. Control systems could compensate for some permanent pressure imbalance, but fluctuating pressures caused instability in flight and hence inaccuracy or even 'toppling' when the missile would literally fall out of the sky.
Soviet missiles used a different fuel combination, which was even more explosive if mixed and stored. Their oxidising agent (a complex compound of ammonium isocyanate) was less prone to deteriorate, but gave off poisonous fumes and was highly corrosive, so it would gradually eat its way through the missile. (It was a bright pink colour so at least leaks could be seen!) Soviet mixer systems were affected by the corrosive action and control systems were less effective than their US counterparts leading to even greater inaccuracy and more in-flight failures.
Finally, firing mechanisms which trigger atomic (and hence hydrogen) bombs are both precise and delicate. Particles of materials which generate radiation physically repel each other very strongly. In nature they occur widely separated by other non-radioactive materials. To produce the 'chain reaction' that creates a nuclear explosion, sufficient quantities of material must be gathered together, then forced into close proximity by the firing mechanism, and held there long enough for the chain reaction to occur. The Hiroshima and Nagasaki bombs had been handled with extreme care before being dropped specifically to protect this mechanism. Although similar mechanisms have been test-flown on missiles without a nuclear warhead, no nuclear explosion has ever yet been triggered after a long-range missile flight; no one can be absolutely certain that any one mechanism will work.
Thus, to the first question above, 'Why were so many weapons required?' the answer: To provide redundancy against the accumulated problems, so that, despite anticipated failures, sufficient missiles would launch and navigate correctly to saturate defences and thus to have at least one explode on target. Of course, the planners acknowledged that several might get through and explode on the same target. Should that happen, a target would not only be destroyed, but turned to dust.
Missile navigation was a huge problem. Firstly, the potential targets move! Cities and airports are generally regarded as 'static'. In fact the earth rotates, and during the time of flight of a long-range missile they will move a considerable distance. Consider the following. The diameter of the earth at the equator is @25,000 miles. The earth rotates once per 24 hours, so that, relative to a point in space, a point on the equator travels 25,000/24 m.p.h. being 1042 m.p.h. Conversely, a point at the poles has no such movement and hence zero speed. The earth is a flattened sphere so the fall off in speed from the equator is not linear but instead is a function of the sine of the latitude. Hence at 50 North or South the speed of rotation is @ 700 m.p.h.
Strong winds at launch or at delivery of a missile cannot only deviate its course (which can be corrected by on board systems) but may also either slow down or speed up that part of the missile flight time. (And at 700 miles per hour the target is moving at 1/5th of a mile per second, so every second counts). Early navigation systems consisted of three gyroscopes set at right angles to each other, and between them could measure relative movement (left/right, up/down, forward/back, relative to the line of each gyro) but not absolute movement over the surface of the world. Additionally, each gyro suffers from 'creep' and 'precession', inherent technical problems beyond the scope of this article, but which have a greater or lesser effect depending upon the speed of the missile, the direction it flies and the time of flight. These effects could be calculated for specific targets, from specific launch sites. Thus each missile had to be 'programmed' not only for the latitude and longitude of its launch site (so it 'knew' where it was), and of its intended target (so it 'knew' where it was going), but also for specific compensation adjustments to get between the two. And here is the final problem: in the early 1950s through to the late 60s the accurate shape of the world was not known. It was assumed for most practical purposes to be a flattened sphere, but for precise navigation greater accuracy was needed. Latitudes and longitudes were known for each site, but the precise relationship between them was not known. At the necessary ranges of ICBMs errors of up to 1/2 a mile were anticipated. Only with the advent of mapping from space have greater accuracies been achieved (see below).
Navigational inaccuracies were compensated for by developing bigger explosive forces. Indeed without the development of hydrogen bombs it is unlikely that ICBMs could have been deployed when they were, at least not until better navigation became available. A further 'technical' explanation will make this clear.
Nuclear bombs produce blast and radiation effects. The distance from an explosion to which blast damage is sustained is known as the 'blast radius'. Targets are more or less susceptible to blast depending upon their construction, 'normal' offices and houses being deemed 'unprotected'. 'Blast radius', strictly therefore, refers to a distance, the type of property (or target) and the degree of damage found (or anticipated). Thus the Hiroshima weapon had a 'blast radius of 1.5 miles in which total destruction of unprotected buildings occurred'. The effect of any blast (and hence the 'blast radius') may be deflected or constrained by geographic features, such as hills, but in any case decreases in accordance with a 'cube root' law. This means that if a bomb has a 'blast radius' in level countryside of, for example, one mile, then a bomb 27 times more powerful would have a 'blast radius' of three miles (as 3 is the cube root of 27).
The radiation that occurs is more complex, as it occurs in three, named specific types (alpha, beta and gamma), plus heat and light. Although all are important, only heat need be considered for the purposes of this article. In the Hiroshima explosion the heat effect was that any exposed flammable material within the blast radius virtually vaporised; beyond that in the line of sight from the blast, out to five miles flash fires occurred in any exposed flammable material, though intervening hills completely sheltered properties in their shadow; beyond that again in unsheltered properties, out to ten miles, scorching occurred, of greater or lesser severity depending upon range and material. The intensity of heat declines in accordance with a 'square root law'. For example, if a bomb produces any given level of heat radiation effect at a range from the blast centre of 1 mile, then a bomb 27 times more powerful would produce the same heat radiation effect at 5.2 miles (5.2 being the square root of 27).
Thus the 50+ megaton weapon tested by the USSR was some 4000 times more powerful than the Hiroshima and Nagasaki weapons that each had a blast radius of 1.5 miles. The cube root of 4000 is approximately 16. The blast radius of such a weapon (against 'unprotected targets') is therefore 16 x 1.5, being 24 miles. The heat effect radius is 63 (being the square root of 4000) x 5 (being the flash fire radius), giving 316 miles, though hills and mountains would provide shadow zones, and, at this scale, the curvature of the earth itself would provide protection beyond 50 miles.
The blast and heat radius decrease against 'hardened' targets. Such a weapon could be therefore used with accurate delivery against hardened targets, or with moderate inaccuracy against unprotected targets.
The answer then to question 2 above, namely 'why was such an increase in power... needed?' is that it compensated for the inaccuracies of the delivery systems. A 'near miss' would still destroy the target...and of course virtually everything else in the vicinity. Military planners had first decided on likely targets (predominantly cities) and specified the number of weapons to strike these. Increased defences led to increased numbers of weapons and targets and to the need for new delivery systems; these, through their inaccuracy and unreliability required more and bigger weapons....and largely to achieve the same 'on target' damage levels that had been originally required. The natural (and foreseen) consequence of this requirement to hit the target would have been the additional destruction of much else besides.
What then has been given up in the various arms limitation and reduction treaties? Answer -- obsolescence!
Developments in weapons technology each take several years to bring into operation, and are (supposedly) secret from the opposition until they appear in a viable form. Country 'A' will know its own development programme, but not fully that of its opponent, Country 'B'. Negotiators therefore seek concessions from their opponent, hoping they will give up something important, and in return give up technology that they know they are replacing. Thus the first Strategic Arms Limitation Treaty (SALT) (1972) limited the number of launch platforms available to both the USA and USSR. Before however it came into force solid fuel motors had been introduced, increasing reliability, and multiple re-entry vehicles (MRVs) were attached to missiles. Although each missile was still targeted at one target the increase in numbers of warheads expanded the blast radius over that target, and compensated for failure of some of the warheads. Increasing numbers of launch platforms were no longer needed to ensure the same effect on tar get, and could thus be given up.
While SALT 1 was being negotiated satellite based ground mapping and navigation systems were introduced. These first provided precise measurements between launch site and target correcting earlier inherent errors. They then allowed missiles to 'navigate' with greatly enhanced accuracy through 'triangulation' between any three such satellites. Developments in miniaturisation enabled each re-entry vehicle to become powered, and self-guided so giving rise to 'Multiple Independently Targeted Re-entry Vehicles' (MIRVS).
SALT 2 in 1979 attempted to limit the deployment of these, and again to further limit the number and type of launch platforms. The treaty however was never ratified. This was partly because of a change of political leadership in the USA, but also because the expected replacement technology was not yet ready. For the ground mapping satellites noted above had a further function. They accurately mapped the surface of the world, albeit slowly. Eventually they provided a precisely related ground reference system, any part of which could be programmed into a missile computer system. Coupled with a ground reference radar, again built into the missile, each missile could (and can) then achieve previously impossible levels of accuracy simply by comparing the received ground radar signal with the stored map. They literally 'navigate' via hills and mountains, and in their 1990s 'cruise missile' formulation between buildings.
These developments paved the way for the 1991 Strategic Arms Reduction Treaty (START 1). Large numbers of missiles were expensive to maintain, and then, no longer necessary, not because the world was a nicer place, but because greater reliability and accuracy meant a greater effect could be achieved on target with less. Discussions to further reduce the numbers of nuclear weapons were announced in November 2001. A breakthrough came in May, when the USA and Russia agreed on the most radical package of strategic weapons cut, exceeding in scope even the START 1 Treaty. Over the next ten years both sides will reduce their operational stockpiles of nuclear weapons to between 1,700 and 2,200 warheads each.
In the early days of nuclear technology, military planners used the concept of 'throw weight' when discussing the balance between the opposing nuclear arsenals. This was originally the number of missiles multiplied by the explosive force carried. It was subsequently expanded to include the number of warheads. Latterly, the concept of 'hit weight' has developed, being a formulation of the explosive force likely to be delivered on a target. While the publicly sensitive figure of 'throw weight' peaked and is now declining to great acclaim by the 'peace lobbyists', the 'hit weight' has gone up dramatically. Is the world a better place? yes and no. Yes, certainly for the areas of the world around the 'targets', as now they are less likely to suffer from near misses, and arriving missiles are likely to have a reduced 'blast radius'. For the targets themselves, it's probably the same as it was. The old missiles would have been fired in significant numbers, some would have probably got through. If used, the new missi les would be fired in lesser numbers, but have a greater chance of functioning, of navigating accurately and of penetrating defences. Living in a target zone is still not a good idea.
The author is a mature undergraduate student at Nottingham Trent University (NTU) undertaking a degree in International Relations. He has previously been an officer in the Royal Navy for some 15 years and studied at the Royal Naval Colleges of Dartmouth, Manadon and Greenwich, covering technical and operational aspects as well as academic studies of 'Peace and War'. The encouragement and helpful criticism of Mr Chris White of NTU in the preparation of this article is gratefully acknowledged.…
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Publication information: Article title: Nuclear Technology: Arms Control in Prespective. Contributors: Wilson, A. H. - Author. Magazine title: Contemporary Review. Volume: 280. Issue: 1637 Publication date: June 2002. Page number: 354+. © 1999 Contemporary Review Company Ltd. COPYRIGHT 2002 Gale Group.
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