IITHE REAL SECRET OF THE HYDROGEN BOMB
Can the hydrogen bomb actually be made? If so, how soon? How much will it cost in money and vital materials? Above all, will it, if made, add enough to our security to make the effort worth while?
As was pointed out by Prof. Robert F. Bacher of the California Institute of Technology, one of the chief architects of the wartime atomic bomb and the first scientific member of the Atomic Energy Commission, “since the President has directed the AEC to continue with the development [‘of the so-called hydrogen, or super bomb’] we can assume that this development is regarded as both possible and feasible.” Many eminent physicists believe that it can be made, and the use by the President of the word “continue” suggests that this belief is based on more than theory. No less an authority than Albert Einstein has stated publicly that he regards the H-bomb as “a probably attainable goal.”
On the other hand, there are scientists of high eminence, such as Dr. Robert A. Millikan, our oldest living Nobel-Prize-winner in physics, who doubt whether the H-bomb can be made at all. And there are also those who express the viewthat, while it probably could be made, it would not offer advantages great enough, if any, to justify the cost in vital strategic materials necessary for our security.
Fortunately, facts mostly buried in technical literature make it possible for us to go behind the scientific curtain and look intimately at the reasons for these differences in opinion. More important still, these facts not only provide us with a clearer picture of the nature of the problem but also enable us to make some reasonable deductions or speculations. The scientists directly involved do not feel free to discuss these matters openly, not because they would be violating security, but because of the jittery atmosphere that acts as a damper on open discussion even of subjects known to be non-secret.
We already know that the so-called hydrogen bomb, if it is to be made at all, cannot be made of the abundant common hydrogen of atomic mass one, and that there are only two possible materials that could be used for such a purpose: deuterium, a hydrogen twin twice the weight of common hydrogen, which constitutes two hundredths of one per cent of the hydrogen in all waters; and a man-made variety of hydrogen, three times the weight of the lightest variety, known as tritium. We also know that to explode either deuterium or tritium (also known, respectively, as heavy and superheavy hydrogen) a temperature measured in millionsof degrees is required. This is attainable on earth only in the explosion of an A-bomb, and therefore the A-bomb would have to serve as the fuse to set off an explosion of deuterium, tritium, or a mixture of the two.
These facts, fundamental as they are, merely give us a general idea of the conditions required to make the H-bomb. All concerned, including Dr. Millikan, fully accept the validity of these facts. But there is one other factor at the very heart of the problem—the extremely short time at our disposal in which to kindle the hydrogen bomb with the A-bomb match. According to statements attributed to him in the press, Dr. Millikan believes that the time is too short; in other words, he seems to be convinced that the A-bomb match will be blown out before we have time to light the fire. Those of opposite view believe that methods can be devised for “shielding the match against the wind” for just long enough to light the fire. As we shall presently see, it is these methods for shielding the match that lead some to doubt whether the game would be worth the candle, or the match, if you will. These honest doubts are based on the possibility that, even if successful, the shielding might exact too high a price in terms of vital materials, particularly the stuff out of which A-bombs are made—plutonium. According to this view, we may at best be getting but a very small return for our investment in materials vitally important inwar as well as in peace. Even though the price in dollars were to be brought down to a negligible amount.
A closer look at the details of the problem may enable us to penetrate the thick fog that now envelops the subject. We may begin with a quotation from Dr. Bacher, who outlined the principle involved with remarkable clarity. “The real problem in developing and constructing a hydrogen bomb,” he said in a notable address before the Los Angeles Town Hall,
is, “How do you get it going?” The heavy hydrogens, deuterium and tritium, are suitable substances if somehow they could be heated hot enough and kept hot. This problem is a little bit like the job of making a fire at 20 degrees below zero in the mountains with green wood which is covered with ice and with very little kindling. Today, scientists tell us that such a fire can probably be kindled.
Once you get the fire going, of course, you can pile on the wood and make a very sizeable conflagration. In the same way with the hydrogen bomb, more heavy hydrogen can be used and a bigger explosion obtained. It has been called an open-ended weapon, meaning that more materials can be added and a bigger explosion obtained.
The phrase that goes to the very heart of the problem is “very little kindling,” which is another way of illustrating the difficulty of lighting a fire in a high wind when you have only one match. Weknow that to ignite deuterium, by far the cheaper and more abundant of the two H-bomb elements, a temperature comparable to those existing in the interior of the sun, some 20,000,000 degrees centigrade, is necessary. This temperature can be realized on earth only in the explosion of an A-bomb. We also know that the wartime model A-bombs generated a temperature of about 50,000,000 degrees, more than enough to light a deuterium fire. The trouble lies in the extremely short time interval, of the order of a millionth of a second (microsecond), and a fraction thereof, during which the A-bomb is held together before it flies apart. In the words of Professor Bacher, we must make our green, ice-covered wood catch fire in the subzero mountain weather before the “very little kindling” we have is burned up.
The times at which deuterium will ignite at any given temperature, in both its gaseous and its liquid form, are widely known among nuclear scientists everywhere, including Russia, through publication in official scientific literature of a well-known formula, originally worked out by two European scientists as far back as 1929, and more recently improved upon by Professor George Gamow and Professor Teller. By this formula, derived from actual experiments, it is known that deuterium in its gaseous form will require as long as 128 seconds to ignite at a temperature of 50,000,000 degrees centigrade, well above 100,000,000times longer than the time in which our little kindling is used up. This obviously rules out deuterium in its natural gaseous form as material for an H-bomb.
How about liquid deuterium? We know that the more atoms there are per unit volume (namely, the greater the density), the faster is the time of the reaction. The increase in the speed of the reaction (in this case the ignition of the deuterium) is directly proportional to the square of the density. For example, if the density, (that is, the number of atoms per unit volume) is increased by a factor of 10, the time of ignition will be speeded up by the square of 10, or 100 times faster. Since liquid deuterium has a density nearly 800 times that of gaseous deuterium, this means that liquid deuterium (which must be maintained at a temperature of 423 degrees below zero Fahrenheit at a pressure above one atmosphere) would ignite 640,000 times faster (namely, in 1/640,000th part of the time) than its gaseous form. Arithmetic shows that the ignition time for liquid deuterium at 50,000,000 degrees centigrade will be 200 microseconds, still 200 times longer than the period in which our kindling is consumed.
The same formula also reveals the time it would take liquid deuterium to ignite at higher temperatures, the increase of which shortens the ignition time. These figures show that the ignition time for liquid deuterium at 75,000,000 degrees centigradeis 40 microseconds. At 100,000,000 degrees the time is 30 microseconds; at 150,000,000 degrees, 15 microseconds; and at 200,000,000 degrees on the centigrade scale, about 4.8 millionths of a second. Doubling the temperature speeds up the ignition time for liquid deuterium by a factor of about six.
The problem thus is a dual one: to raise the temperature at which the A-bomb explodes, and to extend the time before the A-bomb flies apart. It is also obvious that if the liquid deuterium is to be ignited at all, it must be done before the bomb has disintegrated—that is, during the incredibly short time interval before it expands into a cloud of vapor and gas, since by then the deuterium would no longer be liquid.
Can we increase the A-bomb’s temperature fourfold to 200,000,000 degrees and literally make time stand still while it holds together for nearly five millionths of a second? To get a better understanding of the problem we must take a closer look at what takes place inside the A-bomb during the infinitesimal interval in which it comes to life.
This life history of the A-bomb is an incredible tale, from the time its inner mechanisms are set in motion until its metamorphosis into a great ball of fire. As explained earlier, the A-bomb’s explosion takes place through a process akin to spontaneous combustion as soon as a certain minimum amount (critical mass) of either one of two fissionable(combustible) elements—uranium 235 or plutonium—is assembled in one unit. The most obvious way it takes place is by bringing together two pieces of uranium 235 (U-235), or plutonium, each less than a critical mass, firing one of these into the other with a gun mechanism, thus creating a critical mass at the last minute. If, for example, the critical mass at which spontaneous combustion takes place is ten kilograms (the actual figure is a top secret), then the firing of a piece of one kilogram into another of nine kilograms would bring together a critical mass that would explode faster than the eye could wink—in fact, some thousands of times faster than TNT.
Just as an ordinary fire needs oxygen, so does an atomic fire require the tremendously powerful atomic particles known as neutrons. Unlike oxygen, however, neutrons do not exist in a free state in nature. Their habitat is the nuclei, or hearts, of the atoms. How, then, does the spontaneous combustion of the critical mass of U-235 or plutonium begin? All we need is a single neutron to start things going, and this one neutron may be supplied in one of several ways. It can come from the nucleus of an atom in the atmosphere, or inside the bomb, shattered by a powerful cosmic ray that comes from outside the earth. Or the emanation from some radioactive element in the atmosphere, or from one introduced into the body of the bomb, may split the first U-235 or plutonium atom, knockout two neutrons, and thus start a chain reaction of self-multiplying neutrons.
To understand the chain reaction requires only a little arithmetic. The first atom split releases, on the average, two neutrons, which split two atoms, which release four neutrons, which split four atoms, which release eight neutrons, and so on, in a geometric progression that, as can be seen, doubles itself at each successive step. Arithmetic shows that anything that is multiplied by two at every step will reach a 1,000 (in round numbers) in the first ten steps, and will multiply itself by a 1,000 at every ten steps thereafter, reaching a million in twenty steps, a billion in thirty, a trillion in forty, and so on. It can thus be seen that after seventy generations of self-multiplying neutrons the astronomical figure of two billion trillion (2 followed by 21 zeros) atoms have been split.
At this point let us hold our breath and get set to believe what at first glance may appear to be unbelievable. The time it takes to split these two billion trillion atoms is no more than one millionth of a second (one microsecond). If we keep this time element in mind we can arrive at a clear understanding of the tremendous problem involved in exploding an A- or an H-bomb.
And while we are recovering from the first shock we may as well get set for another. That unimaginable figure of two billion trillion atoms represents the splitting (explosion) of no more than onegram (1/28th of an ounce) of U-235, or plutonium.
Now, the energy released in the splitting of one gram of U-235 is equivalent in power to the explosive force of 20 tons of TNT, or two old-fashioned blockbusters. Since we know from President Truman’s announcement following the bombing of Hiroshima that the wartime A-bomb “had more power than 20,000 tons of TNT,” it means that the atoms in an entire kilogram (1,000 grams) of U-235 or plutonium must have been split. In other words, after the A-bomb had reached a power of 20 tons of TNT, it had to be kept together long enough to increase its power a thousandfold to 20,000 tons. This, as we have seen, requires only ten more steps. It can also be seen that it is these ten final crucial steps that make all the difference between a bomb equal to only two blockbusters, which would have been a most miserable two-billion-dollar fiasco, and an atomic bomb equal in power to two thousand blockbusters.
With the aid of these facts we are at last in a position to grasp the enormousness of the problem that confronted our A-bomb designers at Los Alamos and is confronting them again today. It can be seen that for a bomb to multiply itself from 20 to 20,000 tons in ten steps by doubling its power at every step, it has to pass successively the stages of 40, 80, 160, 320, and so on, until it reaches an explosive power of 2,500 tons at the seventh step. Yet it still has to be held together for three moresteps, during which it reaches the enormous power of 5,000 and 10,000 tons of TNT, without exploding.
Here was an irresistible force, and the problem was to surround it with an immovable body, or at least a body that would remain immovable long enough for the chain reaction to take just ten additional steps following the first seventy. There is only one fact of nature that makes this possible, or even thinkable—the last ten steps from 20 to 20,000 tons take only one tenth of a millionth of a second. The problem thus was to find a body that would remain immovable against an irresistible force for no longer than one tenth of a microsecond, 100 billionths of a second.
This immovable body is known technically as a “tamper,” which pits inertia against an irresistible force that builds up in 100 billionths of a second from an explosive power of 20 tons of TNT to 20,000 tons. The very inertia of the tamper delays the expansion of the active substance and makes for a longer-lasting, more energetic, and more efficient explosion. The tamper, which also serves as a reflector of neutrons, must be a material of very high density. Since gold has the fifth highest density of all the elements (next only to osmium, iridium, platinum, and rhenium), at one time the use of part of our huge gold hoard at Fort Knox was seriously considered.
With these facts and figures in mind, it becomesclear that an H-bomb made of deuterium alone is not feasible. It is certainly out of the question with an A-bomb of the Hiroshima or Nagasaki types, which generate a temperature of about 50,000,000 degrees, since, as we have seen, it would take fully 200 microseconds to ignite it at that temperature. It is one thing to devise a tamper that would hold back a force of 20 tons for 100 billionths of a second, and thus allow it to build up to 20,000 tons. It is quite another matter to devise an immovable body that would hold back an irresistible force of 20,000 tons for a time interval 2,000 times larger, particularly if one remembers that in another tenth of a microsecond the irresistible force would increase again by 1,000 to 20,000,000 tons. Obviously this is impossible, for if it were possible we would have a superbomb without any need for hydrogen of any kind.
It is known that we have developed a much more efficient A-bomb, which, as Senator Edwin C. Johnson of Colorado has inadvertently blurted out, “has six times the effectiveness of the bomb that was dropped over Nagasaki.” We are further informed by Dr. Bacher that “significant improvements” in atomic bombs since the war “have resulted in more powerful bombs and in a more efficient use of the valuable fissionable material.” It is conceivable and even probable that the improvements, among other things, include better tampers that delay the new A-bombs long enoughto fission two, four, or even eight times as many atoms as in the wartime models. But since, as we have seen, the ten steps of the final stages require only an average of 10 billionths of a second per step, increasing the power of the new models even to 160,000 tons (eight times the power of the Hiroshima type) would take only three steps, in an elapsed time of no more than 30 billionths of a second. And even if we assume that the improved bomb generates a temperature of 200,000,000 degrees, it would still be too cold to ignite the deuterium during the interval of its brief existence, since, as we have seen, it would take 4.8 microseconds to ignite it at that temperature. In fact, calculations indicate that it would require a temperature in the neighborhood of 400,000,000 degrees to ignite deuterium in the time interval during which the assembly of the improved A-bomb appears to be held together, which, as may be surmised from the known data, is within the range of 1.2 microseconds.
From all this it may be concluded with practical certainty that an H-bomb of deuterium only is out of the question. Equally good, though entirely different, reasons also rule out an H-bomb using only tritium as its explosive element.
There are several important reasons why an H-bomb made of tritium alone is not feasible. The most important by far, which alone excludes it from any serious consideration, is the staggeringcost we would have to pay in terms of priceless A-bomb material, as each kilogram of tritium produced would exact the sacrifice of eighty times that amount in plutonium. The reason for this is simple. Both plutonium and tritium have to be created with the neutrons released in the splitting of U-235, each atom of plutonium and each atom of tritium made requiring one neutron. Since an atom of plutonium has a weight of 239 atomic mass units, whereas an atom of tritium has an atomic weight of only three, it can be seen that a kilogram, or any given weight, of tritium would contain eighty times as many atoms as a corresponding weight of plutonium, and hence would require eighty times as many neutrons to produce. In other words, we would be buying each kilogram of tritium at a sacrifice of eighty kilograms of plutonium, which, of course, would mean a considerable reduction in our potential stockpile of plutonium bombs.
We would cut this loss by more than half because a kilogram of tritium would yield about two and a half times the explosive power of plutonium. But even this advantage would soon be lost, since tritium decays at the rate of fifty per cent every twelve years, so that a kilogram produced in 1951 would decay to only half a kilogram by 1963. Plutonium, on the other hand, can be stored indefinitely without any significant loss, since it changesslowly (at the rate of fifty per cent every twenty-five thousand years) into the other fissionable element, U-235, which in turn decays to one half in no less than nine hundred million years. What is more, plutonium, if the day comes when we can beat our swords into plowshares, will become one of the most valuable fuels for industrial power, the propulsion of ships, globe-circling airplanes, and even, someday, interplanetary rockets. It holds enormous potentialities as one of the major power sources of the twenty-first century. Tritium, on the other hand, can be used only as an agent of terrible destruction. It will yield its energy in a fraction of a millionth of a second or not at all. The only other possible uses it may have would be as a research tool for probing the structure of the atom, and as a potential new agent in medicine, in which it may be used for its radiations.
How much tritium would it take to make an H-bomb 1,000 times the power of the wartime model A-bombs? Since tritium has about 2.5 times the power per given weight of U-235 or plutonium, it would take 400 kilograms (about 1,880 quarts of the liquid form) of tritium to make a bomb that would equal the power of 1,000 kilograms of plutonium. Such a bomb, we can see, would have to be made at the sacrifice of 32,000 kilograms of plutonium. In other words, we would be getting a return, in terms of energy content, of1,000 kilograms for an investment of 32,000. And we would be losing fully half of even this small return every twelve years.
How many A-bombs would we be sacrificing through this investment? On the basis of Professor Oliphant’s estimate that the critical mass of an A-bomb is between 10 and 30 kilograms, we would sacrifice at least 1,066, and possibly as many as 3,200, if we take the lower figure. And we must not forget that a bomb a thousand times the power will produce only ten times the destructiveness by blast and thirty times the damage by fire of an A-bomb of the old-fashioned variety.
These cold facts make it clear that a tritium bomb, particularly one a thousand times the power of the A-bomb, is completely out of the picture.
But, one may ask, if a deuterium bomb is not possible and a tritium bomb is not feasible, and these are the only two substances that can possibly be used at all, isn’t all this talk about a superbomb sheer moonshine? And if so, how explain President Truman’s directive “to continue” work on it?
To find the answer let us go back for a moment to Dr. Bacher’s man in the mountains, confronted with the problem of lighting a fire with green, ice-covered wood at twenty degrees below zero with “very little kindling.” Obviously the poor fellow would be doomed to freeze to death were it not for one little item he had almost forgotten. Somewhere in his belongings he discovers a containerfilled with gasoline, which increases the inflammability of the wet wood to the point at which it will catch fire with a quantity of kindling that would otherwise be much too small.
Something closely analogous is true with the H-bomb. It so happens that a mixture of deuterium and tritium is the most highly inflammable atomic fuel on earth. It yields 3.5 times the energy of deuterium and about twice the energy of tritium when they are burned individually. Most important of all, the deuterium-tritium mixture, known as D-T, ignites much faster than either deuterium or tritium by themselves. For example, the D-T combination ignites 25 times faster than deuterium alone at a temperature of 100,000,000 degrees, and the ignition time is fully 37.5 times faster than for deuterium at 150,000,000 degrees.
The published technical data show that at a temperature of 50 million degrees the D-T mixture ignites in only 10 microseconds, or 20 times faster than deuterium alone. At 75 million degrees it takes only 3 microseconds, as against 40 for deuterium, while at 100 million degrees it needs only 1.2 microseconds to catch fire, a time, as we have seen, only 0.1 microsecond longer than it took the wartime A-bomb to fly apart. Since the latter held together for 1.1 microseconds at a temperature of about 50 million degrees, it is reasonable to assume that the improved and more efficient models generate a temperature at least twice as high, and thatthis is done by holding them together for about 1.2 microseconds.
It can thus be deduced that the only feasible H-bomb is one in which a relatively small amount of a deuterium-tritium mixture will serve as additional superkindling, to boost the kindling supplied by the improved model A-bomb, for lighting a fire with a vast quantity of deuterium. This, it appears, is the real secret of the H-bomb, which is really no secret at all, since all the deductions here presented are arrived at on the basis of data widely known to scientists everywhere, including Russia. And since it is no secret from the Russians, whom the arch-traitor Fuchs has supplied with the details still classified top secret, the American people are certainly entitled to the known facts, so vitally necessary for an intelligent understanding of one of the most important problems facing them today.
A deuterium bomb with a D-T booster would become a certainty if the temperature of the A-bomb trigger could be raised to 150 million or, better still, to 200 million degrees. At the former temperature the D-T superkindling ignites in 0.38 microseconds; at the higher temperature the ignition time goes down to as low as 0.28 microseconds. Now, the D-T mixture releases four times as much energy as plutonium, and the faster the time in which energy is released, the higher goes the temperature. Since four times as much energy isreleased at a rate four times faster than in the wartime model A-bomb, it is not unreasonable to assume that the temperature generated would be high enough to ignite the green wood in the bomb—its load of deuterium.
How much tritium would be required for the kindling mixture? On this we can only speculate at present. Since the D-T kindling calls for the fusion of one atom of tritium with one atom of deuterium, and the atomic weight of tritium is three as compared with two for deuterium, the weight of the two substances will be in the ratio of 3 for tritium to 2 for deuterium. Thus if the amount to be used for the kindling mixture is to be one kilogram, it will be made up of 600 grams of tritium and 400 grams of deuterium. Since, as we have seen, it would take eighty kilograms of plutonium to produce one kilogram of tritium, we would have to use up only 48 kilograms of plutonium to create the 600 grams, or the equivalent of one and a half to about five A-bombs, according to Dr. Oliphant’s estimate.
But would we need as much as 600 grams of tritium? Such an amount, mixed with 400 grams of deuterium, would yield an explosive power equal to 80,000 tons of TNT, an energy equivalent of 100 million kilowatt-hours. A twentieth part of this amount would still be equal in power to 4,000 tons of TNT, equivalent in terms of energy to 5,000,000 kilowatt-hours. Now one twentieth of600 grams, just 30 grams of tritium, could be made at a cost of no more than 2.4 kilograms of plutonium. Thus we would be paying only one twelfth to one fourth of an A-bomb (in addition to the one used as the trigger) to get the equivalent of ten A-bombs in blasting power and of thirty times the incendiary power, which would totally devastate an area of more than 300 square miles by blast and of more than 1,200 square miles by fire.
Would 30 grams of tritium be enough to serve as the superkindling for exploding, let’s say, 1,000 kilograms (one ton) of deuterium? We shall probably not know until we actually try it. It will largely depend on the temperature generated by our more powerful A-bomb models. If it is true, as Senator Johnson informed his television audience, that they have “six times the effectiveness of the bomb that was dropped over Nagasaki” (which, by the way, had more than twice the effectiveness of the Hiroshima model), it is quite possible that their temperature is as high as 150 million, or even 200 million, degrees. In that case, the extra kindling of a 20–30 gram D-T mixture, with its tremendous burst of 5,000,000 kilowatt-hours of energy in 0.28 to 0.38 microseconds (added to the vast quantity already being liberated by the exploding plutonium, or U-235), might well heat the deuterium to the proper ignition temperature and keep it hot long enough for its mass to explode well within 1.2 microseconds. In any case it wouldappear logical to expect that a mixture of 150 grams of tritium and 100 grams of deuterium, which would release an energy equal to that of the Hiroshima bomb, should be able to do the job with plenty of time to spare.
We thus have a threefold answer to the question: Can the H-bombactuallybe made? As we have seen, the deuterium bomb is definitely not possible. The tritium bomb is theoretically possible, but definitely not practicable. But a large deuterium bomb using a reasonably small amount of a deuterium and tritium mixture as extra kindling is both possible and feasible.
We now also stand on solid ground in dealing with the questions of cost and of the time it would take us to get into production. With these questions answered, we can then decide whether the H-bomb, if made, will add enough to our security to make the effort worth while.
We know at this stage that the H-bomb requires three essential ingredients. It needs, first of all, an A-bomb to set if off. We have a sizable stockpile of them. It needs large quantities of deuterium. We have built several deuterium plants during the war, and they should be large enough to supply our needs. Since it is extracted from water, the raw material will cost us nothing. The only item of cost will be the electric power required for the concentration process, and this should not be above $100 per kilogram, and probably less. The third vitalingredient, tritium, can be made in the giant plutonium plants at Hanford, Washington. Thus it can be seen that all the essential ingredients of the H-bomb, the costliest and those that would take longest to produce, as well as the multimillion-dollar plants required for their production, are already at hand.
This means that as far as the essential materials are concerned, we are ready to go right now. And as for the cost, it would appear to require hardly any new appropriations by Congress, or, at any rate, only appropriations that would be mere chicken feed compared with the five billion we have already invested in our A-bomb program.
The raw material out of which tritium is made is the common, cheap light metal lithium, the lightest, in fact, of all the metals. It has an atomic weight of six, its nucleus consisting of three protons and three neutrons. When an extra neutron invades its nucleus, it becomes unstable and breaks up into two lighter elements, helium (two protons and two neutrons) and tritium (one proton and two neutrons). They are both gases and they are readily separated. And while lithium of atomic weight six constitutes only 7.5 per cent of the element as found in nature (it comes mixed with 92.5 per cent of lithium of atomic weight seven), there is no need to separate it from its heavier twin, since the latter has no affinity forneutrons and nearly all of them are gobbled up by the lighter element.
The production of tritium, even in small amounts, will nevertheless be a formidable process. As we have seen, it takes eighty times as many neutrons to produce any given amount of tritium as to produce a corresponding amount of plutonium. Since the lithium will have to compete with uranium 238 (parent of plutonium) for the available supply of neutrons, and since the number of atoms of U-238 per given volume is nearly forty times greater than the number of lithium atoms, the rate of tritium production would be very much slower than that of plutonium. On the other hand, even if it took as much as two hundred times as long to produce a given quantity of tritium, the handicap would be considerably overcome because of the relatively small amounts that may be required. If, for example, we should need only 30 to 150 grams of tritium per bomb, it would take our present plutonium plants only six to thirty times longer to produce these quantities than it takes them to produce one kilogram of plutonium. A hypothetical plant such as the one mentioned in the official Smyth Report, designed to produce one kilogram of plutonium per day, would thus yield 30 grams of tritium in six days.
How much tritium would be needed for an adequate stockpile of H-bombs? Since our primaryreasons for building it are to deter aggression, to prevent its use against us or our allies, and as a tactical weapon against large land armies, it would appear that as few as twenty-five, or fifty at the most, would be adequate for the purpose. On the basis of the larger figure (assuming 30 to 150 grams of tritium per bomb), it would mean an initial stockpile of only 1.5 to 7.5 kilograms of tritium, which would entail the sacrifice of about 120 to 600 kilograms of plutonium. Once this initial outlay had been made, however, our plutonium sacrifice would be reduced annually to only one twenty-fourth of the original respective amounts—namely, 5 to 25 kilograms a year—just enough to make up for the decay of the tritium at the rate of fifty per cent every twelve years.
One of the major problems to be solved, in addition to the main problem of designing the assembly, arises from the fact that the deuterium and the tritium booster will have to be in liquid form. Liquid hydrogen boils (that is, reverts to gas) at a temperature of 423 degrees below zero Fahrenheit under a pressure of one atmosphere (fifteen pounds per square inch). To liquefy it, it is necessary to cool it in liquid air (at 313.96 below zero F.) while keeping it at the same time under a pressure of 180 atmospheres. To transport it, it must be placed in a vacuum vessel surrounded by an outer vessel of liquid air. This would point to the need of giant refrigeration and storage plants,as well as of refrigerator planes for transporting large quantities of liquid deuterium and its tritium spark plug.
Will the H-bomb, if made, add enough to our security to make the effort worth while? We have seen that the required effort may, after all, not be very great. In fact, it may turn out to be a relatively small one, in view of the fact that all the basic ingredients and plants are already at hand and fully paid for. But supposing even that the effort turns out to be much more costly than it now appears? The question we must then ask ourselves is: Can we afford not to make the effort?
It is true, of course, as some have pointed out, that ten or even fewer A-bombs could destroy the heart of any metropolitan city, while only one would be quite enough, as we know, for cities the size of Hiroshima or Nagasaki. But that neglects to take into consideration the fact that one H-bomb concentrates within itself the power of thirty A-bombs to destroy by fire and by burns an area of more than 1,200 square miles at one blow. Nor does it take into consideration the military advantage of delivering the power of a combination of ten and thirty A-bombs in one concentrated package, which would make it a tremendous tactical weapon against a huge land army scattered over many miles, or its possible enormous psychological effect against such an army.
Most important of all, this view grossly minimizesthe apocalyptic potentialities of the H-bomb for poisoning large areas with deadly clouds of radioactive particles. It is a monstrous fact that an H-bomb incorporating one ton of deuterium, encased in a shell of cobalt, would liberate 250 pounds of neutrons, which would create 15,000 pounds of highly radioactive cobalt, equivalent in their deadliness to 4,800,000 pounds of radium. Such bombs, according to Professor Harrison Brown, University of Chicago nuclear chemist, could be set on a north-south line in the Pacific approximately a thousand miles west of California. “The radioactive dust would reach California in about a day, and New York in four or five days, killing most life as it traverses the continent.”
“Similarly,” Professor Brown stated in theAmerican Scholar, “the Western powers could explode H-bombs on a north-south line about the longitude of Prague which would destroy all life within a strip 1,500 miles wide, extending from Leningrad to Odessa, and 3,000 miles deep, from Prague to the Ural Mountains. Such an attack would produce a ‘scorched earth’ of an extent unprecedented in history.”
Professor Szilard, one of the principal architects of the A-bomb, has estimated, as already stated, that four hundred one-ton deuterium bombs would release enough radioactivity to extinguish all life on earth. Professor Einstein, as we have seen, has publicly stated that the H-bomb, if successful,will bring the annihilation of all life on earth within the range of technical possibilities. The question we must therefore ask ourselves is: Can we allow Russia to be the sole possessor of such a weapon?
There can be no question that Russia is already at work on an H-bomb. Like ourselves, she already has the plutonium plants for producing both A-bombs and tritium. She can produce deuterium in the same quantities as we can. In Professor Peter Kapitza she has the world’s greatest authority on liquid hydrogen.
Furthermore, she has great incentives to produce H-bombs. Since she is still behind us in her A-bomb stockpile, she can, in a sense, catch up with us much more quickly by converting her fewer A-bombs into H-bombs that would be the equivalents of ten to thirty A-bombs each, thus increasing the power of her stockpile ten to thirty times. Equally if not more important from Russia’s point of view is the stark fact that an H-bomb could be much more easily exploded near a coastal city from a submarine or innocent-looking tramp steamer, since most of our great cities are on the seacoast, whereas Russia practically has no coastal cities.
Even if we openly announced that we would not make any H-bombs, it would not deter Russia from making them as fast as she could, not only because she would not believe us but also becauseher sole possession would greatly weight the scales in her favor. If, God forbid, she finds herself one day with a stockpile of H-bombs when we have none, she would be in a position to send us an ultimatum similar to the one we sent to the Japanese after Hiroshima: “Surrender or be destroyed!”
Valuing their liberty morethan their lives, the American people will never surrender. But while there is time, would anyone advocate that we run the risk of ever facing such a choice?