Secretly Going Nuclear

The world received its abrupt introduction to atomic energy at Hiroshima and Nagasaki. The atomic age, ushered in by the bombs dropped on those cities, was the product of a massive effort known as the Manhattan Project. Yet several years before the Manhattan Project got under way, an apparatus was secretly being built in a U.S. government laboratory to attempt to make use of the energy of nuclear reactions—not from fission but, even more difficult, from fusion.

The time was the spring of 1938, and the place was Langley Memorial Aeronautical Laboratory, in Hampton, Virginia. Langley was the flagship facility of the National Advisory Committee for Aeronautics (NACA), NASA’s predecessor, and its staff of four hundred government employees was hard at work improving the performance of the aircraft with which the country would eventually fight the war.

At least, that is what they were supposed to be doing. Inside one of the wind-tunnel buildings at Langley, however, a bizarre doughnut-shaped electromagnetic device the size of a big truck tire was being built. Although it was welded together from half-inch plates of aircraft aluminum, it had nothing to do with aerodynamics. Its creators were two of NACA’s freer spirits: Arthur Kantrowitz, a young physicist just out of Columbia University, and his section head, Eastman N. Jacobs, an accomplished aerodynamicist from the University of California who had been with NACA since 1925. Kantrowitz and Jacobs could not admit to their superiors that the object of their device was controlled nuclear fusion.

Nuclear reactions differ fundamentally from the chemical reactions that we encounter every day. In a chemical reaction, while the bonds between atoms within various molecules are rearranged, the atoms themselves are unchanged; a hydrogen atom remains a hydrogen atom, for example, and is not converted into anything else. In a nuclear reaction atoms themselves are transmuted. This can happen by means of fission (an element splitting into two lighter ones) or fusion (two elements uniting to form a heavier one). A chemical reaction leaves the atomic nuclei alone, so any energy released is the result of reshuffling electrons. A nuclear reaction involves the much greater forces needed to hold protons and neutrons together within a nucleus, so its potential energy yield is comparatively enormous.

What makes fusion so difficult to achieve is that it is very hard to get nuclei together so that they can react. A sample of the element must be heated to the point where it ceases being a collection of separate atoms, each with a positively charged nucleus surrounded by its own cloud of electrons, and becomes instead a sea of unattached electrons with nuclei swimming in it. This state is called a plasma. If the nuclei in the plasma are to bump into one another and react, they must have enough energy to overcome the repulsive force between them caused by their electric charges. That is why extremely high temperatures are needed to get fusion to work. Controlled energy-yielding fusion has never been achieved; fusion bombs work by using a fission bomb to ignite a trigger for the thermonuclear reaction.

Early in 1938 Kantrowitz read in a magazine that Westinghouse had just bought a Van de Graaff generator. He knew that this big electrical device, which produced sparks several feet long, was being used in atom-smashing experiments, and he suspected that Westinghouse had bought the machine to begin exploring the ways of making nuclear power a reality.

After discussing the story with Jacobs, Kantrowitz consulted Reviews of Modem Physics for a recent paper by Hans Bethe. This paper summarized all the known types of nuclear reactions, including those that Bethe suggested were taking place inside the stars. Soon “Arky,” as Jacobs called Kantrowitz, came to believe that if a sample of hydrogen could be heated to sunlike temperatures, an effective fusion reactor could be built.

Jacobs was a freewheeling boss with a research temperament to match. He agreed with Kantrowitz and encouraged him to keep working on the problem. Three years earlier he had asked Kantrowitz to design a small supersonic wind tunnel. He had made this decision on his own, in defiance of a cautious NACA policy against supersonics. Kantrowitz built the supersonic tunnel, NACA’s first, in less than eighteen months. An unauthorized order from Jacobs had thus led to one of the world’s pioneering high-speed research facilities.

With this success in mind, and with Kantrowitz working out the problems of reactor design on paper, Jacobs tried to persuade Dr. George Lewis, NACA’s director of research and not a terribly daring or imaginative man, to authorize a little money for the unusual project. Jacobs’s justification—the only possible one at NACA in 1938 for such a radical piece of equipment—was that it could provide basic information that might someday have applications in the propulsion of aircraft.

The timing of the request was good. Jacobs’s work on laminar-flow airfoils looked very promising, and NACA headquarters wanted to keep him happy. Furthermore, Lewis wanted to give his best men enough leeway to pursue their own dreams, at least up to a point. He gave Jacobs five thousand dollars. That was just enough money to begin building the reactor.

The choice of a plasma to use in the reactor was simple: it had to be hydrogen. Because of problems with electrostatic repulsion, only very light nuclei of low charge—hydrogen and helium—could be made to react. Kantrowitz would have preferred to attempt what Bethe called the “D-D reaction”; this involved fusion of deuterium nuclei, in a plasma of pure deuterium, to form helium. But deuterium, a rare isotope of hydrogen that had been discovered only in 1932, was not readily available. In a normal sample only one atom of the stuff could be found for every 6,700 hydrogen atoms. So Kantrowitz’s only option was ordinary hydrogen. He hoped later to be able to use deuterium.

To fire up hydrogen to the temperatures needed, Kantrowitz planned to use highpower radio waves. He built a 150-watt oscillator similar to the transmitters used by radio stations. With it he could cause the electrons and ions in the plasma to oscillate. At one specific frequency, known as the resonant frequency, the effect would build up enormous amounts of energy, which would be transferred to the rest of the sample as heat. According to Kantrowitz’s calculations, his transmitter would be able to get the plasma up to about ten million degrees Centigrade. In that kind of heat X rays powerful enough to show up on photographic film would be emitted.

One obvious problem was what to keep the plasma in. What kind of structure could confine a sample at ten million degrees? The problem was not that the reactor would blow up like a bomb but that the plasma would lose its heat to the walls of the container.

Kantrowitz’s answer to this problem was to create magnetic fields that would force the plasma away from the walls of his torus (as the doughnutlike structure was called). The magnetic fields would also crowd the nuclei closer together, increasing the frequency of atomic collisions and thus the chances of fusion reactions.

To achieve the magnetic fields needed to contain the plasma, Kantrowitz and Jacobs wound water-cooled electric cables around their torus, making a magnetic coil. Then, using Kantrowitz’s radio oscillator and electricity from the drive motor of Jacobs’s wind tunnel, the two men tried to excite the assembly of hydrogen ions and electrons to a high enough temperature to produce X rays. For Kantrowitz this was his daily assignment; for Jacobs it was an after-hours affair.

In an interview for T. A. Heppenheimer’s 1984 book The Man-made Sun: The Quest for Fusion Power , Kantrowitz recalled that both he and Jacobs built up “a lot of enthusiasm” for their fusion research. “It was a very exciting thing,” he said. The more they got into it, the more “all this business about an endless supply of energy” became “perfectly apparent.”

Kantrowitz and Jacobs dubbed their device the “Diffusion Inhibitor.” They called it that because they knew that George Lewis did not want anything on record that suggested experiments with atomic energy. Neither Lewis nor anyone else at NACA headquarters had more than the vaguest notion of what a Diffusion Inhibitor was. Jacobs wanted to keep it that way.

For several reasons the testing took place at night. First of all, Jacobs wanted to participate, and he was busy during the day. Because of the project’s secrecy, it made sense to test it when no one else was around to ask questions. Moreover, the city’s electric plant could supply only a limited amount of power. Langley’s larger wind tunnels were restricted to no more than half their maximum horsepower during the day. The only time a motor big enough to drive the fusion apparatus could operate at full power, without causing some sort of blackout, was late at night or early in the morning.

On the appointed night, with Jacobs stroking his goatee and looking in through a small window built into the torus, Kantrowitz injected little wisps of hydrogen gas into the chamber and turned on the radio oscillator. Quickly the plasma began to heat up and glow blue. Using a camera loaded with dental film, Jacobs snapped pictures of the plasma. What the pictures would show, he hoped, was the emission of X rays. But when Jacobs developed the film in his darkroom at home that night, he found nothing—no evidence of fusion reactions. Somehow they had to get the plasma hotter.

In an emergency a homeowner sticks a penny in the fuse box to turn his electric lights back on, even though it can be dangerous. To get more electric current running through their oscillator, Kantrowitz and Jacobs took the same sort of risk: they held in the circuit breakers in the oscillator’s power supply. Still they found nothing on the film.

The problem, they believed, was that the plasma was somehow flowing out of its trap to the wall, where heat was being lost. We know today that the source of the trouble was inherent in their basic design: by wrapping a simple coil of wire around a doughnut-shaped chamber, they had not made a perfect magnetic trap. The plasma was drifting out of its confining magnetic field. Modern plasma physicists would call this problem a lack of equilibrium.

Kantrowitz and Jacobs did not understand this lack of equilibrium very well, nor did they understand anything about plasma instabilities—oscillations or wavelike disturbances. No one at the time knew about these things. Had they continued to pursue their experiments, the two Langley researchers would probably, as Heppenheimer suggests, have discovered the source of their problems and “might even have started to learn what to do about them.”

Before they could learn anything more, however, Lewis came by the laboratory on one of his occasional visits and happened upon the apparatus. The director of research listened quietly to Jacobs’s explanation of the equipment, which was hooked up to one of NACA’s main wind tunnels. Then he canceled the project on the spot. Lewis had a lot of faith in Jacobs and Kantrowitz, but he could not support their fantastic experiment.

After all, Lewis, a conscientious leader of the government agency responsible for aircraft development, saw two of his prized minds spending five thousand dollars of the taxpayers’ money, exhausting hundreds of hours of research time, and endangering a precious wind tunnel, all in a far-fetched attempt to “bust atoms,” as Lewis erroneously .put it. As Heppenheimer explains, Lewis was “face to face with an experiment that might almost have come down a time-warp.” Who can blame him for putting an end to it?

It was not something to blame Lewis for, but to both Arky and Jacobs the cancellation was still a tragedy. Their experiments with the torus had led them to several important discoveries. As Kantrowitz recalled some forty-five years later in his conversation with Heppenheimer, “It was a heartbreaking experience. I had just built a whole future around this; I wanted to make it a career. This was just a tremendous blow to me that I wasn’t allowed to go on with this.”

Kantrowitz stayed on at Langley through the end of World War II, working on airfoil cascades, axial-flow compressors, and the dynamics of gas turbines. Several times he turned down offers to join the Manhattan Project. By 1946 he was ready for broader activity. He left NACA for a professorship at Cornell University. In 1955 he went to work for the Avco Research Laboratory, in Everett, Massachusetts. There he contributed to the development of ICBMs and America’s first manned space flights. Later he studied the science of blood clotting with his brother Adrian, a famous cardiologist, and designed a series of cardiac assist devices, including an artificial heart. In 1979 he left Avco for a position at Dartmouth College, where he remains in retirement today.

Eastman Jacobs retired from NACA in 1944, at the age of forty-two, after working during the war on laminarflow airfoils and a hybrid form of jet propulsion modeled after the Campini ducted fan. NACA’s cancellation of his ducted-fan research airplane project in 1943 was one of several factors behind his decision to leave NACA. He spent the rest of his life, until his death in 1987, in Southern California in semiretirement, an unusually long period of professional inactivity for one who had been so productive. Neither man ever worked on fusion again.

Eventually the two men learned how close they had come to inventing the kind of fusion reactor that later became known as a “tokamak.” (The name derives from a Russian acronym for a doughnut-shaped magnetic chamber.) The first of these experimental devices was built in the early 1950s by a team of Soviet scientists under the direction of Lev A. Artsimovich at the Institute of Atomic Energy in Moscow. Artsimovich’s tokamak operated on a quite different principle, however. To generate the magnetic field required for confinement, and thereby guarantee equilibrium, he passed an electric current directly through the plasma, something Kantrowitz and Jacobs had not tried.

While the Russians were developing their first tokamaks, Lyman Spitzer, Jr., of Princeton University was building a device called a “stellarator.” Spitzer initially made his fusion reactor in the shape of a figure eight. In later models he changed it into a doughnut with the electromagnetic field coils wrapped helically around the plasma chamber. Unfortunately the alignment of these copper windings was not precise enough to make a perfect magnetic trap, so the results were disappointing. In 1969 American scientists abandoned their use of the stellarator and turned to the tokamak. In the late 1970s, however, fusion experts began to overcome some of the stellarator’s problems. Spitzer’s design has now rejoined the tokamak as a leading reactor concept.

None of today’s toroidal chambers were influenced in any way by the device tested at Langley in 1938. By the time the first of them were tried in the 1950s, the existence of Kantrowitz and Jacobs’s Diffusion Inhibitor—for which a patent application had been filed in March 1939 but not granted, for unknown reasons—had long since been forgotten. The wheel had to be reinvented by other brilliant minds.

Kantrowitz and Jacobs’s 1938 experiment was an extraordinary nonevent in the early history of fusion research. It was an abruptly canceled project that made no news, that very few people in the world ever heard about, and that led directly to no important results. In retrospect, however, the Langley fusion experiment was a major happening. Not only was it the world’s first attempt to achieve controlled fusion, but it was also one of the first serious experiments anywhere in the world aimed at getting energy from the atom—three years before the Manhattan Project began.

Nuclear fusion is still a hot topic. Researchers are investigating containment vessels of various exotic shapes (a few of them closer to pretzels than doughnuts), and some are using lasers to heat their plasmas. With deuterium and tritium (another isotope of hydrogen) readily available, today’s scientists have much more energetic reactions to work with than Kantrowitz and Jacobs did with their plain hydrogen. In 1938 the two men from Langley could hardly have foreseen where fusion research would lead, or realized how much would remain to be done a half-century later. Still, it is tempting to speculate about what directions the nation’s atomic-research program might have taken had they been allowed to continue their work and had it become widely known. And one cannot help wondering what other non-events lurk in technology’s past, loose ends waiting to be picked up years or decades after the fact.