(1914- ) American Astrophysicist
James Van Allen is a pioneering astrophysicist who played a vital role in the early development of the U.S. space program. His work in magneto-spheric physics led to the discovery of a zone of high-level radiation around the Earth caused by the presence of trapped charged particles, known as the magnetosphere or the Van Allen belt.
He was born in Mount Pleasant, Iowa, on September 7, 1914, the second of four sons of Alfred Van Allen and Alma Olney Van Allen. Although his father was an attorney in a family of lawyers, he encouraged the boy to follow his own path. Van Allen writes:
My boyhood activities were all centered around our closely knit family, which had a strong resemblance to that of other pioneer families. The virtues of frugality, hard work, and devotion to education were enforced rigorously and on a daily basis by my father. My mother exemplified the pioneer qualities of affection and nurture for her husband and their children and of comprehensive self-reliance.
A studious boy, with a consuming interest in science and mechanical and electrical devices, he was an avid fan of the magazines Popular Mechanics and Popular Science. When he graduated from Mount Pleasant High School in 1931, he was class valedictorian.
From there he went on to Iowa Wesleyan College, where he was drawn to both physics and chemistry and received a B.S. in 1935. The opportunity to work in a high-pressure research lab assisting his professor helped him to decide in favor of physics. He then went on to the University of Iowa, where he earned an M.S. in 1936 and a Ph.D. in 1939, writing a dissertation on nuclear disintegration. From 1939 to 1942, Van Allen worked as a research fellow at the Carnegie Institute in Washington, D.C., in the Department of Terrestrial Magnetism, where he studied the photodisintegration process. It was there that he “crossed the culture gap from nuclear physics to the department’s traditional research in geomagnetism, cosmic rays, auroral and ionospheric physics,” which he resolved to make his future fields of research.
During World War II, he “plunged into the war effort with the patriotic fervor of those days.” In April 1942, he moved to the applied physics department at Johns Hopkins University, where he worked on the creation of a rugged vacuum tube. He helped to develop the proximity fuze, a device attached to a missile such as an antiaircraft shell that detonated when it neared the target, when the radio waves it emitted were reflected back to it with sufficient intensity from the target. The proximity fuse allowed the detonation to occur even if the missile had not been aimed accurately enough for a direct hit and greatly increased the effectiveness of antiaircraft weapons. By the fall of 1942, Van Allen had been commissioned as an officer in the United States Navy and was sent to the Pacific to field test and complete operational requirements for the proximity fuze.
James Van Allen discovered a zone of high-level radiation around the Earth caused by the presence of trapped charged particles, known as the magnetosphere or the Van Allen belt.
In 1946, the war now ended, Van Allen married his lifetime companion, Abigail Fithian Halsey, with whom he would have five children. For the next four years he was involved in high-altitude research, as supervisor of the high-altitude research group and proximity fuse unit at Johns Hopkins, working on utilization of the unused German stock of V-2 rockets and of the Aerobee rockets for research purposes. The group developed devices for measuring the levels of cosmic radiation that were sent to the outer reaches of the atmosphere in these rockets, which radioed the data back to Earth. Van Allen’s experience in miniaturization of electronic equipment enabled him to include a maximum of instrumentation in the limited payload of these rockets, an achievement that was to be crucial in the early stages of the U.S. space program.
After a year at the Brookhaven National Laboratory on a Guggenheim Fellowship, in 1951, he became professor of physics and head of the physics department at the University of Iowa. Working with his students, he invented the rocket-balloon (rockoon), which went into use in 1952. It consisted of a small rocket that was lifted by means of a balloon into the upper regions of the atmosphere and then fired off, thus reaching heights otherwise attainable only by a much larger rocket.
From 1949 to 1957, Van Allen also organized and led scientific expeditions to Peru (1949), the Gulf of Alaska (1950), Greenland (1952 and 1957), and Antarctica (1957) to study cosmic radiation. During an Arctic expedition in 1953, rockoons fired by Van Allen and his students were the first to detect a hint of the radiation belts surrounding the Earth.
He became part of the organizing panel of International Geophysical Year (IGY), July 1957-December 1958, whose members actively promoted the adoption of scientific satellites of the Earth as an element of the IGY program and laid the foundations for the scientific program of the National Aeronautics and Space Administration, created in 1958. In the mid-1950s, the U.S. government had first seriously considered the possibility of sending a rocket into orbit around the Earth, thereby creating an artificial satellite. In 1955, President Eisenhower announced the Vanguard Program, designed to put an artificial satellite into orbit within two years, to coincide with the scheduled IGY, which was itself timed to coincide with a peak in solar activity. Van Allen was given responsibility for the instrumentation of the project.
On October 4, 1957, the day that the Soviet Union launched Sputnik 1, the world’s first artificial satellite, Van Allen was on a scientific expedition to the Antarctic. On hearing the news, the American team lost no time in launching Explorer 1, on January 31, 1958. It was carrying a Geiger counter Van Allen had intended to use to measure the levels of cosmic radiation, but at a height of about 500 miles the counters registered a radiation level of zero. This nonsensical reading led Van Allen to suspect instrument failure. When the same result was recorded on Explorer 3, launched on March 26, 1958, he realized that the zero reading could have resulted from the counters’ being swamped with very high levels of radiation. On July 29, 1958, Explorer 4 was sent up with a counter shielded with lead in order to allow less radiation to penetrate, and this method showed clearly that parts of space contained much higher levels of radiation than previously suspected. Van Allen studied the size and distribution of these high-radiation zones and found that they consisted of two toroidal (i.e., donut-shaped) radiation belts around the Earth, which arise by the trapping of charged particles in the Earth’s magnetic field. The inner belt was made up of high-energy protons, the outer belt of high-energy electrons and other particles. These radiation belts were found to be part of the tear-shaped magnetic region around the Earth called the magnetosphere. The radiation belts started at an altitude of several hundred miles from the Earth and extended for several thousand miles into space. In 1993, other scientists discovered a third belt, enclosed by the inner belt, containing ions of oxygen, nitrogen, and neon.
Van Allen was elected to the National Academy of Sciences in 1952 and became president of the American Geographical Union in 1982. In 1959, he was made professor of astronomy at Iowa and, from 1972 to 1985, was Carver Professor of Physics; after retirement, he eventually became professor emeritus there. At age 85, he was still mentoring graduate students, doing research, and monitoring transmissions from the system he invented on Pioneer 10, launched in 1972, as the first artificial object to carry sounds and images from Earth into outer space.
As an astrophysicist, James Van Allen played a vital role in the early development of the U.S. space program. In one capacity or another, he was involved in the first four Explorer probes, the first Pioneers, several Mariner efforts, and the orbiting geophysical observatory. From 1966 to 1970, as a member of the Space Science Board and the Lunar and Planetary Missions Board, he became a leading advocate for missions to the outer planets, especially Jupiter. The first fruits of these efforts were the National Aeronautics and Space Administration’s (NASA’s) two missions to Jupiter, Pioneer 10 and Pioneer 11, launched in 1972 and 1973.
