Scientific Research Using Balloons in the First Part of the Twentieth Century

A great many balloon flights of the twentieth century focused on science and particularly the sun and cosmic rays. Balloons could provide a stable instrument platform free from the vibration and the electrical interference generated by aircraft engines. They could also climb above most of the Earth's atmosphere and measure atmospheric and cosmic conditions without atmospheric interference.

Much of our knowledge of the universe began with a 1912 balloon flight that physicist and professor Bruno Rossi called "the beginning of one of the most extraordinary adventures in the history of science." On August 7, 1912, Austrian physicist Victor Hess took three electroscopes up to 16,000 feet (4,877 meters) in an open balloon basket. With these instruments, which detected and measured radiation, he made an unexpected discovery—high-energy particles not seen on the surface of the Earth were bombarding the upper atmosphere. He concluded that "a radiation of very great penetrating power enters our atmosphere from above" and is absorbed by the atmosphere before reaching the Earth's surface. These particles received the name “cosmic rays” in 1936 by physicist Robert Millikan of the California Institute of Technology (Cal Tech).

In 1914, Charles Greeley Abbot, director of the Smithsonian Astrophysical Observatory, sent specially designed instruments that measure solar radiation into the upper atmosphere to study solar energy and its impact on the Earth. Since the Earth's atmosphere absorbs much of the light and radiation from the sun, balloons helped Abbot study solar energy by taking instruments above most of the atmosphere—15 to 20 miles (24 to 32 kilometers) above the Earth's surface.

Jean Piccard, Auguste Piccard's twin brother, led a research team on the 1933 Century of Progress balloon flight that included two U.S. Nobel laureates, Arthur H. Compton of the University of Chicago and Millikan, who would soon coin the term “cosmic rays.” The scientists provided two instruments that measured how well gasses conducted cosmic rays. The balloon also carried a cosmic ray telescope that determined the direction where the rays originated, a polariscope that investigated the polarization of light at high altitudes, equipment to take air samples, single-celled organisms and fruit flies for tests for genetic mutations, and an infrared camera and spectrograph to study the ozone layer.

Jean Piccard was given the Century of Progress balloon after the flight. In 1934, he and his wife and collaborator Jeanette Piccard flew the reconditioned balloon on another research flight. Their 1934 experiments included a burst apparatus to study the simultaneous bursting of lead atoms bombarded by cosmic radiation. Millikan supplied a cosmic radiation experiment--an ionization chamber shielded with 700 pounds (318 kilograms) of lead dust.

During the worldwide depression of the 1930s, organizations and researchers such as Jean Piccard concentrated on developing better equipment for atmospheric research. Piccard teamed with physicist John Ackerman at the University of Minnesota to improve the latex rubber balloons then used and started experimenting with plastic film balloons. At the time, the only plastic available was cellophane, which tended to crack during cold weather inflations. They also tried using multiple latex balloons to lower the cost of balloons. On July 18, 1937, Piccard piloted the Pleiades on a successful low-altitude test flight. His gondola was carried aloft by 92 latex balloons.

Most research stopped during World War II. When the war ended, Piccard returned to his work on plastic balloons. In 1947, he received funding from the Office of Naval Research (ONR) for the Helios project. Helios would consist of 80 to 100 plastic balloons that carried a sealed gondola as high as 100,000 feet (30,480 meters). Working in a wartime-created bombsite laboratory at General Mills in Minneapolis (the cereal company), Piccard worked with Otto Winzen, a young man he had met in 1946 while visiting the University of Minnesota's aeronautical laboratory, to find a suitable plastic for their balloons. They finally decided on polyethylene and then worked on how to manufacture balloons from sheets of this plastic that were only 1/1000 of an inch (0.0254 millimeters) thick.

On September 25, they launched the first large balloon since the end of World War II. The first in a series of four launches, the polyethylene balloon had a capacity of 100,000 cubic feet (2,832 cubic meters), but carried only 70 pounds (32 kilograms) of equipment. The next two test launches failed. On the fourth launch, the balloon refused to descend for three days, and the high-altitude controls, radio equipment, and insulated containers malfunctioned. The delay was a goldmine for cosmic ray researchers. Two Brookhaven National Laboratory physicists, J. Hornbostel and E.O. Salant, had flown a pair of cosmic ray plates on the mission, and they were delighted with the results that the three-day delay brought. The success of their experiment led the ONR to abandon the idea of human balloon flights and focus on unmanned research.

From 1947 on, polyethylene plastic balloons demonstrated their superiority over natural or synthetic rubber balloons for high-altitude flights. The lightweight and reasonably low-cost means of lofting instrument payloads to altitudes of more than 100,000 feet (30,480 meters) made it easier for researchers to conduct scientific experiments above 99 percent of the Earth's atmospheric mass that could measure atmospheric and cosmic effects without interference. Cosmic ray physicists were the first to use these new plastic balloons. From 1947 to 1957, literally hundreds of cosmic ray instruments and photographic plates were carried aloft under polyethylene balloons.

After the Brookhaven physicists, one of the early researchers was Dr. James Van Allen of the University of Iowa physics department. In 1952, under an ONR grant, he developed “rockoons” to extend the altitude from which data could be collected. Rockoons are balloons that carry sounding rockets—rockets that are launched straight up from the Earth and that carry instruments to observe and measure various natural phenomena. By launching the sounding rocket from a balloon at an altitude of 70,000 feet (21,336 meters), Van Allen could send instruments up to 300,000 feet (91,440 meters). Van Allen used sounding rocket technology when he measured the energy in cosmic rays and the interaction of cosmic radiation with the Earth's atmosphere near the North Pole. His team launched the rockoons to altitudes between 20 and 70 miles (32 to 113 kilometers). As the rockets fell back into the atmosphere, they returned data to the scientists below on cosmic rays, pressures, heat, and other conditions. These early experiments suggested the existence of trapped radiation in near-Earth space. This trapped radiation was later confirmed by satellites and became known as the Van Allen radiation belts.

Skyhook was one of the first major programs to take advantage of the new balloon technology. On August 19, 1957, an unmanned Skyhook balloon lifted a cargo from the Stratoscope project, a program developed through the National Center for Atmospheric Research (NCAR) with the cooperation and joint sponsorship the National Science Foundation (NSF), the U.S. Navy, and the National Aeronautics and Space Administration (NASA). The main instrument was a 12-inch (30-centimeter) telescope with a special light-sensitive pointing system and a closed circuit television camera that researchers could guide—the first balloon-borne telescope. The telescope took more than 400 photographs of sunspots. These were the sharpest photographs taken of the sun up to that time. The photographs increased scientists' understanding of the motions observed in the strong magnetic fields of the sunspots.

--Linda Voss

Sources:

Abbot, Charles Greeley. The Sun and the Welfare of Man. N.Y.: Smithsonian Institution Series, 1944.

Crouch, Tom D. The Eagle Aloft: Two Centuries of the Balloon in America. Washington, D.C.: Smithsonian Institution Press, 1983.

Kirschner, Edwin J. Aerospace Balloons – From Montgolfiere to Space. Fallbrook, Calif.: Aero Publishers, Inc. 1985.

Payne, Lee. Lighter Than Air: An Illustrated History of the Airship. N.Y.: Orion Books, 1991.

Piccard, Jeannette. "Speech and Writing File." untitled manuscript, box 77, Piccard Papers.

Rossi, Bruno. Cosmic Rays. N.Y.: Wiley & Sons, 1964.

On-Line References:

"Rockoon," Encyclopedia Astronautica. http://www.friends-partners.org/mwade/project/rockoon.htm