McDonald’s and Webber’s balloon programs, 1953-1955

During the late 1940s and early 1950s, important advances were made in balloon technology. Large balloon development received a major boost at the Instrument Division of General Mills in Minnesota, Minneapolis. That work was spearheaded by Otto Winzen, Jean Piccard, and others. The ONR supported the developmental work and many flights over a period of years. Those large balloons were known from the beginning as Skyhook balloons.

The University of Minnesota Physics Department was an early adopter of balloons for cosmic ray research. In 1948, they employed them to loft nuclear emulsions and a cloud chamber to make the important discovery of heavy cosmic rays. In late 1949, John R. Winckler arrived and joined the cosmic ray program. Key graduate students associated with that early work included John E. Naugle, who went on to serve with great distinction as a senior official in NASA Headquarters. They also included Frank B. McDonald and Kinsey A. Anderson, both of whom later joined the SUI faculty.

In 1952, frustrated by a number of unexplained early balloon failures, Minnesota scientists Charles Critchfield, Edward Ney, and John R. Winckler undertook a then – classified military project to improve balloon performance. Their primary motivation was to develop a system that could photograph military installations in the Union of Soviet Socialist Republics (USSR). Although development of the U2 reconnaissance aircraft supplanted the need for such a balloon system, a number of the techniques worked out in that program were applied to cosmic ray and other high-altitude atmo­spheric research.12

Two key developments in that developmental project made very large balloons possible. The first was the “natural shape” balloon configuration, in which the inter­nal pressure of the balloon-lifting gas was spread out over the envelope by a network of load-bearing meridional tapes, thus keeping the circumferential stresses within tol­erable limits. The second key improvement was the “duct” appendix. Earlier balloons had been vented at their bases to permit them to valve their excess gas at ceiling altitude. That, however, permitted the premature admixture of air into the balloon envelope, and the balloons would not remain for long at their peak altitude. The new approach used a duct that extended from the base to well up within the gas envelope, so that venting could occur without diluting the lifting gas.

OPENING SPACE RESEARCH

Frank B. McDonald was one of the University of Minnesota cosmic ray researchers who profited greatly from these developments.