Stratobowl

In 1934 the NGS and Air Corps co-sponsored the Explorer, a manned high-altitude balloon capable of stratospheric flight. After the crash of the Soviet Osoaviakhim-1 that nevertheless set an altitude record of , the sponsors redefined their primary objectives from record-setting to scientific research and tests of new navigation instruments. Kepner and Anderson, experienced balloonists, were in charge of locating a suitable launch site. According to Kepner, an ideal site would be a crater or canyon, a clear grassy valley encircled with rocky ridges high enough to shield the tall balloon from any wind. Ideally, the launch site it would have a high-voltage electric line, road and rail access, "and a trout stream". Anderson directed construction of a temporary village, housing over 100 people, with the help of the South Dakota National Guard and the army's 4th Cavalry Regiment. At the remaining hydrogen exploded, sending the gondola in a free fall. According to Ryan, the pilots managed to bail out after the explosion, Kepner at an altitude of barely ; The accident was linked to folds in the balloon's fabric that put it under extreme stress as the balloon expanded in stratosphere. The NGS and Air Corps vowed to launch a new balloon in June 1935, Watched by 20,000 spectators, Anderson, Kepner, and Stevens became the first men to view the Earth's curvature. ==Strato-Lab balloons==

In the 1950s, Project Manhigh and Project Strato-Lab launches were made from the man-made crater of an iron mining pit near Crosby, Minnesota, and, if weather allowed, from Fleming Field in South St. Paul, Minnesota. The Stratobowl was a backup location. There was one Stratobowl launch in 1956, three in 1958, and seven in 1959. On November 8, 1956, the Strato-Lab I gondola lifted Malcolm Ross and M. L. Lewis from the Stratobowl to a world altitude record for manned balloon flight of . The purpose of the flight was to gather meteorological, cosmic ray, and other scientific data necessary to improve safety at high altitudes. The most publicized flight, Strato-Lab IV piloted by Malcolm Ross and Charles B. Moore, lifted off from Stratobowl on November 28, 1959, reached an altitude of , and landed safely in Kansas after 20 hours in the air. The purpose of the flight was to perform spectrographic analysis of the planet Venus with minimal interference from the Earth's atmosphere. ==Notes and references==