Paul Edward Yost (June 30, 1919 – May 27, 2007) was the American inventor of the modern hot air balloon and is referred to as the "Father of the Modern Day Hot-Air Balloon." He worked for a high-altitude research division of General Mills in the early 1950s until he left to establish Raven Industries in 1956, along with several colleagues from General Mills. Inventor Born on a farm seven miles south of Bristow, Iowa to Charles L. Yost and Fleta Ferne Burman Yost, Paul Edward Yost first became involved in lighter-than-air ballooning when he leased his single-engine plane to General Mills to track their gas balloons. He became a senior engineer in the development of high-altitude research balloons. In the 1950s, Yost's own interests turned toward reviving the lost practice of manned hot-air ballooning. This technology had first been invented in France in the late 18th century by pioneers led by the Montgolfier brothers, but under the Montgolfier system, the balloon's air was heated by a ground fire prior to the balloon being released. The inherent danger of this type of balloon flight led to the system being abandoned when hydrogen and later helium became available. One of Yost's key engineering insights was that a hot-air balloon could be made to carry its own fuel. The invention of relatively light burners fueled by bottled propane made it possible for the balloonist to re-heat the air inside the balloon for a longer flight. Yost’s invention improved modern hot-air balloons into semi-maneuverable aircraft. Yost patented further refinements he made to the hot-air balloon, including nonporous synthetic fabrics, maneuvering vents, and deflation systems for landing. Yost also designed the distinctive “teardrop” shape of the hot air balloon envelope itself. Aviator In October 1955, Yost developed and flew the first prototype of the modern hot-air balloon in a tethered flight. The envelope was plastic film, and heat was provided by burning kerosene. This prototype flight uncovered conceptual flaws that Yost worked to overcome. Raven Industries pioneered hot air balloons manufacturing. Raven was founded in 1956 by Paul Edward Yost, J. R. Smith, Joseph Kaliszewski, and Dwayne Thon, while working in the General Mills scientific balloon program. Headquartered in Sioux Falls, SD; Raven was contracted by the US Navy's Office of Naval Research (ONR) to create a reusable, lightweight balloon that would carry a pilot to 10,000 feet and fly for three hours. Yost made