[excerpted from Chapter 3 - Guggenheim Aeronautical Laboratory]When Dr. von Kármán took his leave of absence in 1944 to head Arnold's newly formed United States Army Air Force Scientific Advisory Board, his successor at the Guggenheim Aeronautical Laboratory was another aeronautical engineer who played a major role in the development of rocketry and missiles, Dr. Frank J. Malina. Dr. Malina and von Kármán had co-founded the Jet Propulsion Laboratory at Caltech in 1943. Drs. Malina and von Kármán, along with Martin Sommerfield, John W. Parsons, and Edward S. Foreman, had earlier founded the Aerojet General Corporation in 1941 to utilize their research in solid fuel rocket motors.
One of the engineers involved with the research work, and one of the signers of the 1943 report to General Arnold, was Dr. Tsien Hsue-shen. In an ironic twist of fate, or a show of unbridled stupidity, Dr. Tsien Hsue-shen, who was also later a member of Arnold's Scientific Advisory Board, was forced to leave the United States at the height of the McCarthy witch-hunts and, after five years of house arrest for having his name on a "suspected" communist meeting attendance list in 1938, returned to his native China in 1955 where he is now considered the father of the Chinese rocket and missile programs.
Dr. Malina was considered the father of the JATO rocket, the Jet Assisted Takeoff booster rocket. His team successfully "launched" an Ercoupe, a small, single engine civilian airplane, in 1941 as a display of JATO’s potential. Development work continued on different types of solid propellants, including asphalt and many other forms of fuels and oxidizers, leading to the development of castable elastomeric (polysulfide rubber) material called Thiokol. The Thiokol fuel, developed by Charles Bartley during a 1945 JPL-ORDCIT project, became the solid fuel to power not only the booster bottles used in launching tactical missiles, but later ballistic Intermediate Range Missiles (IRBMs) and Intercontinental Ballistic Missiles (ICBMs) as well. It was the work done with solid fuel propellants by this research team that allowed American design teams to soon develop the Zero Length Launcher, called ZEL, which made the first completely American designed and built tactical missile possible. The first operational U.S. tactical missile was to be built by the Glenn L. Martin Company and be called the Matador.
From my 2008 book, U.S. Air Force Tactical Missiles - 1949 - 1969 The Pioneers - Chapter 3 - "Laying the Groundwork" - co-authored with Robert Bolton