Doctor William K. Kroeger was born on June 6, 1906 and graduated in 1937 from the University of Pittsburgh with a doctorate in physics. He was employed at Frankford Arsenal, Pennsylvania, from January 1940 to July 1966, where he was Director of the Institute for Research.
In June 1943, at the direction of the Chief of Ordnance, Dr. Kroeger worked on a project to develop a recoilless rifle. Along with Mr. C. W. Musser, he worked out the fundamental theory for such a weapon and experiments were immediately begun with a simple, smoothbore gun, embracing a complete study of its interior and exterior ballistics. In September 1943, the design of the actual weapon was started. By the following year, a demonstration of the 57mm and 75mm recoilless rifles was conducted at Aberdeen Proving Ground.
Dr. Kroeger also pioneered the development of personnel escape systems for military aircraft, specifically the pilot ejection seat. Dr. Kroeger died on July 23, 1966.