William Julius D. ("Bill") Escher (1931 – May 12, 2014) was an aerospace engineer involved in the early development of the United States rocket programs and long time aerospace industry visionary. He was an internationally recognized expert in the field of high-speed airbreathing propulsion and hypersonic flight. He was a long been a proponent of combined-cycle propulsion systems for space access and his visionary 'Synerjet' concept is industry recognized. He wrote over a hundred technical papers on this subject and others such as hydrogen energy and lunar exploration.