"In 1938, the Army Air Corps decided they needed an official song. Liberty Magazine sponsored a contest whereby 757 scores were submitted. Of those, one written by Robert Crawford was selected by a committee of Air Corps wives and officially introduced at the Cleveland Air Races in 1939. Crawford himself sang it in its first public performance. When the Army Air Corps became a separate branch of the military in 1947, Crawford’s march changed names from 'The Army Air Corps' to the 'U.S. Air Force.'
"Since that time, the first line of 'Nothing’ll Stop the U.S. Air Force' became a motto and tradition. On July 30, 1971, the original first page submitted by Robert Crawford in 1939 was carried into space in the Apollo 15 'Falcon' and broadcast to the world by Major Alfred W. Worden, who had a tape recorder aboard the 'Endeavor' command module. The 'All-Air Force' crew arranged to take the sheet music with them as a tribute to Crawford and the U.S. Air Force." (Military Songs - United States Department of Veterans Affairs)
Hear it [here].