September 1941
From The Space Library
Messerschmitt Me-103A powered by "cold" H. Walther rocket successfully flown at Augsburg, Germany, development of which had begun in 1937, but "cold" engine proved unreliable. Flights were also made in October which reached speeds of 1,003 km/hr, or Mach 0.85.
Dr. Robert H. Goddard began work on liquid-propellant JATO under contract to USN and AAF, delivering a device to both agencies on September 1942.