James Wyld was an American engineer and one of the founders of the American Rocket Society who, in 1938, built the first rocket engine to use regenerative cooling. Some preliminary work with this technique had been done in 1993 by Harry W. Bull who used it to cool the nozzle area only. The first tests of Wyld's 1-kilogram engine were carried out under the direction of the Rocket Society's Experimental Committee on 10 December 1938, with satisfactory results. In December 1941, Wyld helped found Reaction Motors, Inc., American's first commercial rocket company.