A discussion of the antecedents of the X-1 from 1928, when a rocket plane designed by Lippisch was flown in West Germany, to such developments as the Me. 163 and the MX-324, with special concentration on the contributions of such people as Opel, Valier, Sanger, Goddard, and Walter. Also included are charts giving some of the important specifications of early rocket aircraft.
Perry, Robert L., The Antecedents of the X-1. Santa Monica, CA: RAND Corporation, 1965. https://www.rand.org/pubs/papers/P3154.html. Also available in print form.
Perry, Robert L., The Antecedents of the X-1, Santa Monica, Calif.: RAND Corporation, P-3154, 1965. As of October 27, 2021: https://www.rand.org/pubs/papers/P3154.html