Developed by the University of Michigan for use by the Air Force Cambridge Research Center, Exos used a three-stage configuration, consisting of a first-stage rocket from an Honest John rocket, a second stage from a Nike-Ajax surface-to-air missile, and a Thiokol XM19 upper stage.[1] It was designated XRM-86 in April 1959, and redesignated PWN-4A in June 1963.[2]
Utilising a rail launcher, the first launch of a full Exos vehicle took place in June 1958,[2] launched from the Wallops Flight Facility.[3] Eight operational launches took place between 1960 and 1965, launched from Eglin Air Force Base.[4]
^Skoog, Å. Ingemar and R. Cargill Hall, ed. (1990). History of Rocketry and Astronautics: Proceedings of the Twelfth, Thirteenth and Fourteenth History Symposia of the International Academy of Astronautics. AAS History Series. Vol. 10. Springfield, Virginia: American Astronautical Society. p. 214. ISBN978-0-87703-329-5.