Page:This New Ocean, a history of Project Mercury, Swenson, Grimwood, Alexander (NASA SP-4201).djvu/39



''Military missiles of the 1950s provided both the technology and the first-generation boosters for the nascent space program. The Air Force's Navaho (left) was a long-range cruise missile overtaken by the onrush of technology; though it was canceled as a project, it had pioneered the development of large rocket engines and guidance systems. The Atlas missile (center) had a hectic on-and-off career in the early 1950s but became the first operational ICBM and the major "large" boost vehicle for manned and unmanned space missions in the first decade of the space age. Thor (right), the sturdy, reliable baby of the Atlas technology, served an interim military role as an operational IRBM and a longer and more illustrious role as the workhorse booster of the first decade of payloads for military and nonmilitary space projects. Shown here with an Able second stage, it accepted a variety of second stages and payloads.'' 24