Interest in such an undertaking was prompted by several factors. For one thing, intelligence had revealed that the Russians were definitely working toward satellites, so the project had a politico- technological value to this nation. Besides that, there was a high-altitude aircraft development project—the X-15—that was slated to attain heights of from 100 to 150 miles, and little data was available as to the environment the pilot or the aircraft would face.  Thus, a minimum satellite (uninstrumented) could be launched to perfect launching techniques, study orbital behavior, and devise tracking methods. Once this was accomplished, more sophisticated satellites could be placed in orbit that had the capability to gather data on conditions outside the  sensible atmosphere. The artificial satellites could also be a part of the International Geophysical Year (IGY) 126 . Just prior to the time that a decision was made as to the course the program would follow, the Air Force and Navy presented DOD with a new instrumented concept based on the VIKING missile. This became known as the VANGUARD program. DOD appointed an ad hoc committee to weigh all the proposals, and the committee chose the VANGUARD approach, based on the contention that the cost would be less and that the Army plan was marginal in assuring success. Their main complaint was against the 75,000 pound thrust REDSTONE power plant 127 . Ironically, when EXPLORER I was boosted into orbit, a slightly more efficient fuel was used to boost the thrust to 83,000 pounds 128 . _____________________________

126. Memo to Rear Adm F. R. Furth & Maj Gen L. E. Simon, 14 Dec 54, subj: Conf on Project Orbiter, and attachments, Hist Off files. 127. Rpt of the Ad Hoc Advisory Group on Spec Capabilities. OASD (R&D), Aug 55, Hist Off files. 128. Hist, ABMA, Jan-Jun 58, p. 102, Hist Off files.