The Ryan Model 147 Lightning Bug reconnaissance drone was enjoying success in Vietnam in the early 1960s, but it lacked the range to fly deep into China and back out again. In particular, the Chinese nuclear development facility at Lop Nor was far out of reach of the Lightning Bugs, and was barely within reach of the Lockheed U-2 spyplane, which had become far too vulnerable to SAMs. US intelligence thus needed a long-range drone with a high degree of survivability. Such requirements spelled out a completely new design, not a modification of a target drone.