Following a nearly 18-month investigation slated to end in April, the Air Force and the United Launch Alliance believe thrust issues that occurred during an October 2012 Delta IV rocket launch are not systemic, officials said today. The investigation was initiated in 2012 when a ULA-built Delta IV rocket booster's second-stage RL10B2 engine provided a lower-than-expected thrust during an otherwise successful GPS IIF-4 launch. The Air Force, ULA and RL10B-2 engine maker Aerojet Rocketdyne conducted an investigation, and Air Force...