Photos: Sunday’s return of X-37B after 718 days in space

The Pentagon has awarded at least $162 million in contracts to Aerojet Rocketdyne and United Launch Alliance for development of the AR1 and BE-4 rocket engines, candidates to power the first stage of a next-generation rocket and replace the Russian-made engine currently flying on the Atlas 5 launcher.

The step-by-step stacking of United Launch Alliance’s final Delta 2 rocket was completed in June at Vandenberg Air Force Base in California for liftoff Sept. 15 with an Earth science satellite for NASA.

SpaceX’s next Falcon 9 rocket is being readied for liftoff Aug. 14 on a space station resupply run. The two-stage rocket completed a hold-down engine firing Thursday at launch pad 39A at NASA’s Kennedy Space Center in Florida.