Video: Liftoff of Atlas 5 on NROL-55

A week after a test-firing of SpaceX’s new crew capsule went awry, SpaceX successfully completed a hold-down firing of its next Falcon 9 launcher Saturday morning at Cape Canaveral in preparation for a predawn liftoff Wednesday carrying several tons of food, supplies and experiments to the International Space Station.

Lockheed Martin, the largest U.S. defense contractor, announced late Sunday that it has reached a deal valued at $4.4 billion to acquire Aerojet Rocketdyne, a supplier of engines to NASA’s Space Launch System moon rocket and United Launch Alliance’s Atlas, Delta, and Vulcan rockets.

A critical test firing Saturday of the four main engines powering the first stage of NASA’s gargantuan Space Launch System moon rocket is the final major hurdle before the fully assembled booster’s costly, oft-delayed launch late this year on an unpiloted test flight.