STS-135: The final space shuttle landing

United Launch Alliance plans to assemble leftover parts for a Delta 2 rocket display at the Kennedy Space Center Visitor Complex in Florida alongside other icons of U.S. rocketry, the company announced Saturday soon after the final Delta 2 launch.

Nine Merlin engines at the base of SpaceX’s next Falcon 9 rocket fired up Tuesday on a launch pad in Florida, wringing out the booster and ground systems ahead of a planned liftoff Sunday with a top secret payload for the U.S. government’s spy satellite agency.

SpaceX scrubbed an attempt to launch a commercial Falcon 9 rocket Sunday less than a minute before liftoff, blaming a sensor issue on the vehicle’s first stage and pushing back the company’s first national security mission for the U.S. government at least 24 hours.