Live coverage: Delta 2 launches

A United Launch Alliance Delta 4-Heavy rocket blasted off from Cape Canaveral at 1:51 p.m. EDT (1751 GMT) today to haul a classified satellite into space for the U.S. National Reconnaissance Office. Follow the mission in our live journal.

United Launch Alliance will salvage the main engines through a mid-air recovery plan and reuse them again aboard the company’s new Vulcan rocket, saving 90 percent in booster propulsion costs, the company announced Monday.

SpaceX’s next Falcon 9 rocket launch, using a previously-flown first stage booster, took a step closer to liftoff Thursday with a countdown rehearsal culminating in ignition of the launcher’s nine Merlin main engines in a hold-down firing at pad 39A at NASA’s Kennedy Space Center in Florida.