Powerful Delta 4 Heavy rocket boosts spy satellite into space from California

A powerful United Launch Alliance Delta 4 Heavy, one of only four remaining on the company's books, blasted off from California on Monday afternoon, lifting a classified National Reconnaissance Office spy satellite into space.

The Aerojet Rocketdyne RS-68A engines powering the rocket's three side-by-side "common booster cores" thundered to life with a roaring rush of flame at 4:47 p.m. EDT, pushing the 233-foot-tall vehicle away from launch complex 6 at Vandenberg Air Force Base northwest of Los Angeles. Generating 2.1 million pounds of thrust — the equivalent of 51 million horsepower — the hydrogen-fueled engines quickly propelled the rocket skyward, consuming 5,000 pounds of liquid hydrogen and oxygen propellants per second as it arced away on a southerly path over the Pacific Ocean.