Big Delta Heavy rocket launches U.S. spy satellite

April 26 (UPI) -- One of the most powerful rockets in the world, the Delta IV Heavy, lifted off into a sunny Southern California sky Monday afternoon, carrying a spy satellite or satellites for the U.S. Reconnaissance Office.

The United Launch Alliance rocket was launched at 4:47 p.m. EDT from Complex 6 at Vandenberg Air Force Base, about 160 miles northwest of Los Angeles.

After one minute in flight, the rocket had accelerated to 1,000 mph.

"The rocket now weighs just half of what it did during liftoff because it is burning propellant at a rate of almost 5,000 pounds per second," Robert Kesselman, a thermal engineer for ULA, said during a live broadcast just minutes after launch.

Delta IV Heavy has three boosters mounted together to form a triple-body rocket. With its second-stage and nose cone, it stands 233 feet high and produces 2.1 million pounds of thrust at sea level.

By comparison, SpaceX's Falcon Heavy stands about 230 feet high and emits about 3.4 million pounds of thrust at liftoff.

Monday's launch was one of the last for the Delta Heavy, as ULA prepares to roll out its new Vulcan series. Only four more Delta Heavy missions are expected, according to ULA.

Little is known about the satellite because the mission is for the reconnaissance office, which "uses a variety of satellites to ... provide global coverage against a wide range of intelligence requirements, carry out research and development efforts, and assist emergency and disaster relief efforts in the U.S. and around the world," according to the agency's mission description.

Data from such satellites goes to the president, Congress, national policymakers, warfighters and some civil users, according to the office.