Delta IV-Heavy launches NROL-15

6/29/12 ~ 9:15 a.m.

A 24-story Delta IV-Heavy rocket, the world's largest, lifts off with the NROL-15 payload for the National Reconnaissance Office. The launch marked the first flight of the RS-68A main engines, an upgrade of the Delta IV rocket's core engines that provides more thrust (over 702,000 lbs at liftoff compared to about 656,000) and which can boost more payload into orbit. It also marked the first daytime launch of a Heavy at Cape Canaveral since the debut mission in December 2004.