An unmanned Delta 4 Heavy rocket, the largest booster in in the U.S. fleet, lifts off from Vandenberg Air Force Base in California

An unmanned Delta 4 Heavy rocket, the largest booster in in the U.S. fleet, lifts off from Vandenberg Air Force Base in California to put a classified satellite into orbit for the National Reconnaissance Office August 28, 2013 REUTERS/Gene Blevins (UNITED STATES – Tags: SCIENCE TECHNOLOGY TPX IMAGES OF THE DAY) – RTX12ZM9