United Launch Alliance called off the planned liftoff of a Delta 4-Heavy rocket and a classified National Reconnaissance Office spy satellite from Vandenberg Air Force Base in California on Wednesday after indications of elevated hydrogen concentrations around one of the launcher’s main engines. Three previous launch attempts were scrubbed by technical concerns and bad weather.
United Launch Alliance kicked off its 2018 launch campaign with a Delta 4 rocket flight at 2:11 p.m. PST (5:11 p.m. EST; 2211 GMT) Friday from Vandenberg Air Force Base in California. Gusty winds forced officials to call off a launch attempt Wednesday, and technical problems halted a countdown Thursday multiple times. The Delta 4 launched with a top secret spy satellite for the National Reconnaissance Office.