The Delta 4 rocket lifted off from coastal Vandenberg Air Force Base at 2:11 p.m. Friday and headed toward orbit.
The third time was the charm for United Launch Alliance and its twice-delayed NROL-47 mission. "Latest weather briefing shows an 80% chance of favorable weather". The secretive nature of this launch is attributed to the fact that it is a mission for the National Reconnaissance Office (NRO) in support of the national defense. Assuming confirmation of a problem-free launch Friday, ULA's record will stand at 124 successful flights in a row, including 27 for the NRO.
The top secret NRO missions are generally classified - so it is unclear what specifically the satellite will be doing on its orbit around earth. It performs launch services for the US government at Vandenberg and Cape Canaveral Air Force Station in Cape Canaveral, Florida.
With operational launch pads on both coasts-Space Launch Complex-37 at Cape Canaveral Air Force Station, Fla., and Space Launch Complex-6 at Vandenberg Air Force Base, Calif. -every Delta IV configuration is available to service the requirements of current and future satellite programs.
United Launch Alliance is set to carry out the classified NROL-47 mission on Thursday.
Colonel Greg Wood, 30th Space Wing vice commander, said: "We are ready and eager to take on this Delta launch". They burned for about 90 seconds and provided more than 560,000 pounds of thrust. The booster and upper stage engines are both built by Aerojet Rocketdyne.
The blastoff and initial phases of the rocket's flight were a success.
Thursday's delays were due to an issue with a ground system valve, according to ULA, which had also earlier reported issues with swing arms, which connect parts of the rocket to the launchpad and typically move away from the vehicle between ignition and liftoff. The NRO publicized the launch with generic tweets, saying the mission was the first of two planned by the agency this year.