United Launch Alliance (ULA) successfully launched the US National Reconnaissance Office's (NRO) NROL-15 spy satellite aboard the upgraded Delta IV Heavy rocket from the Cape Canaveral Air Force Station in Florida, US.
The launch of US military's secret mission marked the initial flight of the upgraded RS-68A engine developed by Pratt & Whitney Rocketdyne.
ULA Mission Operations vice president Jim Sponnick said the successful launch of the NROL-15 mission on June 29 was the third of four launches for the NRO this year and the second EELV launch for the NRO in just nine days.
"The upgraded Delta IV Heavy vehicle was developed with an extremely thorough and comprehensive system engineering process by the ULA and Pratt-Whitney Rocketdyne teams, along with substantial involvement by our US Government customers," he said.
The first stage of the 232ft-tall rocket, comprising three liquid-fuelled common core boosters, was powered by upgraded RS-68A liquid hydrogen/oxygen engines, while Pratt and Whitney RL10B-2 liquid hydrogen/oxygen engine powered the second stage.
ULA said that the payload was enclosed within a 5m diameter, 65ft, metallic tri-sector payload fairing.
According to ULA, the launch was scheduled for 28 June, but was delayed by 24 hours due to the adverse weather conditions caused by tropical storm Debby.
ULA's evolved expendable launch vehicle programme (EELVP) is commercially developed in collaboration with the US Air Force to offer secure access to space for payloads of government and the US Department of Defense.
The agency is also planning to launch NRO's Atlas V NROL-36 mission on 2 August from Space Launch Complex-3 at Vandenberg Air Force Base in California, US.
Image: ULS Delta IV Heavy rocket, carrying NRO's national security payload during its launch. Photo: courtesy of United Launch Alliance, LLC.