A United Launch Alliance Delta 4 rocket carrying a classified National Reconnaissance Office spy satellite thundered into space Wednesday after a fiery pre-dawn launch from California.
The towering Delta 4, equipped with two solid-fuel strap-on boosters for extra liftoff power, thundered to life at 6:40 a.m. EST (GMT-5; 3:40 a.m. local time) and quickly climbed away from Space Launch Complex 6 at Vandenberg Air Force Base northwest of Los Angeles.
Arcing away to the south, the Delta 4 put on a brilliant pre-dawn show, lighting up the launch site with a jet of flame from its Aerojet Rocketdyne RS-68A first-stage engine and Orbital ATK solid rocket boosters.
The strap-on boosters burned out and fell away about a minute and a half into flight. The rocket's hydrogen-fueled first-stage engine followed suit a few minutes later, followed by stage separation and ignition of the Aerojet Rocketdyne RL10B-2 engine powering the Delta's second stage.
But as usual with classified military flights, United Launch Alliance, builder of the Delta 4, cut off its mission commentary near the end of the first stage burn at the request of the NRO. The identity of the payload was classified and no details were released beyond the mission designation: NROL-45.
But the trajectory of the Delta 4 indicated the objective was an orbit around Earth's poles, which allows satellites to pass over all points on the planet's surface as it rotates below. Polar orbits are favored by optical and radar-imaging spy satellites.
Ted Molczan, a respected satellite analyst who tracks military payloads, said the satellite launched Wednesday is probably the fourth in a series of radar imaging satellites built by Boeing for the NRO's troubled Future Imagery Architecture program.
Spaceflight Now (http://www.spaceflightnow.com) reported two firings by the Delta 4's second stage were required to boost the latest spysat into a 685-mile-high "retrograde" orbit tilted 123 degrees to the equator.
Radar imaging satellites are able to carry out high-resolution reconnaissance regardless of lighting or cloud cover. The first of the "Topaz" radar satellites is believed to have been launched in 2010. Plans for higher-resolution optical recon satellites in the FIA program were canceled in 2005 because of technical issues and cost overruns.
Wednesday's launch was the 31st Delta 4 flight since the rocket's debut in 2002, the sixth to take off from Vandenberg, the eighth to launch an NRO payload and the second of as many as 15 flights planned by ULA in 2016.
ULA, a partnership between Boeing and Lockheed Martin, plans to phase out the Delta over the next few years as it brings its new Vulcan booster on line around the end of the decade.