A powerful United Launch Alliance Delta 4 Heavy, one of only four left on the company’s books, lifted off from California on Monday afternoon, lifting a classified National Reconnaissance Office spy satellite into space.
The Rocketdyne RS-68A Aerojet engines powering the rocket’s three side-by-side “common thruster cores” came to life with a roaring wave of flame at 4:47 p.m. EDT, pushing the vehicle 233 feet away from Launch Complex 6 at Vandenberg Air Force Base northwest of Los Angeles.
Generating 2.1 million pounds of thrust – the equivalent of 51 million horsepower – the hydrogen engines quickly propelled the rocket skyward, consuming 5,000 pounds of liquid hydrogen and oxygen propellants per second as it was moving away on a southerly trajectory over the Pacific Ocean.
The two common-core outboard thrusters, after helping to lift the rocket out of the dense lower atmosphere, were jettisoned about four minutes after takeoff. The center thruster continued to fire another minute and 40 seconds before it was also thrown out.
The flight continued on the power of the RL10B-2 rocket’s only second-stage engine, but as usual with classified NRO missions, the United Launch Alliance ended its mission commentary moments later and the remainder of the theft was carried out in secret.
The moment of launch and the rocket’s trajectory, tilted about 98 degrees off the equator based on safety advisories displayed prior to take-off, closely matched the in-orbit trajectories used by previous classified optical imaging satellites. capable of collecting extremely detailed views of ground targets.
But the National Reconnaissance Office does not provide any information on its classified payloads or their orbits, and does not comment on outside speculation.
United Launch Alliance is a partnership between Lockheed Martin, maker of the Atlas 5 rocket family, and Boeing, which designed the Delta 4. Monday’s launch was the 13th of the most powerful Delta 4 Heavy variant.
ULA is phasing out the Delta 4 and eventually the Atlas 5 in favor of new Vulcan rockets that will be available in multiple configurations with reusable first stage engines.