A Delta 4-Heavy rocket is awaiting launch from Cape Canaveral on the NROL-44 mission, carrying a classified satellite for the National Reconnaissance Office. Credit: United Launch Alliance
United Launch Alliance said Thursday it is targeting Sept. 26 for the next attempt to send a classified U.S. government spy satellite into orbit aboard a Delta 4-Heavy rocket, following an abort Aug. 29 just three seconds before liftoff from Cape Canaveral.
A computer automatically called the abort Aug. 29 after one of the rocket’s three Aerojet Rocketdyne RS-68A main engines had already ignited. ULA said Thursday that the launch team determined “a ground system regulator internal component failure was the cause of the on-pad abort.”
Three flow rate regulators are used in the high-pressure helium gas system that spins up the turbines on the Delta 4-Heavy’s three RS-68A main engines. The rocket’s starboard engine fired up normally, but a regulator for the center engine’s regulator did not open.
The Delta 4-Heavy is made of three common booster cores, each powered by a single RS-68A engine. The engines are timed to ignite in a staggered sequence in the last few seconds before launch, beginning with the starboard engine and followed by the center ...