Even before Tuesday's failure, Orbital Sciences had been reviewing alternatives to the Russian-made engines, Thompson said. The company recently had selected a different main propulsion system for use in another couple of years, and the switch may be accelerated if the Russian engines are the culprit, he said.
The AJ26 engines — modified and tested in the U.S. — originally were designed for the massive Soviet rockets meant to take cosmonauts to the moon during the late 1960s.
Three years ago, an AJ26 leaked kerosene fuel and ignited on the test stand at a NASA center in Mississippi. Just this past May, another of the engines exploded during a test firing there.