The investigation found the shutdown was caused by unexpected shift in fuel pressure differential across the RD-180 Mixture Ratio Control Valve (MRCV) and a reduction in fuel flow to the combustion chamber caused an oxidizer-rich mixture of propellants and a reduction in first stage performance.
"The engine supplier has implemented a minor change to the MRCV assembly to ensure the anomaly does not occur on future flights," the release stated.
Cygnus is an unmanned spacecraft that carries cargo to the International Space Station. Cygnus was launched on an Atlas V — a two-stage rocket that uses the Russian-made RD-180 engine and a Centaur rocket as its second stage.
The ULA is a joint venture owned by Lockheed Martin and the Boeing Company that brings together two of the launch industry’s most experienced and successful teams — Atlas and Delta — to provide reliable, cost-efficient space launch services for the US government.
