ULA Traces Atlas V Anomaly to Malfunctioning RD-180 Valve

ULA Traces Atlas V Anomaly to Malfunctioning RD-180 Valve

The United Launch Alliance (ULA) announced today that the anomaly on its Atlas V rocket during the launch of Orbital ATK’s OA-6 cargo mission to the International Space Station (ISS) was due to a malfunctioning valve.  The Atlas V first stage under performed, but the Centaur upper stage was able to compensate and OA-6 reached the ISS successfully.

During the March 22 launch, the Atlas V first stage shut down six seconds early.  The Centaur upper stage rescued the mission by firing 60 seconds longer than planned, placing Orbital ATK’s Cygnus cargo spacecraft into its proper orbit nonetheless.  Cygnus reached the ISS on schedule.

ULA quickly determined the problem was in the RD-180 engine’s fuel system and decided to postpone the next scheduled Atlas V launch until it understood and remedied the problem.  The Navy’s fifth Multi-User Objective System (MUOS-5) communications satellite was scheduled for launch on May 5.  That date slipped to May 12 and then indefinitely.

Today, ULA issued a statement that the RD-180’s Mixture Ratio Control Valve assembly had caused a reduction in fuel flow during launch and all RD-180 engines are now being inspected.   It did not announce a new launch date for MUOS-5, saying only that the launch will be in “early summer.”   The company asserted that all its Atlas V launches planned for 2016 “are expected to be successfully executed by the end of the year.”   That includes NASA’s robotic asteroid sample return mission OSIRIS-REx, scheduled for September.

Russia’s RD-180 engines are currently the topic of considerable controversy.  Following Russia’s actions in Ukraine, Congress and the Administration became determined to end U.S. reliance on Russian rocket engines to launch U.S. national security satellites.   Efforts are underway to develop a U.S.-built engine to replace it, but there are disputes about the timing of transitioning from the RD-180 powered Atlas V rockets to something new.

The full text of the emailed ULA statement is as follows:

Centennial, Colo., (April 29, 2016) — ULA successfully delivered
the OA-6 Cygnus spacecraft to its precise orbit as planned on March 22.
During the launch, the system experienced a premature first stage
shutdown. Atlas is a robust system. The Centaur upper stage compensated
for the first stage anomaly, delivering Cygnus
to a precise orbit, well within the required accuracy. The ULA
engineering team has reviewed the data and has determined an anomaly
with the RD-180 Mixture Ratio Control Valve (MRCV) assembly caused a
reduction in fuel flow during the boost phase of the flight.
In addition to analysis and testing, all RD-180 engines are being

Friday, in preparation for the MUOS-5 launch, the Atlas V completed the
Launch Vehicle on Stand (LVOS) operation, erecting the Atlas V into the
Integration Facility at Cape Canaveral Air Force Station. LVOS will
allow configuration of the vehicle to support RD-180 engine
inspections and confirm all engine components are ready for launch. The
Atlas V MUOS-5 launch is targeted for early summer; a new
launch date has not been secured on the Eastern Range. The impact to
the remainder of the Atlas V manifest is in review with new launch dates
being coordinated with our customers. All missions manifested for 2016
are expected to be successfully executed by
the end of the year, including OSIRIS-REx, which will remain in early
September to support its critical science window


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