Atlas V Anomaly Traced to Fuel System

Atlas V Anomaly Traced to Fuel System

The United Launch Alliance (ULA) has determined that the first stage of its Atlas V rocket shut down prematurely on March 22 because of a problem in the first stage fuel system.   The rocket’s Centaur upper stage compensated for the first stage anomaly and placed Orbital ATK’s OA-6 Cygnus cargo spacecraft in the correct orbit, but ULA needs to determine what happened before conducting the next Atlas V launch.

In a statement today, ULA said that a review team “has been successful in isolating the anomaly to the first stage fuel system and it associated components.”   The team will “thoroughly assess all flight and operational data to determine root cause and identify appropriate corrective actions prior to future flights.”

The next Atlas V launch was scheduled for May 5, but ULA has already postponed it until at least May 12 while it investigates the anomaly.  That rocket will place the Navy’s fifth Mobile User Objective System (MUOS-5) communications satellite into orbit.

During the OA-6 launch, the Atlav V first stage shut down 6 seconds early.   The Centaur upper stage fired approximately 60 seconds longer than planned to compensate for the under performance and placed Cygnus into the proper orbit for its later rendezvous and berthing to the International Space Station, where it is today.    Thus, the launch was a “mission success.”   It was the 62nd Atlas V launch and the first to experience any problems.   Atlas Vs are powered by Russian RD-180 engines.

Orbital ATK was launching Cygnus on an Atlas V because it is still recovering from the launch failure of its Antares rocket in October 2014 that destroyed an earlier Cygnus spacecraft.  It purchased two Atlas V launches from ULA so it could fulfill its contractual commitments to NASA to send 20 tons of cargo to the ISS by the end of 2016.  This was the second of the two, although Orbital ATK says that future Cygnus spacecraft also could be launched on Atlas Vs depending on NASA’s needs.

Antares also uses Russian rocket engines.  The original version that failed in 2014 used NK-33 engines built four decades ago and refurbished in the United States by Aerojet Rocketdyne and redesignated AJ-26.  Orbital ATK is “re-engining” Antares, replacing the NK-33/AJ-26 engines with new Russian RD-181s.  A hot fire test of the first RD-181 powered Antares is expected in May, with Antares launching the next Cygnus in June or July, according to comments by NASA Administrator Charlie Bolden at a meeting of the NASA Advisory Council this morning.

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