NASA is unable to fully determine the cause of the 2011 failure of an Orbital Sciences Taurus XL that resulted in the loss of an Earth observation satellite. A report, released on 20 February, concluded that a payload fairing failed to release but was unable to fully explain the cause.

On 4 March, 2011, a three-stage Taurus XL lifted off from Vandenberg AFB, California, carrying the Glory satellite and three small cubesats aloft for NASA. After three successful stage firings and separations, one of the two halves of the payload fairing failed to separate. The extra weight and instability caused the third stage and attached satellite to fall back into the Pacific Ocean.

Payload fairings protect the delicate satellites from heat generated by atmospheric friction, but are discarded as soon as they are no longer needed.

The report points to a problem with the fairing separation system at its base, where the fairing attaches to the third stage. "The detailed analysis pointed to a failure to fracture near the forward end of one of the fairing side rails, which prevented full separation," says the report summary. Investigators were unable to definitely explain what may have caused the issue, noting that neither the rocket nor the satellites were recovered.

It was the Taurus launch vehicle's ninth launch. The eighth launch, on 24 February, 2009, also failed due to a payload fairing release malfunction, resulting in the loss of NASA's Orbiting Carbon Observatory.

The full report was not released, citing information proprietary to the companies involved and international trafficking in arms restrictions.

Orbital Sciences continues to offer the Taurus XL, but has no manifested flights.

Source: Flight International