Numbering system

Different configurations are designated using a four-digit code, similar to the numbering system used on Delta rockets. The first digit denotes the type of first stage being used, and whether the second and third stages use a standard or "XL" configuration.^[10][11] The second digit denotes the diameter of the payload fairing.^[10] The third digit denotes the type of fourth stage.^[10] The fourth digit denotes an optional fifth stage, so far unused.^[10]

Orbview-4

On 21 September 2001, a Taurus XL rocket failed during launch. When the second stage ignited at T+83 seconds, a nozzle gimbal actuator drive shaft seized for approximately 5 seconds causing loss of control. The vehicle recovered and continued to fly the mission profile, but failed to reach a stable orbit and reentered near Madagascar.^[14]

Orbiting Carbon Observatory

On 24 February 2009, a Taurus XL rocket failed during the launch of the US$270 million Orbiting Carbon Observatory spacecraft.^[15] Liftoff occurred successfully at 09:55 UTC from Vandenberg Air Force Base, but data received at a later stage of the flight suggested that the fairing failed to separate. The rocket did not reach orbit,^[4] owing to the extra weight of the fairing.^[6][13] Launch vehicle and services for OCO are estimated at US$54 million.^[16] The replacement satellite, Orbiting Carbon Observatory 2, was launched on 2 July 2014 aboard a Delta II rocket.^[17][18][19]

Glory

On 4 March 2011, a Taurus XL rocket failed again during the launch of NASA's US$424 million Glory climate change monitoring satellite. In total, the last two failures of the Taurus XL have resulted in payload losses worth $700 million.^[7] The reason for the failure was the same as with OCO: the payload fairing failed to separate, although the rocket's manufacturer Orbital Sciences Corporation had spent the last two years trying to fix the problem and had made several design changes to the fairing separation system. Ronald Grabe, manager of Orbital Sciences Corporation, which also built the Glory satellite itself, said the employees of his companies are "pretty devastated" because of the latest failure.^[6] The fairing was built by the Vermont Composites company, and the frangible rail pyrotechnic separation system was built by the Ensign-Bickford Company. A NASA MIB panel concluded that the failure was most likely caused by a section of the frangible rail somewhere near the nose cap failing to separate. While a root cause could not be identified, two likely causes were identified: the rubber charge holder in the frangible rail slumping due to launch acceleration and random vibration, or a failure of the frangible rail system due to it operating outside the environment for which it was tested.^[20]

A continued investigation eventually revealed that sub-standard parts provided by Sapa Profiles, Inc. (SPI) with falsified test results were the likely cause of both of the OCO and Glory fairing failures.^[21]