SS2 Pilot Siebold Unaware Critical Lever Moved Prematurely

SS2 Pilot Siebold Unaware Critical Lever Moved Prematurely

The National Transportation Safety Board (NTSB) issued an update on its investigation into the October 31 SpaceShipTwo (SS2) accident that claimed the life of co-pilot Michael Alsbury and seriously injured pilot Peter Siebold.   Siebold’s injuries prevented the NTSB from interviewing him until last Friday and the update includes a brief summary of what he told them.

SS2 was a spaceplane developed by Scaled Composites for Richard Branson’s Virgin Galactic enterprise to take anyone who could afford the $250,000 ticket price on a suborbital trip to space.  The October 31 mission was a test flight from the Mojave Air and Space Port, CA, in preparation for commercial operations that were to begin early in 2015.  The two pilots were Scaled employees.

The spaceplane is carried aloft by a large aircraft, WhiteKnightTwo, which drops the spaceplane at about 45,000 feet altitude.  The spaceplane then fires a rocket engine to ascend to at least 100 kilometers, an internationally recognized (but not legally defined) boundary between air and space, and after about six minutes in weightlessness, returns to land on Earth.

The NTSB previously determined based on video from the SS2 cockpit and other data that Alsbury prematurely moved a lever to initiate a “feathering system” designed to slow the spaceplane during its descent.  The lever should have been moved only when the spaceplane reached Mach 1.4, but Alsbury moved it from locked to unlocked at Mach 1.02 during ascent.  A second step, where the pilot would move another lever, ostensibly was required to actually activate the feathering system.  That second step never took place, but the feathering system deployed itself, changing the position of tail booms on the vehicle.  NTSB investigators stress that they have reached no conclusions about the accident and only are stating facts, but there is widespread supposition that with the feathering system activated at the wrong time, aerodynamic forces tore the spaceplane apart. 

The two men fell from a very high altitude (which has not been revealed, but SS2 was released at about 45,000 feet and fired its rocket engine for about 11 seconds, so they were quite high).  They were wearing parachutes, but no pressure suits.   The vehicle did not have ejection seats.  Alsbury was found dead in his seat on the ground.

Siebold survived, which many consider a miracle.  According to today’s NTSB update, Siebold told them he was “extracted from the vehicle as the result of the break-up sequence and unbuckled from his seat at some point before the parachute deployed automatically.”   He told the NTSB that he was not aware that the feathering system had been unlocked by Alsbury.

The NTSB said it has completed its on-site investigation work at Mojave. The SS2 wreckage has been recovered and is in secure storage.  Analysis of the data will continue at the NTSB’s Washington, DC laboratory.   NTSB acting chairman Christopher Hart said earlier that the complete investigation could take 12 months.  

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