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Nov 032014
 

1818f57 - Structural Anomaly Not Engine Failure Downed SpaceShipTwo

Christopher Hart, acting chairman of the National Transportation Safety Board (NTSB), said the agency has gathered much of the wreckage of SpaceShipTwo scattered over five miles of the Mojave Desert.

The NTSB is now pouring over the spacecraft debris, which includes the broken spaceship hull, fuel tanks and the rocket engine, to determine the facts, and not quite yet the causes, surrounding the downed Virgin Galactic SpaceShipTwo on Friday, October 31.

Hart said in a press conference on Sunday, November 2 that the rocket engine “came down intact, with no signs of breach or burn-through,” signaling many to surmise that the spacecraft crash was not allegedly caused by engine failure.

Hart described the additional facts about the NTSB’s preliminary investigation of the spacecraft wreckage that focused instead on a structural mishap received by the telemetry and cockpit video feed sent down by the spacecraft, that may have caused a loss of engine thrust power of SpaceShipTwo, while performing its test flight to 62 miles in attitude on Friday over the Mojave Desert.

Hart alluded that as SpaceShipTwo was performing its normal flight envelop outside of the pilot and copilot controls, a catastrophic structural mishap of the feather — “essentially a giant speed brake” — malfunctioned as the SpaceShipTwo was accelerating through its rocket engine power in relatively dense atmosphere that would significantly impede the rocket engine’s designed thermal ratio, thrust power and overall efficiency at its normally high operational Mach number, say at close to one and a half times the speed of sound.

Nevertheless, said Hart, “Approximately two seconds after the feathering parameters indicated that the Lock/Unlock lever was moved from “Lock” to “Unlock,” the feathers moved toward the extended position, the deployed position, even though the feather handle itself had not been moved.”

Basically, said Hart, “the feather operated prematurely.”

“Normal launch procedures are that after the release (of SpaceShipTwo from the WhiteKnightTwo carrier aircraft), the ignition of the rocket (thrust power is initiated) and acceleration (of the spacecraft commences).”

At this point, “the feathering devices are not to be moved — (that is) the lock/unlock lever is not to be moved into the unlock position — until the acceleration up to Mach 1.4 (or nearly one and a half times the speed of sound). Instead, as indicated, that (feathering) occurred (at) approximately Mach 1.0 (spacecraft flight speed),” Hart said.

He added: “We have months and months of investigation to determine what the cause was. We’ll be looking at training issues. We’ll be looking at, was their pressure to continue testing. We’ll be looking at safety culture. We’ll be looking at the design, the procedure. We’ve got many, many issues to look into much more extensively before we can determine the cause.”

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Photo Credit: Clay Center Observatory/Virgin Galactic, SpaceShipTwo’s feathering system is seen deployed on a test flight in 2011.

What Specifically Went Wrong With SpaceShipTwo’s Normal Operation?

According to a definitive technical description of the proper flight performance reported on Monday, November 3 in Popular Mechanics:

“The ship uses a unique design devised by SpaceShipOne designer Burt Rutan to return to safely to Earth after rocketing out of the atmosphere. After the engine cuts off and the ship coasts through its highest point, or apogee, the twin tail booms are designed to hinge upward. When the ship comes back through the atmosphere, the upward-hinged, or “feathered,” booms are designed to catch the air like the feathers of a shuttlecock and slow the craft down in what Rutan called a “carefree reentry.” Once the ship has slowed enough, the feather swings back down, and the pilots spirally glide the ship back down to the runway for landing.”

“The spaceship was released normally,” said Acting NTSB Chairman Chris Hart, referring to SpaceShipTwo’s separation from the WhiteKnightTwo aircraft carrier at 45,000 feet in normal flight operation. Subsequently thereafter release, the rocket engine ignited.

The rocket’s hybrid rocket motor, consuming a mix of nitrous oxide and a plastic-based solid fuel mix, ignited a few seconds after SpaceShipTwo’s release from the carrier aircraft.

Friday’s test flight marked the first time the rocket motor was used on SpaceShipTwo, since Virgin Galactic switched from a rubber-based to a plastic-based fuel, according to Space Flight Now.

Hart added: “About nine seconds after the engine ignited, the telemetry data showed us that the feather parameters changed from “Lock” to “Unlock,” and to get the feather up, two things normally must happen.”

“First, the feather Lock/Unlock handle must be moved from the “Lock” to the “Unlock” position. Next, the feathering handle must be moved to the feathered position.”

Hart said that video images from cameras in the cockpit confirmed that the copilot, Mike Alsbury, had moved the handle from the “Lock” to the “Unlock” position.

Moving the feather lock handle is supposed to happen after the ship hits Mach 1.4. Instead, it happened “just above Mach 1.0,”

Such action on a SpaceShipTwo flight is not expected until the rocket plane reaches Mach 1.4, Hart told reporters during the NTSB press conference Sunday night in Mojave, California.

“Still, that shouldn’t cause the feather to operate — not until the feathering handle is also moved. That second handle didn’t move,” according to Hart.

The tail booms extended after they were unlocked, even though they were not commanded to do so, Hart said. SpaceShipTwo’s pilots in performing normal flight operations must unlock the feathers, upon which moments later, the pilots send a separate command to move the tail booms into position for descent.

Regardless, said Hart in responding to this particular procedure, “This was what we would call an uncommanded feather, which means the feather occurred without the feather lever being moved into the feather position,” Hart said.

“After it was unlocked, the feathers moved into the deployed position, and two seconds later we saw disintegration,” Hart said.

“Shortly after the feathering occurred, the telemetry data terminated and the video data terminated,” Hart said, shortly after the feather deployed, presumably as the ship broke apart.

On January 10, 2014, Virgin Galactic’s SpaceShipTwo completed its third powered flight, breaking the speed of sound in an important test flight. In command on the flight deck for the first time under rocket power was Virgin Galactic’s Chief Pilot Dave Mackay. The video below shows how SpaceShipTwo’s feathering system works from a camera attached to one of the ship’s tail booms on the January 10 test flight.


Virgin Galactic founder, Sir Richard Branson paid his respects to the bravery of his company’s test pilots, and vowed to find out the cause of the SpaceShipTwo spacecraft test flight crash on Friday, October 31 that killed the test co-pilot and injured the pilot, during a news conference at the Mojave Air and Space Port (about 95 miles northeast of Los Angeles) in Mojave, California, on Saturday, November 1, 2014.

Officials also identified the two pilots in Friday’s Virgin Galactic SpaceShipTwo spacecraft crash. Co-pilot Michael Alsbury, 39, who died, was a married father of two. He lived in Tehachapi, California, near the Mojave Air and Space Port, where the test flights were conducted, USA Today reported.

Alsbury was a project engineer and test pilot at Scaled Composites, based at the Mojave Air and Space Port, and a Northrop Grumman Corp subsidiary that built and designed the spacecraft for Virgin Galactic, The Guardian (U.K.) reports. He was flying for the ninth time aboard SpaceShipTwo, including serving as the co-pilot on the vehicle’s first rocket-powered test flight on April 29, 2013, according to his biography on Scaled Composite’s website. Photo Credit: David McNew, Getty Images, Michael Alsbury in April 3, 2003, Mojave, California.

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Peter Siebold, 43, who was injured as pilot, parachuted out of the SpaceShipTwo spacecraft, but suffered major injuries. He was to undergo surgery, but there were no other details on his condition, Kern County Sheriff Donny Youngblood said Saturday, November 1, according to Mashable. Photo Credit: Scaled Composites, Peter Siebold (shown in flight suite years earlier).

20b3583 - Structural Anomaly Not Engine Failure Downed SpaceShipTwo

 

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