Part 3 in a Series
By Douglas Messier
With World War II-era structures still dotting its flight line and industrial park, the Mojave Air and Space Port sometimes reminds visitors of the training base where Marine Corps fighter pilots learned to fly 70 years earlier. Just beyond the airport’s three runways is a giant boneyard full of scrapped 747s and other aircraft that would not look all that out of place to a time traveler who ventured forward from 30 or 40 years ago.
The illusion of Mojave being some sort of a throwback, a graveyard for sand-blasted relics from another age, is punctured every time WhiteKnightTwo roars down Runway 30. A majestic dual fuselage aircraft with an enormous 141-foot wing span constructed of advanced, lightweight composite materials, WhiteKnightTwo is a true product of the 21st century. It almost seems to float off the runway on its enormous wings as it passes the boneyard.
As WhiteKnightTwo lifted off at 9:19 a.m. on Oct. 31, 2014, it carried aloft something even more exotic: Virgin Galactic’s SpaceShipTwo, a futuristic space plane bound for its fourth powered flight test. On board the spacecraft were Scaled Composites pilots Pete Siebold and Mike Alsbury.
After takeoff, pilot David Mackay banked WhiteKnightTwo right and headed north. His destination was a spot in the sky more than 45,000 feet above Koehn Lake about 20 miles north of Mojave. In addition to the dry lakebed, the remote area features large stretches of scrub brush bordered by craggy mountains. It has a very low population density, which was of primary concern for regulators from the Federal Aviation Administration (FAA).
During the halcyon days of SpaceShipOne’s historic flights in 2004, commercial space supporters had convinced Congress to pass a law that strictly limited the ability of the FAA to regulate the emerging industry. A moratorium was put in place under which the agency would formulate safety regulations in response to a serious incident or accident. Unlike commercial airliners, spaceships would be licensed but not be put through a rigorous certification process. Passengers would fly at their own risk under an informed consent regime designed to protect spaceflight providers from lawsuits.
The idea was to allow the industry to experiment with different designs and approaches without being tied down by restrictive regulations. During this learning period, the FAA’s main responsibility would be to protect the “uninvolved public.” That meant ensuring that a spaceship didn’t kill or injure bystanders on the ground if it crashed during a flight or blew up while being fueled at a spaceport.
It would take 48 minutes before WhiteKnightTwo would be ready to release SpaceShipTwo over the remote, lightly populated drop zone. The time was taken up by a carefully rehearsed series of pre-flight checks conducted by the two flight crews in coordination with Mission Control in Mojave. There were checks of the vehicles immediately after takeoff, at 18,000 feet, 30,000 feet and finally at 40,000 feet.
It was a routine that Siebold and Alsbury knew well. They had flown a dry run of this powered flight together at the end of August, and they had practiced the test many times since in the simulator.
Siebold had previously flown SpaceShipTwo 15 times, 14 times as pilot-in-command. This would be his first powered flight aboard the spacecraft. Alsbury had flown the space plane eight times previously, all as co-pilot. He and Mark Stucky were at the controls for SpaceShipTwo’s first powered flight on April 29, 2013.
There were some changes of personnel in Mission Control. Virgin Galactic pilot Todd Ericson was serving as test conductor for the first time. Jim Tighe had previously filled the role, but he had left Scaled for a new job three weeks earlier. Tighe continued to serve as an adviser to the program, and he was back in the control room for this flight.
Ericson’s prominent role was part of a gradual shift of operations to Virgin as Scaled prepared to turn SpaceShipTwo over to its customer in December. A number of personnel from Virgin Galactic and its subsidiary, The Spaceship Company, were at work stations in Mission Control for this flight test.
Ericson sat amid four rows of engineers who monitored the flight. They faced two large plasma televisions on the wall. The left screen included video streams and status information about the rocket motor. The right screen included additional data about SpaceShipTwo, including vehicle altitude and temperature, a moving map display and a caution advisory.
In the air, the vehicle checks were moving along smoothly. Everything was fine with the rocket motor, nitrous oxide tank, cabin pressure, directional antennas, and other essential systems. The only major glitch occurred when SpaceShipTwo’s center multi-function display (MFD) – which the pilots used to access key data – crashed nine minutes after takeoff. The MFD was quickly rebooted and caused the pilots no further problems.
The drop was set for 10:07 a.m. As the release time neared for what he called a “high risk” test, Siebold took some time to prepare for the worst.
“About 10-15 minutes prior to release there was a period of low workload when he was able to physically feel for the parachute D-ring rip cord, oxygen activation pud, and the dual-lever seatbelts to improve his ‘muscle memory’ in the event of an emergency,” according to an NTSB interview summary. “This was not a written procedure, but something he personally did on some flights.”
At 10 a.m., Alsbury successfully unlocked and then re-locked SpaceShipTwo’s feather system. The feather is a system that deploys the spacecraft’s twin tail booms to reconfigure the vehicle into the form of a shuttlecock for a safe re-entry from space.
The safety check was designed to ensure the feather could be unlocked after being cold soaked during the flight up to the drop altitude. The flight test card called for deploying the feather during descent after SpaceShipTwo had soared to its planned altitude of about 138,000 feet. Nobody was sure the spacecraft could survive a descent with the feather down.
During the powered ascent, the locks were needed to keep the feather from deploying in the transonic region around Mach 1. Feather deployment during powered ascent before Mach 1.2 would be catastrophic.
Alsbury would unlock the feather once SpaceShipTwo hit Mach 1.4, when aerodynamic forces were sufficient to keep the booms in place. This was a second safety check to make sure the locks worked. If they didn’t unlock, he and Siebold would have to turn off the engine and abort the flight.
As the release time approached, the pilots discussed how they would fly the ship.
“Alright, you’re clear to arm, uh, at pylon release, I’ll call for fire,” Siebold told Alsbury. “And uh…call the pitch up, pitch down, trim, feather unlock one point four.”
At just before 10:07 a.m., Mission Control gave the pilots a “green for release.” WhiteKnightTwo co-pilot Clint Nichols conducted the final countdown. “Three two one release release release.” SpaceShipTwo fell away from its mothership at 10:07:19.10 a.m.
There was a visible jolt to the SpaceShipTwo cockpit and the sounds of hooks disengaging as the spacecraft dropped toward the desert floor. Relieved of a giant weight, WhiteKnightTwo shot upward into the blue desert sky.
“Fire,” Siebold said as the shadow of one of WhiteKnightTwo’s wings passed across the cabin.
“Arm,” Alsbury responded. “Fire.”
“Good light,” Siebold said in a strained voice as the pilots were pushed back into their seats. Siebold had both hands on the control stick as he made lateral corrections to SpaceShipTwo’s left and right rolls. Alsbury began to move his left hand off his control stick and toward the Feather Locks Handles.
“Yeehaw,” Siebold exclaimed.
“Point eight [mach],” Alsbury announced.
The call was to alert the pilots to prepare for the pitch bobble SpaceShipTwo would experience as it approached Mach 1. The ship’s wings and tails don’t shock up at the same time; as a result, SpaceShipTwo would pitch nose up and then nose down. Siebold would need to trim the vehicle immediately after the bobble in order to maintain control of the ship.
Alsbury placed his left hand on the Feather Locks Handles and leaned forward.
“Unlocking,” he said.
The lock mechanism had a detent that required the pilot to move the handles to the right before pulling them down. It was safety feature to prevent a pilot from accidentally moving the levers as they might a throttle. Alsbury calmly moved the handles to the right, then pulled them all the way down. The Feather Not Locked light illuminated on the instrument panel.
In Mission Control, The Spaceship Company’s Toby Earl Sorenson was awaiting the trim maneuver when he saw the feather coming unlocked out of the corner of his eye. “Good unlock,” he called out instinctively, feeling that something was wrong.
It was. Alsbury had unlocked the feather too early. SpaceShipTwo had just three seconds left to fly.
The ship began a slight but noticeable right roll as the Feather OK to Lock light was extinguished on the instrument panel.
“Pitch up,” Siebold said, straining against the ship’s movement.
“Pitch up,” Alsbury repeated.
Siebold suspected something is wrong. The pitch up is much higher and more violent than he expected. The pilots grunted as the g forces begin to build up.
Back in Mojave, astonished controllers watched with alarm as the feather began to deploy with the rocket engine still firing at full power. Scaled Vice President of Operations Jason Kelley immediately ran out of the control room to his office to retrieve the blue zebra protocol book that contained the procedures for an in-flight emergency.
A camera on the tail boom gave controllers a bird’s-eye view as the ship rapidly broke apart. First cracks appeared on the outboard root fairings. Silvery Kapton foil that covered the inside of the tail boom stripped away as the upper feather flap skin and root fairings failed. A skin panel from the bottom surface of the vehicle then peeled away.
SpaceShipTwo’s right boom began to rotate inboard toward the centerline of the vehicle. Then a crack appeared from the feather’s hinge line into the fuselage near SpaceShipTwo’s tail cone as the aft fuselage began to separate.
SpaceshipTwo started to pitching up wildly, subjecting Siebold and Alsbury to g forces much higher than the 5 to 6 g’s for which they had trained. They could do nothing to save the ship as their heads moved toward their laps.
The giant tank of nitrous oxide then began to vent a large white cloud into the air as the pilots felt the ship begin to pitch over on its back.
Siebold then heard a loud bang followed by the sound of “paper fluttering in the wind” as the cabin depressurized, At the rear of SpaceShipTwo the engine’s case throat nozzle assembly and twin tail booms then separated, falling away from the disintegrating ship.
In Mission Control, all telemetry from the doomed ship suddenly stopped. The last frame of SS2 boom camera remained frozen on video screen.
“Knock it off! Knock it off! Knock it off!” Ericson called into his microphone to tell Siebold and Alsbury to stop the feathering.
It was already too late.
- Part 1: SpaceShipTwo’s PF04: A High Risk Fight
- Part 2: SpaceShipTwo Pilots Faced Extremely High Work Loads
- Part 3: A Good Light, Then a Fatal Mistake
- Part 3.1: SpaceShipTwo Powered Flight No. 4 Flight Transcript
- Part 3.2: The Breakup of SpaceShipTwo Frame by Frame From the Tail Boom
- Part 4: Pete Siebold’s Harrowing Descent
- Part 4.1: SpaceShipTwo Emergency Response Timeline
- Part 5: Shock, Tears & Spin: The Aftermath of the SpaceShipTwo Crash