- Parabolic Arc
- March 30, 2023
SpaceShipTwo Pilots Faced Extremely High Work Loads
Part 2 in a Series
By Douglas Messier
The Mojave Air and Spaceport sits on 3,300 acres of California’s High Desert about 100 miles north of Los Angeles. Since it opened in 1935, the facility had seen multiple uses – rural airfield for the mining industry, World War II Marines Corps training base, U.S. Navy air station and general aviation airport.
In its most recent incarnation, Mojave serves as a R&D and flight test center for advanced aviation and space systems. Taking advantage of more than 300 days a year of good flying weather and restricted military airspace overhead, Mojave aspires to be a civilian version of the nearby Edwards Air Force Base. In June 2004, the Federal Aviation Administration (FAA) designated Mojave as the nation’s first inland spaceport just in time for SpaceShipOne’s historic flight into space.
Mojave was a perfect location for what test pilots Pete Siebold and Mike Alsbury would be doing this October morning: flying an advanced suborbital space plane Scaled Composites was developing for Richard Branson’s Virgin Galactic.
When Siebold arrived at the spaceport at 4:15 a.m., he went directly to one of the spaceport’s newest buildings, Virgin’s Final Assembly, Integration, and Test Flight Hangar (FAITH). A sleek, modern hangar located on Taxiway B on the airport’s south side, FAITH was where WhiteKnightTwo and SpaceShipTwo were prepared for flight tests. The mated vehicles had been outside the hangar since the previous day, a clear sign to locals that a test was coming the next morning.
Siebold had a little bit more time to take a look at the vehicles than he had anticipated. The 4:30 a.m. pre-flight conference – known as the delta brief – had been postponed by a half hour. Siebold inspected the vehicles, spoke with the ground crew, and then headed up to Building 78 on the Mojave flight line for the meeting.
The delta brief was a shorter version of a longer, more thorough review conducted the previous day. The flight crew of WhiteKnightTwo was there along with the key ground personnel involved in the test. Siebold and co-pilot Alsbury made a short presentation to the group about SpaceShipTwo’s fourth powered flight, picking up at the point when the vehicle would be dropped from the mother ship and walking through the test card that described what they would do when.
They would be testing the spacecraft’s new nylon hybrid engine for the first time. The hot fire would last 38 seconds and propel SpaceShipTwo as high as 138,000 feet. Both the burn time and altitude would be nearly double the 20-second burn and 71,000 feet spacecraft had achieved in three previous flights with a different hybrid rubber hybrid motor. Another key objective was to increase the maximum speed to Mach 2.0 from the previous Mach 1.4.
The pilots would then make SpaceShipTwo’s first supersonic descent at Mach 1.2 using the vehicle’s unique feather mechanism. The feather featured movable twin tail booms that reconfigured SpaceShipTwo into something akin to a shuttlecock to ease its re-entry into the Earth’s atmosphere. Designer Burt Rutan had developed the feather to ensure the vehicle would re-enter in a safe configuration no matter what attitude it was in during its time in space.
This sounded simple enough in theory. In practice, the system was actually fairly complicated. The feather had locks to keep it from deploying as the ship went through the rough transonic flight region around Mach 1. If they were unlocked during this phase of the powered ascent, the ship would be torn apart by aerodynamic forces. Scaled’s engineers considered that to be an extremely remote possibility, however; it would require the co-pilot to pull the feather unlock handle in the cockpit prematurely.
Once the ship was past the transonic region, Alsbury would unlock the feather system at Mach 1.4 to make sure the locks worked. If they didn’t unlock, Siebold and Alsbury would need to quickly shut down SpaceShipTwo’s engine and abort the flight. Engineers could not guarantee that SpaceShipTwo would survive a supersonic re-entry without the feather being deployed.
“They had a procedure for that, but it ends up with very high g’s, very high speeds, and they were concerned about flutter and heat loads on the vehicle,” Virgin Galactic Chief Pilot David Mackay told National Transportation Safety Board (NTSB) investigators.
Accomplishing all these tasks required careful attention from the two pilots during the high-speed boost phase of the flight when they were extremely busy flying the ship. Scaled Composites pilot Mark Stucky, who had flown all three previous powered tests, called powered ascent a catapult shot that did not quit. Henry Lampazzi, who evaluated SpaceShipTwo for the FAA , said the pilots’ work load during the boost phase was “higher than any I’ve seen.”
“To have to use two hands to hold pitch and then have another critical task going on at the same time, yeah, I would say that’s a pretty good work load, especially in a situation where you can’t verify each others critical steps,” he told NTSB investigators.
Pilot work loads were something Lampazzi understood well. Before coming to work for the FAA in 2012, he had spent 26 years as an aerospace engineer at NASA’s Johnson Space Center, where he trained space shuttle crews. “I was a test and procedures specialist there. I designed and briefed and taught aborts, contingency aborts, you know, that sort of thing, and then became a training director there,” Lampazzi said.
The presentation by Siebold and Alsbury was relatively short. Most of the hour-long delta brief was conducted by Mackay, the pilot-in-command of WhiteKnightTwo that day. The Scotsman had spent 16 years in the Royal Air Force, including the final seven years as a test pilot. Mackay then flew Boeing 747s for Richard Branson’s Virgin Atlantic Airways for 14 years before joining Virgin Galactic in 2009.
Mackay told the group the flight would be delayed from a planned 7 a.m. takeoff. The temperature of the nitrous oxide in SpaceShipTwo’s tank was too low at -16 degrees Fahrenheit. It could take as long as four hours to warm up, but Scaled engineers had methods they could use to shorten that time to about two hours. Takeoff was forecast for about 9 a.m.
The timing of the flight was crucial for two reasons. Scaled typically conducted flight tests in the morning when Mojave’s famously strong winds tended to be calm. Scott Wiley, a meteorologist for the test who worked full time over at NASA Armstrong Flight Research Center, told the group that surface winds at the spaceport were projected to exceed the 10-knot crosswind limit for a safe landing by SpaceShipTwo at around 11 a.m.
Previous powered flights had taken roughly an hour to complete. WhiteKnightTwo typically released SpaceShipTwo about 45 to 50 minutes into the flight from an altitude of around 50,000 feet about 20 miles north of Mojave. Previous SpaceShipTwo powered flights had taken up to 14 minutes to land back on Runway 30. This flight might take a little longer because it would feature a longer engine burn and higher altitude.
The second concern was pilot fatigue. Siebold and Alsbury had both awakened by 3 a.m. Everyone else was up earlier than usual. The longer the delay, the more likely it was that the pilots would grow fatigued from the wait. They were also testing on a Friday. Although practices varied throughout the industry, some organizations would not conduct a major flight test at the end of the work week when everyone involved would be more tired than normal.
The danger associated with a long delay was demonstrated three years earlier during a SpaceShipTwo flight that nearly ended in disaster. On Sept. 29, 2011, SpaceShipTwo suffered a tail stall that progressed into an inverted flat spin after being dropped from WhiteKnightTwo.
Pilot Mark Stucky, co-pilot Clint Nichols and flight test engineer (FTE) Wes Persall struggled to regain control of the upside down spaceship as it dropped like a rock toward the desert floor. They managed to right the ship after deploying the feather mechanism, bringing the spacecraft down to a safe landing after a hair-raising flight that lasted only 7 minutes 15 seconds.
The flight had been delayed many hours. A post-flight investigation indicated the crew had mis-configured a wing setting. Scaled officials vowed never to delay a flight that long again. They also put a positive spin on the incident in the test log on Scaled’s website, mentioning the stall but not the inverted flat spin. “Great flying by the team and good demo of feather system,” the test log concluded.
In addition to the nitrous oxide temperature, there were a few other concerns about SpaceShipTwo discussed during the delta brief. One of vehicle’s data acquisition units had failed. The problem was easily fixed by replacing its power unit. The group discussed what they would do if any of the new valves on the spacecraft leaked. The new propulsion system would require an additional procedure to safe the vehicle after landing.
The briefing broke up at about 6 a.m. Siebold and Alsbury stayed at Hangar 78, while Mackay and the WhiteKnightTwo flight crew went to FAITH. MacKay would be joined in the mother ship by co-pilot Clint Nichols and flight test engineer Matthew Stinemetze, both from Scaled Composites.
There would be one other plane in the air that day. Virgin Galactic pilot Frederick “C.J.” Sturckow would pilot an Extra chase plane. The former NASA astronaut would be accompanied by a photographer, Mark Greenberg, who had been hired to document the flight.
At about the time the delta brief ended, Mercy Air 14 ambulance helicopter descended out of the black pre-dawn sky toward its base on the Mojave flight line. Its crew noticed something they hadn’t seen when they had departed the spaceport on a call earlier that morning: WhiteKnightTwo and SpaceShipTwo were being prepared for another flight test. As strange as it might sound, it was their first clue that Scaled Composites and Virgin Galactic were planning anything that day.
One of 16 helicopters operated by Air Methods Corporation in California and Nevada, Mercy Air 14 is a full-service air ambulance with advanced life support capabilities that operates under contract to the Kern County Fire Department (KCFD). Mercy Air 14 is the primary medevac helicopter in eastern Kern County, and it is located closest to the drop zone where SpaceShipTwo conducted its flight tests.
Despite is ideal location and advanced capabilities, Mercy Air was “never” integrated into emergency response planning for SpaceShipTwo test flights or other activities at the spaceport, lead pilot David Walls told a NTSB investigator.
“He explained that Mercy Air was simply a tenant at MHV and there was no other established relationship. Mr. Walls stated that, to his knowledge, Mercy Air staff were ‘never’ included on briefings prior to test flights or any other activity on the airport,” the interview summary states. “He was uncertain why they were not included but suspected it was due to some sort of privacy concerns. He stated that the only way they know when Scaled Composites was having an operations was ‘when we see their employees walking out of their hangar.”’
At 6 a.m, Mojave spaceport CEO/General Manager Stu Witt gave a final briefing to emergency personnel and airport staff. The title of the 11-page PowerPoint presentation read, “SpaceShipTwo (SS2) Powered Flight No. 4 (PF04) Objective: be prepared for any outcome”.
Like the delta brief, Witt’s session was a down scaled version of a safety briefing held on Oct. 28. Those present at Witt’s meeting included representatives from KCFD, Kern County Sheriff’s Office (KCSO), Virgin Galactic and the FAA.
The division of labor in the event of an accident was straightforward. Airport officials would be responsible for any incident occurring on its property. The county fire department would respond to any emergencies elsewhere. KCFD’s response would be under the direction of Assistant Chief Mike Cody.
“According to the emergency response plan, if a mishap were to occur, Scaled was to notify the MHV ATC [Mojave Air Traffic Control] tower, which would notify the East Kern Airport District aircraft rescue and firefighting (ARFF) at MHV. ARFF would then notify the Kern County Emergency Communications Center about the mishap, which would initiate a three-engine response from KCFD, the Kern County Sheriff’s Office, and the California Highway Patrol,” according to the FAA final report on the SpaceShipTwo crash.
On the nights prior to the previous three powered flights, KCFD had pre-positioned one of its rescue helicopters at Mojave. The chopper was normally based at Keene, a small community located about 37 miles northwest of the spaceport on the other side of a large mountain range. Having the helicopter in Mojave had two benefits; it shortened the response time to any in-flight emergencies that were likely to occur; and it eliminated the possibility that early-morning fog to which Keene was prone would ground the rescue helicopter.
This test would be different, however. Scaled officials told the NTSB that during the briefing, a KFCD representative suggested leaving the helicopter in Keene so it could more easily respond to any emergencies near its base. Despite the high-risk nature of the flight, none of the officials present at the briefing objected to the change.
Scaled Composites President Kevin Mickey would later sum up Scaled’s attitude on rescue helicopters in his NTSB interview. On the morning of the flight, Mickey “saw police cars and fire equipment there but did not recall seeing any helicopters,” according to his interview summary. “He stated that ‘they are a nicety. It’s not a go/no-go item for us, but they support us when they can.’ He added that there was emergency response helicopter based at MHV [Mojave] that was present that day but he was not certain what the protocol was for them getting dispatched.”
Pat Williams, the KCFD’s supervising chief pilot, was usually notified two to four days ahead of time about a scheduled SpaceShipTwo flight test. This time, he had no idea one was schedule until Chief Cody called him the night before the flight. Williams told a NTSB investigator that even with the late notice, he “absolutely” could have pre-positioned the helicopter at Mojave early on the morning of the flight test. But, Cody told him to remain on standby in Keene.
In a NTSB interview a month after the flight, Witt would claim that two other helicopters – Mercy Air 14 and one from the National Test Pilot School – were on standby in Mojave for the test. But, when the time came, neither helicopter would be immediately ready to respond. Nor were these emergency assets mentioned as being on standby in Witt’s safety briefing that morning.
Kern County Sgt. Steve Williams and six sheriff’s deputies attended Witt’s briefing. The sheriff’s office’s main responsibilities were security at the airport and at a crash scene, and to work with the California Highway Patrol on road closures. In addition to six deputies at the airport, Williams had three other officers in Mojave ready to respond to an incident.
Williams told the NTSB that KCSO’s response plan for SpaceShipTwo’s fourth powered flight was “toned back” from the first one in April 2013.
“For that flight he pre-placed many officers down range with off-road ATVs, dirt bikes, etc. and utilized the California Highway Patrol (CHP) to be able to shut down local highway in case there was an accident,” an interview summary states. “The program engineers had calculated possible debris areas in advance and provided estimates of how long it would take debris to hit the ground from different altitudes. CHP officers were placed in locations where they could close the roads and ensure that any traffic would have passed possible impact areas prior to debris reaching the ground.”
This time, all the deputies were based in Mojave – about 20 miles south of the drop zone – and would respond from there.
Rich Fauble, chief of the spaceport’s fire department, did not take the upcoming test lightly. “Chief Fauble stated that, in addition to himself, he had a ‘full crew’ of 9 firefighters on duty at the time of the accident. The type of operation determined how many personnel were called in. He had a full crew on the day of the accident because it was a powered flight and he had a ‘bad feeling in [his] gut,’” according to the NTSB summary of his interview.
By 6 a.m., Pat Williams had his team assembled at the KCFD base in Keene. The crew included himself, a rescueman/hoist operator, an EMT/paramedic, and a safety officer. They received a briefing from Cody, then completed a pre-flight of the helicopter at 6:30 and were on standby for a flight they still believed was scheduled for a 7 a.m takeoff. It wasn’t until Cody called four minutes after the scheduled takeoff time that they learned about the lengthy delay.
In Mojave, Siebold and Alsbury continued their preparations for the mission as they waited for the nitrous oxide to warm up. They felt well prepared for the flight, having practiced all aspects of it for many weeks in the SpaceShipTwo simulator.
“SS2 had the highest fidelity of any simulator they created at Scaled,” a summary of a NTSB interview with Siebold reads. “The visuals and the displays and avionics were very close or identical to that actual vehicle. The avionics and flight displays were essentially identical. The environment that was very hard to model was the high g phase, the vibration and the adrenaline pilots had during flight. That was something they compensated for in workload and flights in the Extra.”
Siebold took some extra time to think through how he would respond to various emergencies, including how to activate his parachute and oxygen supply. Despite flying to very high altitudes, Siebold and Alsbury would not be wearing pressure suits. The emergency oxygen canisters might save their lives.
At 7:30 a.m., Mackay and his WhiteKnightTwo crew drove over to Hangar 78 in a van to pick up Siebold and Alsbury. They then traveled over to the staging area at the end of Runway 30 where the mated vehicles were located to begin their pre-flight preparations. At 8:13 a.m., Alsbury entered the cockpit and began securing himself in the right seat. Siebold followed two minutes later.
At around 8:50 a.m., the nitrous oxide temperature in SpaceShipTwo’s tank reached an acceptable range. Nearly a half hour later, WhiteKnightTwo received takeoff clearance from the Mojave Tower and began its takeoff roll. It was 9:18 a.m.
- 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