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06 November 2014

Rethinking space related risk in the wake of SpaceShipTwo

'This Week in Airline Safety' for 7 November 2014 discusses how the SpaceShipTwo mishap led to a rethinking of how will look at space related safety and risk.

Last month's mishap that led to a loss of SpaceShipTwo, the vehicle designed and built by Scaled Composites that Virgin Galactic plans to use to provide anyone with the right combination of desire, adventure, and money a chance to go into space on a suborbital flight. While some in the media, most notably Wired Magazine have questioned the value of what Virgin Galactic is trying to do (referring to SpaceShipTwo as the "world's most expensive roller coaster"), there can be no question that the accident, and the ongoing NTSB investigation, has led to a new examination, both within the aerospace community and by the general public, of the value of space travel.

At, that examination led to a rethinking of how to look at the history of space from the perspective of risk. As has been the case with airline safety and security, the goal of is to provide useful information about risk, safety, and security. To that end, there were several changes made to the site, to put the risk of current and future human spaceflight activities into a broader, and perhaps more appropriate, context. The key changes to the site include the following:

Expanding the range of noteworthy events
A revamped and expanded page on space related mishaps will now include mishaps involving any vehicle capable of traveling above the internationally recognized boundary of space (the Karman Line, which is at 100 km above the Earth), where at least one occupant was serious injured or killed, or where the vehicle was lost or destroyed. In the mishaps listed on this page, the vehicle was engaged in a flight, a ground test, or a training session.

Including additional space programs
The pages listing space related mishaps and deaths associated with US space programs now has additional government sponsored or privately sponsored space programs, including the Manned Orbiting Laboratory and X-15 programs that were run by the US government and which both ended in the 1960s, and the current civilian program run by Virgin Galactic.

Expanding the definition of US space program
This page will include deaths of any astronaut or astronaut candidate in any space program sponsored by the US government, or of any person killed while associated with a private or corporate space travel project. The first category would include professional astronauts who were full time astronauts or astronaut trainees and who were killed accidentally whether on duty or off duty.

The second category would include anyone who was killed in a flight, ground test, or training session involving a vehicle capable of traveling into space. This latter category would include people such as NASA payload specialist Ilan Ramon, who was killed in the inflight breakup of Space Shuttle Columbia, and Michael Alsbury, who was killed in the SpaceShipTwo mishap.

This expanded definition of US space program deaths was not possible to do for all the world's space programs, because of the lack of independently verifiable information on space related training deaths in programs previously run by the government of the former Soviet Union, and programs currently being run by the government of the People's Republic of China.

Interesting observations from the updated pages
The newly updated and expanded pages on space related events led to some new observations about the safety history of the world's space programs:

  • There have been 14 events involving fatalities in US space programs, killing a total of 29 people, with 16 of the deaths occurring in a vehicle capable of traveling into space.

  • Two people have survived a mishap that resulted in the loss of a space vehicle. The first was Virgil (Gus) Grissom in the 1961 flight of Mercury 4, and the second was Peter Siebold in last month's mishap involving SpaceShipTwo.

  • Siebold is also the first person to survive a fatal mishap involving a space vehicle.

  • Grissom is the only person to have been involved in more than one mishap. He survived Mercury 4, but died in a fire aboard Apollo 1.

  • While there have been 10 serious mishaps involving a space vehicle, only seven involved a vehicle that had traveled, or was intending to travel, into space, and only one event (the 1971 flight of Soyuz 11) involved fatalities that occurred in space.

  • Based on the internationally recognized boundary of space, the first person to fly into space twice was X-15 pilot Joe Walker, who twice flew above 100 km in 1963.

Additional resources
SpaceShipTwo accident investigation
Space flight related mishaps
Deaths associated with US space programs

04 November 2014

NTSB provides timeline of SpaceShipTwo mishap

The following is an overview of the preliminary findings presented by the NTSB on the third day of their investigation.

During the fourth media briefing on the third day of the on site portion of the NTSB investigation of the crash of SpaceShipTwo, the most significant information provided by acting NTSB chair Christopher A. Hart was a general timeline of the events between the release of SpaceShipTwo from its mothership WhiteKnightTwo, and the loss of telemetry from SpaceShipTwo. In that roughly fifteen second span, a number of events occurred inside SpaceShipTwo:

  • SpaceShipTwo released from mothership WhiteKnightTwo at 10:07:19 PDT (17:07:19 UTC)
  • The rocket engine was ignited about two seconds later.
  • About eight seconds later, and 10 seconds after release, SpaceShipTwo was traveling at about Mach 0.94
  • Sometime during the next two seconds, the feather lock handle was moved from the locked to the unlock position by the person sitting in the right seat.
  • At about 12 seconds after release, the vehicle was traveling at Mach 1.02
  • The feathers began to deploy at about 13 seconds after release.
  • Telemetry and video data was lost about two seconds later, roughly 15 seconds after release.

In addition to the timeline, the NTSB stated that lightweight debris was recovered about 30-35 miles northeast of the main wreckage area, and it was not clear what role wind may have played in the distribution of that wreckage. Also, while there was clear evidence that the pilot in the right seat moved the feather lock handle, during the media briefing, Hart was not clear if it was the pilot or the copilot who did so.

Shortly after the media briefing, NTSB clarified its position on Twitter, stating that the copilot, who did not survive the mishap, was the person in the right seat who moved the lock/unlock handle into the unlocked position.

Additional resources
Initial NTSB SpaceShipTwo accident investigation
Review of first two NTSB briefings on 1 November 2014
Review of third NTSB briefing on 2 November 2014
Review of fourth NTSB briefing on 3 November 2014

03 November 2014

NTSB hints that SpaceShipTwo breakup was not related to an engine failure

The following is an overview of the factual data presented by the NTSB on the second day of their investigation.

During the media briefing on the second day of the NTSB investigation of the crash of SpaceShipTwo, acting NTSB chair Christopher A. Hart, reported on some of their early findings that implied that there was no fire, explosion, or other kind of breach or failure involving the engine, fuel tank, or oxidizer tank. Early evidence instead points to an un uncommanded deployment of the feathering system just prior to the loss of telemetry from SpaceShipTwo.

The feathering system on SpaceShipTwo allows the twin booms on the vehicle, referred to as the feathers, to rotate upward in order to provide more aerodynamic drag on reentry. They are intended to be deployed after the engine has shut down and prior to reentry. According the information provided at the briefing, deploying the feathers takes two actions from the flight crew. The feathering system has to first be unlocked before they can be deployed by moving the feather handle into the feathered position.

There is a feathering handle that moves the feathers into the feathered position. Based on video evidence from inside SpaceShipTwo, the copilot unlocked the system, but the system deployed without any crew input.

Model of SpaceShipTwo in unfeathered position

Model of SpaceShipTwo in feathered position

The sequence of events was roughly as follows:

  • After being released from its carrier aircraft, the crew of SpaceShipTwo ignited the rocket engine.
  • About nine seconds after engine ignition, telemetry data showed that the feather parameters changed from locked to unlocked.
  • Video from the cockpit showed that the copilot had unlocked the feathering system, and is consistent with the telemetry data.
  • About two seconds later, the feathers moved toward the deployed position even though the feather handle had not been moved into the feather position.
  • The feather deployment occurred at a speed just above Mach 1.
  • Shortly after feathering occurred, video data and telemetry data terminated.
  • The engine burn was normal prior to the deployment of the feathers.
  • Normal procedures would have had the crew unlocking the feathering system at a speed of about Mach 1.4.
  • Unlocking the feathering system alone should not have allowed the feathers to deploy.
  • The inflight breakup of the vehicle began sometime after telemetry ceased.
  • The NTSB has not determined if the inflight breakup was caused by aerodynamic forces or from some other cause.
  • The rocket engine, fuel tank, or oxidizer tank showed no evidence of a breach or burn through consistent with some sort of fire, explosion or structural failure affecting those components.

The NTSB emphasized that their statements were statements of fact rather than a determination of a cause of the mishap. Below is a video of the third media briefing.

Additional resources
Initial NTSB SpaceShipTwo accident investigation
Review of first two NTSB briefings on 1 November 2014
Review of third NTSB briefing on 2 November 2014

Note: An earlier version of this story inadvertently stated that there was evidence of a breach or burn on some components.

01 November 2014

Virgin Galactic SpaceShipTwo NTSB accident investigation

The NTSB is leading the investigation into yesterday's crash of Scaled Composites SpaceShipTwo north of Mojave, CA. Saturday November 1st was the first day of the investigation, and the NTSB has already had one one media briefing with a second planned for late in the evening.

The following is an overview of the crash and comments on the early media briefings.

31 October 2014; Scaled Composites; Model 339 (SpaceShipTwo); N339SS; near Cantil, CA: The vehicle, which is designed to fly into the lower reaches of space (above 100 km above Earth) was on its first powered test flight with a new engine fuel and oxidizer combination (nylon and nitrous oxide). SpaceShipTwo was dropped from its carrier vehicle at about 45,000 feet, and ignited its engine.

Roughly two minutes after release from the carrier aircraft White Knight Two, the SpaceShipTwo vehicle experienced an inflight breakup. One of the two crew members was killed, and the other was able to bail out of the vehicle and was injured.

Prior to the accident flight, there had been the 54 test flights of SpaceShipTwo, of which 34 involved a release from the carrier aircraft, including three powered flights.

Scaled Composites, which conducted the flight test, is a partner of Virgin Galactic, which had planned on using SpaceShipTwo to take passengers on suborbital trips into space in the near future.

Summary of first two NTSB briefings on 1 November 2014
Both NTSB briefing were given by acting NTSB chair Christopher A. Hart, was short, and provided the following preliminary information about the accident:

  • While the NTSB has previously participated in the investigations of the Challenger and Columbia Space Shuttle accidents, this will be the first time it has taken the lead role in the investigation of a crewed space launch vehicle accident.
  • The NTSB team consists of about 13-15 investigators and specialists in the areas of structures, including systems, engines, vehicle, performance, and operations.
  • The parties to the investigation are the FAA, Scaled Composites, and Virgin Galactic
  • The vehicle was flying in a southwesterly direction, and the wreckage field is about five miles (8 km) long, and is oriented from the northeast to the southwest.
  • The wreckage pattern indicates that an inflight breakup occurred, but the NTSB has not yet determined why this happened.
  • The left and right tail booms were near the beginning of the wreckage trail, followed by the fuselage, fuel and oxidizer tanks, cockpit, and the rocket engine.
  • There were a total of three tanks in the vehicle, a fuel tank, an oxidizer tank, and a methane tank.
  • The NTSB was unaware of the altitude of the mishap.
  • There was extensive video data available from the flight, including six cameras on SpaceShipTwo, another three on White Knight Two, one in a chase aircraft, and one on the Edwards AFB test range.
  • The NTSB does not know if the six cameras on board SpaceShipTwo have been recovered.
  • There were six data sources on SpaceShipTwo and about 1000 parameters of telemetry available from the flight. There was also a radar on the chase aircraft.
  • Interviews have been conducted, but NTSB will not reveal what has been discovered until later in the investigation.
  • The surviving pilot has not yet been interviewed because his doctors recommended against doing so at this time.
  • The NTSB does not know how the surviving pilot exited the vehicle.
  • The on scene portion of the investigation will continue for another four to seven days, and the full investigation will take about a year.
  • Scaled Composites can continue operations during the investigation.
  • News and updates to the investigation will be available at the NTSB's web site ( Twitter feed (@NTSB).

Initial SpaceShipTwo NTSB briefings

Initial NTSB SpaceShipTwo briefings 1 November 2014