In 2011, Microsoft co-founder Paul G. Allen and Scaled Composites founder Burt Rutan announced the creation of Stratolaunch Systems. With the goal of reducing the associated costs of space launches, the company set out to create the world’s largest air-launch-to-orbit system. After many years, these efforts bore fruit with the unveiling of the massive Scaled Composites Model 351 Stratolaunch air carrier in the Summer of 2017.
Similar in principle to Virgin Galactic’s SpaceShipTwo, this behemoth is designed to deploy rockets from high altitudes so they can send payloads to Low-Earth Orbit (LEO). After multiple tests involving engine preburns and taxiing on the runway, the aircraft made its inaugural flight last weekend (Saturday, April 13th) and flew for two and half hours before safely landing again in the Mojave Desert.
When it comes to the dream of commercial space exploration and space tourism, a few names really stand out. In addition to Elon Musk and Jeff Bezos, you have Richard Branson – the founder and CEO of the Virgin Group. For years, Branson has sought to make space tourism a reality through Virgin Galactic, which would take passengers into suborbit using his SpaceShipTwo class of rocket planes.
Unfortunately, Virgin Galactic suffered a number of setbacks in recent years, at the same time that competitors like SpaceX and Blue Origin emerged as competitors. However, the VSS Unity (part of the Virgin Galactic fleet) recently conducted its second powered test flight from the Mojave Air and Space Port on Tuesday, May 29th. While this test is years behind schedule, it marks a significant step towards Branson’s realization of flying customers to space.
This was the second time that the VSS Unity flew since 2014, when the VSS Enterprise suffered a terrible crash while attempting to land, killing one pilot and injuring the other. The first propulsive test took place two months ago after several additional tests were performed on the craft. And with that last success, Virgin Galactic moved ahead with its second powered test earlier this week.
The focus of the latest test flight was to learn more about how the spaceship handles at supersonic speeds. It was also intended to test the control system’s performance when the vehicle was closer to its ultimate commercial configuration. As the company stated, “This involved shifting the vehicle’s center of gravity rearward via the addition of passenger seats and related equipment.”
This statement is a possible indication that the test program is reaching the final stretch before Virgin Galactic allows passengers on the vehicle. However, the company will need to conduct a full-duration flight (which will include a full-duration burn of its rocket motor) before that can happen. This latest test involved only a partial rocket burn, but nevertheless demonstrated the spacecraft’s capabilities at supersonic speed.
The company live-tweeted the entire event, which began at 8:34 AM with the VSS Unity and its carrier mothership (VMS Eve) taxing out to the runway for final checks. For this flight, the pilots were Dave Mackay and Mark “Forger” Stucky while CJ Sturckow and Nicola Pecile piloted of the carrier aircraft. At 8:42 AM (PDT), both craft lifted off, with the company tweeting, “We have take-off. VMS Eve & VSS Unity have taken to the skies and have begun their climb.”
By 9:43 AM, the company announced that the VSS Unity had detached from the VMS Eve and was “flying free”. What followed was a series of live-tweets that indicated the ignition of the VSS Unity’s rocket motor, the shutting down of the motor, and the raising of the tail fins to the “feathered” re-entry position. By 9:55 AM, the company announced a smooth landing for the VSS Unity, signaling the end of the test.
Branson, who was at the Mojave Air and Space Port for the test, released the following statement shortly thereafter:
“It was great to see our beautiful spaceship back in the air and to share the moment with the talented team who are taking us, step by step, to space. Seeing Unity soar upwards at supersonic speeds is inspiring and absolutely breathtaking. We are getting ever closer to realizing our goals. Congratulations to the whole team!”
Branson was also at the center to take in a tour of the facilities of The Spaceship Company (TSC), a sister company of Virgin Galactic that is responsible for developing Virgin Galactic’s future fleet. While there, Branson viewed the next two spaceships that TSC is currently manufacturing, as well as the production facilities for TSC’s spaceship rocket motors.
With the latest test flight complete, the company’s teams will be reviewing the data from this flight and making preparations for the next flight. No indication has been given as to when that will be, or if this test flight will include a full-duration burn of the motor. However, Branson was very happy with the test results, stating:
“Today we saw VSS Unity in her natural environment, flying fast under rocket power and with a nose pointing firmly towards the black sky of space. The pathway that Unity is forging is one that many thousands of us will take over time, and will help share a perspective that is crucial to solving some of humanity’s toughest challenges on planet Earth.”
Meanwhile, Bezos continues to pursue his plans for sending passengers into orbit using his fleet of New Shepard rockets. And of course, Musk continues to pursue the idea of sending tourists to the Moon and Mars using his Big Falcon Rocket (BFR). And with many other private aerospace ventures looking to provide trips into orbit or to the surface of the Moon, there is sure to be no shortage of options for going into space in the near future!
And be sure to check out this video of the VSS Unity’s second test flight, courtesy of Virgin Galactic:
In 2011, Stratolaunch Systems was founded with a simple goal: to reduce the costs of rocket launches by creating the world’s largest air-launch-to-orbit system. Similar to Virgin Galactic’s SpaceShipTwo, this concept involves a large air carrier – Scaled Composites Model 351 (aka. the “Roc”) – deploying rockets from high altitudes so they can deliver small payloads to Low-Earth Orbit (LEO).
Recently, the aircraft reached a major milestone when it conducted its second taxi test at the Mojave Air and Space Port. The test consisted of the aircraft rolling down the runway at a speed of 74 km/h (46 mph) in preparation for its maiden flight. The event was captured on video and posted to twitter by Stratolaunch Systems (and Microsoft) co-founder Paul Allen, who was on hand for the event.
The Roc is essentially two 747 hulls mated together, making it the largest aircraft in the world – spanning 117 meters (385 ft) from one wingtip to the other and weighing 226,796 kg (500,000 lbs). It is powered by six Pratt & Whitney turbofan engines, giving it a maximum lift capacity of up to 249,476 kg (550,000 pounds). This would allow it to air-launch rockets that could deploy satellites to Low-Earth Orbit (LEO).
Captured new video of @Stratolaunch plane as it reached a top taxi speed of 40 knots (46 mph) with all flight surfaces in place on Sunday. The team verified control responses, building on the first taxi tests conducted in December. pic.twitter.com/OcH1ZkxZRA
As with other alternatives to rocket launches, the concept of an air-launch-to-orbit system is a time-honored one. During the early days of the Space Race, NASA relied on heavy aircraft to bring experimental aircraft to high altitudes (like the Bell X-1) where they would then be deployed. Since that time, NASA has partnered with companies like Orbital ATK and the Virgin Group to develop such a system to launch rockets.
However, the process is still somewhat limited when it comes to what kinds of payloads can be deployed. For instance, Orbital ATK’s three-stage Pegasus rocket is capable of deploying only small satellites weighing up to 454 kg (1,000 pounds) to Low-Earth Orbit (LEO). Looking to accommodating heavier payloads, which could include space planes, StratoLaunch has created the heaviest commercial airlift craft in history.
Back on May 31st, 2017, the aircraft was presented to the world for the first time as it was rolled out of the company’s hangar facility at the Mojave Air and Space Port in California. This presentation also marked the beginning of several tests, which including fueling tests, engine runs, and a series of taxi tests. The engine testing took place in September, 19th, 2017, and involved the aircraft starting it’s six Pratt & Whitney turbofan engines.
The testing followed a build-up approach that consisted of three phases. First, there was the “dry motor” phase, where an auxiliary power unit charged the engines. This was followed by the “wet motor” phase, where fuel was introduced to the engines. In the final phase, the engines were started one at a time and were allowed to idle.
This test was followed in December 18th, 2017, with the aircraft conducting its first low-speed taxi test, where it traveled down the runway under its own power. The primary purpose of this was to test the aircraft’s ability to steer and stop, and saw the aircraft reach a maximum taxing speed of 45 km/h (28 mph). This latest test almost doubled that taxing speed and brought the aircraft one step closer to flight.
The aircraft’s maiden flight is currently scheduled to take place in 2019. If successful, the Roc could be conducted regular satellite runs within a few years time, helping to fuel the commercialization of LEO. Alongside companies like SpaceX, Blue Origin, and the Virgin Group, StratoLaunch will be yet another company that is making space more accessible.
In 2011, Microsoft co-founder Paul G. Allen and Scaled Composites founder Burt Rutan announced the launch of their private space venture. Known as Stratolaunch Systems, this Seattle-based company was founded with the intention of developing air-launch-to-orbit systems. Similar to Virgin Galactic’s SpaceShipTwo, this concept involves a large air carrier flying rockets to launch altitude as cost-effective means of delivering small payloads to orbit.
On Thursday, May 31st, the company unveiled their launch vehicle, the Scaled Composites Model 351 (aka. the “Roc”). Consisting of two 747 hulls mated together, this aircraft is the the largest in the world – spanning 117 meters (385 ft) from one wingtip to the other and weighing 226,796 kg (500,000 lbs). This plane will make its first test flight in a few days time, and the company hopes to make its first commercial launch by 2019.
The rollout of the Roc – which took place at the company’s hangar facility at the Mojave Air and Space Port in California – was a media circus. In addition to being the first time that the public got to see the aircraft since construction began, the occasion marked the beginning of several tests which will take place over the coming days – including fueling tests, engine runs, taxi tests, and its first test flight.
“We’re excited to announce that Stratolaunch aircraft has reached a major milestone in its journey toward providing convenient, reliable, and routine access to low Earth orbit. Today, we’re moving the Stratolaunch aircraft out of the hangar – for the first time ever – to conduct aircraft fueling tests. This marks the completion of the initial aircraft construction phase and the beginning of the aircraft ground and flight testing phase.”
Measuring about 72.5 meters (238 ft) from nose to tail, the aircraft also stands 15.24 meters (50 ft) tall, measured from the ground to the top of the vertical tail. It has a maximum takeoff weight of 589,670 kg (1.3 million lbs), meaning that it is capable of airlifting payloads of up to 249,476 kg (550,000 lbs). These kinds of payloads mean that it will be capable of flying rockets and heavy space planes to launch altitude.
Last fall, the company announced their plan to conduct a launch using a single Orbital ATK Pegasus XL vehicle, a three-stage rocket used to deploy small satellites to Low-Earth Orbit (LEO). This agreement was part of a multi-year collaboration between the two companies, which would see the former combining their aircraft with the latter’s extensive air-launch experience.
First unveiled in 1990, the Pegasus XL quickly established itself as a cost-effective means for launching small payloads to LEO. These typically would consist of small satellites weighing up to 443 kg (977 lbs) from beneath a NASA B-52 aircraft. Since then, the Pegasus has carried out 43 space launch missions and successfully placed a total of 94 satellites into orbit for various reasons – ranging from scientific research and communications to defense.
In time, the company plans to explore a wide range of launch vehicles that can provide flexibility in terms of missions and payloads. But in the meantime, they will be conducting ground and flight line testing from the Mojave Air and Space Port to ensure that Roc is capable of doing all it was designed for. If all goes well, they plan to make their first commercial launch by 2019.
“This marks a historic step in our work to achieve Paul G. Allen’s vision of normalizing access to low Earth orbit,” said Floyd. “It is proud day for us at Stratolaunch, for our partners at Scaled Composites, and for our founder Paul Allen. We have a lot of exciting activity ahead as we enter the testing process, and we look forward to sharing our progress during the coming months.”
One of the hallmarks of the commercial aerospace (aka. NewSpace) industry has been the development of cost-saving measures. Whereas companies like SpaceX and Blue Origin has looked to reusable rocket technology, other companies have sought to reduce costs with Single-Stage-to-Orbit (SSTO) rockets and plug-in payloads. Air-launch-to-orbit systems are just another way in which space is becoming more accessible.
And be sure to check out this video of the Roc’s unveiling:
The surviving co-pilot of the Virgin Galactic crash was unaware that SpaceShipTwo’s re-entry system was unlocked prematurely during the flight test, according to an update from the National Transportation Safety Board.
In an interview with investigators, the board said Peter Siebold provided testimony that was consistent with other information gathered so far since the crash. The incident, which killed fellow co-pilot Mike Alsbury when the craft plunged into the Mojave desert, took place Oct. 31.
“The NTSB operations and human performance investigators interviewed the surviving pilot on Friday. According to the pilot, he was unaware that the feather system had been unlocked early by the copilot,” read an update on the board’s website.
“His description of the vehicle motion was consistent with other data sources in the investigation. He stated that he was extracted from the vehicle as a result of the break-up sequence and unbuckled from his seat at some point before the parachute deployed automatically.”
Accidents are due to a complex set of circumstances, which means the NTSB finding that the re-entry system was deployed prematurely is only a preliminary finding. The investigation into the full circumstances surrounding the crash could take anywhere from months to a year, according to multiple media reports.
Virgin was performing another in a series of high-altitude test flights in preparation for running tourists up to suborbital space early next year. A handful of ticket-holders, who made deposits of up to $250,000 each, have reportedly asked for their money back. The Richard Branson-founded company has not revealed when the first commercial flight is expected to take place.
Meanwhile, Virgin does have another version of SpaceShipTwo already under assembly right now, which is considered 95% structurally complete and 60% assembled, according to NBC News. The prototype could take to the skies before the NTSB investigation is complete, the report added.
Yes, there was a thumbs up. Through an interview with the father of the SpaceShipTwo pilot, the Daily Mail has reported more details of the near fatal plunge of Peter Siebold from the explosive event that destroyed Scaled Composites’ space vehicle. The ill-fated test flight resulted in the death of the co-pilot, Mike Alsbury. Siebold was visited by his father, Dr Klaus Siebold of Seattle, Washington, after Siebold was released from the hospital.
The Daily Mail story confirms what had been rumor from anonymous sources inside Scale Composites, the company founded by Burt Rutan that created the first privately developed vehicle to exceed the Karman line and reach the environs of outer space. As has been rumored, pilot Siebold, while on parachute, gave a thumbs up sign to a nearby chase plane to indicate he was conscious.
Dr. Siebold, speaking to a Daily Mail reporter, described how his son fell from 50,000 feet (15,240 meters) after SpaceShipTwo broke apart while traveling at a speed of mach 1.2, that is, 913 mph (1,470 km/hr). Early findings of the NTSB investigation have revealed that SpaceShipTwo’s twin tails feathered, that is, folded up, prematurely, creating excessive forces on the carbon composite air frame and led to the craft’s break up.
Dr. Siebold told the Daily Mail that his son is not sure how he separated from the vehicle during the violent event at supersonic speed. He could not recall any details of the sudden event. Such high speed events can take place in a matter of a second or less.
His co-pilot and close friend, Mike Alsbury, was not able to escape from the broken vehicle and fell with the debris to his death to the floor of the Mojave desert. The fall to Earth of the broken vehicle and the two test pilots took over four minutes traveling at a terminal velocity of approximately 150 mph (220 ft/sec, 67 m/s).
Dr. Siebold went on to describe his son’s narrow escape. Pilot Siebold could not recall the breakup and only recalls waking up at 20,000 feet (6096 meters). Both pilots flew with emergency parachutes. Such parachutes would not deploy or deploy correctly without the pilot separating from his pilot seat. As he awoke, Peter Siebold was sufficiently coherent to realize his circumstances and unbuckled himself. The parachute subsequently deployed but the accounting by the father, Dr. Siebold, did not make clear whether his son pulled the rip cord or the parachute was deployed automatically. Both pilots’ parachutes had mechanisms to force automatic deployment at 20,000 feet altitude. However, when a pilot is still strapped into his pilot seat, parachute deployment would be disabled or if executed, would cause severe injury to the person due to the propulsive forces that push the chute from the bag. Such forces would be forced upon the pilot’s body while locked into his seat.
The break-up led to three coinciding invasive events: sudden deceleration forces, the creation of high velocity projectiles – debris – surrounding the pilots, and a decompression event. The pilots wore simple oxygen masks without pressure suits, so their bodies withstood a split second change from cabin pressure of 1 atmosphere to that of a near-vacuum pressure. Any or all three events at breakup were responsible for the pilots’ losing consciousness within seconds if not immediately. The investigation has not revealed how co-pilot Alsbury lost his life, whether during the break-up or at impact with the Earth.
The story provides more details of Peter Siebold’s life. He has two young sons and was inspired by his father, a private pilot, to learn to fly and ultimately receive a job with Scaled Composites over ten years ago. Having no knowledge of a powered test flight that morning, Dr. Siebold described to the Daily Mail how he received a frantic call from his daughter in-law. Siebold’s wife and children were standing alongside their close friends – the children and wife of Mike Alsbury when the catastrophic event unfolded in the skies above them.
The flight took off during the early hours of October 31, 2014, on what appeared to be the beginning of a final phase of testing to qualify the spaceship for commercial flight. With early findings revealing that the event was apparently triggered by Alsbury’s inadvertently releasing the safing mechanism for feathering the tail sections, Scaled Composites and Virgin Galactic are beginning to express a likelihood that test flights will restart in as short as 6 months. Apparently, neither the NTSB nor FAA has enforced any grounding of the test program and vehicle. While pilot error may have been involved, the NTSB has included that the act of feathering the tails to slow down the vehicle during its descent from a high altitude requires unlocking the safing mechanism followed by a second step that folds the tail section. The second action would be similar to the act of lowering one’s landing flaps for landing: something which would be well understood by any private or commercial pilot.
In this reporter’s initial article for Universe Today on the SpaceShipTwo accident, it was already clear that the survival of one of the two pilots was remarkable. How did the SpaceShipTwo pilot Peter Siebold survive while co-pilot Michael Alsbury did not? The SpaceShipTwo test pilots do not wear pressure suits. There are no ejection seats like in a jet fighter but they do wear parachutes.
During the powered test flight of SpaceShipTwo on October 31st, at the moment that the vehicle broke up, its altitude was approximately 50,000 feet (15,240 meters) and it was traveling at mach 1.0 (1225 kph, 761 mph). Sudden decompression at that altitude leaves a pilot a few seconds before losing consciousness. To understand how Siebold survived, consider how this breakup compares to the Space Shuttle Challenger disaster. Challenger was at 48,000 feet (14,600 meters) and SpaceShipTwo was at 50,000 feet (15,240 meters) when their breakups occurred. Both were within the same speed regime – between mach 1 and mach 2.
I was a graduate student stationed at the Space Science Lab at Marshall Space Flight Center on that winter day in 1986. The NASA research researchers and professors, students from the University of Alabama, Huntsville, were sitting together in a conference room. The presenter concluded his final remarks on his research work then said, thank you and we can now turn around (to the NASA TV monitor) and watch Challenger launch. The countdown was at about T-20 seconds and so we watched, then a cloud appeared that with each passing moment did not seem normal. I recall watching and thinking, come on out, come on, you can make it. Challenger never did. There was no miraculous recovery with the Shuttle pilots steering it out of the cloud and back down to the Cape to cheers and a heroes welcome. We all filed out of the room in silence knowing what had happened but not wanting to believe it. Months later, experts concluded that the Challenger crew, most likely, survived the plunge back to Earth only to perish when the cabin impacted the ocean surface at over 200 mph (321 kph).
That was the first of two Space Shuttle accidents. The other, the Columbia disaster, occurred at a much higher altitude and velocity. That was a Saturday morning. Sleeping in after a long week of analyzing design documents and source code for the Mars Rovers, my girlfriend at the time nudged me awake to say, Tim, something is wrong with the Space Shuttle. I grudgingly got up, not wanting to see anything bad on a pleasant Saturday morning, but CNN was showing it break up over Texas.
I never worked in the Space Shuttle program but Shuttle was larger than life and every NASA employee took its triumphs and tragedies personally. For all those working on SpaceShipTwo and friends and family and those at the Mojave Air and Space Port on that day, it is no different. The tragedy and the moments surrounding the incident stay with you forever.
With all this in mind, I consider the question of how one man survived and the other did not with SpaceShipTwo. Both pilots were wearing only simple jump suits. No pressurization. They had supplemental oxygen through masks just like a fighter pilot has during flight. SpaceShipTwo did not afford them ejection seats like a fighter jet. Fighter jet pilots can eject at supersonic speeds but chances of surviving the shock of ejection rapidly falls with speed.
SpaceShipTwo is equipped with an escape hatch but once SpaceShipTwo disintegrated, the hatch was of no use. Both pilots were suddenly exposed to open air and a supersonic slipstream. So how did Siebold survive?
When the vehicle broke up, the sudden decompression surrounding them stripped objects from the interior. They were surrounded by lethal projectiles. It was a matter of chance whether one or both were struck by debris and lost consciousness. In the case of Shuttle Challenger, the astronauts experienced a sudden 20 G force at break up, however, analysts concluded that they likely survived the initial breakup. Challenger astronauts had helmets and a supplemental oxygen supply. One or two of the oxygen supplies had actually been activated and drained by their respective astronaut as the cabin was falling back to Earth. The Shuttle cabin survived the breakup largely intact and protected the astronauts from the supersonic slipstream outside.
SpaceShipTwo’s breakup likely exposed both pilots to the slipstream at still over mach 1. Flying debris was their first challenge. Second, the sudden decompression and then deceleration forces struck them. According to an anonymous source within Scaled Composites, the Washington Post reported yesterday that both pilots remained buckled into their seats. Alsbury never separated from the seat and cabin, and information reaching the public reveals that he impacted at high speed still within some fraction of the remaining cabin.
The anonymous sources within Scaled Composites revealed that Siebold was able to unbuckle from his seat and deploy his chute at 17,000 feet (5,181 m). It is very likely that even Siebold fell unconscious from the initial stresses of the breakup and from decompression at 50,000 feet (15,240 m). He would have fallen into an unconscious state at that height and only have woken up once near 17,000 feet (5,181 m) where the atmosphere is denser and at which a human can survive, such as at mountain altitudes in the Andes and Himalayas. Whether he gave a thumbs up to a nearby chase plane is sensational but it would indicate that he was conscious and aware. With the parachute integrated into his test pilot suit, it was critical for Siebold to regain consciousness and unbuckle from his seat in order to give his parachute any chance of deploying. This is likely where the fate of the pilots differ.
Alsbury quite possibly was struck by debris or was injured by G forces and decompression more severely than Siebold. He either never regained consciousness or was somehow trapped in his seat and surrounding debris of the cabin. The circumstances for Siebold in his descent after the breakup were apparently fortuitous and gave him the chance to re-awaken and unbuckle. Comments in press reports from people around the incident or aware of the technology included that the pilots’ parachutes had automatic deployment mechanisms which activate at 10,000 feet (3048 m). In Alsbury’s or Siebold’s situation, without releasing themselves from their seats, the automatic deployment system would not have worked. If the chutes were to automatically deploy while the pilots were still strapped to their seats, the force from the deploying chute would have caused serious injury to the pilot. I’ve never jumped from a perfectly good flying airplane — as pilots often comment to jumpers — but I recall hearing that a deploying chute will knock a person on their backs with injury if they’re within 20 feet (6.1 meers) of it.
So, Siebold’s survival is miraculous or lucky, however you want to perceive it. For Michael Alsbury, godspeed. There are many factors that lead up to a powered test flight. Then, the moment — the rush of acceleration, the roar of the SpaceShipTwo engine — has some effect on the clarity of any pilot. NTSB analysis might reveal that the Human-Machine Interface (HMI) was also a factor in the actions that took place inside the cockpit. If only one of two necessary steps to execute the tail section’s feathering took place and yet it feathered, then again, something was beyond the control of the pilots.
In a Monday afternoon press conference, acting NTSB chairman Christopher Hart confirmed that the safety lock on Virgin Galactic’s SpaceShipTwo feathering mechanism was prematurely unlocked moments before breakup. Hart also quickly stated that this would be the last on-site press conference. The NTSB is nearing the completion of data gathering and the team will be returning to Washington DC with the data to undertake the facts compilation followed by the analysis.
Hart reiterated that the test flight was rich in telemetry. He said that the supply of data could expedite the analysis but he cautioned that they still expect the investigation to take 12 months to conclude and release a final report. He also added that as analysis proceeds, the NTSB would provide updates and he encouraged interested parties including the public at-large to undertake analysis of the available data; however, he emphasized that the conclusions drawn would be based on NTSB analysis alone.
From the data released and statements by Hart during the press conference, it is now clear that the NTSB recognizes that the feathering was not to be deployed until SpaceShipTwo achieved mach 1.4. The statement that acting chairman Hart made appeared to be explicitly referencing the Flight Card – the plan of actions and constraints for the flight. If this was the specific wording on the Flight Card, then it would have permitted a pilot to interpret it in various ways.
Sunday, it was reported that SpaceShipTwo was flying at about Mach 1.2 when break up occurred. As a private pilot familiar with the impact that flight conditions have on operations of an aircraft, I would add that the SpaceShipTwo constraint of mach 1.4 for executing feathering is likely intended to be viewed by the pilots-in-control as the descent speed after SpaceShipTwo had achieved maximum altitude during a flight to the edge of the atmosphere. During descent, mach 1.4 would be achieved at a much higher altitude where the air density is much lower and stresses from the feathering would also be much lower; SpaceShipTwo is designed to feather with those environmental conditions. During previous tests of SpaceShipTwo when feathering was tested at low altitude, the vehicle was flying far below mach 1, i.e., subsonic. The vehicle in that flight regime had no difficulty withstanding stresses during the test of feathering. It should be emphasized that the strict rules under which the NTSB proceeds with an investigation do not allow the investigators to inject assumptions based on their past experience.
A timeline of events leading up to catastrophic breakup of SpaceShipTwo was stated by the NTSB acting chairman:
10:07:19: SpaceShipTwo is released from the carrier craft, WhiteKnightTwo
10:07:21 SpaceShipTwo’s engine starts
10:07:29 SpaceShipTwo reaches mach 0.94
10:07:31: SpaceShipTwo exceeds the speed of sound – mach 1.02. Between 10:07:29 and 10:07:31, the feathering safety was unlocked.
10:0 7:34: All telemetry was lost
The NTSB has also created a new team responsible for evaluating the Human-Machine Interface (HMI) on SpaceShipTwo. HMI is a discipline that has gained increased interest within several manufacturing sectors, particularly in aircraft cockpit design. The performance of modern aircraft, places greater demand on human performance. The formulation of a Human performance team evaluating the HMI of SpaceShipTwo indicates that the NTSB wants to assess the quality of the cockpit control panels and whether the configuration of switches contributed to pilot error.
While most of the debris is confined to a 5 mile swath of desert, Hart stated that debris has now been found as far as 30 to 35 miles from the immediate debris field.
Besides the apparent focus by the NTSB on the unplanned feathering, Hart stated that they are checking the subsystems of the spacecraft for integrity – pneumatics, flight control, electrical, and so on.
Hart concluded the press conference by taking questions from reporters.
Q. Had the pilot been interviewed?
A. Not yet and not until he is fit to be interviewed.
Q. Was the Flight Card reviewed?
A. The NTSB has reviewed the flight card for procedures and constraints. According to Hart, the card stated not to release the safety lock of the feathering mechanism until mach 1.4. The Flight Card describes the steps that a flight crew is to take to complete a successful mission.
Q/A. Hart confirmed that 2 pilot actions were necessary for feathering. 1) Unlock the safety, and 2) engage feathering lever. U.T. – Hart could not say if both pilots were necessary, that is, shared the two step process.
Q/A. A reporter contentiously asked Hart who was in the right seat. Hart stated that he did not know and also was unwilling to assume that it was the co-pilot, Alsbury. The reporter probing him further asked about his statements from Sunday. Hart agreed that he was mistaken to have assumed on Sunday that it was the copilot.
Finally, a review of the NTSB press conference video, placed on YouTube, presented a clarification as text on video. It stated that the co-pilot was residing in the right seat and was responsible for unlocking the feathering. At this preliminary stage of the investigation, it would appear that Alsbury’s death in the accident was due to his premature unlocking of the feathering mechanism. Hart did not state this but the circumstantial evidence so far is pointing in that direction.
In a press conference at the Mojave Air and Sport Port Sunday evening, acting NTSB Chairman Christopher Hart revealed preliminary findings in the investigation of the Virgin Galactic SpaceShipTwo test flight accident. According to Hart, review of cockpit video during the flight showed that the co-pilot Michael Alsbury turned the tail feathering lock-unlock lever to the unlocked position too early. But Hart was quick to add that the NTSB has not concluded that this represents a cause and effect, and more analysis is necessary.
“I am not stating this was the cause of this mishap,” he said. “We have months and months of investigation to determine what the cause was.”
Feathering of the tail is an action taken during re-entry at high altitude in order to increase drag and accelerate the space vehicle’s descent. The apparently unscripted action by Alsbury was taken just seconds into the flight of SpaceShipTwo when the suborbital space vehicle had reached the speed of sound, Mach 1 in the denser atmosphere at roughly 50,000 feet. However, unlocking the feathering mechanism was not followed by the second step – moving of another lever which actually rotates the twin tail sections relative to the fuselage to increase the drag for the feathering, which is like a shuttlecock effect. Two seconds after Alsbury’s action and the feathering, SpaceShipTwo experienced a catastrophic breakup.
Feathering of the twin tail section of SpaceShiptTwo requires the pilots to execute two steps. The co-pilot Alsbury executed the first step — unlocking. According to the NTSB investigators, the unlocking of the mechanism should not have been enough to cause the feathering during the ill-fated test flight. The lock-unlock mechanism represents a safety feature. The feathering should only occur after the pilot moves a second lever which is not unlike the lever in a conventional aircraft that lowers the landing flaps to increase lift, but as with feathering, at the expense of adding more drag.
Clearly this discovery by the NTSB is turning their focus away from the rocket engine which has posed so much difficulty for Scaled Composites project life cycle of SpaceShipTwo. The propulsion system has been primarily to blame for the delays which Virgin Group founder, Richard Branson has stated stands at five years; the project development now at the 10 year mark.
Discussions in the blogosphere involving aeronautic and propulsion experts and average citizens had quickly turned to criticism of the SpaceShipTwo rocket motor. However, review of the debris appeared to show the rocket motor intact. With this NTSB finding, there is likely to be a pause and change in the focus. However, if the NTSB investigation concludes that the feathering is the cause of the accident, this may not discharge the many concerns about safety of the SpaceShipTwo propulsion system design.
Virgin Galactic CEO Richard Branson responded harshly to the criticism of the propulsion system. “I’ve never seen such irresponsible innuendo and damaging innuendo,” he told Sky News television in the UK. “The fuel tanks and the engine were intact, showing there was no explosion, despite a lot of self-proclaimed experts saying that was the cause,” he said.
The SpaceShipTwo test flight accident occurred at 10:12 AM PDT on October 31st. One day later, NTSB agents had arrived in the Mojave desert to begin the investigation. During the first press conference, Hart stated that while the investigation is expected to last most of a year, he emphasized that the telemetry recorded during the flight was comprehensive and would be instrumental to uncovering a cause and effect.
The telemetry included several video recordings from the carrier aircraft WhiteKnightTwo, from ground video cameras, and also from inside the cockpit. It is a review of the latter that showed the releasing of the feathering safety lock mechanism by Alsbury. Co-pilot Alsbury died as a result of vehicle’s breakup while the pilot, Peter Siebold, escaped or was thrown from the vehicle and parachuted to the ground. Siebold is in serious condition but conscious and speaking to family and attending physicians.
Another point of comparison between the feathering of the SpaceShipTwo tail section with conventional aircraft flaps is that flaps are given a maximum speed at which they can be safely deployed. Deployment at beyond the maximum speed risks severe mechanical stress to the airframe. The feathering that occurred during the test flight at Mach 1 and at the low altitude of the early phase of powered flight by SpaceShipTwo would also have caused sudden and severe stress and potentially the breakup of the vehicle.
NTSB’s Christopher Hart stated that a follow-up press conference would be held on Monday, November 3rd, and will provide more details regarding the NTSB discovery. Hart, during the Sunday press conference, reiterated that despite this early discovery, the investigation is still expected to take a year to conclude. Universe Today will follow with an update after the completion of the Monday press conference.