SpaceShipTwo crash brings down Richard Branson with it

Virgin Galactic’s commercial spaceflight program was pushed back by more than a year after the test flight of its SpaceShipTwo rocket-plane over the California desert blew up mid-air and killed one of its two pilots on October 31. Virgin Galactic had planned to go start operating suborbital flights as soon as 2015 before the incident. Later, an investigation into the details of the accident by the National Transportation Safety Board (NTSB) said it would take until 2016 to conclude.

That date may be pushed further back as far as Virgin Galactic is concerned because new details have emerged that SpaceShipTwo had been plagued by numerous technical issues, that none outside its engineering and contracting teams knew about, even before the test flight. The Wall Street Journal reports,

Engineers and subcontractors working on SpaceShipTwo spent years wrestling with difficulties, ranging from inadequate rocket-motor thrust to problems in the flight-control system to structural deficiencies affecting the wings of the rocket’s carrier plane.

… Fixes were devised, flight tests were delayed and the result, [Virgin Galactic employees] said, was that some important elements of the project remained in flux for several years. It isn’t unusual for complex vehicles such as spacecraft and airliners to face repeated pitfalls and delays during development. Yet throughout the process, Virgin Galactic founder Richard Branson repeatedly announced timetables that were more aggressive than technical advances warranted, the people said.

Peter Siebold, the surviving co-pilot, had told NTSB officials while in hospital that Mike Alsbury, who was killed, had prematurely unlocked the feathering mechanism and that he (Siebold) didn’t know about it. This then violated the principle that the unlocking be announced verbally, although it remains to be seen if Siebold simply didn’t hear it. SpaceShipTwo boasts of two ‘feathers’, one on each wing, which are hinged booms that can be moved to become vertical to the wings to provide extra drag during atmospheric reentry (obviating the need for heat shields).

SpaceShipTwo schematic.
SpaceShipTwo schematic showing the raised feathers. Image: Virgin Galactic

Related: Feathering malfunction, not hyped motor, suspected in SpaceShipTwo crash

It is unclear why Branson would make such vaunted promises but for the money Virgin Galactic stood to make as one of the first commercial spaceflight operators. Tickets on the flight were going to be priced at $250,000 apiece, with each flight ferrying six passengers and two crew. Soon after the October 31 accident, in fact, the company’s CEO George Whitesides said in an interview to Financial Times that another SpaceShipTwo model being built in New Mexico was 65% complete. In 2015, Virgin Galactic would’ve then had at least two flights to operate (it had announced in 2013 that it would eventually operate five). However, it is unknown if the second model is also as problem-prone as the first one was.

Branson’s impatience to get started on a profitable note is brought out by another example. Earlier, media concerns focused on a new hybrid engine that SpaceShipTwo was going to use in the ill-fated test flight. Designed by the Sierra Nevada Corporation, it used solid HTPB fuel – a plastic – and a liquid nitrous oxide oxidizer. A previous version of the engine using a different fuel couldn’t provide enough bang to power the 60-foot vehicle and Sierra Nevada had asked Branson to reduce the passenger limit. However, according to WSJ, Branson had declined saying Virgin Galactic wouldn’t make money unless it flew six people per flight, prompting the switch to the plastic fuel.

NTSB investigation in the week following the accident had managed to recover all the parts of disintegrated SpaceShipTwo, which had blown up at an altitude of 50,000 feet (15.2 km). The lack of commensurate burn marks exonerated the engine but the fragmentation of components meant investigation would take at least a year to complete. Moreover, with news emerging that Virgin Galactic’s business practices could have severely conflicted with technical issues during development, Richard Branson’s dreams of commercial spaceflight even by 2016 could be pixie dust.

Feathering malfunction, not hyped motor, suspected in SpaceShipTwo crash

On October 31, a manned suborbital test flight broke up mid-air and crashed into the California desert, a 50,000-foot dive that left it smashed. The pilot was killed and the copilot was critically injured. The vehicle was SpaceShipTwo (SS2), owned by British businessman Richard Branson’sVirgin Galactic enterprise, which wants to debut commercial spaceflight in 2015. With SS2’s crash, that’s not going to happen before 2016. The investigation of its crash alone is due to take a year.

In a press conference on November 3 (IST), the National Transportation Safety Board (NTSB), an autonomous federal agency in the United States tasked with investigating civilian aviation accidents, revealed more information about the SS2’s behavior before it tumbled to the ground. The agency didn’t blame any specific incidents or actions, and only addressed some anomalous events that could have contributed to the tragedy. Specifically, the hyped ‘feathering’ mechanism appeared to have been executed abnormally.

On the SS2, a portion of the vehicle’s wings are capable of folding upward and becoming almost perpendicular to the fuselage (see image below; more here). This is called feathering: it controls the pitch, roll and yaw motions of the vehicle, and is used to achieve aerodynamic stability during reentry. It is feasible only for reentry achieved at speeds much lower than the orbital velocity, around 25,000 km/hr. This is why the now-retired NASA Space Shuttle couldn’t use feathering to stabilize itself.

SpaceShipTwo schematic.
SpaceShipTwo schematic.

Feathering increases the aerodynamic drag generated by the vehicle while ensuring the surface isn’t heated up. This eliminates the need for heat shields.

According to the NTSB, on October 31, the engine first fired for nine seconds. Then, a pilot prematurely unlocked the feathering (at Mach 1 instead of at Mach 1.4). However, he didn’t push the lever that moves the feathers to their perpendicular position – but the feathers moved anyway. This caused SS2 to brake suddenly and induce significant structural loads in its frame leading to the mid-air disintegration.

Before the presser, there was speculation that SS2’s motor, the predictably named RocketMotorTwo, might have been responsible for the accident. It is derived from an older variant built by the Sierra Nevada Corporation first tested in April 2013. On the day of the crash, SS2 was debuting a new version of the motor that was using a polyamide plastic fuel. The NTSB said that, after ascertaining they’d found all the parts of the crashed vehicle, they couldn’t find any burn marks that might’ve implicated RocketMotorTwo.

According to an article in Financial Times on November 2,

A second spacecraft under construction for the last three years in New Mexico is “65 per cent complete”, Mr [George] Whitesides [CEO, Virgin Galactic] said, adding that it could be ready to fly next year, once the cause of last week’s accident has been resolved. “The second spaceship is getting close to readiness,” he said.

All eyes on the investigation now…