SpaceShipTwo: Consequences

The loss of Virgin Galactic's prototype sub-orbital space craft is a tragic derailment of their space ship programme. Already tainted by the deaths of three engineers and injuries to three more in a failed rocket test, the project is now effectively stalled while investigations are carried out into the causes of the vehicle's breakup with the loss of co-pilot Michael Alsbury and injuries to the command pilot Peter Siebold.

Each vehicle is basically a one-off hand-built example, hugely expensive to construct and test, so the money invested into the crashed SpaceShipTwo is to all intents lost, despite the data obtained from the construction experience and by the telemetry recorded. Even without the fatal mishaps that have occurred, the funds required to construct the second ship have been difficult to raise. So one can only imagine the difficulty of attracting new investment to the initiative now.

Recent reports suggest that a major backer has withdrawn funding and that the day-to-day costs of continued development are being met by Virgin honcho Sir Richard Branson. It seems unlikely that even his great wealth can sustain something as vast as this commercial space travel undertaking. So it's not hard to feel that the prognosis for this adventurous undertaking is a pessimistic one.

As we've seen repeatedly with past aviation tragedies, the media clamouring for instant answers has resulted in talking heads of mixed expertise and experience weighing in on the cause of SpaceShipTwo's demise, a large proportion pointing the finger at an untried rocket fuel formulation as being inherently dangerous and thus the obvious cause of the calamity. These pundits presented their case for blame in apparent outrage that their warnings about the danger were blithely ignored by the engineers and management at Virgin Galactic.

But the wreckage showed that the rocket motor and its fuel system were not destroyed in an explosive event, and the NTSB offered a preliminary finding of fact that the propulsion system was not the cause. Not that the news stopped those who criticised the rocket motor from day one from continuing their attacks on the company for its propellant choice. However, their voices have now taken on the tone of conspiracy theory rather than concern for safety.

Further information has come to light in the last two days that points the blame in a totally different direction. Images have been made available that show the vehicle's breakup at altitude and they clearly show that the twin "feathering" tail booms deployed into their descent profile while the ship was under power. This information has also been confirmed by the NTSB as a finding of fact.

And there is video from the flightdeck that allegedly shows the co-pilot unlocking the tail booms at a time that sources close to the programme claim to be "premature", with specific reference to a minimum target speed requiring SpaceShipTwo to be travelling at mach 1.4 or faster before unlock is authorised.

That so-called premature unlocking cannot, of itself, result in the tail boom articulation taking place. An additional control must be employed to activate the process, the unlock lever being a safeguard against accidental deployment of the feathering control. And the video, it appears, shows that neither pilot activated that feathering control.

So what went wrong?

The truth is that we don't know and as you'd expect, and quite correctly, the NTSB refuse to find a likely cause until their investigation is complete - probably some months away. But we're not bound by such constraints and there's room to speculate a little based on the assumption that the information acknowledged by the NTSB as findings of fact is in fact true,

First, we don't yet have a reason why the feathering unlock lever was employed at that time - prematurely, if the sources are correct - but we do know that this was a test flight of limited duration and test flights are exactly that - you do stuff and find out if what you expect actually happens and when you have a very tight time frame, you execute things in a timely manner so that you can accomplish all of your goals.

We can be confident that the activation of the feathering manoeuvre was uncommanded - that neither pilot initiated it either by mistake or by accident. But without knowledge of the activation and deployment processes, how it came to happen must wait for the official report. However, happen it did, and demonstrates a fault in that mechanism - software, hardware or design - that was inherent in the vehicle.

It's worth noting also that although the breakup of SpaceShipTwo began just a couple of seconds following the tail boom feathering unlock lever being activated, there is no direct evidence here of a cause and effect relationship. Assuming that it did have an effect, is raises questions about just what form of feathering lock design was implemented whereby it could possibly physically compromise the flight integrity of the ship. Surely a more likely design would simply have prevented the feathering lever being deployed, and the physical unlock and articulation would be controlled via the feather activation control itself?

If the unlock control did actually unlock the tail booms, then that design decision must surely be cause for deep concern. Continued flight with the booms held in their unfeathered state only by the integrity of the articulation system would be a recipe for disaster. I prefer to think that it wasn't the case here.

There is another possibility - that the forces experienced by the vehicle as it was pushed through mach one were simply so great that they exceeded the loads designed for and the forces on the locks and articulation mechanisms caused them to fail catastrophically.

But how? Well, in the case of an aircraft accelerating through the speed of sound, for instance, and adopting in error an attitude that departs from the aerodynamic profile expected, it would doubtless be exposed to loads that weren't anticipated or engineered in. Such anomalous flight regimes have resulted in test flight failures in the past so it's not beyond the realm of possibility that such a situation occurred here.

Having made those speculations, however, I hasten to add that I'm not making a case for reasons why SpaceShipTwo crashed, after all I have no crystal ball or insider info, I'm simply restating what we know and what we think we know, while explaining why I don't expect any answers for quite some time. And at the same time to express some concerns about the project's future.

We humans have an astonishing history of exploring the limits of our abilities and knowledge, and although I'm never going to have a quarter million dollars to benefit from Virgin Galaxy's endeavours, I'm in awe of their ambitions.

I hope they recover from this setback and I wish them all the best for the future.