Virgin SpaceShip Two destroyed in test :(

[markhudson6 13]

Following on from what Martin said,

 

"NTSB acting chairman Christopher Hart said that video from the cockpit and telemetry both show that the co-pilot, Michael Alsbury, unlocked the feathering mechanism prematurely. The locking handle was moved to the unlocked position when the spacecraft was at just Mach 1, and not 1.4.

However, the actual feathering deployment handle was not engaged. For reasons as yet unknown, despite this, the mechanism deployed anyway two seconds after the locking handle was thrown. At this point, telemetry was lost, and the spacecraft broke apart.

Again, as Hart points out, we don’t know yet if this was the cause of the crash or not. There will be a lot more investigation before firm conclusions can be made. It’s not at all clear why the feathering lock mechanism was disengaged prematurely, and no doubt that will be a focus of the investigators".

 

Extract from:

 

http://www.slate.com/blogs/bad_astronomy/2014/11/03/spaceshiptwo_crash_update_feathering_deployed_prematurely.html

 

Regards,

M.

 

[Christopher Low 63]

Could higher aerodynamic forces have caused the feathering mechanism to deploy? I don't know the difference in altitude between the premature unlocking and when the handle is supposed to be engaged, but it was presumably a procedural error by the copilot?

[MartinW 0]

Includes Branson interview. Bottom of page.

http://www.bbc.co.uk/news/health-29880688

[allardjd 1,853]

I think this is akin to "arming" spoilers or reversers in an airliner. Actually deploying them is a two step operation. In some cases the second step may be automatic based on sensor inputs and for other things, it requires a second manual input. Not sure which is the case here but if I'm understanding it correctly, the crew manually and seemingly intentionally "armed" the feathering operation, which then actuated at a time in the flight when it should not have, causing the airframe disintegration.

If, by design, the feathering required a second manual input, something must have been out of position or out of calibration or shorted or something along those lines. Much the same if the actual initiation of feathering is automatic - something that should have inhibited it in that flight mode did not.

Not sure if the early manual step of "arming" will be classified as human error or not. There's some speculation that it is normally done that early but the jury (and NTSB) are still out on that one. I suspect that arming was intentional and per procedure. If so, that will probably be deemed a non-conservative, flawed procedure. Once armed, the feathering deployment may no longer be single-failure proof.

John

[MartinW 0]

Latest from the BBC.

 

 

 

http://www.bbc.co.uk/news/science-environment-29895140

 

This "feathering" technology, which is designed to slow and orientate the craft on its return to Earth, should not have been unlocked so early in the flight, and certainly should not have engaged at the time it did - on an accelerating ascent.

 

 

'Uncommanded' deployment

The vehicle, he said, was dropped from its carrier aircraft, WhiteKnightTwo, at an altitude of almost 50,000ft at 10:07:19 US Pacific time.

The ship's hybrid rocket motor was then ignited just a couple of seconds later, at 10:07:21.

Eight seconds after that (10:07:29), the vehicle was travelling just under the speed of sound (Mach 0.94). Two further seconds into the flight (10:07:31), it was travelling at Mach 1.02.

It is in that period between Mach 0.94 and Mach 1.02 that Michael Alsbury is seen on recovered cockpit video moving a lever to unlock the feathering system - an action that in the pilots' checklist was not called for until the vehicle had reached Mach 1.4.

Investigators have previously described how the feathering system then deployed, apparently "uncommanded" by the pilots. It is probable that aerodynamic forces deployed the mechanism, resulting in the break-up of the ship. This is timed at 10:07:34 - the instant at which video and telemetry were lost.

One line of inquiry will be to ascertain whether the pilots were getting the correct information on their cockpit display throughout this critical period.

 

 

[Christopher Low 63]

Does anyone know when the feathering mechanism is normally deployed? Presumably after the rocket powered ascent phase?

[MartinW 0]

Not sure, in the decent sometime. Max altitude is 110km, I would imagine the feather is deployed pretty soon after the vehicle begins it's decent.

[allardjd 1,853]

Since they want to maximize the time of weightlessness, my guess is they are going to ride their energy as long as possible and would only deploy when increasing drag begins to spoil the weightlessness experience and airframe friction heating begins to manifest itself.  Deploying any earlier seems counter-productive to the experience that is the entire object of the program.

 

John