SpaceShipTwo

[paperburn1]

Hart told a news conference that investigators had determined the "feathering" system, which helps it descend into the atmosphere from space, should have been deployed when the vehicle was traveling about 1.4 times the speed of sound.

Instead, the feather began rotating when the rocket-powered vehicle was traveling at Mach 1, he said, using a technical term for the speed of sound at a given altitude.

Hart said the feathering system, which folds the vehicle in half to create more atmospheric drag, was unlocked early by the co-pilot, according to video from the spaceship’s cockpit. About two seconds later, the spaceplane’s tail section began to fold.

"I'm not stating that this is the cause of the mishap. We have months and months of investigation to determine what the cause was," Hart said.


NO EXPLOSION

SpaceShipTwo was released normally from its carrier aircraft, WhiteKnightTwo, at an altitude of about 45,000 feet. Shortly afterwards its hybrid rocket motor, which was flying for the first time with a new plastic propellant, ignited as planned, Hart said.

Investigators also recovered SpaceShipTwo’s propellant tanks and engine intact, indicating there was no explosion.

[Maui]

Certainly seems to point to about the least damaging cause imaginable to the program.

[DeltaV]

The idea that either pilot would intentionally unlock the feathering system prior to motor burnout and trajectory apogee seems bogus to me.

That would violate common sense about how the system is supposed to operate.

If the feathering system was accidentally unlocked during motor burn, that would make more sense.

[swamijake]

I'd really like to know how the pilot survived.

[Maui]

The idea that either pilot would intentionally unlock the feathering system prior to motor burnout and trajectory apogee seems bogus to me.

That would violate common sense about how the system is supposed to operate.

Agreed. Except...

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.

http://www.bbc.com/news/science-environment-29895140

As to your point, why even Mach 1.4 though? Why would you ever want it unlocked at any point before the engine cut out, let alone before apogee? Seems like the entire point of the locking mechanism would be to ensure against deployment during the burn.

[Betruger]

The idea that either pilot would intentionally unlock the feathering system prior to motor burnout and trajectory apogee seems bogus to me.

That would violate common sense about how the system is supposed to operate.

If the feathering system was accidentally unlocked during motor burn, that would make more sense.

Instrument error?

[DeltaV]

As to your point, why even Mach 1.4 though? Why would you ever want it unlocked at any point before the engine cut out, let alone before apogee? Seems like the entire point of the locking mechanism would be to ensure against deployment during the burn.

I can see no reason to unlock the feather mechanism prior to the top (low dynamic pressure) portion of the trajectory. It is unlikely that they were going for max altitude on this flight, so the stated M1.4 could be the expected peak value at apogee.

According to Wikipedia, the preceding powered test peaked near that value:

The first powered test flight of 2014—and third overall—occurred 10 January 2014. The spacecraft reached an altitude of 22,000 metres (71,000 ft) (the highest to date) and a speed of Mach 1.4.

It seems reasonable that they would not want to exceed the prior apogee/speed with first flight of a new engine design.

[DeltaV]

Instrument error?

Or, a misread value due to high vibration from motor combustion + transonic buffeting?

But that doesn't make sense either, as the pilot flipping the lever would know that the burn was still in progress and that they were in an unsafe regime for feathering...

Hand hits lever due to buffeting?

[dkfenger]

There's some really good discussion on the NASA Spaceflight Forum. The consensus there seems to be that the feather unlock is done during the burn so that you have the option to abort the burn if it won't unlock. Once the burn is done you're headed for space no matter what you do. If you find out at that point that you can't configure for reentry, it's too late.

[Maui]

I guess they neglected to consider that you are just as F'd if it deploys during the burn as you are if it doesn't deploy after. At least you probably have a short bit of time to deal with the issue of it not opening vs the instant dis-assembly when it deploys too soon.

[paperburn1]

Remember the NTSB said it was just unlocked and the did not "hit the switch" to tilt the tail section.

[paperburn1]

A point I'd like to make it and I don't think a lot of non-aviation types understand is that how violent control reversal or flutter can be. It's not unheard of for a pilot to break his neck or otherwise severely injure themselves. I personally walked away with a nasty knot on my head after experiencing control reversal in the simulator. The simulator motions are limited in response to help protect the equipment when we are demonstrating this phenomenon.
http://www.scaled.com/projects/test_log ... aceshiptwo

[Betruger]

Instrument error?

Or, a misread value due to high vibration from motor combustion + transonic buffeting?

But that doesn't make sense either, as the pilot flipping the lever would know that the burn was still in progress and that they were in an unsafe regime for feathering...

Hand hits lever due to buffeting?

Yes that's possibly it. But so far they've only said the pilot did the unlock - without describing the action as recorded by inflight video.

There's some really good discussion on the NASA Spaceflight Forum. The consensus there seems to be that the feather unlock is done during the burn so that you have the option to abort the burn if it won't unlock. Once the burn is done you're headed for space no matter what you do. If you find out at that point that you can't configure for reentry, it's too late.

By far the best public discussion I've seen.

[GIThruster]

http://www.reuters.com/video/2014/11/02 ... st+Popular

[Maui]

Without actually watching that, I assume a lava video wasn't what you meant to paste?