News Virgin Galactic SpaceShipTwo accident during powered test flight

[Urwumpe]

Hopefully, there will be enough of the pieces found to discover the cause(s) of the "anomaly" (sic).

You have to differ between your emotions (which would cry tragedy there) and the scientific/engineering language, which can only say anomaly as long as the current state of the investigation does not know better. Using correct, accurate words is very important for engineers, so every engineer involved does not get confused by too much creativity in the choice of words.

For example, the investigators also say "catastrophic structural failure". While this includes catastrophic now, it is again, a very well-defined engineering term, describing how fast and how complete the structure of the spacecraft failed. Just "structural failure" could also mean that some minor part just buckled, without affecting the mission.

It is like medicine. When your doctor tells you, that you got again a bad cold, for going to work too soon with a previous one, he will tell to his collegues that you have a "recidividic acute rhinopharyngitis", for describing how bad you should feel.

 

[rhoude57]

To be precise, we are talking about an accident here, not an anomaly. We can add, in terms of the SAE ARP 4761 Aircraft Safety Analysis standard that the accident can be categorized as catastrophic, given the sustained failure resulted in the sudden termination of the flight with loss of life.

 

[Urwumpe]

To be precise, we are talking about an accident here, not an anomaly. We can add, in terms of the SAE ARP 4761 Aircraft Safety Analysis standard that the accident can be categorized as catastrophic, given the sustained failure resulted in the sudden termination of the flight with loss of life.

Wrong. The flight ended with an accident, but the symptoms are called anomaly. Study the Space Shuttle anomaly reports for details.

 

[rhoude57]

Are you talking about the NASA Anomaly Report? One such compilation report is generated for each NASA miasion and lists every "anomalous event" encountered during that mission. I'm not sure Virgin Galactic has adopted the practice.

 

[Urwumpe]

Are you talking about the NASA Anomaly Report? One such compilation report is generated for each NASA miasion and lists every "anomalous event" encountered during that mission. I'm not sure Virgin Galactic has adopted the practice.

You can be very sure: They do. It is a common practice among many test campaigns, even software testing. Maybe not always by the same name, but by the same attributes.

---------- Post added at 03:10 PM ---------- Previous post was at 02:32 PM ----------

The statement by the ESA director, Jean-Jacques Dordain on the SpaceShipTwo accident:

http://www.esa.int/About_Us/DG_s_Ne...on_the_loss_of_Virgin_Galactic_s_SpaceShipTwo

 

[garyw]

To be precise, we are talking about an accident here, not an anomaly

No, it's an anomaly of the vehicle that lead to an accident.

The anomaly was the cause, the accident was the effect of the anomaly.

 

[Thunder Chicken]

This report says that the "motor" itself was found intact, but not a lot of coherent technical detail.

http://www.bloomberg.com/news/2014-11-02/spacecraft-s-rocket-motor-landed-intact-ntsb-chief-says.html

It sounds like the motor casing did not fail, but that does not rule out a blowback failure of the NO2 tank, or even simply an structural failure unrelated to the engine. I'm personally wondering if a fatigue failure of the feathering mechanism is a possibility

God, I wish journalists had to take a competency test on the subjects on which they report. Some of these folks are barely qualified to report on Justin Bieber's wardrobe. :facepalm:

 

[Cairan]

God, I wish journalists had to take a competency test on the subjects on which they report. Some of these folks are barely qualified to report on Justin Bieber's wardrobe. :facepalm:

Agence France Presse... When I see these 3 words, I usually stop reading. Yet yesterday I felt compelled to read what they had to say about the SS2 accident...

Turns out, it happened in the Mojave desert, 3 hours WEST of Los Angeles...

:facepalm:

...then I stopped reading their "piece" on the subject.

 

[MaverickSawyer]

This report says that the "motor" itself was found intact, but not a lot of coherent technical detail.

http://www.bloomberg.com/news/2014-11-02/spacecraft-s-rocket-motor-landed-intact-ntsb-chief-says.html

It sounds like the motor casing did not fail, but that does not rule out a blowback failure of the NO2 tank, or even simply an structural failure unrelated to the engine. I'm personally wondering if a fatigue failure of the feathering mechanism is a possibility.

Yeah, the B-roll footage seemed to show the casing. Nozzle's embedded in the ground, if it's still there.

My dad and I were going over the footage... It's not clear how the motor casing and the oxidizer tank are linked. Perhaps it failed there?

 

[Kyle]

NTSB briefing going on now, the engine was found intact with no sign of burn through, the feathers were moved from locked to unlocked at about 9 seconds into powered flight by the copilot. Feathers were then moved into the "deploy" position without a command given, confirmed by internal video, which appears to have resulted in the vehicle's disintegration.

 

[Urwumpe]

NTSB briefing going on now, the engine was found intact with no sign of burn through, the feathers were moved from locked to unlocked at about 9 seconds into powered flight by the copilot. Feathers were then moved into the "deploy" position without a command given, confirmed by internal video, which appears to have resulted in the vehicle's disintegration.

So, it is going towards "pilot error"?

 

[Quick_Nick]

So pilot error combined with bad luck. No engine problems or any major vehicle issues. The pilot unlocked the feathers too early, aerodynamic forces deployed the feathers as the vehicle went transonic, and that tore it all apart.
Bad luck only to the extent that there's maybe some chance the feathers would not deploy uncommanded when unlocked and transonic.

 

[Urwumpe]

Bad luck only to the extent that there's maybe some chance the feathers would not deploy uncommanded when unlocked and transonic.

Doubtful. In neutral position, the elevons would produce lift to keep the vehicle in horizontal position. If you unlock the feather mechanism, this lift would deploy the feather mechanism, unless you force it into its normal position by powering the actuator.

 

[Cosmic Penguin]

I think this is too early to presume that pilot error is in play...

...because I wonder if SS2 lost attitude control (pitch/yaw/roll) after engine ignition? That might be one reason why Alsbury pushed the feathering system to the unlock position. Remember the SS1 1st X-prize flight (16P) in September 2004? Mike Melvill had to deploy the feathers early after it entered a violent roll late in the engine burn. Maybe something was wrong early in the engine burn this time and Alsbury decided to arm the system early in order to get it deploy ASAP after it gets above the atmosphere and engine shuts down?

(starts at the 20:30 mark)

 

[Urwumpe]

I think this is too early to presume that pilot error is in play...

Would still be pilot error because he deployed it too low and too fast.

---------- Post added at 09:28 AM ---------- Previous post was at 07:10 AM ----------

Looks like Enders, the CEO of Airbus, also encourages Branson to keep on trying... I can't yet find a direct source of the message, but the newspapers here cite him as saying: "When governments retreat from manned spaceflight, private pioneers continue the adventure of spaceflight. I raise my hat to Richard Branson and all others, who risk a lot here."

 

[gwiz]

Seeing how everyone was pointing the finger at an engine failure until the latest data, it is perhaps not helpful to suggest causes while the investigation is at such an early stage.

 

[Urwumpe]

Seeing how everyone was pointing the finger at an engine failure until the latest data, it is perhaps not helpful to suggest causes while the investigation is at such an early stage.

The engine is still not free of guilt, so take your own advice to your own heart as well. Multiple ground observers noticed a hard start of the engine. Also, the even if the copilot unlocked the feathering, it does not explain why the engine was still thrusting.

We just know now, that the engine did not explode initially and reached the ground fairly intact (but in separated assemblies). We do know that the copilot manually unlocked the feathering mechanism.

Among the many things that we do not know:
- Did the hard start have any further effect on the vehicle?
- Could the sudden change in acceleration have made the copilot accidentially unlock the feathering?
- Could the hard start have damaged the valves to shut down the engine?
- Did the hard start maybe also cause another structural failure of the spacecraft?
- Is it possible to accidentally unlock the feathering without actually intending it? (UI design)

While there is no manual to refer to, there are some images - in one, the copilot is seen holding one of two large levers at the center pedestral, not sure if this lever is for throttling the rocket engine or for controlling the feathering.

http://aviationweek.com/blog/spaceshiptwo-next-supersonic-flight

 

[N_Molson]

the copilot is seen holding one of two large levers at the center pedestral, not sure if this lever is for throttling the rocket engine or for controlling the feathering.

If it is, an unexpectedly violent shock caused by an hard engine start might simply have moved the lever in the wrong position, especially if it was armed ?

This might seem a very simplistic comparison, but I remember once driving at night in a poorly lightened area, hitting one of those nasty "slow down" bumps at full speed and having my (manual) gearbox lever juming itself into the "Neutral" position because of the shock... Now replace the bump by an engine hard start and the gearbox lever by the feather position lever...

 

[Urwumpe]

If it is, an unexpectedly violent shock caused by an hard engine start might simply have moved the lever in the wrong position, especially if it was armed ?

This might seem a very simplistic comparison, but I remember once driving at night in a poorly lightened area, hitting one of those nasty "slow down" bumps at full speed and having my (manual) gearbox lever juming itself into the "Neutral" position because of the shock... Now replace the bump by an engine hard start and the gearbox lever by the feather position lever...

There are much more similar events in space- and airflight. There is a good reason why you needed quite some force for moving an abort handle.

Such an engine hardstart means going from 2 g to 0g and back to 2g in fractions of a second. Quite a shake, first you are pressed against the windshield, next hard back into your seat.

 

[Thunder Chicken]

A bit more coherent report:

http://spaceflightnow.com/2014/11/03/virgin-galactic-rocket-plane-deployed-braking-system-prematurely/

Would unlocking the feathering system that early in the flight actually be OK procedure wise, rather like arming the thrust reversers on an airliner prior to touchdown?