Virgin Galatic Spaceship Two down in the Mojave. [Archive]

peekay4

31st Oct 2014, 23:51

@radix

They had abandoned the engine mixture related to the 2007 accident. That engine had a rubber-based fuel (HTPB) and was being developed by a sub-contractor (Sierra Nevada Corp -- SNC).

That 2007 accident actually had nothing to do with the engine all. They were testing the flow of nitrous oxide between two tanks. No cause was ever released, but there is speculation that one of the nitrous oxide tanks was overheated in the desert sun, and the gas inside reached critical temperature.

The HTPB engine SNC was supplying had serious vibration issues with burns longer than 20 seconds.

So earlier this year, Scaled decided to abandon HTPB and take the engine design in-house. They switched to a fuel based on plastic (polyamide) and they subsequently completed several successful ground test firings with the new polyamide fuel.

Today was the first attempt to use the new polyamide fueled engine in a powered flight test.

Carbon Bootprint

1st Nov 2014, 00:19

In before someone else asks it: given this was the first actual flight with the new fuel mix, could not this have been accomplished remotely with an unmanned craft?

Isn't that the way the protocol has worked previously for "non-commercial" space flights?

PrivtPilotRadarTech

1st Nov 2014, 01:08

Regrets for the casualties, hats off to test pilots, they pay the price for progress.
Was interested in the rocket motor. It burns rubber or plastic?!! It's called a "hybrid rocket engine" as it is neither a solid nor a liquid fueled rocket. It uses a solid fuel, and a liquid or gaseous oxidizer which can be throttled. If the oxidizer is oxygen, it can't explode. However, in this case they use nitrous oxide, which has been criticized by rocket scientists as dangerous, as it can explode on its own. I'm NOT a rocket scientist, so I'm just repeating what I read. So perhaps the flame propagated backwards thru the throttle to the tank of nitrous oxide. In any case, they will figure this out and we will move forward.

peekay4

1st Nov 2014, 02:30

I believe it was the same "back then".

During the Bell X-1 flight program there were numerous rocket engine failures. In fact, on the very first X-1 powered flight (flown by Chalmers Goodlin), the engine caught on fire. Throughout the X-1 program, the rocket engine (XLR-11) caught fire on many occasions. At least one exploded in flight. On several other flights, the pilot had to jettison the propellant.

During the X-15 program, Scott Crossfield had an XLR-11 exploded on him in flight. The next summer, Scott was in the cockpit for a static ground test of the more powerful XLR-99 rocket -- which also exploded. When the XLR-99 was finally ready for its first powered flight (on a manned X-15), Scott was again the pilot. The guy had no fear.

Those X pilots were of a different breed. Same with these Scaled Composite pilots today. They got the Right Stuff, as Yeager might say.

Bevo

1st Nov 2014, 02:58

as a reminder, us faa ATC would have had to clear them to 50,000 feet

LA center should have tapes of this, at least the ATC portion...anyone have a link?

These flights take place in the Edwards AFB R-2508 restricted area complex. Much of this air space is under Edwards control and is surface to unlimited.

West Coast

1st Nov 2014, 04:45

Virgin Galactic's SpaceShipTwo Has Crashed, One Pilot Confirmed Dead (http://gizmodo.com/virgin-galactic-experiences-first-major-accident-possi-1653360863/+mattnovak?utm_campaign=socialflow_gizmodo_facebook&utm_source=gizmodo_facebook&utm_medium=socialflow)

Pics

PrivtPilotRadarTech

1st Nov 2014, 06:42

Those are excellent photos. The "comet" photo appears to show a largely intact fuselage, with the wings separated and a gas cloud. I see what I believe are the cockpit windows on the nose. It appears to be falling backwards, and the photo appears upside down judging by the debris trail.

MAINJAFAD

1st Nov 2014, 07:39

Change of Solid Rocket Fuel for this flight to give more specific impulse according to the news (from rubber to grain type). Grain biased propellant + Cracks in said propellant = Engine Explosion.

Green Guard

1st Nov 2014, 07:41

Did it break up on ditching ?
Did pilots use any parachutes ?

mickjoebill

1st Nov 2014, 08:15

Reports of "pilot ejection" and one parachute seen.
Also a unconfirmed report by a first responder of one body in the cockpit.

Helen49

1st Nov 2014, 08:40

Sorry to appear a bit dim, but what happened to the mother ship? I cannot see and have not heard, any media reports about this and yet the shots on TV [if of this accident] indicate a successful separation......?

Dysonsphere

1st Nov 2014, 08:53

Mother ship landed safley and not damaged so there has been no other comment

Kerosene Kraut

1st Nov 2014, 09:05

Looks like a long way to go if the engine still not works as intended. They still seem to not get the thrust needed.

I still very much admire Scaled. These are true geniuses. If it can be done they will do it. Good luck.

Basil

1st Nov 2014, 09:19

and to push the boundaries of commercial space for us all, funded by said celebs.
Yes, good point.

Radix

1st Nov 2014, 09:32

Change of Solid Rocket Fuel for this flight to give more specific impulse according to the news (from rubber to grain type). Grain biased propellant + Cracks in said propellant = Engine Explosion.
From what I understood it is still a Hybrid motor so your point, which refers to dangers of a solid fuel rocket is invalid.

Tu.114

1st Nov 2014, 09:57

I am sure that the new engine/fuel configuration was satisfactorily run on a test stand several times before being tried on this flight?

Peter47

1st Nov 2014, 10:46

Only really repeating what the first few posts said, but rocket science is still not safe. The loss of two space shuttles is, from what I've read, in line with what you would expect. Even now a fair proportion of satellite launches fail - one very recently. Yes, after every loss you can look back and say that we did this wrong and what happened was inevitable and could have been avoided, but if we all had the benefit of hindsight you could close all casualty departments and a lot else and there would be a lot fewer liability lawyers. The trouble with spaceflight is that simple failures can be catastrophic particularly at launch. Had one of the five engines on the Saturn V failed in the first few seconds that would have been it. The escape tower might have worked but from what I've read I wouldn't have counted on it.

There were two unmanned Saturn V launches before it lifted men into space. The first (Apollo 4 I believe) was successful, the second (Apollo 6) had serious problem with rocket oscillations - the pogo effect - and it was lucky that no one was on board. These were fixed before men were put on the top of the rocket.

Doubtless the "anomalies" that caused the crash will be overcome but even when the technology matures there will likely still be disasters. It will be interesting to see that effect that this has on bookings.

wiggy

1st Nov 2014, 10:59

Peter

Good points.

I'll give Sir RB credit for enabling/driving others to push the boundaries - somebody needs to, and I'm sure all those involved at a hands on level are well aware of the risks, but I do wonder any of the celebs/high rollers who booked flights have heard Richard Feynman's statement that:

"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled."

TURIN

1st Nov 2014, 11:38

The trouble with spaceflight is that simple failures can be catastrophic particularly at launch. Had one of the five engines on the Saturn V failed in the first few seconds that would have been it. The escape tower might have worked but from what I've read I wouldn't have counted on it.

Oh I dunno...
Apollo Launch Abort System Test

wiggy

1st Nov 2014, 11:57

TURIN

Whilst that film is impressive I think Peter is talking about a "pad fall back".

Atlas-Centaur 5 pad fallback 1965 - Sonicbomb.com (http://www.sonicbomb.com/xv1.php?vid=atlas-centaur_fallback&id=924&s=5&w=720&h=497&ttitle=Atlas-Centaur%205%20pad%20fallback%201965)

Escaping one of those demands a fast decision (?automated) to intitate the abort and then a propulsion/guidance system that can get the spacecraft and occupants away from the fireball far enough fast enough.

50 years down the road from that Atlas-Centaur video it's still the case that any spaceflight, even a sub-orbital hop, using any current technology is sadly always going to be several orders of magnitude more risky than jumping on a commercial flight or using one's executive jet. I suspect everybody here knows that.......

Apologies for any thread drift.

joema

1st Nov 2014, 12:16

There were two unmanned Saturn V launches before it lifted men into space. The first (Apollo 4 I believe) was successful, the second (Apollo 6) has serious problem with rocket oscillations - the pogo effect - and it was lucky that no one was on board. These were fixed before men were put on the top of the rocket.

Actually the pogo problem was only reduced, not fixed. On Apollo 13, the 2nd stage had such severe pogo vibration the entire launch vehicle almost broke up. The five engines experienced 68 g fore/aft vibration at 16 Hz, flexing the steel I-beam thrust structure by three inches. The vibration apparently tricked the center engine into fuel cutoff, which accidentally saved the vehicle.

13 Things That Saved Apollo 13, Part 5: Unexplained Shutdown of the Saturn V Center Engine (http://www.universetoday.com/62672/13-things-that-saved-apollo-13-part-5-unexplained-shutdown-of-the-saturn-v-center-engine/)

On the new Virgin Galactic engine, I wonder if it was tested in altitude chamber, or simply at ground level? If it was never tested in an altitude chamber, then this past manned mission was essentially the first realistic test.

Interested Passenger

1st Nov 2014, 12:47

BBC has photos of the explosion taken from the ground, only a few seconds after separation

BBC (http://www.bbc.co.uk/news/world-us-canada-29861486)

deptrai

1st Nov 2014, 13:46

"Flight testing" implies the technology is not yet proven. Hardly surprising that accidents can happen.

The A380 went through about 2500 hours of flight testing. It wasn't enough to uncover the uncontained engine failure waiting to happen. Spaceship Two is radically new technology, in comparison.

Doubtless the "anomalies" that caused the crash will be overcome but even when the technology matures there will likely still be disastersI agree. Nitpicking: Every single loss of life is a disaster, however I'd be hesitant to use that word. I'd venture a guess the driver who apparently lost his life would prefer the word "accident", rather than "disaster".

Groucho

1st Nov 2014, 15:07

Any one know what the escape system was for the crew?

barit1

1st Nov 2014, 15:30

deptrai:The A380 went through about 2500 hours of flight testing. It wasn't enough to uncover the uncontained engine failure waiting to happen.

There are early failures, and there are late failures.

The A380 (QF R-R Trent 900) problem was an early failure, immature manufacturing quality issue, which revealed an architecture problem in the engine design. Unloaded turbine discs have been failing for many decades!

Late failures are associated with old tired hardware (fatigue), or with second or third party operators who lack the experience of the original owners.

silverstrata

1st Nov 2014, 15:47

Radix

From what I understood it is still a Hybrid motor so your point, which refers to dangers of a solid fuel rocket is invalid.

From what I understand, the solid-gasseous rubber/polymer engine was suffering from surges or stuttering, especially at start up or shut down.

One possible reason (among many) for such surges, is cracking of the rubber/polymer fuel. If there are cracks and pieces of rubber/polymer break off, the burn will not be smooth and consistent and surging may well take place.

Hopefully, the reasons for this engine malfunction can be discovered, replicated, and cured. A change at this point in time to a liquid fuel engine, would probably mark the end of this project.

pchapman

1st Nov 2014, 17:48

Just musings:

It does indeed look like the aircraft did a complete 180, as PrvtPilotRaderTech wrote, but it isn't certain. And it possibly happened very suddenly. (The Daily Mail does have good large photos.) After all, the smoke plume in one photo starts at the upwind end, as does a bit of flame on a slightly earlier photo. Also looks in one of those photos like both tails have just come off with the aircraft backwards, but that's very hard to tell. It suggests it wasn't just explosion leading to complete tail failure then leading to tumble & disintegration.

Instead something caused it to flip suddenly, while largely intact, followed by disintegration. Could a partial tail failure, either a simple structural failure or after an explosion, cause that? Seems less likely. That would more likely cause a more progressive loss of heading/yaw/pitch, then structural failure and breakup. On the other hand, what do I know about trim angles on the tail and its aerodynamic stability.

Still surprising how fast it seems to have actually happened, given that photos suggest it didn't just "blow up" completely. But although a witness described a sudden puff, as I've only seen stills, it isn't clear just what the timeline is.

What about the explosion itself flipping the craft? That would take a pretty good explosion.

Photos on the ground from the side make it look like the nitrous oxide tank is largely intact, ahead of the line where everything broke off -- the tails at the hinges, the wing panel flaps, and the solid part of the rocket motor and any oxidizer piping/valving/pumps. (I don't know the actual setup). (Photos were seen in a video in the UK's Telegraph newspaper website, interviewing a photographer.)

So if there were some combustion instability in the solid rocket part, with whatever nitrous oxide was being pumped in, what kind of explosion would result? I'm still surprised at how quickly the craft swapped ends -- IF indeed that's what I'm seeing. Maybe an explosion broke some of the rocket support structure, it started to jackknife, and the off-axis thrust was enough to make the craft swap ends.

In some hours or weeks this speculation will likely be dated by new information, but it's my best amateur effort at the curious sequence of events...

Edit: Some news is now reporting that it happened two minutes after drop. This changes the timeline as from photos and interviews I previously saw, it made it sound as if it was shortly after engine ignition.

Radix

1st Nov 2014, 18:59

From what I understand, the solid-gasseous rubber/polymer engine was suffering from surges or stuttering, especially at start up or shut down.
One reason for using a hybrid is that this doesn't lead to an explosion. I.e. the engine is more tolerant to propellant cracks. All these motors seem to suffer from surges.
Unless the surges were so severe that it had an effect on other parts of the motor causing the flame to reach the liquid fuel it doesn't explain what happened.

tdracer

1st Nov 2014, 20:10

To add to what Radix wrote:
In the rocket community, hybrid motors are considered to be significantly safer and more fault tolerant than either solid or liquid propellants. The downside being that hybrids typically don't have the same level of specific impulse.
I suspect that the 'safer' aspect was why hybrid technology was chosen for the SS2 application. Unfortunately, when it comes to rocket motors, 'safer' is a relative term:uhoh:

Smilin_Ed

1st Nov 2014, 20:34

and to push the boundaries of commercial space for us all, funded by said celebs.

The "celebs" have put up some $80 million which helps to fund the research.

radarman

1st Nov 2014, 21:43

Who, or what, is the regulatory body that will eventually authorise Sir RB to launch SS2 with fare-paying passengers, and what certification criteria will apply? If a conventional aircraft like the A380 requires 2,500 hours of flight testing before being certified, surely a spaceplane with so many novel and advanced features will require a vastly more complicated test regime before being certified for passenger flight. If so we are unlikely to see this venture coming to fruition for another 50 years or so at the present rate of testing.

FlightlessParrot

1st Nov 2014, 22:03

I don't think "fare-paying passengers" is quite the description for the target market.

I don't normally defend mega-rich celebrities, but Richard Branson has a history of taking part in high-risk activities, and even if potential participants can't assess the dangers on an engineering basis, they ought to be able to look at who's doing it, and conclude that it's not like an Oprah Winfrey tour. And the lawyers will make sure that they do, really, understand that it's dangerous.

So I think what the regulators ought to be concerned with is the risk to non-participants, and that the costs of cleaning up after a private jolly don't fall on the public, and then let people take their own risks.

Alber Ratman

1st Nov 2014, 22:19

If it is taking fare paying passengers, it surely must be certified under the various regulations of CFR14 for type certification and operation.. It surely cannot be put under an X plate or is a bit of bribery involved?

Machinbird

1st Nov 2014, 22:19

I found an article (just updated today) that seems to address most of the hybrid rocket motor technology problems that we will hear about later when more is known.
Hybrid Rocket Motor Design (http://www.spacesafetymagazine.com/aerospace-engineering/rocketry/hybrid-rocket-overview-part-2/)
Worth a read.

G-CPTN

1st Nov 2014, 22:24

something caused it to flip suddenly, while largely intact, followed by disintegration

'Expert' on BBC Radio Five has described the craft 'inverting' and flying backwards at supersonic velocity whereupon the wings were torn off (as they weren't stressed for negative direction travel) and the survivor was thrown free.

There was no 'explosion' other than catastrophic failure of the structure.

There is no ejection system and the pilots do not wear pressure suits - though they do wear parachutes.

Escape would be through a 'rear hatch'.

The deceased pilot was not thrown free when the craft broke up.

SpannerInTheWerks

1st Nov 2014, 23:45

If it proves not to have been a problem with the propulsion system could it be structural failure caused by flutter and/or fatigue?

TIMTS

2nd Nov 2014, 01:00

Could it have been an inadvertent, or uncommanded, activation of the feathering mechanism? This would pitch the tails up rather dramatically, and could easily, I guess, flip the craft on its back. Or at least present such a large area to the aerodynamic forces that it disintegrated.

Just my musings...

The Sultan

2nd Nov 2014, 02:07

Groucho,

The 'escape system" is a coarse net which the crew can use to drag themselves to the hatch.

Shadoko

2nd Nov 2014, 04:23

If those published pics are from the last flight (link from post #23 by West Coast), it seems there was some trouble in the propulsion (extinction and/or instabilities?) before any abnormal attitude:

http://i39.servimg.com/u/f39/14/14/01/64/spaces11.jpg

LongTimeInCX

2nd Nov 2014, 06:35

For those concerned that colleagues or friends may be involved, the names of the injured and deceased crew have spparantly been released and are reported here:
Focus on fuel in Virgin crash probe - 9news.com.au (http://www.9news.com.au/technology/2014/11/02/03/14/branson-heads-to-spacecraft-crash-site)

SOPS

2nd Nov 2014, 07:56

They were just talking on Sky News about this. They said that no insurance company in the world is willing to insure the 'current ticket holders'.

So, at the moment at least, if you do happen to be onboard, you might as well consider yourself part of the test flight crew.

Having said that, I wish them all the best. NASA went through a lt of failures in the early days as well.

9Aplus

2nd Nov 2014, 07:58

cZnQcMpzunM

Regarding #51 there are some comments from Carolynne Campbell here ->
http://www.parabolicarc.com/2014/10/31/spaceshiptwo-explodes-crashes-1-dead-1-injured/#disqus_thread

TyroPicard

2nd Nov 2014, 08:04

Shadoko
The light-off in those pics looks the same as other videos I have seen..... Brief flame to start with, then diamond shocks, then back to a big flame. Looks normal to me.

deptrai

2nd Nov 2014, 08:32

"We were doing a test that we believed was completely safe. ... We don't know why it exploded," said RutanI stumbled across this amazingly honest quote about the 2007 scaled accident on the ground that killed 3 and severely injured 3 more. These tests are well documented and the root cause of the recent crash will be found, but it's a steep learning curve.

I was just wondering if "space tourism" is worth the (apparently) inevitable loss of lives. Maybe it's the wrong question to ask, and anyway I'm not qualified to have an opinion; the professional test pilots and engineers involved can judge the risks better than anyone else. They are pushing the envelope of aerospace technology, and I really do admire them for that.

9Aplus

2nd Nov 2014, 09:10

It is much more than just and only "space tourism", it is whole new
industry. Scaled and VG are just bit more exposed, because of
red carpet in front of hangars... The life/industry is going on...
Here ->
ldoCqrQ1A00

janrein

2nd Nov 2014, 10:30

Trying to get something from the pictures.

From the NTSB B-Roll video 0:18 top of tank, 0:34 bottom of tank/interface (though hard to see) and 2:47 rocket motor(?) which appears intact at least the front end, one might think of a connection failure between the tank and motor, rather than an "explosion". Or the invisible motor bottom end burried in the sand may hide a failure that provoked the tank-motor separation. In both cases an immediate vehicle break-up would be a likely next effect.

The motor will have been subjected to ground tests multiple times, however it´s behaviour integrated in the vehicle in flight conditions cannot be investigated beforehand other than by modelling, and unexpected effects may be revealed in actual flight. Propulsion dynamics coupled with aero-elasticity? One can only guess at this stage.

Perhaps someone can fill-in at some point about state of tank-bottom and motor-bottom/throat/nozzle?

Just my 2 pence.

9Aplus

2nd Nov 2014, 11:22

Regarding technical matters, may be useful to read ->
Scaled Composites accident - Mojave Desert, California | Knights Arrow (http://www.knightsarrow.com/rockets/scaled-composites-accident/)

SKS777FLYER

2nd Nov 2014, 14:31

Huge fan of space flight development since a kid in the 60's. Thru some little reading and internet chasing, it appears ......... Who knows how accurate....

2014 change of engine
In May 2014, Virgin Galactic announced a change to the hybrid engine to be used in SpaceShipTwo, and took the development effort in-house, terminating the contract with Sierra Nevada and all development on the first-generation rocket engine.

Rather than use rubber-based HTPB in the solid portion of the hybrid rocket motor—which had experienced serious engine stability issues on firings longer than approximately 20 seconds—the Virgin Galactic-developed SS2 hybrid rocket engine would now use thermoplastic polyamide (i.e., nylon) as the solid fuel component of the propellant. The plastic fuel was projected to have better performance (by several unspecified measures) and was expected to allow SpaceShipTwo to make flights to a higher altitude.

As of May 2014, the new engine formulation had already completed full-duration burns of over 60 seconds in ground tests on an engine test stand. However, four additional ground tests of the polyamide-fueled engine are anticipated before the SpaceShipTwo flight test could resume with the new-fuel rocket motor.

PF04 malfunction
On 31 October 2014, the new polyamide engine fuel formulation was used in flight for the first time in the PF04 powered test flight of SpaceShipTwo. At 10:12am PDT, VSS Enterprise suffered an engine malfunction, and subsequently broke up in mid-flight. The inflight mishap resulted in the death of one test pilot and severe injuries to the other test pilot, and a total loss of the vehicle.
.............
Appears it may have been the first inflight ignition of the new propellant combination in the motor

metrognomicon

2nd Nov 2014, 17:02

Following up on the crash site photos. The large rounded black item has been referred to by some as a portion of the oxidizer tank. After discovering some photos of the composite section assembly I actually think what we're looking at is the aft bulkhead of the pressure hull.

http://www.ghostnasa.com/posts2/IMAGES2/073sstbody.jpg

silverstrata

2nd Nov 2014, 17:31

radix.

Unless the surges were so severe that it had an effect on other parts of the motor causing the flame to reach the liquid fuel it doesn't explain what happened.

Surges can become quite severe, as the quote earlier in this thread about the Saturn 5 surges demonstrates. Pushing the quoted 68g lateral surge acceleration though an airframe, is likely to cause damage.

It is not at all clear that this is the problem here, but surging was mentioned as a problem on previous flights, even when using the rubber fuel.

Jackneville

2nd Nov 2014, 19:05

What would happen if during a nose-down pitch input the tail booms became unlocked ?

TylerMonkey

3rd Nov 2014, 01:15

The assembly photo above shows that pilot ejection seats are not an option in this design. Nor would I expect them to be, passengers are not happy being left behind.
Some mention in press that pilots rode ejection seats down, worst reports are in the Daily Mail. They have a graphic which shows ejection pods from a B-58 Hustler no less .... quite bizarre reporting.
Irregardless, to survive that accident from that altitude in freefall means serious planning was put into the bailout bottle system, whatever they used.

rh200

3rd Nov 2014, 01:43

I was just wondering if "space tourism" is worth the (apparently) inevitable loss of lives.

I could imagine someone saying the same thing a 100 years ago about aircraft.

We need the remind ourselves that in some part we are where we are in aviation safety, off the backs of dead people, many of them innocent. We make mistakes, we learn. (well sometimes we learn)

DH_call

3rd Nov 2014, 03:09

A hundred years ago the US began it's airmail service. 31 out of the first 40 pilots who were hired to fly airmail died in a plane crash. Progress has a price and this world owes a lot to those brave adventurers who are willing pay that price.

peekay4

3rd Nov 2014, 03:39

Sunday PM NTSB briefing:

- N2O oxidizer tank found intact

- SpaceShipTwo appear to have had an "uncommanded feather"

- In order to feather, normal procedures involve two steps: 1) co-pilot moves "feather lock" lever to unlock; 2) a second feather lever must then be operated to actually initiate the feather

- Procedure calls for "feather lock" lever to remain in "locked" position until Mach 1.4 due to aerodynamic forces. However the "copilot" unlocked the lever at around Mach 1.0. (reason unknown).

- The second lever was never operated. An "uncommanded feather" took place approximately 2 seconds after the feather unlock.

- After the uncommanded feather, SpaceShipTwo subsequently disintegrated.

- No determination of cause at this point

SAMPUBLIUS

3rd Nov 2014, 04:49

SpaceShipTwo's unique tail section, which can "feather" at an angle to help the Virgin Galactic spacecraft make a safe descent, unfurled as it was ascending during the flight that ended in a fatal breakup Friday and without being ordered to do so, federal investigators said Sunday night.

The "feathering" mechanism isn't supposed to be unlocked until the spacecraft reaches 1.4 times the speed of sound, Christopher Hart, the NTSB's acting chairman, said at a news conference. But on the flight that crashed Friday, co-pilot Michael Alsbury moved the mechanism's lock-unlock lever into the unlocked position earlier, at just slightly above Mach 1, Hart said.

The "feathering" procedure is supposed to require two separate steps to engage: First, a pilot must unlock the feather parameter; then he or she must move a feather handle into position. SpaceShipTwo's feather mechanism began moving almost immediately — even though neither pilot took that second step,

Dogma

3rd Nov 2014, 06:27

The Old Fat One

3rd Nov 2014, 06:43

Regardless of cause, is it correct that they were both amateur "Test Pilots"?

I don't know...and some may deem it insulting in the circumstances. However, having viewed a photo of the "construction line", I'm afraid "amateur" was very much to the fore in my head.

RIP the pilot and thoughts with his family.

deptrai

3rd Nov 2014, 06:52

Were these Pilots qualified for the job of Test Pilot? Seems worrying to me that they were on the leading edge of such a flight test program without much more than being the right PR men. Regardless of cause, is it correct that they were both amateur "Test Pilots"?

yes, they were qualified. no, they were not amateurs. you win the award for the most ignorant post on pprune for ages, and that's quite an achievement.

Simplythebeast

3rd Nov 2014, 06:54

Seems that Pilot error is now being touted in the Media despite in the next breath telling us that it will take many months to find the actual cause.
Why drip feed information which may or may not have relevance?
Of course it may help to retain those investors who have put money into this project as well as provide some reassurance to those who have paid hundreds of thousands to fly on Virgin Galactic.
Call me a cynic but releasing any information at this stage is just wrong and smacks of project damage control.

peekay4

3rd Nov 2014, 06:58

The "project" did not release the information.

The NTSB did. They released factual information. Reason? It's their job to do so.

Load Toad

3rd Nov 2014, 07:05

'...touted in the Media...'

So, veracity value = 0

PrivtPilotRadarTech

3rd Nov 2014, 07:12

Thanks Peekay4. That explains why the ship was upside down and going backwards in the photos. It pitched end over end, ripping off the tail feathers and the delta wings. Those parts and a glowing piece, presumably the motor, are visible. The lighter pieces are trailing the fuselage, and the heavier motor is some distance ahead.

BTW, I looked up the term "fuel grain" as used in rocket motors. It refers to the entire cylinder-shaped mass of solid fuel.

Simplythebeast

3rd Nov 2014, 07:13

I accept NTSB released the information, I just dont think it is helpful to drip feed facts. The press are already claiming pilot error and "Initial indications are, that this was not equipment failire".
Initial indications mean nothing, facts mean nothing in isolation, the only thing that matters is the result of a full and proper investigation. That is the stage when NTSB should be briefing.

Massey1Bravo

3rd Nov 2014, 07:46

A few facts:

1) Video evidence showed the co-pilot manually unlocking the feathering system early (Mach 1) and against normal procedures. (Mach 1.4)

2) The pilots did not manually deploy the feathers, but the feathers deployed anyway after being unlocked.

3) The rocket motor and propellant tanks were recovered with no signs of burn-through or breaching.

Source:
Virgin Galactic rocket plane deployed braking system prematurely | Spaceflight Now (http://spaceflightnow.com/2014/11/03/virgin-galactic-rocket-plane-deployed-braking-system-prematurely/)

Dogma

3rd Nov 2014, 08:35

Thanks for the award. It's a very serious point, were these poor Pilots qualified? If they were, please direct me to their credentials and experience. I agree that the drip feeding of information from the NTSB is unhelpful. Who knows, the unlock of the empennage for auto feather might have become the normal variation to procedure?

I think their families deserve answers to understand if these Pilots were adequately trained and qualified.

steve611

3rd Nov 2014, 08:58

OK- some published stuff-
Michael Alsbury, 39, was an experienced flier who co-piloted the same craft when it first broke the sound barrier last year. He worked for Scaled Composites — which built and operates SpaceShipTwo — for more than a decade, according to his biography.

Alsbury held the titles of project engineer and test pilot, and was also sitting in the co-pilot's seat when the craft was first dropped in 2010 from its carrier aircraft several miles above the Earth for an unpowered glide test. According to test logs, Alsbury flew primarily as the craft's co-pilot, logging at least seven trips from 2010 to early 2014.

Alsbury's official bio says he held a B.S. in Aeronautical Engineering from California Polytechnic State University-San Luis Obispo and was a member of the Society of Experimental Test Pilots and Society of Flight Test Engineers. The undated bio said he had 15 years and more than 1,800 hours of flight experience, and held his single and multiengine instrument commercial, glider commercial and single and multiengine instrument flight instructor certificates.

Peter Siebold obtained his pilot's license at age 16.[4] (http://en.wikipedia.org/wiki/Peter_Siebold#cite_note-DailyMail-2014-10-31-4) Siebold has been a design engineer at Scaled Composites since 1996.
Siebold holds a degree in aerospace engineering (http://en.wikipedia.org/wiki/Aerospace_engineering) from California Polytechnic University (http://en.wikipedia.org/wiki/California_Polytechnic_State_University) at San Luis Obispo, from 2001.[4] (http://en.wikipedia.org/wiki/Peter_Siebold#cite_note-DailyMail-2014-10-31-4)
Siebold was responsible for the simulator, navigation system, and ground control system for the SpaceShipOne project at Scaled.
Although he was one of four qualified pilots for SpaceShipOne, Siebold did not pilot the craft during the flights later in 2004 to meet the requirements of the Ansari X Prize (http://en.wikipedia.org/wiki/Ansari_X_Prize).[5] (http://en.wikipedia.org/wiki/Peter_Siebold#cite_note-5) Although Siebold flew SpaceShipOne to an altitude of 32 km (just under 20 miles), he did not cross the 100 km Kármán line (http://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line) -- the international standard for reaching space.
For his contribution to the SpaceShipOne project, Siebold, along with Mike Melvill (http://en.wikipedia.org/wiki/Mike_Melvill) and Brian Binnie (http://en.wikipedia.org/wiki/Brian_Binnie), received the 2004 Iven C. Kincheloe Award (http://en.wikipedia.org/wiki/Iven_C._Kincheloe_Award) presented by the Society of Experimental Test Pilots (http://en.wikipedia.org/wiki/Society_of_Experimental_Test_Pilots).
Siebold became the Director of Flight Operations at Scaled.[2] (http://en.wikipedia.org/wiki/Peter_Siebold#cite_note-Scaled-2014-11-01-300pm-2)
He was the pilot who flew the White Knight Two (http://en.wikipedia.org/wiki/White_Knight_Two) on its maiden flight on the 21st of December 2008.[6] (http://en.wikipedia.org/wiki/Peter_Siebold#cite_note-6) He won the Iven C. Kincheloe Award a second time in 2009, this time individually, for his work on the first WhiteKnightTwo, VMS Eve (http://en.wikipedia.org/wiki/VMS_Eve), as chief test pilot.[4] (http://en.wikipedia.org/wiki/Peter_Siebold#cite_note-DailyMail-2014-10-31-4)

[/URL]
[URL="http://en.wikipedia.org/wiki/Peter_Siebold#cite_note-DailyMail-2014-10-31-4"]Mixed sources.
(http://en.wikipedia.org/wiki/Peter_Siebold#cite_note-DailyMail-2014-10-31-4)

khorton

3rd Nov 2014, 09:13

It seems quite strange to me that their procedures called for unlocking the tail feathers at M1.4. I would have thought that you wouldn't want to unlock the feathers until you were at a point in the flight profile that an uncommanded feather would not create a hazard. M1.4 is early in the motor burn, so even if the feathers had been unlocked per procedure, an uncommanded feather would have had the same catastrophic consequence.

It will be very interesting to learn why their procedures called for unlocking the feathers so early.

The Old Fat One

3rd Nov 2014, 09:17

The NSTB are not "drip-feeding" - they are reporting facts as they gather them in accordance with their procedures. Each accident will be different and require different actions. This accident is unusual in that there is so much recording equipment on board, thus hard evidence will come quicker and faster. There will still need to be a full analysis which will take time and the NSTB have clearly pointed this out.

There is an excellent article in the Financial Times regarding the commercial, marketing and PR motivations and issues - I won't post the link because it won't work if you don't have an FT account, but it sums up the situation very well indeed.

Euclideanplane

3rd Nov 2014, 09:33

The NTSB briefing seemed to posit two distinct accounts of the assumed feathering application.
The first, early in the resume, seemed to say that all communication and recording got lost two seconds after the feathering has been unlocked. Implying the possibility that feathering would have occurred two seconds later resulting in catastrophic failure.
The second account, during questioning, seemed to state that after unlocking, the feathering was (immediately?) activated, and two seconds later, all communication got lost, due to catastrophic failure.
Which of the accounts is the correct one? :confused:

Case One

3rd Nov 2014, 09:40

Originally posted by khorton:
It will be very interesting to learn why their procedures called for unlocking the feathers so early.

Probably to ensure reasonable confidence in feather capability before committing to the ballistic pull-up. SS1 and 2 cannot safely re-enter unfeathered.

funfly

3rd Nov 2014, 09:57

Enlighten me as to why the feathering of the tail would be more dangerous at mach 1 that at 1.4 ?

MATELO

3rd Nov 2014, 09:57

amateur "Test Pilots"?

100% of test pilots were amateur test pilots at one point in their career.

Nemrytter

3rd Nov 2014, 10:05

Enlighten me as to why the feathering of the tail would be more dangerous at mach 1 that at 1.4 ?Feathering the tail is dangerous at any high speed in dense atmosphere.
Unlocking the feather, however, may well be more dangerous at around mach 1 than 1.4. Reason being that the airflow may be less stable at this speed as you're in the trans-sonic regime.

KRviator

3rd Nov 2014, 10:08

Enlighten me as to why the feathering of the tail would be more dangerous at mach 1 that at 1.4 ? I'd guess it'd be to do with the way the shockwave is formed around the aircraft. Below M1.40 it may be impinging on parts of the airframe or control surfaces that aren't stressed for it.

LGW Vulture

3rd Nov 2014, 10:10

OFO - if you tell us the title of the FT piece and then type it into google - then you have it free of charge!

ASRAAM

3rd Nov 2014, 10:16

Is the problem with deploying the feathering system due to the low Mach number or because the rocket motor was still producing thrust.In other words should the system only be deployed when it's a glider?

Dont Hang Up

3rd Nov 2014, 10:20

The second account, during questioning, seemed to state that after unlocking, the feathering was (immediately?) activated, and two seconds later, all communication got lost, due to catastrophic failure.
Which of the accounts is the correct one?

I think the NTSB report was fairly categoric that the system was unlocked but the deployment handle was not used.

But here is what is confusing me. We are told the feathering is for re-entry deceleration and never used at this stage in flight. Yet we already know about tail stalls in earlier test flights...

Virgin's SpaceShipTwo Stalls During Test Flight (http://www.spacesafetymagazine.com/press-release/virgins-spaceshiptwo-stalls-on-test-flight/)

Upon release, the Spaceship experienced a downward pitch rate that caused a stall of the tails. The crew followed procedure, selecting the feather mode to revert to a benign condition. The crew then defeathered and had a nominal return to base. Great flying by the team and good demo of feather system.

So we have some suggestion here that the feathering could be legitimately deployed at this early stage.

Twiddle

3rd Nov 2014, 10:36

Not sure you're comparing Apples with apples about the stage of flight though?

On release they're not ballistic and when they are ballistic and deploy the feather, it's in thin air.

Presumably the real criteria is below a certain aerodynamic loading, so fast and high in thin air, or slower down lower.

janrein

3rd Nov 2014, 11:09

Any drastic configuration change like feathering is not to be expected until well after q_max and most likely after motor burn-out (except perhaps for considerations as mentioned in Case One´s post, not sure if such considerations apply in the SS2 flight profile).

Could anyone enlighten about dynamic pressure vs time/altitude for SS2?

The video footage of the third powered flight shows feathering action just after motor burn-out.

p.s. Just read DontHangUps´s comment, it does seem there is multiple use of the feathering system, interesting.

togsdragracing

3rd Nov 2014, 11:12

Isn't the point for discussion not so much the fact that the feather was enabled, which one would assume has some tolerance, but the fact that the feather subsequently deployed uncommanded?

Case One

3rd Nov 2014, 11:14

Procedure is to unlock the feather not to deploy or activate it. Initiating feathering at high q is a terminal no no.

deptrai

3rd Nov 2014, 11:16

It's a very serious point, were these poor Pilots qualified? If they were, please direct me to their credentials and experience.It's a serious question, yes, but what's the point of speculating. Do you have any indications that they were not qualified? How about you wait for the ntsb report, they'll figure it out. In the meantime, google is your friend. Here's a few hints. Just last year, the deceased pilot received the the "Ray Tenhoff award" for "the most outstanding technical paper presented at the annual Society of Experimental Test Pilots Symposium". He also received the Northrop Grumman’s President’s Award. He had 1600 hours of flight time in research aircraft, roughly 15 years of experience, and was not only an accomplished pilot, but also a highly qualified engineer.

Scaled is not a pay to fly program.

TIMTS

3rd Nov 2014, 11:17

How fast would SS2 be accelerating at this point? I mean, would the time between M1.0 and M1.4 be just a few seconds, 30 seconds, or longer?

janrein

3rd Nov 2014, 12:19

Timings and statements from the various videos:

Powered flight 1, rubber fuel, 17 seconds
Powered flight 3, rubber fuel, 20 seconds, Mach 1.4
Powered flight 4, plastic fuel, 9 seconds to break-up at around Mach 1

Ultimate operational goal Mach 3.4 (?) ...

The Old Fat One

3rd Nov 2014, 13:12

The FT title is...

Space tourism is a high risk publicity strategy

and you could see it easily if you head down any of the multiple links to the FT coverage, including the one posted above.

It is of interest because it examines the motivation for the enterprise. As aviators of one form or another here, we might be prone to excepting that this project is all about "what it says on the tin"...pushing forward human boundaries, advancing technology etc etc etc

The article reviews yer man Branson's commercial savvy where large scale PR is concerned as well as his appetite for self-promotion.

Nothing wrong with any of that IMO...I'm just as much a capitalist as he is. What he does with his billions is his own affair, just so long as not one penny of tax payers money flows into his coffers.

As for the people involved (whether employees, or hugely over-optimistic potential passengers) if they did not know the risks before they do now.

Mozella

3rd Nov 2014, 13:40

Enlighten me as to why the feathering of the tail would be more dangerous at mach 1 that at 1.4 ? I think the information is either incomplete or someone has gathered a fact and reported it without understanding what it means.

My understanding is that the wing/tail feather mode is normally used only during re-entry and perhaps M 1.4 is the Mach number at which is is normally deployed. I don't really know, but that factoid might be inadvertently or incorrectly blended into the current news. Anyway, I imagine going into feather mode would most likely be at very high altitude with low dynamic pressure. In other words, the true speed, measure in either mach number or true airspeed, would be rather high but because the air is so "thin" the airframe wouldn't have a lot of load on it; i.e. indicated airspeed (dynamic pressure) would be low............ very low.

Contrast that with going into feather at 50,000 feet and Mach 1.0; i.e. shortly after release. Working from memory (you should look it up to get the real number) the indicated airspeed would be about 250 knots and that, I would imagine, is too fast to feather the wing/tail system. I have no idea how high they are when they go into "normal feather mode" during re-entry, but if it's up around 150000 feet, the indicated airspeed would be way down, perhaps 50 knots or so at M 1.4. Again, look up the real figures. My brain isn't what it used to be and high mach number flying as well as my university aerodynamics training are both now only a distant semi-memory.

Of course, depending on who you talk to about flying around on the fringes of "Space", the measurement of the speed of sound and the concept of indicated airspeed begin to unravel a little bit, but you get the idea. That is to say, M 1.4 at high altitudes might be perfectly safe for a major configuration change while doing so at M 1.0 at low altitudes would be a disaster. It has a great deal to do with the dynamic pressure (indicated airspeed to most folks).

I think we're victims of bad reporting and/or lack of aerodynamic understanding and/or ignorance of just what the flight profile is normally like.

John Farley

3rd Nov 2014, 14:06

Well said Mozella

So far as the future of this programme is concerned I would comment that given the NTSB statement it seems likely that the breakup was caused by a simple mechanical/electrical system failure. That is a very much simpler thing to sort compared to a failure in the rocket system which the flight set out to test.

In this life it is so often what you least expect that gets you.

what next

3rd Nov 2014, 14:30

I think we're victims of bad reporting and/or lack of aerodynamic understanding and/or ignorance of just what the flight profile is normally like.

Exactly. And I don't believe for a second that the switch selection the may have lead to the feathering of the tailplane was done by mistake. A little way up someone posted the credentials of the crew. They were highly qualified and had over half a year of preparation for this flight. These pilots would not arm (or activate) a system at Mach 1 that must not be armed before Mach 1.4 unless they had a reason for it. Engine problems, control problems, whatever. But "by mistake"? Certainly not.

NigelOnDraft

3rd Nov 2014, 14:48

that must not be armed before Mach 1.4I do not believe that was what the NTSB said... but more along the lines of "would be armed at M1.4" i.e. that was what the SOP / Checklist / Test Card etc. said.

One needs to understand the rationale for the "locking" lever.. what "hazard" was it trying to mitigate? What eventually might have happened? Or was the greater hazard considered that of "feathering" whilst under WK2? Or might one need the feathering quickly in an emergency hence it was armed well in advance of when it would normally be needed.

As others have said, under 60Klb of rocket thrust, the acceleration from M1 to M1.4 I doubt would be many seconds, and guess feathering equally catastrophic at either on the ascent phase?

The NTSB updates / docket system will be interesting...

Dogma

3rd Nov 2014, 14:51

TIMTS

3rd Nov 2014, 15:01

Anyone know what speed this test was meant to reach?
Since it was the first live test of a new propellant type, maybe M1.4 was the final speed sought for this flight, as opposed to VNE for the feathering mechanism? Reporters have been known to get numbers mixed up...

deptrai

3rd Nov 2014, 15:34

In truth, the advances we enjoy in Commercial aviation today were hard earned by very specialist flight test Test Pilots.

you're probably referring to test pilots like Brian Binnie here: Scaled Composites: SpaceShipOne (http://www.scaled.com/projects/tierone/pilots/brian_binnie)

if he's a qualified test pilot, in your opinion, I suggest you ask him if he thinks his former colleagues at scaled are qualified or not. He worked alongside them for many years, he should know.

peekay4

3rd Nov 2014, 15:35

I think the information is either incomplete or someone has gathered a fact and reported it without understanding what it means.

My understanding is that the wing/tail feather mode is normally used only during re-entry and perhaps M 1.4 is the Mach number at which is is normally deployed.

Dynamic pressure is greatest at transonic flight (Max Q), then reduces as the aircraft goes supersonic and accelerates past Mach 1.2.

So for safety, the feathering mechanism must be locked when flying through this region. Otherwise, the aerodynamic forces can twist SS2 into feather mode.

Which is what apparently happened.

MG23

3rd Nov 2014, 16:54

As others have said, under 60Klb of rocket thrust, the acceleration from M1 to M1.4 I doubt would be many seconds, and guess feathering equally catastrophic at either on the ascent phase?

Presumably, you want to verify you can unlock it before you go flying off into space, so you can cut the engine and abort the flight if you can't?

Though that may not make sense in this case, if it was just a short engine test.

PrivtPilotRadarTech

3rd Nov 2014, 17:38

Doesn't seem like there would ever be a case when you'd want to feather while the engine was producing any appreciable amount of thrust.

thf

3rd Nov 2014, 17:41

And I don't believe for a second that the switch selection the may have lead to the feathering of the tailplane was done by mistake.

Me neither. Two questions:

Is unlocking the feather mechanism something the captain has to order verbally and the co-pilot to acknowledge before unlocking?
If the answer is yes: did the captain order it?

thcrozier

3rd Nov 2014, 17:42

Is the "lock" an electronic switch or a mechanical cover?

WingNut60

3rd Nov 2014, 18:21

Sorry crew, but why would you be able to select (unlock) an unsafe flight mode at any time during the flight envelope.

If the craft is so sophisticated, and feathering intrinsically dangerous (as identified by a thorough design risk assessment) I'd have thought that "
Feather Unlock" might be handled by something a bit more " sophisticated" than a handle.

Giving the crew the ability to UNLOCK in an emergency and outside of the normal envelope is, surely, different from giving them the ability to UNLOCK by mistake and / or inadvertently.

gums

3rd Nov 2014, 18:42

Beg your pardon, Wingnut

The U.S. N. jets with wing fold use a MECHANICAL system to enable the hydraulic wing fold feature. My A-7 had a cable on the cover of the electric switch. Raising the handle pulled a cable that removed a mechanical lock on the wing fold mechanism for each wing.

So we had a two step safety system. You couldn't get to the switch unless you raised the cover that mechanically removed something to enable the hydraulics to move the large metal rod connecting the outer wing segment to the inner. And then another system cranked the outer segment up or lowered it.

As with others, I question early removal of the feather lock. However, I understand an earlier mission had a bad pitch moment excursion and used the feather system to stay under control. If subsonic at a low mach, seems O.K. At transonic conditions, all bets are off.

WingNut60

3rd Nov 2014, 19:03

Thanks GUMS. Got that and agree
But what I was chasing was an interlock to prevent inadvertent selection at some unsafe phase of flight.

Mechanical or electrical doesn't matter provided the selection is possible either a) within design parameters or b) with an explicit procedure that knowingly overrides the protection features

Reports so far indicate that feather unlock was selected outside of design parameters.
Looks like it might have been an oops moment. And sophisticated systems just should not allow oops moments.

west lakes

3rd Nov 2014, 19:27

However, I understand an earlier mission had a bad pitch moment excursion and used the feather system to stay under control.

So did the knowledge of this prompt the removal of the lock in case of another instability?
i.e. a situation that arose during testing has shown up a possible failure in the design parameters.
Isn't that what test flying is partly about?

thcrozier

3rd Nov 2014, 19:46

"Upon release, the spaceship experienced a downward pitch rate that caused a stall of the tails. The crew followed procedure, selecting the feather mode to revert to a benign condition. The crew then de-feathered and had a nominal return to base," according to an updated flight log posted by Scaled Composites, builder of the WhiteKnightTwo/SpaceShipTwo launch system."

Space.com

http://www.space.com/13297-virgin-galactic-spaceshiptwo-test-flight-glitch.html

khorton

3rd Nov 2014, 19:55

Reports so far indicate that feather unlock was selected outside of design parameters.
Looks like it might have been an oops moment. And sophisticated systems just should not allow oops moments.The problem is that you must be 100% sure you can feather the tail for reentry, or you will die. If there are too many safety interlocks that can prevent the tail from feathering, you run the risk of those interlocks failing to unlock the tail when you need it later.

The best design is probably a simple, reliable mechanical lock, and redundant feather actuators, so you can feather the tail after any single failure in the unfeather system. A mechanical unlock system relies on the crew leaving it locked until it is safe to be unlocked (i.e. after the end of the rocket motor burn and the EAS is less than XXX).

thcrozier

3rd Nov 2014, 20:12

Thinking about going out there and hearing the latest local speculation at the bar ;)

tdracer

3rd Nov 2014, 20:22

Dynamic pressure is greatest at transonic flight (Max Q), then reduces as the aircraft goes supersonic and accelerates past Mach 1.2.
Actually dynamic pressure continues to increase as the speed increases, while dynamic pressure decreases with increasing altitude (less density). The speed at which Max Q occurs is a function of the Mach/altitude profile that is being flown.
That being said, the center of pressure relationships move around in the transonic range, which can result in unwanted movement of the control surfaces when traveling transonic.

ExSp33db1rd

3rd Nov 2014, 20:47

Giving the crew the ability to UNLOCK in an emergency and outside of the normal envelope is, surely, different from giving them the ability to UNLOCK by mistake and / or inadvertently.

Of course I know nothing about what happened in this case, but - "there's nowt so queer as folk" ( Yorkshire saying) and I know of an aircraft accident where the crew selected reverse thrust in the air on short finals, secure in the knowledge that the engines wouldn't go into reverse until the undercarriage 'squat' switch was activated when the wheels touched the ground. Guess what happened ? Many died.

There's nowt so queer as folk, and anything operated by humans is subject to human error, whereas with automatic /computer systems nothing can go wrong, go wrong, go wrong.

At this stage it doesn't really matter what went wrong, so long as those who need to know eventually find out.

SAMPUBLIUS

3rd Nov 2014, 22:20

BBC News - Virgin Galactic crash: Descent system 'deployed early' (http://www.bbc.com/news/world-us-canada-29876154)

...Christopher Hart, NTSB: "A couple of seconds after the move from lock to unlock, all the data stopped"

Did 'feathering device' cause crash? Watch
Unique 'feathering' system
US official explains early findings Watch

A safety device on the Virgin Galactic spacecraft that crashed on Friday, killing a test pilot, had been deployed early, US investigators have said.

Mad (Flt) Scientist

3rd Nov 2014, 22:55

To add to ExSp33db1rd's point, it's also practically impossible to design to eliminate human error, because humans must execute the design. The most you can do is move the potential for error around. And if we ever did somehiow have a design which wasn't done by humans, we'd just have substituted AI-error for human error in all likelihood.

Indeed, overdesigning systems "to be safe" is rarely very successful either. Sometimes you have to trust to the training and skill of someone suitably qualified. (And I'm not saying they were not; even the best pilot in the world can however make a mistake. See, "error, human")

thcrozier

3rd Nov 2014, 22:58

Hart's comments in SAMPUBLIUS' link above suggest that the locking mechanism might have the secondary function of strengthening the structure.

Hart's bio: https://www.ntsb.gov/about/bio_hart.html

gums

3rd Nov 2014, 23:42

Anyone have a description of the feather activation and control?

Do they "streamline" according to aero loads? Think some shock absorbers and no powered actuactors other than letting them go "free"?

Are they controlled by hydraulic or electric or pneumatic?

Sheesh, imagine the suckers allowed to be moved by aero loads even if the hydraulic/electric actuators normally used at low "q" and 200,000 feet are not a player.

So far, NTSB says the data stopped 2 seconds after..... But is this just the video? Can't imagine the flight data recorders stopped.

etudiant

4th Nov 2014, 00:45

Would an experimental type such as this even have a separate FDR?
Presumably the aircraft is wired pretty extensively just for the flight testing.

thcrozier

4th Nov 2014, 01:44

If I had to guess, I'd say it was loaded with them.

MrDK

4th Nov 2014, 02:02

@gums
So far, NTSB says the data stopped 2 seconds after..... But is this just the video? Can't imagine the flight data recorders stopped.

That sure makes the case for keeping video out of the cockpit ... experimental as well as commercial.

IMHO, I cannot for the life of me understand why video (for the purpose of incident investigation) is not on all commercial aircrafts.
In lack of better, ANY video system is better than none.

peekay4

4th Nov 2014, 02:30

IMHO, I cannot for the life of me understand why video (for the purpose of incident investigation) is not on all commercial aircrafts.
In lack of better, ANY video system is better than none.
Pilot privacy, fear of enforcement action (FAA & law enforcement), and possibility of damaging evidence in civil lawsuits in case of a mishaps.

Little remembered now, but before voice recorders were mandated in cockpits, there was a huge backlash from pilot unions. Concessions were made and early CVRs were limited to 30 minutes (now expanded to 2 hours), no recordings can be made public (only transcripts), only NTSB investigators may access the recordings, and pilots can erase recordings once back on the ground.

The NTSB, UK AAIB, French BEA, etc., have all called for cockpit video or image recorders to be made mandatory for commercial flights, but given very strong union opposition I doubt it will happen anytime soon.

WhatsaLizad?

4th Nov 2014, 02:32

"IMHO, I cannot for the life of me understand why video (for the purpose of incident investigation) is not on all commercial aircrafts.
In lack of better, ANY video system is better than none."

I vote for video recording in my cockpit only if every meeting of Airline Managers and Senior Managers/CEO's are recorded as well and any decisons made regarding expenses for training, policies and procedures and the lack thereof, and the statements during such meetings are transcribed and signed by the attendees afterwards. Same goes for the US FAA when meetings deal with the costs of regulatory changes and enforcement. The statements of airline CEO's should mesh in nicely with the legions of YouTube junkies just salivating at the thought of a pilot getting smeared on the aft cockpit GoPro lens just before the recording ceases due to impact.

Let me know when that board room recording happens.

Derfred

4th Nov 2014, 04:56

IMHO, I cannot for the life of me understand why video (for the purpose of incident investigation) is not on all commercial aircrafts.

How do you get all the jurisdictions around the world to respect the "(for the purpose of incident investigation)" bit. That's the problem.

deptrai

4th Nov 2014, 05:47

Anyone have a description of the feather activation and control? here: http://www.pprune.org/tech-log/550547-virgin-galactic-tech.html#post8726231

The 2nd column of the 3rd page (numbered 56) of http://www.boulder.swri.edu/suborbital/press-releases/Aviation-Week-Article-Suborbital-Spacecraft.pdf
states that:

Two main pneumatic 625-psi actuators with a 9.5-in bore and 31-in stroke, change the position of the feather ...

pchapman

4th Nov 2014, 06:19

Just for reference, to wrap one's head around how a vehicle like SS2 might work, here's info on Space Ship ONE. I don't know what systems and methods may have changed when scaling up to Space Ship Two -- with so much more mass to deal with. Info is from "Space Ship One - An Illustrated History", a ~2011 book by Dan Linehan.

Drop at 47,000'
Speed ??
C of G is aft with full fuel
3-4 G accel with rocket
Pull up to avoid overspeeding, Vne about 260 kts EAS.

[As an example, 250 kts EAS at 45,000' is almost exactly Mach 1.0]

Use electric trims after 8-9 seconds of burn due to high stick pressures (slow control by trims only)
Back to control stick once in very low density atmosphere
Maximum it achieved at engine shutdown was Mach 3.1 at 213,000 ft after 84 sec burn.
[That gives only 22 kts EAS - using a calculator on aerospaceweb. Many online calculators don't model the desired altitudes]

Apogee at about 3 min after engine start, 328,000 ft plus at best.
3.5 min weightless
Reaction Control System (pneumatic) at high altitude

Feathering done shortly before apogee. (Do it early in case of issues to deal with)

Feathering has redundant locks.
Feathering takes 13-14 seconds [A video for a prior SS2 flight shows much more rapid movement]
Feathering is by pneumatics, dual redundant interconnected systems.
Feather when under 10 knots EAS. [Low!]

Fastest speed reached (going down) was Mach 3.25, below 160 kts EAS.
5.5 G max on reentry (above 5 for 10 sec)
Max air temp ~ 1200F but with low density, heating rate is low.
(Heat resistant coating on nose and wings needed for boost phase only, not reentry but provides added margin).

Terminal velocity when feathered, if at low altitude, would be about 60 kts with its low wing loading of 12 ft/lb^2.

Un-feather once subsonic and below 1.2g on reentry.

As for SS2 planning to feather at M1.4, what kind of EAS might we be talking about?
If achieved at 100,000 ft, it would be 97 kts EAS.
If achieved at 200,000 ft, it would be 12 kts EAS.
The altitude certainly matters...

Edit:
Another bit of background as to prior achievements, and speeds and altitudes: The January 2014 flight achieved the following in an online article:

The SS2 rocket engine fired for 20 seconds, pushing the suborbital spacecraft to an altitude of 71,000 ft (18 km) and a top speed over Mach 1.4, both of which were new records for SS2. The Reaction Control System, feather re-entry system, and a thermal protection coating were successfully tested during the flight.

Not sure what that implies for feathering -- under 71k and Mach 1.4 would have a high EAS. If the numbers are right, one would expect feathering at a much lower Mach number.

robdean

4th Nov 2014, 06:19

Article which includes prescribed crew interaction regarding feather procedure plus Pete Siebold's primary injury apparently being to his shoulder

Two pilots who were close friends, now tied together by one fatal flight - The Washington Post (http://www.washingtonpost.com/news/business/wp/2014/11/03/two-pilots-who-were-close-friends-now-tied-together-by-one-fatal-flight/)

deptrai

4th Nov 2014, 06:40

Media, after first spreading unsubstantiated rumours about explosions, now seem to be speculating about pilot error. Methinks this is one of many possibilities, and it can not be ruled out, yet its a premature to jump to conclusions. The NTSB will be more responsible.

Unsurprisingly, it seems someone already pointed out the feathering system as a potential complication in this 4 year old article (it's somewhat "colorful"): "the feathered reentry system is another mechanical system that must absolutely work well for a safe return of the craft, but like all kind of mechanical system can have some malfunctions"

::: Why the suborbital space tourism is TOO DANGEROUS ::: (http://www.ghostnasa.com/posts2/073spacetourism.html)

Some previously brought up the question of certification in this thread. I really do wonder according to what ruleset this is going to be certified for commercial passenger transport, and what the risk analysis will look like, but there doesn't seem to be too much information about that? Nevertheless, its commendable that scaled and vg didnt aggressively push their initital schedule.

Satellite_Driver

4th Nov 2014, 08:37

Ah, that article is by Gaetano Marano, who pops up on space discussion boards all over the place regularly spouting his theories of how spaceflight ought to be done, apparently quite unconstrained by any knowledge of physics, engineering, propellant chemistry or any of the other relevant technical fields...

deptrai

4th Nov 2014, 08:44

The graphical design of his website and liberal use of various colors made me suspect he might not be the most credible source. Sadly, he may not have been completely wrong.

No Fly Zone

4th Nov 2014, 09:28

I'm all in favor of Sir Richard's private research projects, but... When there is significant risk to human life, perhaps he should slow down a bit and take a second look. Other than a major TOY for the very wealthy, I'm not sure that I see any real benefit in this expensive program, short of employinnng a few engineers. When a project includes significant risk to human life (rocket engines, altitudes beyond 50K ft etc.) perhaps a second and third look is necessary. What is the REAL benefit of this program - if there is one? Is it appropriate to risk human like for 1) a personal fantasy or 2) an ultimately commercial venture with no significant contribution to the flying sciences?

what next

4th Nov 2014, 11:25

What is the REAL benefit of this program - if there is one? Is it appropriate to risk human like for 1) a personal fantasy or 2) an ultimately commercial venture with no significant contribution to the flying sciences?

That's of course difficult to tell at this stage. When I studied aerospace engineering in the 1980ies, the Space Shuttle was just becoming operational. But it was generally agreed, that the next step in manned spaceflight would be something very similar to SpaceShip 2: A small orbiter, launched from a stratospheric carrier plane or reuseable booster rocket. A number of projects were launched by NASA, ESA and some national space administrations (eg. Hermes, HOTON, Sänger,... ) but proved to be too ambitious or expensive. Still I believe that manned spaceflight should follow this route instead of the 1950ies space capsules that seem to be the preferred option right now - not because they are better, but because the budgets don't allow for more.

Therefore personally I welcome Virgin's commitment in this project. Even if at the present stage it is not much more than a funfair ride for some bored celebrities (even Lady Gaga is said to have booked a ticket), the next evolution might be a true spacegoing orbiter. Which then could also be used for science and exploration for which our taxpayers money seems to be too precious right now.

The Old Fat One

4th Nov 2014, 11:53

What I find fascinating is that if this discussion were to be taking place on a marketing internet forum it would be all about virals, social optimization and conversion rates. As I said earlier, we see all this through the prism of aviation...business people such as RB see it entirely differently.

Whether or not space tourism is a reality (I'm giving that a massive thumbs down) is kinda moot to the marketing team promoting all things Virgin. They are interested in "top of the funnel" social media marketing, and further down how all that traffic converts.

What makes it even more fascinating is that RB - for the first time - might have got this one very, very wrong.

Time will tell.

jindabyne

4th Nov 2014, 12:24

No Fly

I entirely agree with your drift. I'm a strong advocate of space exploration and the pushing of human boundaries, and acknowledge the associated factors of risk to life and financial expense. But that view, for me, does not embrace Richard Branson's private experiment, and given all previous and continuing national and international space exploits, I'm unable to fathom the Virgin project's contribution. His desire to enable commercial tourism in space seems a vacuous notion, fuelled by a handful of celebrated wealthy individuals to whom the prospect of a brief excursion into a very low orbit holds an attraction: and it is only they who might have access to that flight of fancy. I find it difficult to imagine how the venture could contribute to the wider and longer term quest for practical commercial space travel on a universal basis. And the prospect of his wife, kids and a band of other laypersons being catapulted into such a hostile environment, without all the necessary fit-for-purpose skills and knowledge, must surely be a non-starter? To me, it is this that sets Sir Richard's activity way apart from most other laudable adventurous pursuits. Should it not be left to others with more appropriate acumen to pick up on previous initiatives as those alluded to by 'what next'?

Methersgate

4th Nov 2014, 12:51

I think that if the programme brings down the cost of getting to low earth orbit, it is absolutely worth while.

People kill themselves on motorcycles and in care every day, achieving nothing.

West Coast

4th Nov 2014, 12:51

Jinda
You excite the public about space again, that's going to go a long way towards securing a continuing, viable future for space exploration.

A fellow pilot who never married, never had kids and lives modestly by outward appearance was contemplating a ride on Virgin's spaceship as a retirement present to himself. This is not the territory of the rich alone. You excite guys like this and good things happen, be it for a corporation or for government.

Admittedly, I've not asked if his plan remains post crash.

Dont Hang Up

4th Nov 2014, 13:07

a brief excursion into a very low orbit

Not even that. The mothership launch technology has not yet overcome the technology hurdle to achieve anything better than a brief parabolic excursion beyond the atmosphere. That is why the experimental craft of sixty years ago did not progress further and the space programme reverted to vertical launch rockets. Early ideas that the Space Shuttle might work this way were also quickly abandoned.

For a real technology progression using this launch method a true hybrid engine would be needed - a combination jet and rocket that can transfer gradually from air-breathing to purely reactive as the air density decreases. And that is a development programme which is probably beyond even Mr Branson's deep pockets.

what next

4th Nov 2014, 13:17

The mothership launch technology has not yet overcome the technology hurdle to achieve anything better than a brief parabolic excursion beyond the atmosphere.

That's correct for manned spaceflight. But stratospheric launches of rocktes first from balloons and later from aircraft are a reality. The Pegasus rocket has been in operational service since the 1990ies (Pegasus (rocket) - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Pegasus_%28rocket%29)). A much larger and more expensive rocket would be required to place the same payload into orbit with a vertical launch.
A manned flight into orbit would require a motership that is Mach 3+ and 100,000ft capable but even that was briefly within reach 40 years ago with the XB-70. There are people out there with ten times as much money as RB. If one of them gets infected with the space bug, who knows where we can be in ten years?

bigjames

4th Nov 2014, 13:21

I think we have to admire anyone who tries, even if he/she fails to push the boundaries of flight. as we say in general/commercial aviation, there is something to learn from every accident/incident. let's do the same here.. I am no expert on fuel systems etc, but surely (Shirley) there must be something we can learn here and do better next time, whether it is Virgin or someone else. I am less concerned with someone's end motives than their willingness to take risks to move forward.

Dont Hang Up

4th Nov 2014, 13:30

what next I agree completely.

The factor between fuel-load and payload makes mothership launching much more efficient than a vertical launch even when using conventional rocket technology. For very low payloads this is actually a practical possibility.

However the one big advantage of a vertical launch is that you can design space vehicles of upwards of 3000 tons (Saturn V). Realistically though a mothership is not going to be able to carry a craft weighing more than a few tens of tons.

So either the mothership or the rocket engine needs a huge technology advance.

Diesel_10

4th Nov 2014, 13:39

Can someone explain how the pilot got out of this 'plane'...I understand the parachute bit but what happens before? Were the punters also to have parachutes??

JCviggen

4th Nov 2014, 13:47

Allegedly nothing but pure luck, being thrown free in the breakup.

It's not like test flights of new passenger aircraft don't have the crew wearing parachutes...

Rocket2

4th Nov 2014, 13:58

"Even if at the present stage it is not much more than a funfair ride for some bored celebrities (even Lady Gaga is said to have booked a ticket)"

Also not forgetting IIRC that NASA had (maybe allegedly) booked a few flights for research projects (& future astronaut training?)

Mozella

4th Nov 2014, 14:00

......... Other than a major TOY for the very wealthy, I'm not sure that I see any real benefit in this expensive program, short of employinnng a few engineers. When a project includes significant risk to human life (rocket engines, altitudes beyond 50K ft etc.) perhaps a second and third look is necessary. What is the REAL benefit of this program - if there is one? Is it appropriate to risk human like for 1) a personal fantasy or 2) an ultimately commercial venture with no significant contribution to the flying sciences?

This makes perfect sense IF you are an advocate of the Nanny State. However, I believe people should be able to build toys, even dangerous ones, and be free to enjoy them even if there is no benefit at all. Race car drivers, sky divers, rattle snake collectors, mountain climbers, or tight rope walkers should not be prohibited from exercising their right to have fun. Neither should space travelers.

Of course, you have to assume that the participant is fully aware of the risks. I would bet that Leonardo di Caprio, for example, would be VERY unlikely to have ever used his space ride ticket once they got down to the nitty-gritty of explaining how dangerous space travel really is.

Unfortunately, I don't think Christa McAuliffe fully understood what risk she was facing when she met her end and probably expected something like a bus ride. Although the statistics have improved lately, for a long while nearly 10% of the Americans who wanted to fly in space died while practicing their chosen profession, or in Ms. McAuliffe's case, her school science project.

Niner Lima Charlie

4th Nov 2014, 14:20

Release from WhiteKnightTwo at 10:07:19 (local time).
10:07:21 Engine Start
10:07:29 Speed 0.94 Mach
10:07:31 Speed 1.02 Mach
At that point the co-pilot moved the feather control from locked to unlocked.
A second step, to engage the feather, was not taken.
10:07:34 The feather began to deploy, telemetry data stops.

The flight plan indicated the feather should be unlocked at Mach 1.4.

pchapman

4th Nov 2014, 15:00

Deptrai quoted: "Two main pneumatic 625-psi actuators with a 9.5-in bore and 31-in stroke, change the position of the feather ..."

625 psi (max?) over an area corresponding to 9.5" diameter gives a force of over 40,000 lb possible on each actuator. Quite a bit, which would seem to make it nearly irreversible, almost as good as a hydraulically operated screw jack on an airliner.

But is there pressure already applied to both sides of the piston before the Feather handle is actuated? From the results, maybe not.

Perhaps the feathering cylinders only receive pressure when the feathering handle is turned to open valves -- Rather than having both sides of the cylinder pressurized. That would be perhaps slightly more complex, more like some always-active hydraulic system. Rather than just "start adding a shot of air when needed to the Feather side". (Even then they would need to be able to let the pressure bleed down and pressurize the other side of the piston to defeather later.)

As for forces on the tail, the stabilizers themselves might well have a down force on them, especially as a typical airplane tends to have a mach tuck due to rearwards movement of the center of pressure in the transonic range (and loss of effectiveness of a conventional elevator, not a factor here).

However, the feathering mechanism also includes the aft end of the wings which will have some lift on them. While I'm a little surprised at it, the results suggest the net forces were to flip the tail up as soon as the locks were removed.

In conclusion, it sound like the feathering system may be set up assuming that there would be very little aerodynamic force once the locks were withdrawn, without the system being pressurized before selecting Unlock, and thus unable to oppose any significant aerodynamic forces.

That would suggest a design which, while entirely effective, lacked some safety redundancy that could have been added probably without too much trouble. Turn that one handle too soon and boom, you pitch up with massive up elevator and loss of lift from the aft end of the tail, you swap ends and disintegrate.

But one would like to know more about the feathering system to better understand whether this speculation is correct or not.
(Edit: And I don't know what kind of leverage the tail might have on the actuator around a pivot point, which also affects to what degree the tail can try to back drive the piston even if pressurized)

peekay4

4th Nov 2014, 15:24

The flight plan indicated the feather should be unlocked at Mach 1.04
That should be Mach 1.40, not Mach 1.04.

There will undoubtedly be some human-performance analysis to see if one of the pilots saw 1.04 and got it confused with 1.40. However the latest NTSB briefing seems to indicate that the unlock happened prior to reaching Mach 1.02.

oldchina

4th Nov 2014, 16:19

This has been raised a couple of times here but to my knowledge no-one has explained what certification 'ticket' they are working towards and who will decide when the beast is fit to carry commercial passengers.

It can't be Sir R who decides just because one day he feels ready to risk himself and his family.

Concorde required lots of new rules to be complied with, yet FAA or FARs hardly get a mention in this story.

Interested Passenger

4th Nov 2014, 18:10

So the investigators are saying the test pilots caused the crash by doing something they shouldn't, and understandably that is being received with scepticism on here. But is it possible the feathering deployment was a test to make sure the interlocks/software etc would prevent it?

Take a completely different situation, try to raise the landing gear while you are on the ground and interlocks/pressure switches will prevent it - but at some point someone has tried to do it, to make sure it doesn't happen.

The only way to test these potentially dangerous side effects is to test them and make sure the systems prevent you doing it - and if they don't then you are in trouble.

flydive1

4th Nov 2014, 18:19

Take a completely different situation, try to raise the landing gear while you are on the ground and interlocks/pressure switches will prevent it

I would not be too sure about it;)

but at some point someone has tried to do it, to make sure it doesn't happen.

Yes, and it wasn't pretty

peekay4

4th Nov 2014, 18:32

This has been raised a couple of times here but to my knowledge no-one has explained what certification 'ticket' they are working towards and who will decide when the beast is fit to carry commercial passengers.

SpaceShipTwo will not be a "certified" aircraft. That's because none of the current commercial certification regimes apply to sub-orbital flight (they are designed for "normal" passenger carrying flights), and there is not enough data available to create a new certification standard.

Note: in a certification regime, not only the aircraft must be certified, but also the pilots, airline, mechanics, etc. E.g., the FAA would have to make a new Category / Class and perhaps new Type Ratings for sub-orbital flight, issue new pilot exam "PTS" standards, update A&P IA requirements to work on rocket motors, issue new FAR Part 1XX for sub-orbital ops, etc.

So instead of going through a (non-existent) certification regime, SpaceShipTwo (and other manned sub-orbital flights) will go through a licensing regime instead.

Under a licensing regime, instead of certifying the aircraft, pilot, mechanic, etc., the FAA will license the launch operation.

Prior to a launch, the FAA will want to see documentation, test flight data, etc., that provides reasonable assurance that the launch will be successful. The criteria is to assure public safety and occupant safety.

Currently the FAA has issued single launch licenses (permits) -- a new launch license was required for each of SpaceShipOne's sub-orbital flights, for example.

Once launches become more routine, the FAA can issue a multiple-launch license for the launch operation.

Now that we've had an in-flight fatality, the FAA will expect even more documentation/data before issuing a new launch license.

robdean

4th Nov 2014, 19:15

BTW I don't know to what extent the philosophy behind SS2 parallels that of SS1, but that craft was approached with maximum simplicity: direct control linkage (a hard landing was caused by a vacuum lock), minimum automation. Ironically, given the patriotism of the likes of SS1 pilot Brian Binnie, more a Soviet-program kind of minimalist pragmatism. When posts here have queried protections in the avionics over the past few days, I have repeatedly been reminded just how seat-of-the-pants SS1 very much seemed to be.

hamster3null

4th Nov 2014, 20:00

Not even that. The mothership launch technology has not yet overcome the technology hurdle to achieve anything better than a brief parabolic excursion beyond the atmosphere. That is why the experimental craft of sixty years ago did not progress further and the space programme reverted to vertical launch rockets. Early ideas that the Space Shuttle might work this way were also quickly abandoned.

For a real technology progression using this launch method a true hybrid engine would be needed - a combination jet and rocket that can transfer gradually from air-breathing to purely reactive as the air density decreases. And that is a development programme which is probably beyond even Mr Branson's deep pockets.

Even a true hybrid engine would not help much, because of elementary energy balance constraints. You need to impart the craft with a certain amount of kinetic energy (Mach 25 or so). There is a hard physical limit on specific impulse of rocket fuel, and the weight of fuel necessary per unit of useful load goes up exponentially as the ratio of target speed to specific impulse. A typical surface-launched rocket with enough payload to get a few humans into orbit has to weigh at least 300 tons.

Launching from a mothership in a two-step fashion, the way Virgin does, assuming that you can add a good ramjet on top of their existing designs, lets you save some money because the mothership is fully reusable, and lets you save some weight because you don't have to carry all oxidizer that you burn up to a certain speed. But even if you can get the "spaceship" out of the atmosphere and up to, say, Mach 3 before you switch to rocket engines, you still need to go from Mach 3 to Mach 25, which means that you still need to carry a heck of a lot of fuel and only a small amount of payload.

SpaceShipTwo reportedly weighs ~10 tons (constrained by the lift capacity of the mothership), and payload to fuel ratio is way too high. You need to scale the mothership by a factor of 10, somewhere to the size of a 777, and you need to turn SpaceShipTwo into something that looks more like a classic rocket (with large separating first stage), and then it would approach being useful for actual space flight. In the present form it's firmly stuck inside Earth's gravitational well.

donotdespisethesnake

4th Nov 2014, 22:02

I'm afraid to say "toy for the rich" is not far off the mark. That is not to belittle the engineering efforts of Burt Rutan, he is smart guy, but the programme will not amount to more than joyrides and very limited microgravity experiments.

If it helps get people interested in commercial exploitation, that's great if it leads to investment by major players, and orbital ships are what's needed for real commercial exploitation of space. Those players are investing, but in satellite launchers and ferry services for NASA, i.e. ones with a real market.

As far as "space-planes" go (i.e. SSTO) with a real chance of innovation and breakthrough in launch costs then Branson would be much better investing in Skylon Reaction Engines Ltd - Space Access: SKYLON (http://www.reactionengines.co.uk/space_skylon.html). Skylon does not carry celebrities, unfortunately.

tartare

4th Nov 2014, 23:05

So if I understand the sequence of events correctly - feather unlock is released early, feathers start to move.
The next bit is purely speculative on my part, but just trying to understand what might have happened.
I assume that would then result in an uncommanded violent pitch up, aircraft presents belly to airflow, pitching through 90 degrees, feathers snap off, remaining airframe breaks up?

ThreeThreeMike

5th Nov 2014, 00:02

I'm afraid to say "toy for the rich" is not far off the mark. That is not to belittle the engineering efforts of Burt Rutan, he is smart guy, but the programme will not amount to more than joyrides and very limited microgravity experiments.

Rutan retired from Scaled Composites in 2011. It is now a division of Northrop Grumman.

They have spent more than $400M on the project. It's not a half hearted effort.

PrivtPilotRadarTech

5th Nov 2014, 00:03

I enlarged the photos. One feather is clearly visible in the debris trail, along with one of the delta wings. The other delta wing appeared to be still attached, and the fuselage largely intact. Something large was beside the fuselage- N2O tank? The rocket motor (judging by the glow) was some distance ahead. A white cloud surrounded the fuselage and trailed it. The fuselage was upside down and going backwards. I believe the camera went upside down as it tracked the ship going over, so the ship is simply falling, though in the photo it looks like it is going upwards. The trailing cloud does not look high velocity. Based on that photo, I believe pieces came off, but it didn't "explode" nor did it disintegrate. I will be very interested to hear what the pilot has to say, and how he got out. Regarding space tourism- Into Thinner Air? Rich people die like flies on Everest, why not in a sub-orbital flight if they wish? Michael Alsbury died like Scott Fischer on Everest- a leader doing something dangerous that he loved. Happens all the time, keep it in perspective. Four out of five people just died off the coast here when a wave flipped their boat. They were sport fishing for crabs, not wearing life jackets. People are not going to stop crabbing because of it, hope Branson and Scaled Composites press on too.

DozyWannabe

5th Nov 2014, 02:30

So the investigators are saying the test pilots caused the crash by doing something they shouldn't...
Are they? I'm certainly not reading anything suggesting that right now - for one thing it'd be incredibly premature.

All I've read is that the investigators will be looking into the actions of the crew, which is standard for any investigation.

LynxDriver

5th Nov 2014, 02:32

I don't get the sensitivity of the question over the Pilots "Piloting Qualification". It's pretty straight forward did they fly complex fast jets solo, were they qualified Test Pilots? In truth, the advances we enjoy in Commercial aviation today were hard earned by very specialist flight test Test Pilots.

It relevant to ask - did they go to Empire or USAF TPS for example. If not, why not?

Have you ever heard of Google? Maybe you should try and find some facts for yourself. To be honest, your questions in my opinion are show a level of ignorance and are offensive.

RichardC10

5th Nov 2014, 05:19

If the hydraulics on the feathers can be overpowered by the aerodynamic forces (with the locks off) it’s odd that a system that would fail at Mach 1.02 is judged fully competent, with margin, at Mach 1.4. It seems unlikely that the aerodynamic forces would change (reduce) by a factor of many over a relatively small speed range. It also means that at lower speeds the unlock lever effectively had a label ‘move this lever to destroy the vehicle’.

If the locks were required to be in until just above the feather speed that would indicate a feather hydraulic system with low torque, but that is not the case.

At the moment the stated facts are consistent with a failed hydraulic system that could not provide the required torque when the locks were removed. If so, the fact the system was unlocked early is irrelevant.

deptrai

5th Nov 2014, 05:21

funfly

5th Nov 2014, 09:25

it’s odd that a system that would fail at Mach 1.02 is judged fully competent, with margin, at Mach 1.4.

I think you will find that the dynamic surface pressure on the aircraft control surfaces under maximum thrust at Mach 1.02 would have been considerably higher than at a higher altitude at Mach 1.4 and where the scenario may also have been in a re-entry state, i.e. reduced thrust.

Hadley Rille

5th Nov 2014, 09:34

I can see that the tail boom is of a horn balance design. Is it possible that this could contribute to the feather 'self-deploying' once unlocked given the right aerodynamic pressure?
Also I believe the actuator is pneumatic. Would this provide less resistance to 'self-deployment' than hydraulics?
Thinking about it some more, the pressure on the horn wouldn't need to deploy the feather but could place enough pressure either side of the pivot to break the boom about that point.

RichardC10

5th Nov 2014, 10:09

@funfly
I think you will find that the dynamic surface pressure on the aircraft control surfaces under maximum thrust at Mach 1.02 would have been considerably higher than at a higher altitude at Mach 1.4 and where the scenario may also have been in a re-entry state, i.e. reduced thrust.

The video of the 2013 second powered flight does not suggest a significant climb during the powered phase of that flight. The unlock call on that flight occurs during powered flight and before the pull-up that reduces the speed to near zero.

Hotelpresident

5th Nov 2014, 10:23

I am afraid this will delay the program, it is a pity because I always believed that this project could create new scenarios and boost the aeronautical sector if finally a civilian airlines was able to conquer the space.

I read an article in an aviation news pubblication (http://www.thelatestpilotjobs.com/aviation_news/virgin-galactic-crash/) saying the technology of SpaceshipTwo is in reality 30 years old and it a military technology developed by B.A.S. to deploy special troops through high area of atmosphere quickly around the World but it was finally dismissed because it was unstable and after many flights it could simply explode. It looks this news was classified but than declassified 10 years ago.

MD83FO

5th Nov 2014, 11:01

what is the local speed of sound at 300 thousand feet?

Dogma

5th Nov 2014, 11:04

Deptrai - I think you are missing the point, apart from being high handed and more than a little conceited. The question of the suitability of the Pilots is not at issue. Its essentially down to their training and relevant experience, I happen to know a couple of Test Pilots whom are also engineers and they had to eat a lot of :mad: in working their way through the various flying programs and into Empire Test Pilot school. The skills and Piloting knowledge gained was significant.

As you say the NTSB should be looking into the adequacy of their Training, SOPs and standards discipline etc. but its good to discuss the issues on here.

deptrai

5th Nov 2014, 13:06

Deptrai - I think you are missing the point, apart from being high handed and more than a little conceited.

Internet forums tend to make disagreements escalate quickly. I'll offer my sincere apologies, and a beer.

DouglasFlyer

5th Nov 2014, 13:10

Speed of sound:

speed of sound at 300000 feet - Wolfram|Alpha (http://www.wolframalpha.com/input/?i=speed+of+sound+at+300000+feet)

sooty655

5th Nov 2014, 14:06

Regarding the "qualified test pilot non-debate". There's always been more or less subtle conflicts between pilots with different backgrounds. Hearsay has it that Chuck Yeager questioned Neil Armstrong's abilities because he was not only a pilot, but also a qualified engineer. (and to the best of my knowledge, none of of them attended any "test pilot school"). If the scaled pilots were not qualified, I have no doubt at all that the NTSB will uncover that. If there ever was a red herring, the question about the pilots qualifications is a prime example.
I think you'll find they did. As an example, according to Michael Collins' autobiography, he attended "Class 60-C, USAF Experimental Flight Test Pilot School, commencing 29 August 60, course duration 32 weeks". AFAIK all the early test pilots and astronauts took a similar route.

SKS777FLYER

5th Nov 2014, 14:13

NTSB states early activation of unlock mechanism.

First flight with new fuel, and first inflight ignition of new fuel.
Significant different vehicle noise/ride/acceleration/vibration feel to the experienced test pilot of the vehicle, perhaps lending itself to confusion/distraction in accomplishing mission profile checklist procedures?

A post stating this was first inflight use of new fuel was quickly removed a few days ago, so it may still be forbidden info here.:=

wiggy

5th Nov 2014, 14:24

FWIW as far as the Astronauts were concerned NASA dropped the mandatory test pilot requirement, and made it a "desirable", as early as Group 3 ("The Fourteen") in '63.

NASA Astronaut Group 3 - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/NASA_Astronaut_Group_3)

It turned out to be a fairly illustrious group.....

Swedish Steve

5th Nov 2014, 14:25

But even if you can get the "spaceship" out of the atmosphere and up to, say, Mach 3 before you switch to rocket engines, you still need to go from Mach 3 to Mach 25,

Can someone explain to a non space man how you measure Mach number when you are out of the atmosphere? Surely in space there is no sound so there cannot be any Mach number? Does this mean Mach 25 in a near vacuum, or Mach 25 at sea level?

I thought that I understood that Mach 1.4 at top of apogee was nearly a standstill because of being in space, and now we have Mach 25 in space?

what next

5th Nov 2014, 14:37

In order to orbit the earth, you need no Mach number - which would be meaningless in vacuum or near vacuum - but a certain speed: The first cosmic speed, 27,800km/hr or 7.7km/s. The often quoted figure of Mach 25 simply comes from dividing that speed by the speed of sound at sea level (0.3km/s) which does not make much physical sense 200km above the surface.

funfly

5th Nov 2014, 15:11

Interesting point about speed outside of the atmosphere. Measuring how fast you are going against…what.
Bit like how fast are you walking when you are on a moving train.

peekay4

5th Nov 2014, 15:16

7.7 km/s is about the velocity required to maintain low-earth orbit.

Due to atmospheric and gravity drag, the velocity required to reach low orbit -- the delta V-- is about 9.4 km/s (33,840 km/h).

As a comparison, SpaceShipTwo will have a delta V of <= 2.0 km/s (7,200 km/h) to fly a suborbital profile.

what next

5th Nov 2014, 15:32

Measuring how fast you are going against…what.

Against nothing. In order to maintain orbit, you have to travel at 7.7km/s. Speed = distance / time. The distance to cover is the circumference of the earth (radius + 200km to stay outside the atmosphere times 2 times pi) and when you come back to the point from which you started - measured against the sun or the stars (the difference will be only a few seconds) in roundabout 90 minutes you have achieved a stable orbit.

Nemrytter

5th Nov 2014, 16:49

Measuring how fast you are going against…what.Relative to the (gravitational) center of the Earth.

TyroPicard

5th Nov 2014, 18:27

Quote:
Relative to the (gravitational) center of the Earth.

Hmmm... In a circular orbit you are neither moving towards nor away from the centre of the Earth ... Speed zero?

wiggy

5th Nov 2014, 18:36

SS

I thought that I understood that Mach 1.4 at top of apogee was nearly a standstill because of being in space, and now we have Mach 25 in space?

Don't overthink it, folks are just using "Mach number" as a handy and convenient yardstick to compare what SS2 might be capable of in the way of velocity vs. what is required for genuine orbital flight. As has been mentioned for a stable circular low earth orbit at any sort of sensible altitude (say a minimum of 160 km or a bit more) you need a "horizontal " velocity of around 8000 metres/ second. Given Mach 1 in air is usually quoted at around 300-330 metres per second orbital velocity equates to a Mach number of around Mach 25...whether it's useful or confusing to use Mach number is another matter.

Hmmm... In a circular orbit you are neither moving towards nor away from the centre of the Earth ... Speed zero?

Sometimes it pays to go off at a tangent.............

pattern_is_full

5th Nov 2014, 19:34

It should be noted that the speed of sound is distinctly non-zero (275 m/s), all the way up past 100 km (target altitude of original SS1).

http://upload.wikimedia.org/wikipedia/commons/thumb/9/9d/Comparison_US_standard_atmosphere_1962.svg/2000px-Comparison_US_standard_atmosphere_1962.svg.png

There is still (very thin) atmosphere up there (and thus molecules to transmit sound energy).

The Kármán Line - BTW - is the altitude where the speed needed for aerodynamic lift/flight become faster than orbital velocity (so you might just as well orbit as "fly").

Higs99

5th Nov 2014, 20:10

And hence the Kármán Line is the accepted definition of the start of (Outer) Space ....

hamster3null

5th Nov 2014, 20:45

The Kármán Line - BTW - is the altitude where the speed needed for aerodynamic lift/flight become faster than orbital velocity (so you might just as well orbit as "fly").

At 100 km you already can't fly, but you still can't orbit (because there's so much air drag that your orbit will decay in a matter of hours). At 300 km you can last about a month in orbit. ISS is at 400 km and it still needs periodic boosts (though its orbital decay is tolerably low).

pumpkin53

5th Nov 2014, 21:34

ah, yes, the dynamics course in early college. What is needed is a certain minimum "angular velocity". Velocity is a vector number, meaning a magnitude and a direction. In orbit, the direction is constantly changing, since gravity pull is acting towards earth center of mass, and inertia, wanting to keep the craft going straight.
So, yes, zero speed relative the distance from the center of the earth, but still a very significant angular velocity!

ChristiaanJ

5th Nov 2014, 21:59

hotelpresident,
Unfortunately your "source" is a highly doubtful website, and there is no such thing as a British Aerospace Agency.
Don't believe all the "urban fiction" on the net......

tdracer

5th Nov 2014, 22:20

Interesting read about Seibold:

Injured test pilot's passion for flying shines through | HeraldNet.com - Aerospace blog (http://www.heraldnet.com/article/20141104/BLOG01/141109562/Injured-test-pilot%92s-passion-for-flying-shines-through)

janrein

5th Nov 2014, 22:23

@patternfull
That link to atmosphere up to Karman line comes in handy.

Inputs from various sources combined with atmosphere structure as per link:
M1 at 45 kft ==> 295 m/s at 0.25 kg/m3 density
M1.4 at 70 kft ==> 413 m/s at 0.10 kg/m3 density
(all approximate)

Would yield for dynamic pressure:
q = 11 kPa at 45kft and M1
q = 8.5 kPa at 70kft and M 1.4

@RichardC10:
Confirms your comment a few pages back:
q does not decrease that much indeed over that part of the flight profile.

That would make it less likely to expect catastrophic failure upon unlocking at M1, while unlocking at M 1.4 would be normally acceptable,
IF(!) q were the only factor in play.

However another possible factor may be:
M1 is in the transsonic regime, while M 1.4 is well beyond that.

Meaning: with lift vectors in the transsonic regime jumping backwards on the tailboom elevators, and likely different in place and time between top and bottom surfaces, aerodynamic effects can be more problematic in the transsonic regime.

Which seems more plausable a factor than a design flaw or malfunction of the pneumatic actuation system as a cause of the uncommanded feather.

jr

Rodney Rotorslap

5th Nov 2014, 22:27

Anyone else struggling with the irony that this vehicle has a feathering system to present maximum drag while a feathering system in a propeller is designed to present minimum drag?

janrein

5th Nov 2014, 22:38

@Rodney
Anyone else ...
Indeed! And what appears initially as irony may in some cases even cause confusion. Human factors, language, ... all that.

(not in this case I believe)

jr

SKS777FLYER

5th Nov 2014, 23:42

Look at flame pattern of amazing inflight video on SS2 on earlier flight with previous version of fuel. Obviously, the previous fuel proved unsat after ground and flight tests. As the accident flight was the first for the new fuel, there are no videos or experience with its flight characteristics. It may have a vibration characteristic, initial acceleration, sound transmitted thru the vehicle and or slightly different thrust vector than previous rocket rides in the vehicle that the veteran test pilots experienced/ expected.

Peter H

5th Nov 2014, 23:53

janrein: Excellent post.
Can I suggest that an uneven rocket burn might also increase aerodynamic forces.
Regards, Peter

Flash2001

6th Nov 2014, 00:27

Janrein

Please don't mix units, you're bringing yourself down to the level of the EPA!

After an excellent landing etc...

peekay4

6th Nov 2014, 01:03

Would yield for dynamic pressure:
q = 11 kPa at 45kft and M1
q = 8.5 kPa at 70kft and M 1.4
The math is a bit off.

Using solely the above parameters:

q = 10.2 kPa at 45kft and M1
q = 6.2 kPa at 70kft and M 1.4

So roughly 40% less.

SKS777FLYER

6th Nov 2014, 01:43

Double post

Radix

6th Nov 2014, 02:52

I put my money on either:
- the pneumatic (!) system failed to pre-pressurize causing the tail booms to move without much effort
- or the aerodynamic forces at the transsonic region were so different from what they thought them to be that the design couldn't cope unless being fully locked. E.g. good old sound barrier strikes again.

Sounds the most plausible from these 10 pages of expert opinion on PPruNe.

The other pilot will be able to tell why they moved the unlock lever at a point different to the brief and whether this was ever discussed with the engineering team.

edited

RichardC10

6th Nov 2014, 07:21

@janrein
Agreed that transonic loads could be highly non-linear. However, the locks are out during the period the speed is reducing through the transonic regime in the test flights, though admittedly at a somewhat higher altitude. If there was marginality in holding the feathers in the correct position at any (high) speed why plan to withdraw the locks above some (low) speed limit?

TURIN

6th Nov 2014, 08:19

I put my money on either:
- the hydraulic system failed to pre-pressurize causing the tail booms to move without much effort

Then you've lost your bet.

My understanding is the booms are pneumatically operated.

mostlylurking

6th Nov 2014, 08:55

I am interested in why the booms feathered prematurely, but I expect there was a simple cause and the solution will also be relatively simple.

More interesting is why the craft broke up. I think that is also relatively simple - the booms deployed while the motor was running. This would cause the centre of resistance to be way above the thrust line. i.e. the forces would cause the craft to tumble violently. At mach 1, no craft could stay together.

Looks like an interlock is needed, or that there was an interlock but failed.

MichaelJP59

6th Nov 2014, 10:00

Anyone know, was this the only prototype? is there another one under construction by Scaled?

I know the order was for more than one, but it must take a lot of time, I get the impression that the build team is not very big?

skadi

6th Nov 2014, 10:07

The second one, VSS Voyager, is under construction:

VSS Voyager - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/VSS_Voyager)

peekay4

6th Nov 2014, 10:12

The second one is 65% complete, should be ready for ground and flight testing in 2015.

FlyingCroc

6th Nov 2014, 10:18

Heathrow Harry

6th Nov 2014, 10:57

actually it didn't totally break up - I expect it came down spinning like a
sycamore leaf with a fair bit of "wing" attached - at least on one side

And I guess a crew compartment built to go into low space at 2500 mph is fairly robust

robdean

6th Nov 2014, 11:09

Supersonic ejection has been survived, but it is somewhat high-risk and non-enjoyable. Notable for facial blast injuries (colossal hemorrhaging) and for knees and elbows bending in the opposite direction to that usually preferred. The Russians came up with a few interesting innovations to try to improve survivability.

In this case there may have been chance benefits of 'ejection-by-disintegration' - Siebold may have been subsonic before being 'ejected' into the windblast and possibly this occurred with his back to the direction of travel.

I very much doubt Siebold 'did' much about escaping SS2. More likely 'WTF?' followed by 'I appear not to be dead, to have mislaid my vehicle, but happily still to be in possession of a parachute'. The very nature of intense chaotic events is that all manner of outcomes are possible, even those which are genuinely or apparently very improbable. In fact, 'WTF?' may have come immediately after rather than before the detailed change in situational awareness.

A_Van

6th Nov 2014, 11:27

To FlyingCroc

First ever ejection at M > 1:

26 February 1955 - This Day in Aviation (http://www.thisdayinaviation.com/26-february-1955/)

AreOut

6th Nov 2014, 12:13

apparently if you are lucky enough you can survive even 3 Mach ejection

Lockheed SR-71A (61-7952) - At 78,000 feet without an Airplane (http://www.thexhunters.com/xpeditions/sr-71a_952_accident.html)

WorkingSection

6th Nov 2014, 12:35

peekay4 agreed:
At 45000ft, the local standard atmosphere temp is 216.5K, speed of sound=295.04m/s, density is 0.2438kg/m^3 so stagnation pressure is 10.6kPa.

At 70000ft, we have T=217.99, a=295.95m/s, TAS=412.9m/s so stagnation pressure is 6.4kPa, and I agree a 40% reduction.

RetiredF4

6th Nov 2014, 13:00

What I don't understand. How did the pilot survive this crash. He is at 50'000 ft at Mach 1 and the airplane breaks apart. I don't think there are ejection seats? How is this possible?

Survivability of a high speed ejection depends on multiple factors. But consider air is denser at lower altitude than at 50.000', therefore the forces at 50.000 feet and Mach1 are less than the same speed at 10.000'. So the speed would not have been a problem here, but the uncontrolled sequence of separation from the aircraft and environmental factors like oxygen and temperature. A crew of our wing had an ejection below 300' and going 540 knots IAS, they both had their helmets torn off their heads and they suffered bruises like boxing with M.Ali for an hour from the air blast. The frontseater had both arms dislodged from his schoulders with multiple fractures. The body position of the WSO was drastically better, as he was the guy who initiated ejection and he therefore was prepared for it and had no fractures at all.

mickjoebill

6th Nov 2014, 13:29

Windchill at Mach 1 at 50,000ft?:eek:

RF4

6th Nov 2014, 13:29

Actually there are a number of similarities between the survival of the SS2 pilot and the survival of Bill Weaver after the in-flight break-up of the SR-71 in 1966.
Both broke up at high speed at high altitude, with the pilots being torn/tossed out of the flight deck - Siebold torn from his seat and Weaver torn from his ejection seat.
Pressure suits have not changed much from those days, and both owe their lives to an intact pressure suit, parachute and supplementary oxygen. I am presuming these things for the case with SS2 - if I am wrong please correct me.
It will be interesting some day to hear Siebold's experiences after his exit from SS2 his free-fall, chute deployment and rescue - a harrowing experience with a decent ending.

RF4

6th Nov 2014, 13:37

Temperature at 40,000 is -56.5 C ( -70 F) and stays constant to about 65,000 feet - not much need to worry about wind chill unless you have exposed flesh :sad:

pchapman

6th Nov 2014, 14:25

For high speed ejections we always have to look at the equivalent airspeed (EAS). That's what basically matters for wind blast. (Although I guess there are heating effects which might not relate directly to EAS - I don't know my high speed aerodynamics.)

So if SS2 were doing Mach 1.0 at say 50,000', the EAS would be only 250 kts. Rough but nothing like ejecting at Mach 1 at sea level, with an EAS of 660 kts!

(It can also be remarked about ejection stories is that it can be hard to tell what the actual speed was at the moment of ejection, which might sometimes be slower than at the moment the pilot last had a chance to look at the gauges.)

I'd just guess Siebold was lucky to not have sustained much injury during the breakup, and despite loss of consciousness from hypoxia, and happened to wake up sufficiently to unlatch the seat belt at some lower altitude and pull. One news article I saw suggested he was just in his seat with little structure around, but I'm unsure about how accurate the article might be.

janrein

6th Nov 2014, 15:35

@RichardC10
... why plan to withdraw the locks above some (low) speed limit?

Maybe because of the following procedure drivers/considerations.

Imagine locks are discovered blocked or the locks operation system is discovered unserviceble. If this is discovered earlier in the burn, an engine shut-off, venting of remaining oxidiser to reduce weight and a reduced energy unfeathered re-entry may be feasible. You would not enter this abort mode unless you knew of the problem.

Imagine locks removed at e.g. Mach 1.4. Now imagine feathering pneumatics are discovered unserviceble much later, after nominal flight profile engine burn-out (2 minutes or so). Same problem! Or perhaps not quite? There may be redundant procedures for e.g. passive feathering (use RCS for correct attitude, then let it fold up "by itself" and keep it so using the trimmable elevators(?)

Fine, but you must unfeather again before hitting good old earth. Perhaps there are "tricks" for that as well. Or else bail out at lower speed and altitude?

In any case, with stuck locks that you´re not aware of, when you wait until full motor burn-out (for the nominal flight regime up to 380kft) there may be no alternatives left. I believe that may be a major driver for a not-too-late unlock action.

Admittedly speculative, but that´s what came up.

@Flash & peekay
I believe I did half rho v-squared on the numbers in SI units,
but will look it over, maybe a blind spot there ...

pchapman

6th Nov 2014, 16:20

Video from 2nd powered flight is instructive about one normal sequence of events, as it looks back over the tail and includes cockpit audio that seems synchronized:

https://www.youtube.com/watch?v=0mCFxAsmnk0

In line with what janrein was talking about, the unlock is done early while the engine is burning, and they are accelerating and indeed still pitching up. The "Unlocking" call came right after the "5 seconds to go" callout, apparently about fuel remaining. About 15 sec into the burn.

Background: Another source [a space.com article] notes about the flight in the video:
Sept. 5 2013: Second Powered Test Flight - SpaceShipTwo burned its engines for 20 seconds—four seconds longer than on the previous flight. The craft beat its previous record for altitude and speed, reaching a maximum altitude of 65,000 feet (21031 meters) and a top speed of Mach 1.6 or 1,217 miles per hour at sea level. The craft was piloted by Mark Stucky and copiloted by Clint Nichols.

glendalegoon

6th Nov 2014, 18:38

RF4

I don't think the crew of spaceship2 wears pressure suits.

Niner Lima Charlie

6th Nov 2014, 21:49

I keep seeing post here about "the crew unlocked the feathers...." I have gone back and watched again the NTSB briefing videos and reviewed the reports. Let's be clear about the facts:

1. "... the copilot, who was in right seat, moved the lock/unlock handle into unlock position."

2. In order for feathering to start, two things have to happen: someone has to unlock the feathering system, and someone has to activate the system with a different handle.

3. “This was what we would call an uncommanded feather, which means the feather occurred without the feather lever being moved into the feather position,” Hart said.

To me, the co-pilot removed the SAFETY LOCK so the feather handle could be moved later when needed. This might be a mechanical blocking handle that prevented the physical movement of the feathering handle. At this point we only know that some unknown failure caused the feathers to move. I see no reference to LOCKS on the feathers being removed, unlocked or actuated by the crew.

Peter H

6th Nov 2014, 23:30

@Niner Lima Charlie
I agree that there is some lack of clarity, and IMHO most [all?] press statements could be interpreted as referring:
- either to a physical lock on the feather mechanism/structure itself
- or to a safety lock on the feather handle.

However the current story is that telemetry indicated that there was an uncommanded feather deployment. Which I can only take to mean
that the feather activation handle wasn't involved in the deployment.

So, is it a physical lock or a safety lock? In the absence of known documentation on the question, lets think about the press releases.
- If it is a physical lock on the mechanism its state could well be important (e.g. in failing to prevent aerodynamic forces triggering deployment).
- If it is a safety lock on the handle its status is unimportant, as the event it might have prevented (movement of the activation handle) didn't happen.

So are the press releases about unlocking the feathers stating potentially important facts, or raising unimportant issues? I feel justified in believing
that a physical lock on the mechanism is involved, but would love to see the matter clarified in official documentation.

Nemrytter

7th Nov 2014, 03:04

Peter H, it is a physical lock yes.

StormyKnight

7th Nov 2014, 08:42

Clarifying the "subsequent aerodynamic forces then deployed the feathering mechanism"

The NTSB also evaluated the vehicle’s feathering mechanism, which is the unique technology that turns the wing booms into position for re-entry. The NTSB indicated that the lock/unlock lever was pulled prematurely based on recorded speed at the time, and they have suggested that subsequent aerodynamic forces then deployed the feathering mechanism, which resulted in the in-flight separation of the wings and vehicle. At this time, the NTSB investigation is still ongoing and no cause has yet been determined – these are purely facts based on initial findings. We are all determined to understand the cause of the accident and to learn all we can.

janrein

7th Nov 2014, 09:11

... is 6.4kPa, and I agree a 40% reduction.

@WorkingSection
Thanks.
Previous commenters were right, I used pattern´s reported graphs but had not read them very accurately, especially density at 70kft is lower than what I mentioned.

funfly

7th Nov 2014, 10:20

If a physical lock is required does that not indicate that there was a perceived 'need' for this.

pchapman

7th Nov 2014, 13:48

I found the following in a forum without any attribution to the original source - so it isn't the best evidence. Still, on the face of it, it confirms that it is a physical lock. It also confirms that the tail is not held in place by the pneumatic system pressures.

As the ship is rocketing upward, the tail is held fast by a large hook that is supposed to remain engaged until the craft reaches supersonic speed, Mike Moses, Virgin Galactic vice president of operations, explained in an interview with Reuters.

At that point, the pilots release the hook, though the tail remains pinned back by aerodynamic pressures. The command to actually move the tail into descent position comes after the rocket motor burns out, near the apex of the ship's altitude. Unlocking the tail is done well before then so that if the mechanism fails, the pilots can abort the flight.(Now in the 2nd powered flight video, the unlock command came before the engine burnt out -- but that was for a lower profile flight where burnout and the apex were closer together. The quote appears to refer to the planned full altitude flights.)

Redredrobin

7th Nov 2014, 14:11

The quote from Mike Moses is in a Reuters article published 6th Nov 9.04am UTC entitled 'New spaceship restoring hope after Virgin Galactic crash' available on Breaking News, Business News, Financial and Investing News & More | Reuters.co.uk (http://uk.reuters.com)

Peter H

7th Nov 2014, 14:58

@pchapman & @Redredrobin Nice find, thanks. That URL didn't work for me, but this one did.
New spaceship restoring hope after Virgin Galactic crash | Reuters (http://www.reuters.com/article/2014/11/06/us-space-crash-virgin-new-idUSKBN0IQ02920141106)

RichardC10

7th Nov 2014, 15:23

I thought Virgin Galactic were not going to be commenting on the causes of accident.

Anyway, the quote is pretty clear. Move the unlock handle in a regime where the net aerodynamic forces work in the pro-feathering direction and the aircraft will be lost. The lack of interlocks made sense for SpaceShipOne but looks terrible in a vehicle designed for passengers.

thcrozier

7th Nov 2014, 16:30

At the lower left corner of this diagram it says "feather actuation and lock pneumatically operated":

Size comparion - Virgin Mother Ship's SpaceShip Two versus White Knight's SpaceShip One (http://tommytoy.typepad.com/.a/6a0133f3a4072c970b015432355a06970c-popup)

Radix

7th Nov 2014, 20:24

... It also confirms that the tail is not held in place by the pneumatic system pressures.
... The command to actually move the tail into descent position comes after the rocket motor burns out,
Actually it confirms the tail is held into place by another mechanism than the locks. He talks about being able to command feather i.e. there is a feather actuator.

Numero1

7th Nov 2014, 21:29

theguardian

Disaster at the speed of sound: the tragedy of SpaceShipTwo?s final flight | Science | The Guardian (http://www.theguardian.com/science/2014/nov/07/virgin-galactic-tragedy-revealed-spaceshiptwo-disaster)

The article explains how the feathering system is supposed to work and present evidences that pilot error caused the accident.

thcrozier

7th Nov 2014, 23:22

I wish VG would release a schematic and detailed description of the feathering and feather-locking machinery.

DozyWannabe

7th Nov 2014, 23:23

...and present evidences that pilot error caused the accident.
Now, that's not quite accurate.

To be fair, as far as mainstream media outlets go, The Grauniad is fairly trustworthy - but the only time the term "pilot error" comes up is in one quote (emphasis mine):

“There’s nothing that tells me that this was anything other than pilot error, sadly,” said Will Whitehorn, the former president of Virgin Galactic, speaking from the UK.
If you read between the lines, what this actually means is that neither the NTSB nor VG are currently commenting on the causes of the accident, so the journalist has called up a former VG bigwig for a comment in lieu of anything official.

thcrozier

7th Nov 2014, 23:55

Some of the comments on the Guardian article seem to be from people who feel that unless VG can achieve current major airline safety, the entire endeavor should be stopped.

I think that's silly. 20 years ago, air travel was not statistically as safe as it is now. Under that logic, we should shut down air travel right now, because certainly it will be safer in 20 years.

pchapman

8th Nov 2014, 03:36

I've edited out what I had just written because of new info I read.

The Guardian article recently mentioned, did make it seem like the pneumatic pistons would hold the tail down at Mach 1.4 as intended, or even Mach 1.2 as in an earlier test. But that could just be simplistic writing. So I'm not sure if it really meant there was already pressure in the pistons to prevent the feathering, pushing against aerodynamic forces, or that the aerodynamic forces alone wouldn't push the tail up at Mach 1.2 and above.

To go back to what I had written in the earlier version of this post, I was wondering whether the pneumatic pistons are really pressurized at all until the feather control is actuated. In keeping with their super simple philosophy, and what I read in the book about SS1 which may be similar, it sounds like there might be no pressure until the control is activated. Maybe, maybe not.

Bill Harris

8th Nov 2014, 06:10

If you read between the lines, what this actually means is that neither the NTSB nor VG are currently commenting on the causes of the accident, so the journalist has called up a former VG bigwig for a comment in lieu of anything official.

And if you read further 'tween the lines, that explanation is sandwiched between quotes from George Whitesides and Will Whitehorn. The writer's explanation is not in quotes and should not be attributed to either official. It's a journalistic trick to lend apparent credence to their idea of what happened.

donotdespisethesnake

8th Nov 2014, 06:55

pchapman: "it sounds like there might be no pressure until the control is activated"

I read it the same way. Apart from aerodynamic forces, the only mechanism holding the tail booms in place is the lock and the only thing moving the booms is the actuator. So it is essential to keep the lock engaged during trans-sonic period. OTOH, the booms absolutely must be unlocked to ensure safe re-entry after high-altitude burnout. Such a critical operational requirement seems like an inherently unsafe design.

I think NTSB will conclude significant design changes are required, and won't pass it off as a "pilot error", merely requiring extra training. IMO they are also looking at whether the FAA should have signed off the design, and even if the FAA are qualified to do so.

This is a major setback for Virgin Galactic, and will put the programme back several years. They won't be back flying in 2015, I am fairly sure of that.

Daysleeper

8th Nov 2014, 07:06

present evidences that pilot error caused the accident

As opposed to the error of the people who designed the system, or those who specified the constraints the designer had to work to, or the regulator who approved the design implementation...etc etc etc.

You don't have to be Sidney Dekker to know that the last person to touch something is not automatically (or even usually) the cause of the accident, though often the one blamed.

Numero1

8th Nov 2014, 10:31

@ Daysleeper

Completely agree with you. Blaming the pilot is the easy thing to do.

Pressing a button at the wrong time should not result in instant death and like you and others have said , it's a wonder this design was approved in the first place.

Anyway wil will find out in due time.

SKS777FLYER

8th Nov 2014, 15:15

Yes, well unfortunately pressing a button at the wrong time sometimes leads to near instant destruction. ..... A300 rudder pedals "pressed" to opposite limits in a jet that supposedly had/has pilot proof computer driven limiters. Pressing a button to jettison external stores after loss of a critical engine, only to have the stores jettison on just one, (the wrong one), wing.
Reading thru the so far released "details"..... I am aware that the VG flight team suggested/requested that the tail feather unlock button/lever/switch NOT be selected on/activated at less than mach1.4 to ensure aerodynamic forces do not unlock the feathers. I cannot help but believe that I'd accurate about about the 1.4 speed caution, the pilots know/knew that limitation/necessity.
When I watched and listened to the SS2 amazing reverse looking camera video and crew communication recording of September, 2013, I was struck by the crew talk and apparent checklist/ flight progress accomplishment. I heard three altitude calls, two at and near apogee 65,000 and 66,000 seemingly surprised; and then descending thru 49,000. I heard the only, I guess, speed called out in the descent "looking for 165"
The cadence and choppy pilot talk, odd (to me) checklist running, especially during the grunting needed to overcome the acceleration and pitch-up G forces leads me to wonder if VG pilots undergo simulated cockpit procedures training in a centrifuge.

connies4ever

8th Nov 2014, 15:43

There has been some discussion in this thread if a supersonic ejection (or bail) is survivable. In deed it is. The link below shows visual evidence of an A-12 mid-air collision with its' D-21 drone. The A-12 broke up into two major pieces at Mach 3, with the crew ejecting. Both survived the ejection phase, sadly, the drone Launch Control Officer drowned when he hit the water. Pilot came through.

https://www.youtube.com/watch?v=GMyC2urCl_4&spfreload=10

There is also the case of Bill Weaver in an SR-71 who had an unstart at M=3, ejected and survived.

Of course, in both these cases, crew had full pressure suit and so forth. Mr Siebold in SS2 did not. It also has to be borne in mind that at the altitude he was at, around FL500, the EAS was much less than what we normally think when someone say "Mach 1".

16024

8th Nov 2014, 17:38

Which is exactly what he has done; those experts being Scaled Composites, headed by the expert (genius?) Mr Rutan.

westhawk

8th Nov 2014, 19:59

While it's regrettable that this testing accident happened, let's not be too quick to apply the same expectation of safety to space tourism as we do to airline flying. Even though the Air Force and NASA did all this six decades ago, doing it now as a small scale commercial venture means some of the old lessons will inevitably have to be re-learned. And even as a more mature and certificated activity, commercial space tourism will always involve a significantly higher level of risk than subsonic mass transport or just staying home.

Re certification:

The proposed commercial activity is much closer to local commercial air tour activity than it is scheduled airline activity. It would be a mistake to believe airline style safety statistics are to be realistically attainable in the near future. The FAA must thread the needle between acceptable risk and absolute safety (ban the activity) in setting certification and operational rule-making standards. It'll be interesting to see where the centerline is drawn and how wide or narrow the path of acceptability ends up being.

As for Branson and numerous other rich dudes sharing a propensity for opulent self promoting style:

Make fun of him all you like! I'm laughing too.

But I'd rather see these flamboyant salesmen Billionaires spending their money on something that pushes boundaries and provides employment for innovators. I'm as envious of their wealth as the next guy, but get a good feeling from seeing their money go to something that captures the public imagination and perhaps boosts the human spirit of endeavor just a little bit. It doesn't necessarily mean I'll favor their *commercially marketed products, but I'm appreciative nonetheless. :)

Accident investigation:

I fully expect the NTSB to thoroughly investigate technical and operational causality and make recommendations as they do with any aviation accident of high public visibility. I'll be interested to see what level of expectation of safety they apply to these recommendations and how the FAA responds in terms of rule-making.

It seems apparent that in the transonic regime of flight, significant changes in pressure distribution over the flight surfaces is expected and that the feather mode is not intended to occur in this regime. Hence the locking mechanism is required in order to assure that aerodynamic forces at work in the transonic regime don't initiate an unintentional deployment.

But the feather mode must be verified (successful unlocking) as being available in case of early engine shutdown/abort scenarios and to assure it is available for use at or near apogee to limit the vehicle velocity during descent. If the feather mode is unavailable beyond a certain height, destruction of the vehicle during descent is highly likely due to dynamic pressure beyond the design limits of the vehicle. It's simply not designed to tolerate the high dynamic pressure which would result from descent from high altitude without the feather.The vehicle design and flight profile is optimized for high velocity flight at moderate dynamic pressures, relying upon the aerodynamic drag of the feather to control dynamic pressure during the descent phase.

As I understand the available information, should an abort become necessary during climb, the feather deployment must be delayed until a very low dynamic pressure level is reached. A pitch attitude change and significant drag increase is induced by the feather deployment. This must not be allowed at dynamic pressure beyond a certain limit or excessive pitch rate and resultant forces will be applied to the airframe.

So learning while the feather was unlocked while still accelerating through the transonic regime is important to understanding what happened. Hopefully the entire sequence of events will eventually be determined with a high degree of certainty and any lessons learned applied to future ops.

Use of the term "pilot error" at this stage is at the very least premature. Let's at least collect and analyze a bit more data before settling for that old cop-out. :ok: