Virgin Galatic Spaceship Two down in the Mojave.
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Six Sigma
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.
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.
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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.
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.
Last edited by pchapman; 8th Nov 2014 at 03:48. Reason: rewritten for new info
Originally Posted by DozyWannabe
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.
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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.
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.
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present evidences that pilot error caused the accident
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.
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@ 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.
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.
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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.
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.
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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=GMyC...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".
https://www.youtube.com/watch?v=GMyC...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".
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.
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.
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First quotes from surviving pilot, via his father:
Space pilot: I came to on the way down ...and gave thumbs up to a passing aircraft to say: 'I'm OK!'* | Daily Mail Online
Space pilot: I came to on the way down ...and gave thumbs up to a passing aircraft to say: 'I'm OK!'* | Daily Mail Online
‘He doesn’t remember anything from the actual crash. He came to during the descent. He must have woken up about halfway down. When he was on the way down the chase plane was circling him and he was waving and giving the thumbs-up to indicate he was all right while he was dangling from the parachute.
‘He’s recovering at home. He broke the head of the humerus bone that sits in the right shoulder. He’s got a rib and lung contusion and there is an issue with his eyes because of the cold. It was around minus 60 degrees up there.'
‘He’s recovering at home. He broke the head of the humerus bone that sits in the right shoulder. He’s got a rib and lung contusion and there is an issue with his eyes because of the cold. It was around minus 60 degrees up there.'
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Their experience might make them qualified Engineers but not Test Pilots as we would know it? These lessons on the right experience and qualifications for the task have been learnt before in areas ranging from UAVs to NASA programs.
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The end of space tourism? - I hope so
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.
VG's project sprang off from genius Burt Rutan, and his Scaled Composites. Now that he's retired, I don't see there being sufficient impetus to push forward the practical side of the project; after all, it's difficult and expensive, and the financial types prefer easy money.
Also, I've learned from reading this thread just how far this technology is from orbital flight. It simply won't be scalable to orbital launches, and so any comments about a stepping stone towards private orbiting hotels are misinformation. Yes to "capturing the public imagination" and "boosting human endeavor". But using misinformation to do so would be counter-productive IMHO.
the real world is not that simple.
I don't think so either. I was just expressing a personal sentiment. I'd rather see the Bigshots put their money into these kind of projects than keep their money out of circulation or invested in boring ventures I care nothing about!
I live in the real world myself. (most of the time)
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Such a critical operational requirement seems like an inherently unsafe design.
headed by the expert (genius?) Mr Rutan.
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Pressing a button at the wrong time should not result in instant death.....
From a design POV, this feathering mechanism is a tricky circle to square. You want as few failure modes as possible, yet have to safeguard against unintended / uncommanded deployment.
Burt Rutan
As far as I can see he retired in 2011. He is now 71 years of age.
I doubt he is much involved with Spaceshiptwo but of course who knows what is going on inside a private company.
I doubt he is much involved with Spaceshiptwo but of course who knows what is going on inside a private company.
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Originally Posted by connies4ever
There has been some discussion in this thread if a supersonic ejection (or bail) is survivable.
B-58: http://www.ejectionsite.com/eb58caps.htm
XB-70: http://www.ejectionsite.com/xb70caps.htm
FB-111A: FB-111A.net
B-1A: http://www.ejectionsite.com/b1amodule.htm
A cabin ejection system requires a many different pyrotechnics, separators, sequencers, aero-stabilization under various conditions, air bags, etc. Yet it's used when the surrounding vehicle is torquing, disintegrating, maybe even exploding. All those complex separation systems have to work in that environment. This probably explains the limited success rate of the above systems.
Also suborbital spacecraft have an even greater problem because the flight envelope is much larger. So the tradeoff is having a conventional ejection system that covers only a fraction of the envelope (e.g, first four Space Shuttle missions), or a heavy, complex ejection system that covers more of the envelope but still not 100%.
Once the flight test phase is over, yet another problem in vehicles like SS2 or the shuttle is handling passenger escape. It's difficult to envision a workable practical system, hence the vehicle itself is the only escape system for much of the envelope.
Scaled Composites has been wholly owned by Northrop Grumman since 2007.
Making any technical judgement only on early reports filtered through the media is rarely worthwhile.
Originally Posted by Volume
At least it looks like a single failure cause resulting in catastrophic failure...