Virgin Galatic Spaceship Two down in the Mojave.
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deptrai:
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.
The A380 went through about 2500 hours of flight testing. It wasn't enough to uncover the uncontained engine failure waiting to happen.
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.
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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 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.
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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.
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.
Last edited by pchapman; 1st Nov 2014 at 17:58. Reason: minor additions & cleanup
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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.
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
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
"Celeb" Funding
and to push the boundaries of commercial space for us all, funded by said celebs.
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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.
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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.
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.
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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?
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Hybrid Rocket Motor Safety
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
Worth a read.
Hybrid Rocket Motor Design
Worth a read.
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something caused it to flip suddenly, while largely intact, followed by disintegration
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.
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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...
Just my musings...
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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:
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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
Focus on fuel in Virgin crash probe - 9news.com.au
short flights long nights
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.
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.
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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.
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.