Virgin Galactic
Discussion
rovermorris999 said:
qube_TA said:
Unsure why you're being so aggressive against it, what harm does it cause you whether VG exists or not?
Because the money should be spent on free lentils for the poor.If only someone would have the foresight to build one!!!!!!!!
scubadude said:
I said "the press are reporting" and they are, on most major news sites they are saying the feather system was unlatched then triggered, two actions a couple of seconds apart but the telemetry didn't record the pilots triggering it, perhaps it was pulled open by air pressure once unlatched?
The press are reporting what the NTSB spokesman told them.It looks like a deliberate human action was what unlocked the feathering system. After that, transonic aerodynamics seems to have caused the unlocked tail surfaces to move - resulting in an aerodynamic breakup of the vehicle.
From Spaceflight Now's piece on NTSB acting chairman Christopher Hart's press briefing;
If the accepted procedure is for the tails to be unlocked at Mach 1.4, it seems unlikely to me as an armchair pundit that the system is structurally so delicate as to fail at Mach 1, even if there is the potential for additional transonic stresses.
I would still like to know why the tails are planned to be unlocked prior to the rocket motor completing its burn.
SFN said:
“About nine seconds after the engine ignited, the telemetry data showed us that the feather parameters changed from lock to unlock,” Hart said.
“Normal launch procedures are that after the release, the ignition of the rocket and acceleration, that the feathering devices are not to be moved — the lock/unlock lever is not to be moved into the unlock position — until the acceleration up to Mach 1.4. Instead, as indicated, that occurred (at) approximately Mach 1.0,”
The tail booms extended after they were unlocked, even though they were not commanded to do so, Hart said. SpaceShipTwo’s pilots normally must unlock the feathers, then send a separate command to move the tail booms into position for descent.
“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.
That is pretty explicit in stating that no crew action deployed the feather.“Normal launch procedures are that after the release, the ignition of the rocket and acceleration, that the feathering devices are not to be moved — the lock/unlock lever is not to be moved into the unlock position — until the acceleration up to Mach 1.4. Instead, as indicated, that occurred (at) approximately Mach 1.0,”
The tail booms extended after they were unlocked, even though they were not commanded to do so, Hart said. SpaceShipTwo’s pilots normally must unlock the feathers, then send a separate command to move the tail booms into position for descent.
“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.
If the accepted procedure is for the tails to be unlocked at Mach 1.4, it seems unlikely to me as an armchair pundit that the system is structurally so delicate as to fail at Mach 1, even if there is the potential for additional transonic stresses.
I would still like to know why the tails are planned to be unlocked prior to the rocket motor completing its burn.
The problem is that the pressure points on the vehicle probably move about quite a bit in the transonic region of flight i.e just below and just above Mach 1.
I could very easily understand why the flight rules stated explicitly that the feathering lever be left alone until the aircraft had moved beyond the transonic zone.
I could very easily understand why the flight rules stated explicitly that the feathering lever be left alone until the aircraft had moved beyond the transonic zone.
Toaster said:
rovermorris999 said:
qube_TA said:
Unsure why you're being so aggressive against it, what harm does it cause you whether VG exists or not?
Because the money should be spent on free lentils for the poor.This is what VG is about, all their literature illustrates the desire for where this development will lead.
Even if it's initially funded by 'rich space tourists' then I fail to see why it should be knocked.
Unsure of this environmental, social and cultural impact of which you speak.
Eric Mc said:
The problem is that the pressure points on the vehicle probably move about quite a bit in the transonic region of flight i.e just below and just above Mach 1.
I could very easily understand why the flight rules stated explicitly that the feathering lever be left alone until the aircraft had moved beyond the transonic zone.
I wonder if the speed is also linked to the altitude, we know its designed to climb steeply while the motor fires, it might be that by the time it normally reaches Mach1.4 its above enough of the atmosphere such that unlatching is less of an issue, perhaps the peak dynamic pressure is slower and lower?I could very easily understand why the flight rules stated explicitly that the feathering lever be left alone until the aircraft had moved beyond the transonic zone.
Given that its such a major issue (the craft changing shape at speed) its hard to understand why you might unlatch it early, as was said I'd have thought its something you'd leave till burnout and the "space" bit of the flight before returning to the atmosphere proper.
scubadude said:
Given that its such a major issue (the craft changing shape at speed) its hard to understand why you might unlatch it early, as was said I'd have thought its something you'd leave till burnout and the "space" bit of the flight before returning to the atmosphere proper.
My guess we have 2 options:1)The Lock/Unlock was used accidentally instead of another control.
2)The pilot who operated the Lock/Unlock did so intentionally as a reaction to something we don't know about yet. What is the "Sub Mach 1 abort procedure"? Did they try to do that but too late and were stuck in a procedure that was the wrong one by the time they decided to do it?
I can't imagine they did it early to save some time later.
Eric Mc said:
I would think so too.
I haven't heard any explanations yet as to why unlocking the feathering mechanism whilst still in the boost phase would be a desirable thing to do.
Perhaps when they do need to deploy it they might be in a hurry, so they want to guard against a 'quick deploy the feather, bugger, it's still locked' scenario.I haven't heard any explanations yet as to why unlocking the feathering mechanism whilst still in the boost phase would be a desirable thing to do.
There was a previous flight were the feather was used to regain control so perhaps they were more preoccupied by ensuring it would be ready when required than by the need to prevent a premature deployment.
Eric Mc said:
I would think so too.
I haven't heard any explanations yet as to why unlocking the feathering mechanism whilst still in the boost phase would be a desirable thing to do.
All i can think of is that it is "safer" to ensure the locks retract BEFORE you carry out the Ballistic Climb into space, as you need to be able to feather the tail surfaces to safely commence re-entry, so were the locks to remain, er, locked, then you'd have a single point of failure resulting in a catastrophic hull loss. I haven't heard any explanations yet as to why unlocking the feathering mechanism whilst still in the boost phase would be a desirable thing to do.
Unfortunately in this case it rather looks like there was also a critical failure node from too early and unlock......
Eric Mc said:
RobDickinson said:
Its all abouy getting 6 people to 85k at suborbital velocities as nastily as possible.
Exactly - which is a useful end in itself. If more "non-professional" are exposed to the wonder of high altitude flight, it helps further the "cause" of spaceflight.To me, it's no different to the very early passenger flights offered by the post World War 1 airlines. In 1919 you could fly from London to Paris in a De Havilland DH4. It was uncomfortable, dangerous and slower than train and ferry - but people still wanted to pay to do it. It was another 20 years before carrying passengers in an aeroplane began to be a properly economic enterprise.
Toaster said:
One would have to ask the question why and whats the point, apart from being cheaper than the $20M a Californian paid to go up in a Russian rocket and visited the space station. Now whilst that is true space tourism rather than the fun fair ride in a Vigin Galactic up-down I still don't quite "get it"
Maybe its just more about Ego than anything else but its worthy of a debate. Cost, risk human benefit as we burn up the earths resources for a rich few.
Eric Mc said:
The actual number of people who will be able to fly in space as paying passengers will remain small for many, many years and even 50 years from now I doubt if the total number of commercial people carrying spacecraft in the world will be less than 100 actual vehicles. So - I doubt very much if space tourism will have even a smidgin of impact on the earth's environment.
I think you're being unduly pessimistic there; if Reaction Engines advance as quickly they have so far Skylon and their proposed hypersonic passenger liner could be appearing by 2030.qube_TA said:
I read that this craft would enable you to fly from London to Melbourne in around 3 hours, there's certainly plenty of scope there for the 'what's the point' brigade.
No. No it wont ever do that. At the moment they cant get enough burn/thrust for 20+ seconds and hit 85kms high. And to do that it needs the help of a carrier plane drop from 15k up.This is not a transport system. it cant be scalled up. Not even from 3 people to 6.
It only manages (in theory , if it works) about 1.6m/s, to get orbital it needs ~9m/s
This isnt even like Stratolaunch ( a 540 ton airplane launching about 6 tons into LEO, compared to falcon 9 , 505tons launching 13 tons or 50 with the heavy booster). Its a toy for rich kids to play in space.
RobDickinson said:
MartG said:
Nothing new in that !
And how did that work out , long term? SS2/virgin galactic is nothing but an expensive and dangerous toy for the rich. if anything they are hurting the space industry by making it look less safe and unregulated.We have already superceeded it.
The only reason SS2 needs the carrier aircraft is because they are using an underpowered hybrid rocket engine that needs the extra lift.
Because they didnt want to try with a more complex liquid fuelled engine and a ground launch.
We have had people skydive from baloons at higher altitude than SS2 has acheived.
The only reason SS2 needs the carrier aircraft is because they are using an underpowered hybrid rocket engine that needs the extra lift.
Because they didnt want to try with a more complex liquid fuelled engine and a ground launch.
We have had people skydive from baloons at higher altitude than SS2 has acheived.
RobDickinson said:
We have already superceeded it.
The only reason SS2 needs the carrier aircraft is because they are using an underpowered hybrid rocket engine that needs the extra lift.
Because they didnt want to try with a more complex liquid fuelled engine and a ground launch.
We have had people skydive from baloons at higher altitude than SS2 has acheived.
The thing is though most ground launched rockets use 80%+ of their fuel in the climb from earth phase and very little in the orbital or sub orbital burn. Taking your rocket 15km up in the sky using air breathing engines seems like a sensible idea if you ask me.The only reason SS2 needs the carrier aircraft is because they are using an underpowered hybrid rocket engine that needs the extra lift.
Because they didnt want to try with a more complex liquid fuelled engine and a ground launch.
We have had people skydive from baloons at higher altitude than SS2 has acheived.
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