Virgin Galactic
Discussion
Max_Torque said:
Fuel tank failure? wow, that just suggests a hurried dev program and not enough ground running doesn't it???
(i assume pressure fluctuations in hybrid motors are one of the big issues, ie combustion stability etc?)
Oxidiser tank, NO2 + 'polyamide' hybrid(i assume pressure fluctuations in hybrid motors are one of the big issues, ie combustion stability etc?)
They are testing for repeated use, so it could be stress failure.
Yes and fuel grain stability.
Instabilities are usually caused by uneven combustion of the fuel grain, which if significant enough will cause catastrophic failure.
Edited by annodomini2 on Sunday 2nd November 09:11
Simpo Two said:
Can they not stay with known technology?
The issue with "known" technology, ie liquid fuelled rockets, is the cost and complexity. Organisations like NASA spent 20 years and hundreds of millions of dollars perfecting that technology to a point where it was reliable (ish) and able to be used "run of the mill" for the Space Shuttle. However, if you look at the work that had to go on behind the scenes to make it "run of the mill" well, wow, the costs were astronomical! There are some interesting papers on SST main engine reliability that show the level of monitoring, complexity, analysis and statistical data progression required to detect and predict "off nominal" engine operation. No way could a commercial organisation swallow the cost and lead time implications of such a powerplant. And of course, as events earlier in the week proved, even when you buy a "proven" engine from someone else, things can and do still go wrong........
Even with the photos released so far, i am unclear if the "explosion" was a powerplant failure leading to a loss of flight control and an aerothermal breakup, or vise versa? ie a loss of flight control, leading to aerodynamic loadings that resulted in a propulsion system failure (rocket nozzle or tank rupture etc)
Max_Torque said:
The issue with "known" technology, ie liquid fuelled rockets, is the cost and complexity. Organisations like NASA spent 20 years and hundreds of millions of dollars perfecting that technology to a point where it was reliable (ish) and able to be used "run of the mill" for the Space Shuttle. However, if you look at the work that had to go on behind the scenes to make it "run of the mill" well, wow, the costs were astronomical!
Well that was my thought - NASA spent 20 years and hundreds of millions of dollars perfecting that technology, therefore why not use/adapt it, than have a small commercial organisation try to start all over again with something else with relative pocket money?Max_Torque said:
Even with the photos released so far, i am unclear if the "explosion" was a powerplant failure leading to a loss of flight control and an aerothermal breakup, or vise versa? ie a loss of flight control, leading to aerodynamic loadings that resulted in a propulsion system failure (rocket nozzle or tank rupture etc)
Good point, I don't think anyone knows yet. Given that it was the first flight since the engine mods the powerplant and fuel tank are the obvious suspects. But given that large pieces remained relatively intact and one pilot survived it clearly wasn't a Challenger style explosion.Simpo Two said:
Max_Torque said:
The issue with "known" technology, ie liquid fuelled rockets, is the cost and complexity. Organisations like NASA spent 20 years and hundreds of millions of dollars perfecting that technology to a point where it was reliable (ish) and able to be used "run of the mill" for the Space Shuttle. However, if you look at the work that had to go on behind the scenes to make it "run of the mill" well, wow, the costs were astronomical!
Well that was my thought - NASA spent 20 years and hundreds of millions of dollars perfecting that technology, therefore why not use/adapt it, than have a small commercial organisation try to start all over again with something else with relative pocket money?One question that is hanging around in my head is do hybrid motors suffer from Pogo effects? Presumably they do? if so, it's not beyond the realms of possibility that this new engine suffered massive surge from Pogo effects, and broke it's mounts, causing an off axis thrust and subsequent diversion from controlled flight? Which would explain why ground running was fine, but the installed system wasn't.
Max_Torque said:
Simpo Two said:
Max_Torque said:
The issue with "known" technology, ie liquid fuelled rockets, is the cost and complexity. Organisations like NASA spent 20 years and hundreds of millions of dollars perfecting that technology to a point where it was reliable (ish) and able to be used "run of the mill" for the Space Shuttle. However, if you look at the work that had to go on behind the scenes to make it "run of the mill" well, wow, the costs were astronomical!
Well that was my thought - NASA spent 20 years and hundreds of millions of dollars perfecting that technology, therefore why not use/adapt it, than have a small commercial organisation try to start all over again with something else with relative pocket money?One question that is hanging around in my head is do hybrid motors suffer from Pogo effects? Presumably they do? if so, it's not beyond the realms of possibility that this new engine suffered massive surge from Pogo effects, and broke it's mounts, causing an off axis thrust and subsequent diversion from controlled flight? Which would explain why ground running was fine, but the installed system wasn't.
Hybrids are not unproven, but rocket engines operate at the very limits of material science, sometimes beyond it with some very special tricks.
For the same thrust and burn duration SS2 would need to be at least physically twice the size with a liquid engine (Kerosene), 3-4x for Hydrogen.
Which have major side effects on the aircraft, it may not be any heavier, but it would certainly be bigger.
annodomini2 said:
For the same thrust and burn duration SS2 would need to be at least physically twice the size with a liquid engine (Kerosene), 3-4x for Hydrogen.
That could be the main reason, yes.Eric Mc said:
And I would expect a bigger craft would be more prone to aerodynamic break up if it deviated from its optimal flight patch compared to smaller more compact vehicle.
I looked at those big twin tail booms and thought they looked vulnerable to vibration etc - like the days of the sound barrier breakups.Hopefully, this time, with the "accident" occurring in the air, and hence involving the NTSB, the investigation and reporting will be significantly more transparent than for the last, ground based, fatalities on the project............
It also strikes me as somewhat odd, given the USA's mastery in high altitude survival suits proven by many survivable high speed / low pressure agency flight test incidents across the years, that the flight crew in this case were not required to wear such pressure suits?
It also strikes me as somewhat odd, given the USA's mastery in high altitude survival suits proven by many survivable high speed / low pressure agency flight test incidents across the years, that the flight crew in this case were not required to wear such pressure suits?
Eric Mc said:
To be fair, it can't have been traveling THAT fast when it broke up. Apparently the engine fired for about 6 seconds so what airspeed would it have been at at the moment of disintegration?
Spaceship 1 had the same configuration and worked fine. It was smaller though.
According to Wiki: Spaceship 1 had the same configuration and worked fine. It was smaller though.
" It launches from its mother ship, White Knight Two, at an altitude of 15,000 metres (50,000 ft), and reaches supersonic speed within 8 seconds. "
So, around six seconds of acceleration would have seen it trans-sonic at the very least, which also is the speed where compressibility effects on flutter and dynamic pressure oscillations can cause issues......
This was the first test flight of the new nylon(ish) based fuel rather than rubber.
They are trying this fuel because rubber didnt have enough go to meet the 85k altitude requirements for USA 'space'
All down to the original guy designing it around the hybrid engine and not understanding scailing issues. Now they have to try find/build an engien that fits in the same place/ same weight as the old one but with more thrust. One that doesnt shake the plane apart.
Total utter dead end project. It will never be any use other than as an expensive fairground ride. Wont further space exporation, wont advance any usable science or be able to meet any other goals.
Its all abouy getting 6 people to 85k at suborbital velocities as nastily as possible. Really sad another person (4 now total) has lost their life in this process.
They should have just built another SS1
They are trying this fuel because rubber didnt have enough go to meet the 85k altitude requirements for USA 'space'
All down to the original guy designing it around the hybrid engine and not understanding scailing issues. Now they have to try find/build an engien that fits in the same place/ same weight as the old one but with more thrust. One that doesnt shake the plane apart.
Total utter dead end project. It will never be any use other than as an expensive fairground ride. Wont further space exporation, wont advance any usable science or be able to meet any other goals.
Its all abouy getting 6 people to 85k at suborbital velocities as nastily as possible. Really sad another person (4 now total) has lost their life in this process.
They should have just built another SS1
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.
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.
So, calling for a stop to this aspect of space flight on environmental grounds is laughable.
As for the "only the rich" argument, up until the mid 1960s, flying as a passenger on a commercial airliner was pretty much only for the rich. Would you have been making the same arguments about Boeing 707s and De Havilland Comets in 1960?
Would you prefer that mankind calls a halt to technical developments in transport?
So, calling for a stop to this aspect of space flight on environmental grounds is laughable.
As for the "only the rich" argument, up until the mid 1960s, flying as a passenger on a commercial airliner was pretty much only for the rich. Would you have been making the same arguments about Boeing 707s and De Havilland Comets in 1960?
Would you prefer that mankind calls a halt to technical developments in transport?
Toaster said:
Eric Mc said:
Would you prefer that mankind calls a halt to technical developments in transport?
No but there has to be a step change to technology, and a reason to travel, space travel in its self has no point, there has to be a destination and a reason to travel to that destination. Space IS the destination.
Seems the engine and propellant tanks has been found intact.
http://www.telegraph.co.uk/news/worldnews/northame...
http://www.telegraph.co.uk/news/worldnews/northame...
Gassing Station | Science! | Top of Page | What's New | My Stuff