Too many people that day jumped to conclusions about the engine. I also think that Doug way overstated the danger of a ground fire near an engine. There is no possibility that I can see from an engineering standpoint where a local fire not in the engine could lead to an explosion that would level half the airport.
Well, given the history, the engine did seem like the most likely suspect.
Given its history, the engine is still suspect, just not for causing that particular crash.
The biggest problem with the Hybrid is its low performance, not explosion hazard. As I commented on the day of the accident, if that had been a liquid fueled or solid fueled vehicle no one would have survived.
It is academically interesting to me in looking at the SS2 breakup vs the recent incident with the Falcon 9. In both cases it was instantly able to be seen that there was no explosion and thus an engine failure could be eliminated from consideration.
The most egregious offenders were the people from England who whined and wailed to the press about the engine and if Virgin had just listened to them all would have been well.
The biggest problem with the Hybrid is its low performance, not explosion hazard.
Not to mention high turnaround cost, and time.
I have to disagree with you on this one, Dennis.
People may well have said “…if that had been a liquid fuelled or solid fuelled vehicle no one would have survived” but I do not understand the justification for this. As the break-up was caused purely by aerodynamic forces, which rapidly separated (disintegrated?) the cockpit from the propulsion module, the implication of you statement is that the propulsion system would have exploded either before or just after this event.
The only way a pure solid would explode is if a chunk of propellant was broke off during the pitch-up and got stuck in the nozzle – something that could also happen to a hybrid. Similarly, the only way a pure liquid would explode is if the fuel and oxidiser were well mixed, which implies rupture of both tanks and significant dispersion of their contents, well before cockpit separation/disintegration.
Given the images of the break-up and the ground debris, I’m not convinced that either mechanism would likely have occurred, though this is obviously a moot point. So, it seems to me that the surviving pilot owes his life more to pure luck, rather than choice of propellant.
Concerning comments from people in England; N2O, like H2O2, is a monopropellant and has the potential to detonate, as witnessed by 2007 accident. As with H2O2, N2O can certainly be tamed but VG have yet to convince most people that they know how to do this safely. I believe they lowered the storage pressure aboard SpaceshipTwo, which resulted in a significant hit on its performance, but there may still be bugs that have yet to manifest themselves.
The biggest problem with the Hybrid is its low performance
I would say ‘not enough data for a meaningful answer’. Elaborating : there is no meaningful flight history of that type of hybrid at that scale. Given the way Virgin is conducting things, there likely wont be.
So i dont think we’ll be much wiser about relative merits and problems of hybrid engines like these, because there simply wont be enough of an opportunity to know.
It’s also likely too expensive to burn for a significant flight test campaign, so apart from Virgins fuckups, there are other reasons why it wont ever be really well characterized.
Yes, immediatly post any accident, it’s a good idea to stick to factual obseravtions about the available evidence. In this case, the photos clearly showed SS2 flying sideways and breaking up, with no immediately obvious cause. Speculation based on limited facts is always tempting, often unwise, but should ALWAYS if indulged be clearly labeled as speculation.
RE the ground fire, you misread Doug on that point. The ground fire was in a rack full of partially-used hybrid test grains stored outdoors – right next to a bulk nitrous storage tank, right in the middle of the industrial/hangar part of the airport.
Storing flammables right next to bulk monopropellant oxidizer is a hugely bad idea. Doug correctly points out that they dodged a bullet that day.
Maybe this is a good subject for a longer essay, but what is the process in creating test aircraft re: the FAA? I’m not sure what Messier thinks they would have learned from the government if regulation was in place? I understand the argument that we need the time to learn best practices for spaceflight/launch, and alternatively that this isn’t really space related as it was in atmosphere. But I could see Messier’s point better if this was XCOR or Masten, but Scaled is supposed to know this stuff themselves? The have a lot of aircraft design experience; what would the FAA have contributed before the fact?
Too many people that day jumped to conclusions about the engine. I also think that Doug way overstated the danger of a ground fire near an engine. There is no possibility that I can see from an engineering standpoint where a local fire not in the engine could lead to an explosion that would level half the airport.
Well, given the history, the engine did seem like the most likely suspect.
Given its history, the engine is still suspect, just not for causing that particular crash.
The biggest problem with the Hybrid is its low performance, not explosion hazard. As I commented on the day of the accident, if that had been a liquid fueled or solid fueled vehicle no one would have survived.
It is academically interesting to me in looking at the SS2 breakup vs the recent incident with the Falcon 9. In both cases it was instantly able to be seen that there was no explosion and thus an engine failure could be eliminated from consideration.
The most egregious offenders were the people from England who whined and wailed to the press about the engine and if Virgin had just listened to them all would have been well.
The biggest problem with the Hybrid is its low performance, not explosion hazard.
Not to mention high turnaround cost, and time.
I have to disagree with you on this one, Dennis.
People may well have said “…if that had been a liquid fuelled or solid fuelled vehicle no one would have survived” but I do not understand the justification for this. As the break-up was caused purely by aerodynamic forces, which rapidly separated (disintegrated?) the cockpit from the propulsion module, the implication of you statement is that the propulsion system would have exploded either before or just after this event.
The only way a pure solid would explode is if a chunk of propellant was broke off during the pitch-up and got stuck in the nozzle – something that could also happen to a hybrid. Similarly, the only way a pure liquid would explode is if the fuel and oxidiser were well mixed, which implies rupture of both tanks and significant dispersion of their contents, well before cockpit separation/disintegration.
Given the images of the break-up and the ground debris, I’m not convinced that either mechanism would likely have occurred, though this is obviously a moot point. So, it seems to me that the surviving pilot owes his life more to pure luck, rather than choice of propellant.
Concerning comments from people in England; N2O, like H2O2, is a monopropellant and has the potential to detonate, as witnessed by 2007 accident. As with H2O2, N2O can certainly be tamed but VG have yet to convince most people that they know how to do this safely. I believe they lowered the storage pressure aboard SpaceshipTwo, which resulted in a significant hit on its performance, but there may still be bugs that have yet to manifest themselves.
The biggest problem with the Hybrid is its low performance
I would say ‘not enough data for a meaningful answer’. Elaborating : there is no meaningful flight history of that type of hybrid at that scale. Given the way Virgin is conducting things, there likely wont be.
So i dont think we’ll be much wiser about relative merits and problems of hybrid engines like these, because there simply wont be enough of an opportunity to know.
It’s also likely too expensive to burn for a significant flight test campaign, so apart from Virgins fuckups, there are other reasons why it wont ever be really well characterized.
Yes, immediatly post any accident, it’s a good idea to stick to factual obseravtions about the available evidence. In this case, the photos clearly showed SS2 flying sideways and breaking up, with no immediately obvious cause. Speculation based on limited facts is always tempting, often unwise, but should ALWAYS if indulged be clearly labeled as speculation.
RE the ground fire, you misread Doug on that point. The ground fire was in a rack full of partially-used hybrid test grains stored outdoors – right next to a bulk nitrous storage tank, right in the middle of the industrial/hangar part of the airport.
Storing flammables right next to bulk monopropellant oxidizer is a hugely bad idea. Doug correctly points out that they dodged a bullet that day.
Maybe this is a good subject for a longer essay, but what is the process in creating test aircraft re: the FAA? I’m not sure what Messier thinks they would have learned from the government if regulation was in place? I understand the argument that we need the time to learn best practices for spaceflight/launch, and alternatively that this isn’t really space related as it was in atmosphere. But I could see Messier’s point better if this was XCOR or Masten, but Scaled is supposed to know this stuff themselves? The have a lot of aircraft design experience; what would the FAA have contributed before the fact?