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SpaceshipTwo crashes shortly after Mojave test flight

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Re: SpaceshipTwo crashes shortly after Mojave test flight

#301

Post by kashkhan »

crikli wrote: post #135
kashkhan wrote: post #109

Earlier quoted context omitted.

there's no need not in this day and age to have test pilots. If they use computers, they can debug the engine in flight conditions by running maybe ten times as many test flights. Delays of months between flights are dangerous. Until you have a 1000-10,000 flights to build up operational data and envelope, this is a death trap causing unnecessary deaths.

The first statement implies that computer testing is so good now that an aircraft can be tested so thoroughly that the maiden voyage of an aircraft could safely also be its first "for real" mission. It is true that computer models have definitely reduced the risks for test pilots by helping to define a much greater percentage of the performance envelope of a given system without the need for test flights. When a pilo…

there's a difference between testing the engine, and testing the handling qualities. But not always.

For testing the engine which in this case is throttleable and has time constants greater than hundreds of milliseconds the time lag from not having a pilot onboard is acceptable.

For flying qualities again the plane is large enough to be slow enough that remote pilot timelag is not significant.

There is no part of the envelope of this vehicle where you need a pilot onboard. Most of the development here can be done without pilot onboard. Space has been done from unmanned vehicles since the beginning and what they are doing is only barely rocket science.

Putting a pair of pilots in a vehicle with a non-flight-tested rocket engine is just irresponsible.

I like Rutan's company. But what they are doing on this program smacks of amateurism. They got engineers killed on the ground and now pilots killed and injured in flight. Both of which were completely preventable by some basic range and flight safety measures.

It looks like they are cutting corners by doing too much too soon because of management pressures to cut delays. And people are paying the ultimate price for their hubris.

Re: SpaceshipTwo crashes shortly after Mojave test flight

#302

Post by kashkhan »

neurotech1 wrote: post #191
kashkhan wrote: post #109

Earlier quoted context omitted.

there's no need not in this day and age to have test pilots. If they use computers, they can debug the engine in flight conditions by running maybe ten times as many test flights. Delays of months between flights are dangerous. Until you have a 1000-10,000 flights to build up operational data and envelope, this is a death trap causing unnecessary deaths.

Your forgetting the countless times that a test pilot has saved the aircraft/spacecraft from destruction. If it was unmanned and flown by computer, it would have been a fireball. At least one shuttle flight would have been lost if the crew didn't fly manually to correct for a malfunction. STS-4 PIO'd on landing and would have crashed if auto-stabilization wasn't overridden by the pilot.

not in this case. They should have more than one rocket craft for testing. it's ok to fly reciprocating and jet prototypes because Scaled has experience with hundreds if not thousands of those kinds of aircraft, and it's easy to bail out at 200mph. It's much harder to bail out at Mach 3 and 100k ft.

Re: SpaceshipTwo crashes shortly after Mojave test flight

#303

Post by seanflyon »

ghostunit wrote: post #269
seanflyon wrote: post #233

Earlier quoted context omitted.

> basic hard laws such as the speed of light, the laws of thermodynamics, etc. say NO This is not true. For travel within the solar system the speed of light is no more than a nuisance delaying communication. The laws of thermodynamics don't stop space travel. No one is saying "we always find a way" to do the impossible. We are saying "we always find a way" to do that thing that we already know how to do and have dem…

a) Travel within the solar system? where do you want to go live, Mercury, Venus? Mars is almost as worthless too, its gravity is 1/3 Earth's. Can't live there for long. b) We just need to make it cheaper? how, exactly, are you going to get up there except by burning obscene quantities of solid (fossil) fuel, as we do now? That's where the thermodynamics things comes in play: you have to pay the energy cost, there's n…

a) Mars.Your notion that humans cannot survive for long in 1/3 gravity is interesting. While it has not been proven that we can live long and healthy lives in 1/3 G, many very intelligent and informed people believe we can. Do you have a particular reason to believe we cannot?

b) You have to pay the energy cost but that is not the hard part. Fossil fuels are finite, but we don't need to use fossil fuels and even if we did setting up a civilization on mars would take a tiny portion of earth's fossil fuels. We are not going to run out of hydrogen as long as we have the energy to split water and plenty of energy hits the earth in the form of sunlight every day, not to mention fission or fusion.

So no, the laws of thermodynamics are not the problem. We "just" need to make it cheaper.

Re: SpaceshipTwo crashes shortly after Mojave test flight

#304

Post by kashkhan »

fnordfnordfnord wrote: post #129
kashkhan wrote: post #109

Earlier quoted context omitted.

there's no need not in this day and age to have test pilots. If they use computers, they can debug the engine in flight conditions by running maybe ten times as many test flights. Delays of months between flights are dangerous. Until you have a 1000-10,000 flights to build up operational data and envelope, this is a death trap causing unnecessary deaths.

>there's no need not in this day and age to have test pilots. Good point. What does the FAA say about unmanned rocket powered flight tests?

plenty of companies do them. Ask Elon Musk.

Re: SpaceshipTwo crashes shortly after Mojave test flight

#305

Post by marze »

lotsofmangos wrote: post #286
marze wrote: post #243

Earlier quoted context omitted.

Well you could be right, but it is very hard to imagine that being true since the plastic hybrid has only been tested once on the ground. Doing a flight test so soon would be totally insane. In any case, the disaster was undoubtably a result of inadequate ground testing. Problems like these are almost always the result of management pushing things faster than the engineering progress warrants.

Officials decided this spring to modify the space plane’s rocket motor to use a different type of fuel. Instead of burning a rubber-based fuel mix known as HTPB used on SpaceShipOne and SpaceShipTwo’s initial test flights, Virgin Galactic selected a new propellant grain known as polyamide which officials said offered improved performance. “This was a new fuel formulation that had been proven and tested on the ground…

Let us hope for Virgin's sake that "many times" doesn't mean six times for ten seconds each.

I have heard of one long duration test on the plastic fuel reported by the "Virgin watchers" in Mojave, so unless they are doing long duration tests somewhere else it doesn't seem like much. Rocket engine testing is extremely noisy so long duration tests are quite noticeable.

Re: SpaceshipTwo crashes shortly after Mojave test flight

#306

Post by kashkhan »

TrevorJ wrote: post #257
kashkhan wrote: post #109

Earlier quoted context omitted.

there's no need not in this day and age to have test pilots. If they use computers, they can debug the engine in flight conditions by running maybe ten times as many test flights. Delays of months between flights are dangerous. Until you have a 1000-10,000 flights to build up operational data and envelope, this is a death trap causing unnecessary deaths.

Did you know an F1 car can drive itself around the track? It seems like there's something in human nature, at least among some people that leads them to want to drive the thing themselves.

not today's F1 car. They don't have auto trans, auto steering or auto brakes. Yes they could and audi has been testing an unmanned race car that does round a track, but there is a little chance that an F1 engine will blow up and kill the driver.

Re: SpaceshipTwo crashes shortly after Mojave test flight

#307

Post by marze »

prof_hobart wrote: post #203
marze wrote: post #69

Earlier quoted context omitted.

Some say this is an "inevitable" result of pushing boundaries. No. This is the result of a poorly managed program. What they are doing is much easier than the Apollo program, which was well managed and had no in-flight failures that resulted in loss of life, while accomplishing an infinitely harder task. This is a tragedy, obviously. But the program is about six years behind schedule, been going for 10 years. The mos…

>Seeing only the first paragraph, I already know that some rubber in the hybrid engine detached blocking the nozzle and causing the whole engine to explode. Can I ask how? What is in there that tells you that?

Sure: intuition, not anything in that paragraph besides the simple fact that the vehicle destroyed itself during rocket powered flight.

You've got a hybrid motor, it's flown a number of times. You have a program that has been going for years but still hasn't got the motor design finalized due to unknown (to us) problems. Failure modes that could destroy the vehicle include things like pressurized oxidizer tank failure, burn-through of the nozzle, burn-through of the main combustion pressure vessel, blocking of the nozzle by unburned solid fuel chunks causing over-pressure failure, and the like. The last one seems most likely, since it's likelihood is modified by modifications to the fuel (which is what they are probably changing, as opposed to the nitrous system or structure or nozzle).

Obviously no one knows for sure yet.

I'd love to see civilian spaceflight become a reality, so this is an unfortunate setback. I hope Virgin will be able to take the time to get it right. I hope they will look back at this accident the same way the Apollo program viewed the Apollo 1 fire, as a much needed chance to fix a lot of potential issues that needed fixing that were thought to have contributed in a fundamental way to the lack of subsequent in-flight failures.

Re: SpaceshipTwo crashes shortly after Mojave test flight

#308

Post by lotsofmangos »

Steko wrote: post #262
marze wrote: post #243

Earlier quoted context omitted.

Well you could be right, but it is very hard to imagine that being true since the plastic hybrid has only been tested once on the ground. Doing a flight test so soon would be totally insane. In any case, the disaster was undoubtably a result of inadequate ground testing. Problems like these are almost always the result of management pushing things faster than the engineering progress warrants.

Virgin has to get Brandon to space this year or their funding is subject to considerable clawback.

Do they still get to keep the funding if he returns?

Re: SpaceshipTwo crashes shortly after Mojave test flight

#309

Post by PavlovsCat »

ceejayoz wrote: post #231
PavlovsCat wrote: post #225

Earlier quoted context omitted.

That's great; but Mars, and even the solar system, is not "the universe".

I suspect we're likely to solve greenhouse gas emissions long before we're able to get humans out of the solar system.

The one easy option, voluntary restraint, isn't even on the table, not that I noticed. So what makes you think that's so likely, what about our current priorities and behaviours makes you so optimistic? Where is the economic incentive to solve the problem? Sure, it means more long-term life and profit, but having even 1% less quarterly profit so that in 1000 years some other company can exist at all is not exactly how we do things around here. Instead companies invested in fossil fuels are happily funding "global warming skeptics".

That proverbial man who plants trees knowing he will never sit in their shade is proverbial for a reason.. it's an amazing and heartwarming little saying because it's a contrast to how we generally behave, as individuals as well as organizations and masses. We learn from repeated catastrophe.. sometimes, maybe. But this problem is not one we can have a lot of attempts at solving. Right now we are still moving into the wrong direction, and probably even accelerating.. sure, hitting a wall can make people change their direction, but not if it breaks their neck, so to speak.

Re: SpaceshipTwo crashes shortly after Mojave test flight

#310

Post by melling »

Turing_Machine wrote: post #245
melling wrote: post #148

Earlier quoted context omitted.

Perhaps, you haven't noticed but I'm using this accident to discuss our national space program. Virgin Galactic has a plane that goes to 62 miles/100km. While this is great, in the short-term, it doesn't help our space program. Btw, you don't think they need to revisit safety to assure their customers that it's not a one way trip? Do they even have a second plane? There's not a chance that there will be a commercial…

"Btw, you don't think they need to revisit safety to assure their customers that it's not a one way trip?" Not from what I'm seeing. No one is planning to cancel their reservation. I wouldn't, if I had one.

Ok, let's revisit in 2 years to evaluate the setback this event turned out to be. Perhaps I'm overstating it.

By the way, the spacecraft cost $500 million.

http://money.cnn.com/2014/10/31/technology/virgin-galactic-s...

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