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SpaceshipTwo crashes shortly after Mojave test flight

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Re: SpaceshipTwo crashes shortly after Mojave test flight

#131

Post by melling »

Turing_Machine wrote: post #102
melling wrote: post #78

Earlier quoted context omitted.

Is that your opinion, or do you have some facts to support that statement? As part of the program, we should be building better machines and not crawling along at 12 inches a day, of course.

Well, sure. Just look at all the jobs that are still being done by humans. Even fairly simple and formulaic jobs like working in a fast food restaurant are still in the human domain (that may be starting to change, finally, but it hasn't happened yet). For that matter, look at the problem of operating an autonomous vehicle right here on Earth. Everyone from DARPA to MIT to Carnegie-Mellon to Google has been working o…

The Google Space "Car" won't need a license on Mars. If it wrecks after 6 months, we send another. The idea is that sending machines is cheaper, and when things go wrong, it's not as much of a big deal.

That's why I keep emphasising developing the machines and sending them.

Re: SpaceshipTwo crashes shortly after Mojave test flight

#132

Post by erobbins »

JshWright wrote: post #54
JanSolo wrote: post #48

Earlier quoted context omitted.

You are right. Hybrid engines are not looking like the safe & reliable middle-ground between solid & liquid engines that they were made out to be.

"The best of both worlds" has an often overlooked twin sibling.. "The worst of both worlds"

all the performance of solids with all the complexities of liquids!

Re: SpaceshipTwo crashes shortly after Mojave test flight

#133

Post by diminoten »

zepolud wrote: post #31

Test pilots? In the 21st century? I find it absolutely reckless and inexcusable to require live humans riding on a prototype rocket when you have all the processing power needed to automate/remote manage the vehicle literally in your pocket. EDIT: To those downvoting, you should really check that all current spaceplanes have the capability to fly and land autonomously--Boeing X-37, Dream Chaser, even Buran was fully…

At some point you need to put people in those ships, and at some point you need to put test people in ships you eventually want to put people into.

Where is the line?

Re: SpaceshipTwo crashes shortly after Mojave test flight

#134

Post by JoeAltmaier »

atlantic wrote: post #120
JoeAltmaier wrote: post #100

Earlier quoted context omitted.

There's no reason for everybody to stay home and do housekeeping, then there's a big beautiful universe out there. Dare to dream big!

If we can't even save our own home world, there is every reason to believe that we will do damage elsewhere. That being the case, best to stay home until we grow up a bit.

The rest of our solar system is rocks. Hard to do much damage there. Anything we do has to be for the better (oxygen, water, life).

Re: SpaceshipTwo crashes shortly after Mojave test flight

#135

Post by crikli »

kashkhan wrote: post #109
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…

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 pilot steps into an untested craft for the first time, the "unknown" area of the envelope is better quantified; in different words, we have a better idea of how much of the performance envelope is unclear.

Yet that unknown area still exists and has to be discovered by actual human test pilots because as good as computerized testing is there still isn't 100% coverage.

(I'm a pilot and have dealt with experimental aircraft. Not on the level of this project, of course, where the envelopes of technology are being pushed, but on the level of small private aircraft where the technology is in many cases half a century old, well understood, debugged, and still has to be tested. By a human.)

Re: SpaceshipTwo crashes shortly after Mojave test flight

#136

Post by jobu »

ggreer wrote: post #28
JanSolo wrote: post #18

This is very bad. Not just for the family and friends of the poor guy who died, but for commercial manned spaceflight in general. SpaceshipTwo is considered the 'simplest' and 'safest' of all the upcoming manned commercial vehicle. It has many features that should help keep it reliable. For example, instead of a real liquid rocket engine, it uses a hybrid engine; it has almost no moving parts apart from a valve or tw…

The engine has been the bane of SS2. The original rubber/N2O design was problematic enough that Virgin switched from rubber to a plastic. Apparently this was the first powered flight to use the new fuel. While the design lacks complicated turbopumps and cryogenic fuels, it does have one drawback: the N2O is contained in a pressure vessel. If that tank is damaged while still full (or close to), bad things can happen.

Looking more into their design turns up all sorts of issues with nitrous oxide as a propellant. It's used all the time in dentist offices, so it's easy to misunderstand as an innocuous gas. At higher pressures and relatively normal temperatures it can go supercritical and become very, very volatile. At that point it's an even better solvent than supercritical CO2, and still a very strong oxidizer:

http://www.knightsarrow.com/rockets/scaled-composites-accide...

http://www.dtic.mil/dtic/tr/fulltext/u2/a489459.pdf

(In that Air Force research lab report there's mention of supercritical N20 causing a spontaneous explosion with coffee grounds.)

Re: SpaceshipTwo crashes shortly after Mojave test flight

#137

Post by smackfu »

untog wrote: post #45
smackfu wrote: post #36

Earlier quoted context omitted.

Yeah, "rocket" + "safe enough to carry tourists regularly" just seems like a difficult combination.

Many years ago, trying to combine "flying in the air" with "safe enough to carry tourists regularly" would be seen in a similar light.

Fair point, but the failure modes of flying seem to be more addressable than those of rockets. Like if the airplane engine is essential, add enough that you can tolerate a failure. If control surfaces are essential, add redundant systems. Whereas the failure mode of rockets tends to be exploding, and that's pretty hard to mitigate.

Re: SpaceshipTwo crashes shortly after Mojave test flight

#138

Post by riffraff »

rdtsc wrote: post #118
JanSolo wrote: post #18

This is very bad. Not just for the family and friends of the poor guy who died, but for commercial manned spaceflight in general. SpaceshipTwo is considered the 'simplest' and 'safest' of all the upcoming manned commercial vehicle. It has many features that should help keep it reliable. For example, instead of a real liquid rocket engine, it uses a hybrid engine; it has almost no moving parts apart from a valve or tw…

Well Soyuz still flies and has exceptionally low human fatality rates in the last decades. So if safetey realiability is desired it could be just "buy a ride on a Souyz" for now. I think it won't be that dire. People who sign up to fly into space on a new design would probably be aware of the risks involved. Many people still climb Everest, dive into caves, and jump from clifs with wingsuits. I think there won't be a…

AFAIR there is an order of magnitude of two between the prospected prices of virgin galactic and a soyuz trip.

Re: SpaceshipTwo crashes shortly after Mojave test flight

#139

Post by jMyles »

mixmax wrote: post #23

What this weeks events show us is that space travel is hard. Really hard. Most systems operate in extreme conditions, sometimes bordering on the improbable. Thousands, sometimes millions of horsepower in an engine smaller than a car, cryogenic liquids at -200 degrees celsius cooling a nozzle that is 3000 degrees celsius 5 millimeters away, heatshields designed to absorb obscene amounts of heat, the list just goes on…

> We wouldn't have explored the depths of the ocean.

We mostly still haven't! I think ocean exploration is pretty exciting too.

Re: SpaceshipTwo crashes shortly after Mojave test flight

#140

Post by ceejayoz »

revscat wrote: post #94
ceejayoz wrote: post #83

Earlier quoted context omitted.

> Space travel is awesome, but so is living, and right now we are not living in a way that is sustainable over the short term. Space travel is fundamental to the human species living sustainably in the long term. Correcting greenhouse gasses doesn't help us if the next day we find a planet-killer asteroid is a few weeks away.

While true, it is also not as direct of a threat. CO2 is affecting us now , whereas asteroids, etc., are (thankfully) only possibilities. Serious ones, to be certain, but not immediately threatening. CO2 is a direct and immediate threat.

Humans as a species will survive CO2, though, whereas asteroids conceivably can go from "not immediately threatening" to "Earth will be destroyed in a few years" without warning.
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