Talk-Polywell.org

krenshala wrote:I haven't seen anything concrete, but I read that there was a change to one of the stages that made it heavier, which may have contributed to the failure. I haven't seen more about that, however, so I'm not sure how accurate that is.

If accurate it raises serious questions about the structural margins.

Looks like the change was to the engines on the second stage. So far nothing from the media I've read indicates the change is suspected of being part of the problem. From my take on the videos it looks like a first stage engine spontaneously disassembled, damaging the other first stage engines to the point it lacked sufficient thrust to continue upward.

". . .spontaneously disassembled. . ."?

I thought they were ad-libbiing the whole tail-landing thing and neglected the point that you want to use those kinds of rockets again and again. Reminds of a SeaLaunch/Zenit Intelsat 27 failure. Anyone know off the top of their heads what the Zenit and Antares have in common? I think the Zenit actually shut down and this was not a shut down, but still makes me curious.

GIThruster wrote:". . .spontaneously disassembled. . ."?

As far as I know this is a commonly used euphemism for "... and then the durned thing blew up!" I've normally seen it used as "spontaneous self disassembly", usually followed by "lithobraking".

Yes, I've seen the euphemism before, as well as "spontaneous decomposition".

I've seen "rapid unscheduled disassembly", which on the NSF forum is often abbreviated RUD.

Whatever you call it, combined with the earlier test stand failure, this is kinda worrying. But of course the thing to do in these cases is hold off making any hasty judgments until the accident investigation comes up with a root cause...

Possibly premature, but it seems I heard that the rocked was purposely self destructed. The actual failure then did not cause the fireball. The videos are hard to interpret, but there did seem to me to be some hesitancy in the assent. I speculate that one of the first stage engines lost thrust, and there was not enough reserve thrust available to continue the mission. Elon Musk has pointed out that this is one of the advantages of the Falcon 9. If one engine loses thrust/ has to be shut down, the remaining eight can complete the launch. I'm not sure how the statistics work out. With nine engines with a predicted mean time to failure of each engine, the occurrence of a failure is more frequent, but with the reserve...

The same applies to one engine versus two engine jet fighters or other rockets, like Apollo 13. One engine of the second stage failed, but the burn was successfully completed by burning the remaining four engines longer. Of course there was then that pesky problem with one of the fuel cells. The Russians are fond of sticking a large number of rocket engines on their older launchers. I wonder how many single engine failures they have had with successful mission completion?

Dan Tibbets

The flight was terminated via control. (they blew it up) the reason is still clouded in mystery thrust loss is presumed.

Executing a "Flight Termination" made little difference. With loss of thrust due to a catastrophic engine failure, lithobraking was inevitable, at which point the fuel and oxidizer tanks burst and you get the same result. The idea of flight termination is to make this happen sooner rather than later, without the vehicle going off in some random direction and toasting something even more valuable.

Lindbergh had a comment (or maybe it was Jimmy Stewart playing Lindbergh), that one engine was better than 2 or 3 because the planes at the time with 2 or 3 engines could not complete a transatlantic crossing with one engine out, and adding engines just increased the odds that one would quit. You could make the same argument for a 2-engine booster. The outcome is different with 9 engines, providing the spontaneous disassembly does not take out adjacent engines.

Falcon 9's have lost engines during launch before, and successfully made orbit.

Keep your expectations low for Falcon 9 tail landings.

1) Musk thinks he has pretty good odds that one attempt to soft land might work out of the next 8 launches.

2) If you're hoping for a spectacular fireball on the failures, the premise is that the rocket is almost out of fuel.

While watching the video, I could swear I heard "thrust, nominal" just before the unit jerked and started to fall.

KitemanSA wrote:While watching the video, I could swear I heard "thrust, nominal" just before the unit jerked and started to fall.

That is what I hear as well.

KitemanSA wrote:While watching the video, I could swear I heard "thrust, nominal" just before the unit jerked and started to fall.

Probably, as I suspect the clamps holding the rocket down are not released till telemetry indicates both liquid fueled engines operating normally with full thrust built up. This is different from solid boosters where it is goodby once the solid rocket is lit. This happend once with the shuttle. The main engines were started, an anomaly was detected before the solids were lit, so the launch was aborted.

Also, any verbal output probably lags at least several seconds behind what is actually happening.

Dan Tibbets

Virgin Galactic just suffered a crash.

http://www.msn.com/en-ca/news/techandsc ... ar-BBce4g4

exploded mid-air. Pilot severely injured. Co-pilot dead.

'Exploded' was still unconfirmed as of my last reading at NSF. E.G. some other problem triggered loss of control and breakup..

I personally don't get much confidence from VG as a non-engineer bystander, but the more mainstream potential consequences of this are a bit concerning, IMHO.