SpaceX McGregor Testing Updates and Discussion THREAD 1

[mustang1]

Any experts here on multiple engine packs?

I guess Soyuz had a number of thrust chamber (32 or more) but not more than 4 next to each other? And spacex did test the M1d on its own so....perhaps its due to the all-up nature of the testing.

I was wondering if variable throttling of different engines can setup up unexpected acoustic standing waves, causing some vibration failure that would be pretty hard to model...Another alternative that one of the engines ingested something within the tank is probably pretty slim at this stage right?

[Lars_J]

It would be interesting to see a video with the sound re-synced with the video. (Compensating for the apparent light/sound speed difference)

[manboy]

Can someone save this video in case they decide to pull it?

Done. Just tell me where to upload it.

[Lurker Steve]

Boss: Man 1 and Man 2, you are fired!

I doubt that would help resolve the issues with why this test failed to run to completion.

Sometimes, after working a long week, and getting called in over the weekend, you just need to speak your mind. I'm sure that they didn't know that SpaceX was going to make their comments public before they made them.

[grakenverb]

Anybody care to transcribe what was said at the end?

"Everything here sucks" is what I heard.

Man 1: Laughing

Man 2: "It fell apart."

Man 1: "Everything pretty much sucks."

Man 2: "Yea."

They could have been talking about anything, really.   Perhaps the first guys cigar fell apart. Maybe his marriage fell apart.  Who knows? 

[R7]

Boss: Man 1 and Man 2, you are fired!

I doubt that would help resolve the issues with why this test failed to run to completion.

True. Just surprised such comment made it into published video.

Captured a few (15...) frames in high res, here a few samples and all of them zipped.

[robertross]

Boss: Man 1 and Man 2, you are fired!

I doubt that would help resolve the issues with why this test failed to run to completion.

True. Just surprised such comment made it into published video.

Captured a few (15...) frames in high res, here a few samples and all of them zipped.

thanks for the captures (can't get Youtube links at work)

Sparks = bad sign (for the engine usually).
This is why we (they) test.

[pippin]

Yea. Better see that on the test stand than with a payload on top of it

[JBF]

Yea. Better see that on the test stand than with a payload on top of it

Still, it was a nice shutdown, no giant kaboom.

[rcoppola]

With regards to the new thrust structure, octoweb engine alignment, I wonder how base / engine heating, acoustics and flow dynamics have behaved in the real-world as opposed to the models?

[aero]

Anybody else think they might have had a LOX pump cause a test abort then pump pieces sticking in the LOX shutoff valve? Just a WAG.

[GalacticIntruder]

At the 1.50 mark the camera person started zooming in. Did that person see something, or was expecting something or it was just a coincidence?

[cambrianera]

One thing that underwent a deep change is the piping feeding the 9 merlins.
This makes also a big difference with single engine test stand.
I wonder if the reduced space available in the new, shrinked engine bay has caused a non optimal design of the piping with the associated problems (cavitations, loss of pressure, turbulence & others).

[LouScheffer]

With regards to the new thrust structure, octoweb engine alignment, I wonder how base / engine heating, acoustics and flow dynamics have behaved in the real-world as opposed to the models?

According to this ( http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110015765_2011016629.pdf ), base heating and flow dynamics are not likely problems at sea level.  "At low altitudes where the ambient pressure is relatively high, the plume expansion ratio is small and the overexpanded or slightly underexpanded rocket plumes do not interact with each other. This causes the free stream air to be entrained by the supersonic rocket plumes from the edge of the base and exit between the nozzles. This leads to a decrease in the base pressure and base heating with respect to the ambient atmosphere."

One thing that underwent a deep change is the piping feeding the 9 merlins.
This makes also a big difference with single engine test stand.
I wonder if the reduced space available in the new, shrinked engine bay has caused a non optimal design of the piping with the associated problems (cavitations, loss of pressure, turbulence & others).

This seems more plausible to me, though this is pure speculation.  It's easy to imagine a pipe breaking after a few minutes of shaking that was harder than anticipated, whereas you'd expect thermal problems to show up earlier, like to previous 10 second abort.  Also this would account for a fire and glowing engine parts, since you have a pressurized tank above and (I think) no valve upstream.

[SebastianB]

Has anybody thought about that the bright pieces just might be ice from the tank? The shutdown might have caused some shock that loosened the ice. Maybe the ice was on the sloped sides of the cap that is on top of the LOX tank instead of the interstage.

[mrmandias]

Has anybody thought about that the bright pieces just might be ice from the tank? The shutdown might have caused some shock that loosened the ice. Maybe the ice was on the sloped sides of the cap that is on top of the LOX tank instead of the interstage.

Possible, although I think we can assume that the test wasn't *completely* successful, or SpaceX would have said something (unless they are having problems elsewhere, like with the fairing, and don't want to focus attention on them by making it clear that the engines and octoweb are ready to go).

[Lars_J]

Has anybody thought about that the bright pieces just might be ice from the tank? The shutdown might have caused some shock that loosened the ice. Maybe the ice was on the sloped sides of the cap that is on top of the LOX tank instead of the interstage.

Possible, although I think we can assume that the test wasn't *completely* successful, or SpaceX would have said something (unless they are having problems elsewhere, like with the fairing, and don't want to focus attention on them by making it clear that the engines and octoweb are ready to go).

Huh? That seems like a leap. For all we know there was no serious problem. Does Elon make a habit out of tweeting videos of tests that are failures?  There seemed to be an early abort (why else not go for full 3 minute duration), but I think people are taking the speculation a weeee bit too far when they propose that chunks of engines fell out.

What I found interesting in the video is how "clean" the exhaust looked... Sure, plenty of smoke at the beginning, but at the 20 second mark most of that was gone, and we could clearly see the water tower on the other side. But perhaps that is typical of KeroLox firings at night.

[cambrianera]

Has anybody thought about that the bright pieces just might be ice from the tank? The shutdown might have caused some shock that loosened the ice. Maybe the ice was on the sloped sides of the cap that is on top of the LOX tank instead of the interstage.

Possible, although I think we can assume that the test wasn't *completely* successful, or SpaceX would have said something (unless they are having problems elsewhere, like with the fairing, and don't want to focus attention on them by making it clear that the engines and octoweb are ready to go).

Huh? That seems like a leap. For all we know there was no serious problem. Does Elon make a habit out of tweeting videos of tests that are failures? 

There seemed to be an early abort (why else not go for full 3 minute duration), but I think people are taking the speculation a weeee bit too far when they propose that chunks of engines fell out.

Sorry but the "sparks" are coming from the engine bay, and the splash they do on the flame deflector doesn't match with ice.
The puff of black smoke coming out the base of the tank (same time as the "sparks") seems really a bad sign for the status of at least one of the engines.

[cambrianera]

One thing that underwent a deep change is the piping feeding the 9 merlins.
This makes also a big difference with single engine test stand.
I wonder if the reduced space available in the new, shrinked engine bay has caused a non optimal design of the piping with the associated problems (cavitations, loss of pressure, turbulence & others).

This seems more plausible to me, though this is pure speculation.  It's easy to imagine a pipe breaking after a few minutes of shaking that was harder than anticipated, whereas you'd expect thermal problems to show up earlier, like to previous 10 second abort.  Also this would account for a fire and glowing engine parts, since you have a pressurized tank above and (I think) no valve upstream.

Yes, it's pure speculation.
But 50% more flow compared to 1C, the new reduced engine bay and the new TPA, fully swinging with the CC (on 1C the TPA was following only one degree of freedom of the CC) gives much more constraint on the piping.

[sittingduck]

I thought it was understood that the Merlin 1D produces a large amount of sparks after firing.

http://www.youtube.com/watch?feature=player_detailpage&v=Jh1JKWQDTp4#t=27s


At 0:27 there is clearly a large amount of "sparks" exiting the nozzle.