Investigating the SpaceX Rocket Explosion of September 1, 2016

[CalcNerd]

I see a vent burst at 66.56 at the midway spot of the rocket, on the opposite side of the explosion. This would support the idea of a fuel leak. Also, it would mean the actual ignition may have happened earlier than the actual catastrophic explosion some 4-5 seconds later. It is a white puff jetting out from the lower midpoint seam between the first and second stage rockets.

 

[mfb]

SpaceX seems confident to have everything sorted out (and a working launch pad) until November:

SpaceX President Shotwell: We anticipate return to flight in November, meaning down for three months. Next flight from CCAFS, then to VAFB.

Source

CCAFS could be either the damaged launch pad or the new one they are currently preparing for Falcon Heavy. VAFB is an independent launch site in California.

Edit: More tweets. 1, 2

SpaceX's Shotwell: Nov return to flight is our best hope. We still haven't isolated the cause or whether its origin was rocket or ground.

SpaceX's Shotwell: We have been told that the Sept. 1 anomaly will not affect Falcon 9's insurance rates. So we expect no impact.

 

[liometopum]

SpaceX still does not know the cause. This article just appeared, from Nature World News, dated Sep 13, 2016 04:10 AM EDT

http://www.natureworldnews.com/arti...osion-most-difficult-complex-failure-ever.htm

 

[GeorgeDishman]

I wouldn't want to speculate on a cause but from the video, the centre of the fireball in the frame at 71.73 seems to coincide with vapour venting from a vertical tube alongside the craft, not internal. That venting is seen from time 49.86 but it already in progress, there is a fade of the video between 49.35 and 49.86 where the onset of the venting has been edited out. It looks as though there was a much lower rate prior to that. It's fairly obvious though so presumably must be part of the plan.

 

[Greg Bernhardt]

What I want to know is why there aren't super high res cameras covering the launch pad? All I've seen is grainy photos and video.

 

[GeorgeDishman]

The videos above are available in 1080p60 but the default is much lower.

 

[Greg Bernhardt]

The videos above are available in 1080p60 but the default is much lower.

Still very weak when we're talking Elon Musk level.

 

[mfb]

What I want to know is why there aren't super high res cameras covering the launch pad? All I've seen is grainy photos and video.

Maybe they have that. Who knows?

Cameras tend to be far away to survive the rocket firing, so getting a good resolution is challenging.

 

[Greg Bernhardt]

Cameras tend to be far away to survive the rocket firing, so getting a good resolution is challenging.

You know better than me, but c'mon, this is space age stuff and Elon Musk. I've seen spy satellite footage better than what I've seen. In this thread are we just seeing footage from visitors watching?

 

[jim hardy]

m, that is not a piece flying away. Go to 71.94 and look at the point at the bottom left hand corner, and then click until about 72.54. You will see the point go to the top right corner. I think that is a jet taking off from a nearby airport.

Good Eye !

I missed that.

 

[jim hardy]

On that sort of time scale? I think it's a bug flying past the camera.

at highest resolution there's several of them, some appearing for only one frame.
makes one wonder if this camera's sensor makes a true instantaneous capture or if the pixels are scanned sequentially, like old fashioned kinescope

If:
these are something real not an electronic artifact, and they're the same thing,
it was behind the fireball for two scans
are they some really fast moving things , or 'bad pixels' ?

 

[RonL]

I did see a couple of what appeared to be bugs, but everything else that wasn't shrapnel, I tend to think was bird movements, especially after things settled down a bit.

 

[mfb]

it was behind the fireball for two scans

You don't see small dark objects in front of very bright objects well with a camera.

 

[.Scott]

I think it's interesting that although the initial flash of flame and smoke expands rapidly, the expansion is in a sideways direction and the rate of expansion seems to be rapidly decelerating.

As I said in a previous post, I believe this is due to the fire starting in a contain space (the interior of the rocket) and bursting out. It's the only explanation I can see for the flames propagating in those first couple of frames much faster that a flame propagation front. Burning material - a fuel and oxidizer mix - must have been ejected through the side of the rocket, bursting along a horizontal seam.

 

[Jonathan Scott]

As I said in a previous post, I believe this is due to the fire starting in a contain space (the interior of the rocket) and bursting out. It's the only explanation I can see for the flames propagating in those first couple of frames much faster that a flame propagation front. Burning material - a fuel and oxidizer mix - must have been ejected through the side of the rocket, bursting along a horizontal seam.

I don't think that idea works, because the fuel and oxidiser are in separate tanks which are kept apart by a barrier which goes right across the 2nd stage, so it would not be possible for a significant amount to get mixed inside, especially together with a source of flame, unless something else had already gone wrong first.
I think that the second stage must have burst open just BEFORE any fire started, in a way which released both fuel and oxidiser, which subsequently caught fire. The only energy source I think could cause a sudden rupture that bad is that the helium pressure vessel inside the tank failed abruptly. I do not think a failure in either the oxidiser or fuel containment would have been able to create a large amount of mixed fuel and oxidiser so rapidly.

 

[mfb]

What would be wrong with a small explosion inside the rocket, quickly bursting the hull (which is not designed to handle significant pressure) for a fast initial expansion?

 

[Jonathan Scott]

What would be wrong with a small explosion inside the rocket, quickly bursting the hull (which is not designed to handle significant pressure) for a fast initial expansion?

I think you'd need quite a significant explosion inside the 2nd stage to push out enough oxidiser and fuel in a short enough time. Neither oxidiser nor fuel on its own will release chemical energy. Even if the LOX were heated locally by an electrical short (as in Apollo 13) I don't believe the expanding gas would have enough energy to cause that much damage that quickly. As I said before, there is a helium pressure vessel in the LOX tank which contains a lot of mechanical energy which could easily destroy the stage in a fraction of a second if it failed, so I think that's the most likely scenario.

 

[Jonathan Scott]

Given that there was a previous failure related to the helium pressure vessel, I might speculate that now that they have ensured that the support struts are strong enough, there might also be a problem with the way in which the supports, valves or other attachments are fixed to the tank, such that forces due to mechanical contraction or buoyancy during oxidiser loading caused the pressure vessel to rupture.

 

[jim hardy]

What single failures would release both fuel and oxidizer( or the ignitor fluid ) at the same time ?

Unrelated - is there a link to a "sequence of events " printout from telemetry ?

 

[nikkkom]

Dedicated spaceflight forum has some 56 pages of discussions already:

http://forum.nasaspaceflight.com/index.php?topic=30981.0

 

[jamalkoiyess]

What is this mist that get out of the top and the bottom at the very beginning and till the explosion? Is that liquid nitrogen ? And what is it used for ?

 

[.Scott]

What single failures would release both fuel and oxidizer( or the ignitor fluid ) at the same time ?

Unrelated - is there a link to a "sequence of events " printout from telemetry ?

The LOX burning through the metal until it reaches the RP. Maybe something that catalyzed the metal oxidation? Maybe something that heated up a spot on the metal? Maybe a material on the surface of the LOX tank that became exposed to high O2 gas concentration?

... or there was a fault in the Flight Termination System?

 

[.Scott]

What is this mist that get out of the top and the bottom at the very beginning and till the explosion? Is that liquid nitrogen ? And what is it used for ?

It's water vapor - condensed out of the air by cryogenic liquids.

 

[.Scott]

Dedicated spaceflight forum has some 56 pages of discussions already:

http://forum.nasaspaceflight.com/index.php?topic=30981.0

Excellent forum. Here is a graphic from reply #751 in that thread.

The point is that the initial "explosion" seems to be aligned with the "common bulkhead", the divider between the 2nd stage LOX and RP tanks.
Several posters in that thread have cited the very energetic blast seen in the first couple of frames as evidence that the source must have been from within the rocket. Although none have specifically mentioned the frame propagation issue.

 

[liometopum]

Here is an X drawn on the first frame of the explosion to match the X of light produced:
ll

 

[liometopum]

Here is where the X is located on the rocket before the explosion (the last frame before explosion). Using the X of light places the point slightly higher than in the image .Scott posted.

 

[jamalkoiyess]

It's water vapor - condensed out of the air by cryogenic liquids.

And what is it's role

 

[jamalkoiyess]

Does anyone have any information about the distance between the camera and the rocket and how much time did the sound take to arrive ?

 

[GeorgeDishman]

The point is that the initial "explosion" seems to be aligned with the "common bulkhead",

Why is everyone assuming the cause was in the rocket? The crosses marked also coincide with the bottom of the dark pipe between the main gantry and the outer casing which is clearly venting something. This image is the last before the explosion. If that vented material was coming from the gantry and detonated, blowing a hole in the side of the craft (it is designed for internal pressure, not external), then who is responsible for the gantry and launch facility?

 

[nikkkom]

Why is everyone assuming the cause was in the rocket?

"Everyone" is not assuming that. In fact, to me it looks like less than half of the theories put forward so far are "blaming" the rocket.

If that vented material was coming from the gantry and detonated, blowing a hole in the side of the craft (it is designed for internal pressure, not external), then who is responsible for the gantry and launch facility?

F9 doesn't have any cryogenic or volatile fuels onboard. It uses RP-1 (a refined grade of kerosene). The visible white venting should be cold oxygen (likely boil-off from LOX tank).
As to "who is responsible for the gantry and launch facility": SpaceX operates its own pad. It does not subcontract launch ops.