SpaceX News

[krenshala]

To me, that implies the station collided with something.

[ladajo]

Or, it had a positioning thrust misfire.

I recall the same kind of speculative drama around Skylab.

[paperburn1]

http://www.reuters.com/article/spacex-b ... SL2N1BZ1AF

Another tank failure?

[DeltaV]

Soooo, that rules out the fan as a propulsor during dash, right?

A supersonic dash by an object a meter or two high near the pad is ruled out by the lack of a sonic boom on the audio recording. It would be much louder than a rifle shot. I don't think the microphone could miss it, and it would be distinctive.

Perhaps an array of these was used:

[kunkmiester]

K.I.S.S it people. Anyone with half a brain would see the idea of a million dollar drone (probably what it would take for all that crazy stuff) chopped off early by Occam's Razor.

[ladajo]

That is always the trouble with propaganda or conspiracy theories; They seek to obfuscate the obvious.
Most fall apart quickly if one can take a step back from immersion, and apply actual reason, vice emotion. See Rossi, et. al.

[DeltaV]

I'm theorizing about technology, not conspiracy.

[Giorgio]

I'm theorizing about technology, not conspiracy.

Except that your "technology" is generally base on unavailable technology, theoretical technology or science fictitious technology. Should be wise to investigate and stick to realistic potential issues before wandering in such scenarios that add nothing to this thread.

[Tom Ligon]

Well, heck, this cause sounds familiar. Keep in mind it is preliminary, and they don't yet know why it failed.

The liquid helium tank in the second stage LOX tank apparently failed catastrophically. Just sitting on the pad!

http://www.space.com/34187-spacex-falco ... line+Feed)

[Giorgio]

The liquid helium tank in the second stage LOX tank apparently failed catastrophically. Just sitting on the pad!

It will be quite interesting to understand if it was a sudden failure (most probable cause) or a constant leak that generated an unregulated over-pressure in the LOX tank (less likely). The LOX tank in the second stage is about 60 M3 volume and a 0.5 M3 Liquid Helium Tank stores 16 M3 of gaseous Helium at standard pressure. I wish we could have access to the piping, sensors and safety diagrams of SpaceX hardware

[D Tibbets]

The liquid helium tank in the second stage LOX tank apparently failed catastrophically. Just sitting on the pad!

It will be quite interesting to understand if it was a sudden failure (most probable cause) or a constant leak that generated an unregulated over-pressure in the LOX tank (less likely). The LOX tank in the second stage is about 60 M3 volume and a 0.5 M3 Liquid Helium Tank stores 16 M3 of gaseous Helium at standard pressure. I wish we could have access to the piping, sensors and safety diagrams of SpaceX hardware

Perhaps I'm wrong, but I read that the helium tank was designed for 6000 psi at full load. That is ~200 atm or at 0.5 cubic meter tank volume, about 100 cubic meters of helium at STP. [edit- correction 400 atm or about 8 times the estimate.Other numbers would be doubled]This is about 4 times your estimate. Also a picture of a possible second stage helium tank from a reentered second stage looks like it might hold ~ 1 to 1.5 cubic meters (~ man height and 1/2 to 2/3rd meters wide). So the actual helium volume at STP may have been as much as ~400-600 cubic meters. That would allow for about 20 to 30 atm overpressure in the oxygen tank (400 m^3/ ~10 times larger volume). I don't know if the oxygen tank could hold this additional pressure and of course conditions are not at STP.

In any case, if the carbon fiber overwraped helium tank ruptured, there may have been finely dispersed carbon fibers and in liquid oxygen this might spontaionously ignite- generating even more overpressure- till the oxygen tank ruptured spewing out oxygen and still burning carbon fragments...

Dan Tibbets

[paperburn1]

here is what they were using for sensors.... no data though

https://www.curtisswrightds.com/infocen ... nsors.html
spacex is about 99% sure a COPV issue was the cause. 'explosion' originated in the LOX tank COPV container that had some weird harmonics while loading LOX."
Update:
SpaceX partially confirmed it:
"The timeline of the event is extremely short – from first signs of an anomaly to loss of data is about 93 milliseconds or less than 1/10th of a second. The majority of debris from the incident has been recovered, photographed, labeled and catalogued, and is now in a hangar for inspection and use during the investigation.
At this stage of the investigation, preliminary review of the data and debris suggests that a large breach in the cryogenic helium system of the second stage liquid oxygen tank took place. "
Background info:
COPV: Composite Overwrapped Pressure Vessel: they are titanium aluminum bottles wrapped in layers of continuously wound carbon fiber + resin.

COPVs are used in the Falcon 9 to store a lot of helium under high pressure: part of the helium is used for engine startup, but most of the helium mass is used to pressurize the propellant tanks to 'press the propellant into the turbopump'. Turbopumps run in a more stable fashion when there's some pressure on their inlets.
Falcon 9 Helium COPVs are under intense pressure (around 5,500 psi, or 380 bar), and for that reason a bursting COPV is very violent, and the pressure wave distributes millions of small broken carbon fibers mixed into the LOX, which carbon acts as "fuel". The mechanical pressure of the wave itself is (possibly) enough to ignite the LOX/CF mixture. Such a bursting event in a LOX tank provides oxidizer, fuel and (possible) ignition all at once.
speculation:
If indeed the COPV turns out to be the root cause, then one way to make the COPVs more robust would be to switch from filament winding to a "braided" carbon fiber pressure vessel:
The problem with tape-wound COPVs is that they are strong mostly in a single direction: most of the fibers are along the circumference of the aluminum bottle. This means they are very strong - but it also means that the fibers can still be 'pushed aside' in the length of the bottle by a violent process like a ruptured bottle - like you can push aside the filaments on a lose tow. This rips apart the pressure vessel along the circumference. Braiding avoids this problem, as it's a 'woven' in two directions and so the fabric is strong in both dimensions of the surface.
My interpretation is that the initial 'flash' in the USLaunchReport video was not air/fuel volume detonating, but an oxidizer-rich mixture of LOX and carbon combusting almost instantaneously. The energy of this initial explosion tore open the LOX tank, and probably also ruptured the RP-1 tank across the common bulkhead. The deflagration then avalanched.
https://www.reddit.com/r/spacex/comment ... the_issue/

[Giorgio]

Perhaps I'm wrong, but I read that the helium tank was designed for 6000 psi at full load. That is ~200 atm or at 0.5 cubic meter tank volume, about 100 cubic meters of helium at STP. This is about 4 times your estimate.

My bad I didn't specify. I was just making an example on expansion volume on old knowledge I had on the Space shuttle Helium Tanks (COPV). I have no knowledge of what SpaceX is actually using into their rockets, that's why I was wishing to have some blueprints.

@paperburn1, thanks for the update!

[paperburn1]

perhaps some relevant events during propellant loading as it relates to the helium COPVs inside the LOX tank.
T-0:25:00 All three Cryo Helium Pumps active
T-0:19:30 Stage 2 Liquid Oxygen Loading
T-0:13:15 Stage 2 Helium Loading
T-0:13:00 Stage 2 LOX Flow Adjustment for Helium Cryo Load
T-0:10:00 Stage 2 Venting for LOX Fast Fill
>~T-0:08:00 Explosion happens here<
T-0:06:45 Stage 2 Helium Transition to Pipeline
T-0:02:05 Stage 2 LOX at Flight Level
T-0:01:25 Helium Loading Termination
T-0:00:50 Stage 1, Stage 2 Pressurization for Flight
T-0:00:20 All Tanks at Flight Pressure

Old memory cell firing off/ one of the apollo missions test firing had the same thing happen right?

[Skipjack]

https://www.youtube.com/watch?v=0qo78R_yYFA