Slashdot Mirror
Elon Musk Asks Twitter For Help In Finding Cause of SpaceX Explosion (gizmodo.com)
On September 1, SpaceX's Falcon 9 rocket exploded on the launch pad at Cape Canaveral, Florida, and destroyed the AMOS-6 satellite that belonged to Facebook, which was going to be used to beam internet to developing parts of the world. Since the cause for the explosion has yet to be solved, SpaceX CEO Elon Musk is asking for help via Twitter. Slashdot reader Thelasko writes: Elon Musk stated on Twitter last night, "Still working on the Falcon fireball investigation. Turning out to be the most difficult and complex failure we have ever had in 14 years." He went on to say, "Important to note that this happened during a routine filling operation. Engines were not on and there was no apparent heat source." Other Tweets mention a "bang" sound before the fire, and that SpaceX "have not ruled out" the possibility that something struck the rocket.
Again, AMOS-6 was not in any way owned by Facebook. They had simply signed a contract to lease a significant portion of the Ka-Band payload pointed at sub-saharan Africa. But don't let facts get in the way of your hate.
...si hoc legere nimium eruditionis habes...
It did not belong to Facebook, but to Spacecom. It was not manufactured by Facebook, but by IAI.
If you had watched the video, you would have seen that his explanation for what happened is that the liquid oxygen most likely froze the kerosene causing a rupture in the holding tanks in the second stage, allowing the fuels to mix; but yeah, no real explanation.
While it's true that liquid oxygen and kerosene make an explosive mixture, they still need something to start the big kaboom. Which is what SpaceX is trying to find - what got the bang started. This provides not clue one....
"I do not agree with what you say, but I will defend to the death your right to say it"
It would have been nice if the summary had mentioned what specifically he asked for, rather than including everything but what he asked for. They make it sound like he asked Twitter to solve the problem. What he actually asked twitter for was any photos or videos of the event that anyone may have:
The connection with the "bang" is precisely what he wrote immediately after the first tweet:
If they have more videos, they can triangulate the location of the sound and determine whether it came from the rocket or elsewhere.
Musk did Not just go on Twitter and say "Well, we're baffled - go on, Twitter, figure out why it exploded for us!" like the summary makes it sound.
"I need swat, tactical, the guys with the flashlights on their guns, those guys with the big shield thingies"
Will anyone read the actual tweets? This summary is one of the worst I've seen on Slashdot in a long time. Musk asked Twitter for pictures and videos, not to "find the cause of the explosion". They're trying to figure out whether a particular sound came from the rocket or elsewhere. The summary makes it sound like - as you put it - they're inviting arm char scientists to solve the issue for them.
"I need swat, tactical, the guys with the flashlights on their guns, those guys with the big shield thingies"
It's trickier than that. They were loading LOX. There was no RP1 in the upper stage yet. So why did the LOX explode?
I've read a fair bit on LOX handling, and while it's tamer than, say, HTP, there are some risks in handling it. The biggest one is contamination - which has taken down craft in the past. Most notably, the X-1A and X-1D were taken down by a contamination from a chemical used in the manufacture of their gaskets. Most organics are incompatible with LOX and become contact sensitive, including - wait for it - tending to be set off by pressure changes.
Another issue is the tank itself. LOX is compatible with most aluminum alloys, hence aluminum is frequently used for LOX tankage. However, there are some caveats. One, it must be well cleaned in a proscribed manner, due to the aforementioned contamination issues. Furthermore, it must have an intact oxide layer. If the oxide layer is damaged (bending, stretching, shearing, overaggressive cleaning) or never formed, it must be exposed to atmospheric air and allowed to reform; it begins reforming immediately but takes about three days to reach maximum thickness (slowing with time). Bare aluminum is still not hypergolic, but it is impact sensitive with LOX. It can also be set off by the same phenomenon that damages the tank - for example, heavy warping, which can create localized hot spots.
Contamination is generally considered more of a concern, however (particularly since SpaceX uses aluminum-lithium, which is more resistant to impact/pressure-induced explosion with LOX than non-lithium alloys). That said, regardless of what causes the initial burn, if temperatures are high enough, the aluminum will burn, and it burns very aggressively. Indeed, it was the addition of aluminum powder that revolutionized solid rocket propellants (powdered to make it easier to ignite and burn completely, as well as to blend), giving them a major simultaneous improvement in ISP, thrust, propellant density, and burn quality. Aluminum has such a high affinity for oxygen that it also burns in CO2 and water, stripping the oxygen from them. The general way firefighters put out large aluminum fires is.... they don't.
All of that said, these sort of problems are rare. Which makes one wonder about the unusual factor in SpaceX's case: densified/superchilled propellants. SpaceX is the only major launcher to use them, and the behavior of superchilled LOX isn't anywhere near as well studied as that of LOX at its boiling point. It changes what may liquify or freeze in contact with it, it changes the flexibility or fracture properties of physical components on contact with it, it has a higher viscosity, etc. Things that freeze into it could melt/boil as the LOX warms up as well. So it obviously draws the question, is this problem a result of the use of superchilled LOX, some unanticipated effect in the production / storage / delivery system that led to problems within the tank, or an unexpected reaction within the tank itself?
"I need swat, tactical, the guys with the flashlights on their guns, those guys with the big shield thingies"
It's trickier than that. They were loading LOX. There was no RP1 in the upper stage yet. So why did the LOX explode?
Do you have a source for that? Typically the RP-1 is loaded first as even though it's chilled, it's far more thermally stable than the super-chilled LOX. The LOX is loaded into the tanks just before launch so that it doesn't have time to warm up before the rocket is ignited.
From the US Launch Report video, it's also pretty clear that the RP-1 was already in both stages when the anomaly occurred. In a deflagration like that, it burns with big movie-style orange flames, and that's exactly what we saw from both the upper stage, and the lower stage as the rocket came apart.
...si hoc legere nimium eruditionis habes...
Because if you look closely, the object is not close to the rocket when it first starts to explode so it's probably a bird a mile closer to the camera.
More dis-information. The kerosene for the Full Thrust version is chilled to -7 degrees centigrade , boosting its density by 2.5 - 4.0 percent.