Quote from: miiser on 07/04/2015 11:30 amQuote from: Im_Utrecht on 07/04/2015 11:23 amI remember that with the launch of the first Falcon v1.1 Elon Musk said that he was afraid of bending.Could this have played a role ?Certainly, bending/torque would contribute to the buckling load on the wall.I also notice that, right before failure, the ring of condensation vapor around the Dragon became asymmetric, with a sort of bump on top. Possibly the vehicle is beginning to flex abnormally at this point in time with the wall starting to buckle on one side. But this could be nothing/optical effects.When Musk mentioned bending I think he was referring to the first stage due to fact that it was long and slender. The issue with this flight appeared to be in S2 and S1 displayed no signs of bending and in fact kept trying to fly even after S2 started to go away.
Quote from: Im_Utrecht on 07/04/2015 11:23 amI remember that with the launch of the first Falcon v1.1 Elon Musk said that he was afraid of bending.Could this have played a role ?Certainly, bending/torque would contribute to the buckling load on the wall.I also notice that, right before failure, the ring of condensation vapor around the Dragon became asymmetric, with a sort of bump on top. Possibly the vehicle is beginning to flex abnormally at this point in time with the wall starting to buckle on one side. But this could be nothing/optical effects.
I remember that with the launch of the first Falcon v1.1 Elon Musk said that he was afraid of bending.Could this have played a role ?
and speed increase as the atmosphere thins and the propellant weight decreases, so they tend to balance each other out, but the atmosphere would still be pretty thick at this point in the flight. The load would still be pretty near MAXQ.
Max Q of F9 v1.1 happens something like 70 seconds into the flight. At the moment of failure, F9 is indeed nowhere near max Q. You can tell that via the bar at the bottom and announcer calling out max Q at 75 seconds or so. New informational displays of spacex show the event and info about it until a new event occurs which must be confusing for some people.
... And if the entire vehicle were slightly bowed, including S1, that would explose S2 to asymmetric loading which would promote buckling.
... but the atmosphere would still be pretty thick at this point in the flight. The load would still be pretty near MAXQ.
Quote from: Jim on 07/04/2015 02:30 amQuote from: jimhillhouse on 07/04/2015 01:44 amA few friends who work at JSC have told me that Gerst has gone from his "everything will be fine" of Sunday to wanting a full-blown NASA-led investigation. That might be just to preempt a congressional investigation. But you're right; the silence is deafening. Anyone else at NASA getting the same vibes?No, that is just nonsense since NASA has no authority to lead the investigation. The friends don't know how things work. It was a commercial launch and hence It is a Spacex led investigation with the FAA as the lead gov agency. NASA also has a rep and it is from LSP vs the ISS program since they have the rocket expertise even though ISS has the contract. Congress also has no authority either. The only thing it can investigate is NASA's contracting mechanism and management of the contract.There is no need for any updates until there are updates to be givenNASA will be the one to approve SpaceX's resumption of CRS launches, manifesting of ISS cargo, and ISS rendezvous. So if NASA wants to conduct its own mishap investigation, SoaceX will either cooperate or face the consequences.
Quote from: jimhillhouse on 07/04/2015 01:44 amA few friends who work at JSC have told me that Gerst has gone from his "everything will be fine" of Sunday to wanting a full-blown NASA-led investigation. That might be just to preempt a congressional investigation. But you're right; the silence is deafening. Anyone else at NASA getting the same vibes?No, that is just nonsense since NASA has no authority to lead the investigation. The friends don't know how things work. It was a commercial launch and hence It is a Spacex led investigation with the FAA as the lead gov agency. NASA also has a rep and it is from LSP vs the ISS program since they have the rocket expertise even though ISS has the contract. Congress also has no authority either. The only thing it can investigate is NASA's contracting mechanism and management of the contract.There is no need for any updates until there are updates to be given
A few friends who work at JSC have told me that Gerst has gone from his "everything will be fine" of Sunday to wanting a full-blown NASA-led investigation. That might be just to preempt a congressional investigation. But you're right; the silence is deafening. Anyone else at NASA getting the same vibes?
Spacecraft Tank Pressures-TypicalHydrazine: 150 PSI at lift offOxidizde: 250 PSK at lift offHelium used for repress of Hydrazine & Oxidizer at launch: 4500 PSI typSoon after SV separation Helium Tank is activatedHydrazine and Oxidizer Pressure at 300 PSITanks are required to be qualified to 50 x 0 to 450 PSI (for Hydrazine and Ox)Then, after that, they are required to not burst at 600 PSIHelium tank no-burst pressure: 9000 psi.Plumbing and valves: similar design/qual regime.Now just manufacture, test, install, operate the flight units as good as the qual unitFor SpaceX, if a helium bottle is inside the LOX tank, what is its pressure:Did this helium tank rupture, causing LOX tank to rupture.Did SpaceX actually test the tanks as they were used in flight (i.e. test-like-you-fly)We shall see.
Quote from: tj on 07/04/2015 07:35 amSpacecraft Tank Pressures-TypicalHydrazine: 150 PSI at lift offOxidizde: 250 PSK at lift offHelium used for repress of Hydrazine & Oxidizer at launch: 4500 PSI typSoon after SV separation Helium Tank is activatedHydrazine and Oxidizer Pressure at 300 PSITanks are required to be qualified to 50 x 0 to 450 PSI (for Hydrazine and Ox)Then, after that, they are required to not burst at 600 PSIHelium tank no-burst pressure: 9000 psi.Plumbing and valves: similar design/qual regime.Now just manufacture, test, install, operate the flight units as good as the qual unitFor SpaceX, if a helium bottle is inside the LOX tank, what is its pressure:Did this helium tank rupture, causing LOX tank to rupture.Did SpaceX actually test the tanks as they were used in flight (i.e. test-like-you-fly)We shall see.No hydrazine in either stage. Both stages use LOX and RP-1 (a highly refined version of kerosene). The LOX is cryogenic (i.e., a liquified gas at extremely cold temperatures), unlike the room-temperature hydrazine (propellant)/nitrogen tetroxide (oxidizer) fuels used in hypergolic engines. Only the Dragon itself uses hypergolic fuels, for the Draco (and, on Dragon v2, Super Draco) engines; none are used in the Falcon stages. All of the hypergolic fuels in that stack popped off the stack when the Dragon came loose; none were involved in the failure or conflagration.It's a little hard to take your numbers seriously when you're not even talking about the same kind of engines and propellants as were actually in use on the stages in question...
Quote from: the_other_Doug on 07/04/2015 03:25 pmQuote from: tj on 07/04/2015 07:35 amSpacecraft Tank Pressures-TypicalHydrazine: 150 PSI at lift offOxidizde: 250 PSK at lift offHelium used for repress of Hydrazine & Oxidizer at launch: 4500 PSI typSoon after SV separation Helium Tank is activatedHydrazine and Oxidizer Pressure at 300 PSITanks are required to be qualified to 50 x 0 to 450 PSI (for Hydrazine and Ox)Then, after that, they are required to not burst at 600 PSIHelium tank no-burst pressure: 9000 psi.Plumbing and valves: similar design/qual regime.Now just manufacture, test, install, operate the flight units as good as the qual unitFor SpaceX, if a helium bottle is inside the LOX tank, what is its pressure:Did this helium tank rupture, causing LOX tank to rupture.Did SpaceX actually test the tanks as they were used in flight (i.e. test-like-you-fly)We shall see.No hydrazine in either stage. Both stages use LOX and RP-1 (a highly refined version of kerosene). The LOX is cryogenic (i.e., a liquified gas at extremely cold temperatures), unlike the room-temperature hydrazine (propellant)/nitrogen tetroxide (oxidizer) fuels used in hypergolic engines. Only the Dragon itself uses hypergolic fuels, for the Draco (and, on Dragon v2, Super Draco) engines; none are used in the Falcon stages. All of the hypergolic fuels in that stack popped off the stack when the Dragon came loose; none were involved in the failure or conflagration.It's a little hard to take your numbers seriously when you're not even talking about the same kind of engines and propellants as were actually in use on the stages in question...I believe that the numbers were pulled off of a web page of some spacecfaft like a comsat. The pressure in the Falcon RP1 and LOX tanks is lower as the engines are pump fed and not pressure fed like those numbers indicate. I have no idea of the exact pressures for the Falcon, but I'd wager that it is under 50psi. More pressure means more metal for strength and that equals weight. I also don't know the numbers for the Falcons Helium bottles, but I'd guess that it's at least 3000 psi and may well be 4500psi. The Helium is in the LOX tank because you can get 3x the amount of Helium in a given tank volume at LOX temperatures of around 100K vs 300 K room temperature. Smaller Helium tanks equals less weight.Helium at 4500 psi in a tank stores a lot of energy. So much that a complete tank rupture would most likely be a more spectacular vehicle failure than was seen.
... what happens to the pressure inside a helium tank pumped up to 4500 psi at LOX temperatures if the temperature in the tank then rises to room temperature again?
Okay, here's a thought --and keep in mind, I have no idea how the initial conditions could have happened -- but if you put three times the amount of helium in a tank at LOX temperatures than you would be able to at room temperatures, and then that helium tank rises to room temperature somehow, wouldn't that dramatically increase the pressure inside said helium tank? Perhaps to the point where the tank or tank fittings would catastrophically fail?
The trouble is, there's no easy way of bring the temperature of the Helium up as the tanks are immersed in LOX.
I can't help but keep coming back to a failure of either one or more of the Helium tanks / or a value sticking open that would result in significant leak of Helium into the LOX tank, resulting in the LOX tank failing. The bit that stops me is the question of whether the Helium COPVs have a sufficient volume of gas inside them that if they were vented into the LOX tank it would cause it to rupture?Presumably there's sufficient Helium in the tanks to fill the LOX tank as the LOX is used up, but not much more. To work out whether open Helium venting into a full tank would cause failure, you'd need to know:- LOX tank volume - volume and pressure of LOX in the tank when full- Volume of ullage (calculated from the above)- Helium COPVs volume- volume and pressure of Helium in the COPVs when full (presumably volume is as above)- bursting pressure of the LOX tank (*at the external pressure applicable at that altitude)
[Basically, is there enough Helium in the COPVs for an unintended venting into the LOX tank to push it beyond its rated pressure?If that's not the case, a rapid failure of a COPV is left as the more likely candidate.
So what does "KICK" stand for at SpaceX? Is this some modality of pitch change that is in some form unique?
Was thinking, the SD card failed in my phone causing it to get hot to the touch. I wonder, do any electronics exist inside the LOX tank that if they failed in a similar manner could generate enough heat to overwhelm the vent valve and cause the stage to burst. I have a hard time imaging anything being able to draw enough current without blowing a breaker, but thought I would ask.Leaking He plumbing sounds more plausible.