More speculation here--the LOX tank explosion appears to be basically
omnidirectional with no visible localized smoke/flame. If there are
submerged metal (presumably titanium) helium tanks in the tank, what would
it look like if one of those ruptured (cracked weld that zippered open)?
Seems it would be a more or less omnidirectional explosion of the oxygen
tank with no visible smoke/flame. I imagine the vent/relief valve on the
LOX tank is designed for pressurization system fail-on or control system
failure, not helium tank rupture.
Again, speculation based on video only...
On Mon, Jun 29, 2015 at 10:32 AM, Ian Woollard <ian.woollard@xxxxxxxxx>
wrote:
Given it's the LOX tank, contamination must always be high up on the list
of possible causes.
On 29 June 2015 at 15:36, Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx>
wrote:
This strongly implies there was no clear cause in the data before the
final milliseconds, which rules out a whole class of things that might
gradually overpressure the second stage LOX tank: Frozen pressure-relief
valves, a stuck-on helium regulator, a heat source boiling the LOX. (Come
to think of it, the latter two would also require stuck-closed
pressure-relief valves.)
As for overpressure sources that split a tank within milliseconds of
onset, the first thing that comes to mind is a failure under flight loads
in the high-pressure helium storage bottles-plus-plumbing submerged in the
LOX tank.
A second possibility is some sort of ignition inside the tank - EG,
something breaking loose and scraping an aluminum surface, or a brace or
baffle cracking, so a significant area of unoxidized aluminum is suddenly
exposed to LOX.
A distant third would be detonation of just that tank's segment of a
flight-termination linear shaped charge. (That assumes the charges are in
separate segments; I couldn't find a detailed description of the system.)
(Note that any such detonation would not likely have been commanded - I can
think of no reason to design in the ability to separately command local
charge segments in such a system.)
A secondary implication of "final milliseconds" is that whatever happened
was violent enough to stop data transmission from the stage, or at least
from the relevant parts of the stage.
Mind, a crack developing in the tank outer skin under flight loads then
unzipping rapidly would also explain the results - it just wouldn't explain
the statement about an "overpressure event".
On 6/29/2015 6:12 AM, Ian Woollard wrote:
*Elon Musk* @*elonmusk* <https://twitter.com/elonmusk> 5h5 hours ago
<https://twitter.com/elonmusk/status/615431934345216001>
"Cause still unknown after several thousand engineering-hours of review.
Now parsing data with a hex editor to recover final milliseconds."
--
-Ian Woollard
