I may have mixed the order of images, but is clear from the text; the first image is a side view with gray (assumed) helium bottle, next two are front view e.g. hatch and parachute compartment side. Those are just CAD images with some parts removed for better viewing; no one is saying anything for actual installation order. Last image is showing COPVs with red cover jackets, which are (if agree with assumption) the propellants tanks. In video the fireball seems to start there.
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My comment was really directed at the NSF poster (unless that’s you), in an effort to clarify what is almost assuredly a misinterpretation of configuration. (Admittedly, it’s a pretty insignificant one all things considered, but still worth checking)
In any case, it’s extremely likely the screenshot of the prop module (the first image) is full-up, with what is most likely 10 tanks...we just can’t see all of them because of the angle of the screenshot. In that configuration there would be four tanks for fuel, four for ox, and one pressurant tank for each propellant. The purple tanks are indeed the propellant tanks (which are the ones with the red RBF covers in the picture) and the grey are the helium tanks. Given the not exactly 1:1 burn ratio and specific gravity of the propellants (and the general Cg needs of the spacecraft), I’d guess that the tank usage is distributed more symmetrically around the spacecraft...so, two of each propellant on either side as opposed to four mmh on one side and four n2h4 on the other. In context of this anomaly, associated plumbing would make it really hard to asses whether the ignition point was fuel or ox related.
Note that rupture of a tank as the root issue is an extreme improbability. Tanks and their service feeders are pretty rock solid and well tested upstream. Given that the whole system would have been tested thoroughly without propellant (run the tanks up to max operating pressure, leak check everything, activate valves and verify flow, etc) I would speculate that the root cause is related more to the specific test than any particular workmanship type issue.
Lastly, I honestly don’t know what kind of tanks they actually use, but it would be surprising to me if SpaceX opted for wrapped propellant tanks (COPV). The flight propellant pressures are quite manageable—in the hundreds of psi (call it 400), which is very within the capacity of a non-wrapped Ti tank. Helium maximum pressure OTOH is many thousands (like, 6000), which is where they’re using wrapped pressurant tanks. For decades Ti prop tanks and wrapped helium tanks have been the solution for mmh and n2o4 systems, so it would be hard for me to imagine how SpaceX would opt for a more complex, more expensive, and seemingly low additional value solution of going wrapped tanks for everything.
