JF Mezei wrote:

On 2016-10-19 10:07, Fred J. McCall wrote:

We're past that. The question is WHY the helium tank cracked.


So at what point would combustion have begun ? when LOX comes into
contact with the carbon over the helium tank, or LOX simply creating
mechanical failure of the HE2 tank, causing overpressure and mechanical
failure of LOX tank, at which point ignition happened on anything
conbustible around it ?


Neither.


or put another way: did ignition begin on the carbon fibre overwrap of
He2 tank, or did it begin after the LOX tank failed, releasing LOX
everywhere ?


That's certainly 'another way', but it's not the same question. Let
me see if I can make this simple enough so that even you get it.

1) LOX infiltrates layers of overwrap
2) Some LOX freezes (SOX?)
3) LOX tank pressure rises
4) Any LOX in layers of overwrap wrings out
5) SOX stays where it was
6) Increasing pressure initiates reaction.
7) Small boom
8) Helium tank breeches, causing massive overpressure in LOX tank
9) LOX tank blows out, including breeching kerosene tank next door
10) Big boom.

Are you getting this yet?


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn