Originally Posted by
MG23
However, as I understand it, the in-flight failure was due to acceleration forces, which would be going in the opposite direction to bouyancy. They've put extra effort into checking every single strut since then. and I presume the second stage has been test-fired (and, hence, previously fuelled), like the first.
It's possible it's a related problem, but, from what I've read, the failure seemed to start around the umbilical attachments, which would make them a prime candidate. If it disconnected and started spraying liquid oxygen around, that would have been bad news.
MG23, re the boyancy forces: during acceleration, the bouyancy forces are actually *increased*. It was counter-intuitive for me too until I read (saw?) Elon Musk explain the thing: During upward acceleration of the rocket, the downward force (in the rocket's frame of reference) on the LOX is larger than the corresponding downward force on the He. Thus, the bouyancy is *increased*, not decreased.
I've seen videos of a car driving round a roundabout with a helium baloon inside. It looks *really* weird when the baloon is pressed toward the *inside* of the roundabout (i.e onto the driver)...