[FPSPACE] More on SpaceX launch failure: "It was a really odd failure mode"

Peter Pesavento pjp961 at svol.net
Sat Jul 25 11:39:39 EDT 2015


I decided to pots Twitter posts from spacenews.com reporter Jeff Foust from
a press conference that Elon Musk had.  They are illuminating.  I will
attempt to post them in chronological order.

 

To begin:

"..

 

Musk: this is an initial assessment. First stage was nominal. Dragon
continued to communicate until it went over horizon after failure.

 

Musk: we could have saved Dragon if we had the right software. Incorporating
changes into future versions.

 

Musk: accident happened quickly: first indication of problem to failure in
.893 sec.

 

Musk: failure in strut in 2nd stage LOX tank that was holding down one of
composite over wrapped helium vessels.

 

Musk: at ~3.2 g, strut holding down He tank snapped, released lots of He
into LOX tank.

 

Musk: strut failed at 1/5th rated force, no evidence of damage to it in
closeout photos before launch.

 

Musk: it was a really odd failure mode.

 

Musk: going to individual testing of struts. Some additional cost as a
result, but won't be passed along in the price.

 

Musk: no sign of any other issues with the launch, looking still for any
misses. May have become complacent over last few years.

 

Musk: won't give a precise return to flight date until we go over all data.
May be just a few months.

 

Musk: strut about 2 feet long, an inch at its thickest point.

 

Musk: software to allow deployment of parachutes in the event of launch
failure will be included in next Dragon flight.

 

Musk: no sooner than September for next F9 launch, not clear who customer
would be.

 

Musk: this will not affect commercial crew timeline; this is not on the
critical path.

 

Musk: strut that failed was from a supplier; not naming the company.

 

Musk: not going to move strut work in-house, but will move to a different
design likely from a different supplier.

 

Musk: able to replicate by taking 1000s of these struts and testing; a few
failed well below rated level.

 

Musk: don't think we need to add more struts, just test them individually.

 

Musk: "acoustic triangulation" in tank points to strut snapping, and not
burst He tank. Also would have seen more He if tank burst.

 

Musk: likely to change the bulk of the material in support struts to
Inconel, but no final decision on that yet,

 

Musk: examination of strut that failed in ground tests showed problems in
the grain structure in the steel.

 

Musk: lost revenue from delays will be "meaningful", in the $100M's.

 

Musk: no evidence of assembly errors of the strut in high-res closeout
photos taken before launch.

 

."

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