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Old December 24th 18, 09:22 AM posted to sci.space.policy
Fred J. McCall[_3_]
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Default BFS drops composite construction

JF Mezei wrote on Mon, 24 Dec 2018
00:23:22 -0500:

On 2018-12-10 00:53, Fred J. McCall wrote:
I saw a report today that SpaceX was dropping composites for tanks and
main structure on BFS in favor of using "heavy metal"


Funny how this group was so convinced the tests for the composite tanks
had been conclusive and that SpaceX had fully tested them, and I was
ridiculed for stating that only certain tests had been done and it
didn't mean those tanks had been fully tested.


Funny how frequently you pat yourself on the back for 'proving wrong'
things that weren't said.


Now, they are allegedly switching to metal and people just accept this,
without reminding themselves that they had fully beleibed the composite
tank tests had been exchaiustive and proved they woudl be in BFS/BFR.


'Allegedly'?


Note: heavy metal doesn't mean steel. If you look at the A380, Airbus
had developped "composites" called Glare which is sandwiched aluminium
and carbon fibre which came out in weight quite competitively with full
carbon (and Boeing's problems with 787 showed that all-carbon doesn't
yield the full promises made by marketing departments).


Nobody said it meant steel. In fact, no one has said it means
anything in particular. However, I'd bet you're wrong here since what
you describe isn't particularly 'heavy' and that is the description
given. Musk quite pointedly ignored repeated questions about WHICH
metal(s).


One issue is fatigue. In this case, not only pressure cycles, but also
tempoerature cycles for tanks. Would be interesting to know which
turned out to tip the balance against all composite tanks.


Tanks aren't the only things that get temperature cycles. It may just
be a matter of expense or difficulty in fabrication.


--
"Some people get lost in thought because it's such unfamiliar
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