Fair point, it's plausible to me that it might be an issue, at least to the
extent that I couldn't say that it wouldn't be enough energy to ignite
without some calcs/testing. If that were a plausible scenario then
practically any mostly inert coating keeping the LOX away from the fibres
would be enough to prevent ignition.
On 18/10/2016 7:03 PM, "Troy Prideaux" <troy@xxxxxxxxxxxxxxxxxxxxx> wrote:
Well, not necessarily. Someone here asked a pretty interesting question
recently – how much thermal energy is released when a single fibre is
stressed to failure. Is that enough to initiate a run-away exothermic
process in a very reactive environment? Probably nobody knows the answer to
that, although it would be easy to measure with thermal imagining and some
lab testing.
Troy
*From:* arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx]
*On Behalf Of *Andrew Burns
*Sent:* Tuesday, 18 October 2016 4:44 PM
*To:* arocket@xxxxxxxxxxxxx
*Subject:* {Spam?} [AR] Re: High pressure storage tanks and thermal
shielding
The problem isn't necessarily a compatibility of the carbon and epoxy with
the LOX in a static sense because they've flown many of these rockets with
that contact happening without problem. The problem arises when the
pressure vessel fails in some way at which point the flammability of the
carbon/epoxy doesn't matter because the energy stored in the COPV is enough
to destroy the tank anyway and no PTFE liner in the world is going to stop
the chunks of pressure vessel ripping the LOX tank to pieces.
The problem is that their press system is failing at all, which is
probably in large part due to the extreme environment it encounters inside
the LOX tank and I'd wager they wouldn't have had these issues with the
same tanks but located outside of the LOX tank. It will probably come down
to some level of lack of understanding to the behaviour of extremely highly
stressed composite-metal structures undergoing significant thermal cycling.
Andrew
On Tue, Oct 18, 2016 at 6:36 PM, Ben Brockert <wikkit@xxxxxxxxx> wrote:
On Mon, Oct 17, 2016 at 10:30 PM, William Valliant <wnvalliant@xxxxxxxxx>
wrote:
About the cryogenic tank, what about spun formed stainless steel 304liner
with carbon fiber over wrap for the oxygen? Isn't that what they arealready
doing?
The COPVs in question are inside the LOX tank, so the carbon fiber
overwrap (and the matrix) are the side that's in contact with the LOX
and is the problem because they're fuels. Their existing liner is
probably aluminum, and there's no big upside to switching to
stainless.
I'll wager they've thought about covering the tanks with something
like PTFE film.
They have to make something work, the tanks on the BFR are supposed to
be linerless carbon fiber, which is the same problem but even worse,
in terms of surface area made of fuel in contact with LOX.
Ben
