Latest candidate for SpaceX pad explosion

JF Mezei wrote:

On 2016-10-21 23:48, Fred J. McCall wrote:

THERE IS NO LAMINATION, YOU IGNORANT ****!!!!


Everytime you have multiple layers of carbon threads (or fabric) they
are laminated agianst each other and help in place by the matrix/resin.


Go look up the meaning of 'laminate', you ignorant ****.



Did you find the word 'laminate' or 'lamination' ANYWHERE in that
article? No, you did not, BECAUSE THERE IS NO LAMINATION, YOU
IGNORANT ****.


Your professionalism rivals that of Trump.


Your intellect rivals that of Alfred E. Newman. If you want
'professionalism' you can pay my consulting rate. You'll have to pay
a premium if you intend to argue when things you don't understand are
explained to you. Otherwise, I don't have to put up with your
stupidity.


--
"Ignorance is preferable to error, and he is less remote from the
truth who believes nothing than he who believes what is wrong."
-- Thomas Jefferson

In article . com,
says...

On 2016-10-20 06:09, Jeff Findley wrote:

Fred does. You don't. Here is a NASA "primer" on COPV:

https://ston.jsc.nasa.gov/collection...P-2011-573.pdf

Delamination is one of the core "stress failure" modes. That article
failes to underline that the various layers of fibres wound over each
other are bound by the resin and gain more strength that way. When the
binding between layer weakened or broken (delamination), the streength
is very much weakened.

This is one of the problems Boeing experienced when it started to test
the 787 fuselages.

Smallish COPV tanks aren't quite the same as a B-787 fuselage. Similar
though. The cite I provided was for COPV tanks, so is applicable to the
topic at hand. Bringing in the B-787 fuselage seems to be only
tangentially related, so why bring it up?

The above is what you don't get. The primary reason a COPV has a liner
is because of the porosity of the composite overwrap.

This porosity is not quantified in that article. Are you intending to
keep the pressurized gas at same pressure for 5 months or 2 hours ?

It's helium in this case, which is such a tiny molecule (pretty sure
only a hydrogen molecule is smaller), so it will leak quite readily out
of the smallest of cracks in a pressurized system. You really don't
want helium from your *high pressure* tank leaking out because it will
get into the LOX tank, messing up the pressurization! The whole point
of the helium is for the tank pressurization system.

As well, the porosity is not qualified in whether there are actual gaps
in material, or whether the passing of pass from one side to the next
happens at almost molecular level (as it does with bicycle tires for
instance, they lose pressure over days, not minutes).

Word salad. You don't want your highly pressurized helium leaking into
the LOX tank. Low leak rates are important, especially in an upper
stage which may be called upon to fire multiple times during a launch in
order to get its payload into the correct orbit.

but note that it might be possible to come up with a manufacturing
technique which would make that form removable (e.g. could be an
inflatable which could be deflated once the composite wrap is complete).

Carbon fibre frames are build that way. Inside of frame "tubes" has an
inflated jacket to hold the shape, fibre wound around (either as fabric
or as prepreg yarn) and then an outer mandrel put in, and the liner then
highly pressurized to squeeze the fibre against the outer mandrel to
give the carbon strength and prevent delamination

Another method is to use wax as the inner mandrel, and once it is
composite has cured, you can melt wax and drain it. (but this requires
curing at room temperature, not an in oven).

Winding warn or applying fabvric against a hard surface is still the
best mean. (but for a shpere, likely they will then wrap in plastic bag
and vacuum it to get rid of any air bubbles/gaps in the layers between
fibres to prevent future weakenin/delamination).

Boeing does different: they put the piecxes in a high pressure room
(which also bakes/cures the resin) which makes any air bubble diminish
to a size where it does not matter.

You're describing how "generic" carbon fiber structures are made. But
this thread is talking about high pressure helium tanks. Stick to the
topic at hand.

But no one has done that, because then the pressure vessel would be like
a bucket with a bunch of holes in the bottom!

Helium leaks through the smallest of cracks. You *do not* want to
design a leaky COPV for a second stage, especially when that tank would
leak directly into your LOX tank, totally throwing off the LOX tank
pressurization.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

Jeff Findley wrote:


Helium leaks through the smallest of cracks. You *do not* want to
design a leaky COPV for a second stage, especially when that tank would
leak directly into your LOX tank, totally throwing off the LOX tank
pressurization.


I think these helium tanks are pressurized to 10,000 psi. That's why
when the helium tank blows it blows the oxygen tank and everything
else.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden

In article om,
says...

On 2016-10-23 09:50, Jeff Findley wrote:

You're describing how "generic" carbon fiber structures are made. But
this thread is talking about high pressure helium tanks. Stick to the
topic at hand.

Carbon fibre can be applied in 2 ways. There is "fabric" or pre-woven
carbon applied in layers, and there is carbon yarn applied to the
surface via a robot. That COPV document describes the later being used.

It's a spectrum. You forgot carbon fiber tape.

There is no "magic" carbon fibre for space which is applied totally
differently and has totally different properties.

The pens used to lay the carbon yarn onto COPV are likely from same
manufacturers as those used to lay the carbon on a 787 fuselage. or
Airbus A350 wing.

Possibly. I know people who used to write the software for the machines
that laid down carbon fiber tape.

There are many variations with regards to the resin, whether it is
prepreg and needs curing at heat, or has a catalyst and the yarn is
impregentated with it just before being layed onto the surface.

The pattern on a COPV is designed for strength, not to make it
impervious to helium gas at thousands of PSI. Which is why the fiber is
wrapped over a thin inner liner designed to actually be that gas
barrier.

Helium leaks through the smallest of cracks.

A crack in any composite structure is a severe failure.

You are WRONG, WRONG, WRONG in this case. Did you even read that NASA
document on COPV?

There are two areas of concern: leak via porosity and leaks at the seam
between the carbon fibre structure and metal pipe fitttings. Having a
metal inner liner that also has the pipe fittings that go out of tank
solves both.

My area of concern is the fact that you keep spewing things that are
simply not true about the way that a COPV is designed and built.

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

Jeff Findley wrote:

In article om,
says...

There are two areas of concern: leak via porosity and leaks at the seam
between the carbon fibre structure and metal pipe fitttings. Having a
metal inner liner that also has the pipe fittings that go out of tank
solves both.


My area of concern is the fact that you keep spewing things that are
simply not true about the way that a COPV is designed and built.


You're a much more patient man than I am, Jeff. I got fed up with him
not knowing what he was talking about and then arguing with people who
explained it to him a while ago.


--
"Ignorance is preferable to error, and he is less remote from the
truth who believes nothing than he who believes what is wrong."
-- Thomas Jefferson

In sci.space.policy message
aweb.com, Sat, 22 Oct 2016 00:31:48, JF Mezei jfmezei.spamnot@vaxinati
on.ca posted:

...

It is more likely that the ultra cold O2 simply went below the carbon
fibre's minium teperature, it became brittle and broke, releasing the
He2 which then caused failure of the LOX tank.

See https://en.wikipedia.org/wiki/Helium_dimer. He2 exists; but it
is not what is being put in the tank.

--
(c) John Stockton, Surrey, UK. Turnpike v6.05 MIME.
Merlyn Web Site - FAQish topics, acronyms, & links.

In article om,
says...

On 2016-10-24 06:13, Jeff Findley wrote:
You are WRONG, WRONG, WRONG in this case. Did you even read that
NASA document on COPV?

Sorry, but a crack in composite means both fibre and resin have cracked
and the crack risks propagating.

No, microscopic cracks or pores between the lengths of carbon fiber that
would otherwise render it unable to hold helium at thousands of PSI will
not result in structural failure, just leakage. Again, that's why they
use a liner in a Composite OVERWRAPPED Pressure Vessel. Note the
emphasis on OVERWRAPPED!!!!!!!

Look at the pictures in that NASA document. The fibers don't all go the
same way. They're layered in different directions.

Have you ever seen one of those large liquid carrying pallets? They use
a plastic liner but their strength comes from the steel cage which
surrounds the liner. It doesn't matter one damn bit if the cage by
itself can't hold liquid (how could it with inches wide gaps between the
steel tubes). What matters is that the cage is solidly welded together.
The cage doesn't even need to be bonded to the liner for this type of
tank.

And if you look at the pictures of the COPV in that document, you see
that the finished product is smooth and no visible carbon patterns.

I can clearly see the direction of the fibers in the outer layer in many
of the pictures.

When
a process yields such a finished product, (as opposed to artisanal
laying of fibre), there are no openings and the resin has filled every
gap between strands.

Ideally yes. But in practice, smallish (i.e. thin) lightweight
composite tanks would leak without a liner.

This doesn't solve the issue of porosity or the joining of carbon
structure with metal fittings. But the use of the word "crack" as a
normal feature of carbon is plain wrong.

A crack in a carbon fibre structure is a failure, not a normal happening.

Fine, we'll call the carbon fiber overwrap leaks "pores" instead of
"cracks". They are still designed to have a liner to stop them from
leaking!

Jeff
--
All opinions posted by me on Usenet News are mine, and mine alone.
These posts do not reflect the opinions of my family, friends,
employer, or any organization that I am a member of.

Is this perhaps a confusion/whatnot as to the "degree" of
pores/cracks/whatnot in the overwrap? I am getting the impression
that the carbon fribre overwrap is kinda/sorta like an exoskeleton for
the tank. A nice, thin, lightweight metal inner tank/liner that is
largely helion-tight but on its own would not be able to withstand the
pressure desired, but can once it is wrapped some number of times with
resin-impregnated carbon fiber.

Some quantity of sufficiently small and spaced-apart
holes/pores/cracks in that carbon fibre overwrap is "OK" in that the
structure as a whole will persist. Once there are either too many, or
too large holes/pores/cracks in that overwrap it becomes "a bad day."

When Oxygen freezes, does it form sharp points/edges as it solidifies?
Might such things then be able to pierce the liner and/or overwrap?
Or just push out the liner or overwrap to the point that there is
enough void to mean the two are no longer complementing one another
structurally and then one or the other snaps/cracks/whatnot.

rick jones
--
"You can't do a damn thing in this house without having to do three
other things first!" - my father (It seems universally applicable
these opinions are mine, all mine; HPE might not want them anyway...
feel free to post, OR email to rick.jones2 in hpe.com but NOT BOTH...

Mr Mezei, you are an idiot and not qualified to express an opinion in
this discussion. You need to learn to STFU and not argue with people
who are trying to explain to you how things actually work.

JF Mezei wrote:

On 2016-10-24 06:13, Jeff Findley wrote:

It's a spectrum. You forgot carbon fiber tape.

Tape is either narrow strips of cloth or is (more commonlty, and as
pictured in that document), multiple strands being layed at same time.

Laying it as multiple strands allows for far better control over
direction it is being laid. Cloth tape is good for patches, but because
horizontal threads are very short and cut at each side of tape, they do
not yield as much strength as continuous fibres.


A crack in any composite structure is a severe failure.

You are WRONG, WRONG, WRONG in this case. Did you even read that NASA
document on COPV?

Sorry, but a crack in composite means both fibre and resin have cracked
and the crack risks propagating.

And if you look at the pictures of the COPV in that document, you see
that the finished product is smooth and no visible carbon patterns. When
a process yields such a finished product, (as opposed to artisanal
laying of fibre), there are no openings and the resin has filled every
gap between strands.

This doesn't solve the issue of porosity or the joining of carbon
structure with metal fittings. But the use of the word "crack" as a
normal feature of carbon is plain wrong.

A crack in a carbon fibre structure is a failure, not a normal happening.

JF Mezei wrote:

On 2016-10-24 17:50, Jeff Findley wrote:

No, microscopic cracks or pores between the lengths of carbon fiber that
would otherwise render it unable to hold helium at thousands of PSI will
not result in structural failure, just leakage.

You are forgetting that composites are a misture of carbon fibres and
resin. The major role of the resin is exactly to fill the gaps between
the fibres to keep them in place.


You are forgetting that you don't know what the **** you are talking
about.


The strength of such structures comes from fibres beung tightly packled
against eache other (laminated against each other) ...


Go look up the meaning of the word 'laminated'. You persist in
misusing it.


...and held in place by
the resin "matrix"). This means a full surface without holes.


You make it sound like the structural strength is in the RESIN, which
is exactly backward.


And if you
look at the finied prodycrt, you do not see fibres on the surface
becayse there is a uniform layer of resin above the topmost layer of
fibres to protect it. There are no holes or cracks or voids on that type
of surface.


Stick 10,000 psi helium in it without an inner metal liner and it will
leak like a sieve.


Again, that's why they
use a liner in a Composite OVERWRAPPED Pressure Vessel. Note the
emphasis on OVERWRAPPED!!!!!!!

I have not argued against the use/need of a liner. The composite
overwrap is likely sufficiently porous that it does not contain those
light gases well for long periods. But this is quite different from
stating there are cracks or holes in the composite that would not
contain the H2.


Except that there are, whether you can see them or not. Perhaps if
you pulled your head out?

snip idiocy


--
"Ignorance is preferable to error, and he is less remote from the
truth who believes nothing than he who believes what is wrong."
-- Thomas Jefferson