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Latest candidate for SpaceX pad explosion



 
 
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  #1  
Old October 18th 16, 05:23 AM posted to sci.space.policy
Fred J. McCall[_3_]
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Posts: 10,018
Default Latest candidate for SpaceX pad explosion

While they haven't confirmed it as the cause yet, the current leading
candidate for the cause of the explosion is SOLID oxygen forming in
the composite overwrapped pressure vessel that helium is stored in.

This is how it would work. For this flight SpaceX was apparently
trying to increase the degree of super-cryo chilling on the liquid
oxygen, so they were pumping it even colder than normal (close to
freezing point). Some of the super-chilled LOX could have gotten into
the COPV and then frozen. As tank pressure went up, the solid oxygen
could not be squeezed back out of the overwrap and detonated with the
carbon composite wrapping. This breeched the helium pressurization
tank, overpressuring the LOX tank and things go up from there.

SpaceX has not confirmed that this is their leading theory (or even a
theory). It is being reported as something that came out of a private
conversation with Musk and SpaceX says they have a policy of not
commenting on private conversations by Musk.

If that's really the problem, it makes a return to flight easier. Just
revert to the 'normal' amount of chilling that they used on previous
flights.


--
"Insisting on perfect safety is for people who don't have the balls to
live in the real world."
-- Mary Shafer, NASA Dryden
  #2  
Old October 18th 16, 07:06 AM posted to sci.space.policy
Sylvia Else
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Posts: 1,063
Default Latest candidate for SpaceX pad explosion

On 18/10/2016 3:23 PM, Fred J. McCall wrote:
While they haven't confirmed it as the cause yet, the current leading
candidate for the cause of the explosion is SOLID oxygen forming in
the composite overwrapped pressure vessel that helium is stored in.

This is how it would work. For this flight SpaceX was apparently
trying to increase the degree of super-cryo chilling on the liquid
oxygen, so they were pumping it even colder than normal (close to
freezing point). Some of the super-chilled LOX could have gotten into
the COPV and then frozen. As tank pressure went up, the solid oxygen
could not be squeezed back out of the overwrap and detonated with the
carbon composite wrapping. This breeched the helium pressurization
tank, overpressuring the LOX tank and things go up from there.

SpaceX has not confirmed that this is their leading theory (or even a
theory). It is being reported as something that came out of a private
conversation with Musk and SpaceX says they have a policy of not
commenting on private conversations by Musk.

If that's really the problem, it makes a return to flight easier. Just
revert to the 'normal' amount of chilling that they used on previous
flights.



Customers might be less than happy with the idea that their production
launch vehicle is being experimented on, though the contract may allow
for that.

Sylvia.
  #3  
Old October 18th 16, 01:23 PM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 2,307
Default Latest candidate for SpaceX pad explosion

In article ,
says...

While they haven't confirmed it as the cause yet, the current leading
candidate for the cause of the explosion is SOLID oxygen forming in
the composite overwrapped pressure vessel that helium is stored in.

This is how it would work. For this flight SpaceX was apparently
trying to increase the degree of super-cryo chilling on the liquid
oxygen, so they were pumping it even colder than normal (close to
freezing point). Some of the super-chilled LOX could have gotten into
the COPV and then frozen. As tank pressure went up, the solid oxygen
could not be squeezed back out of the overwrap and detonated with the
carbon composite wrapping. This breeched the helium pressurization
tank, overpressuring the LOX tank and things go up from there.

SpaceX has not confirmed that this is their leading theory (or even a
theory). It is being reported as something that came out of a private
conversation with Musk and SpaceX says they have a policy of not
commenting on private conversations by Musk.

If that's really the problem, it makes a return to flight easier. Just
revert to the 'normal' amount of chilling that they used on previous
flights.


Nice summary of the latest theory (saw it on ARocket).

Thanks,
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.
  #4  
Old October 18th 16, 01:31 PM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 2,307
Default Latest candidate for SpaceX pad explosion

In article ,
ess says...

On 18/10/2016 3:23 PM, Fred J. McCall wrote:
While they haven't confirmed it as the cause yet, the current leading
candidate for the cause of the explosion is SOLID oxygen forming in
the composite overwrapped pressure vessel that helium is stored in.

This is how it would work. For this flight SpaceX was apparently
trying to increase the degree of super-cryo chilling on the liquid
oxygen, so they were pumping it even colder than normal (close to
freezing point). Some of the super-chilled LOX could have gotten into
the COPV and then frozen. As tank pressure went up, the solid oxygen
could not be squeezed back out of the overwrap and detonated with the
carbon composite wrapping. This breeched the helium pressurization
tank, overpressuring the LOX tank and things go up from there.

SpaceX has not confirmed that this is their leading theory (or even a
theory). It is being reported as something that came out of a private
conversation with Musk and SpaceX says they have a policy of not
commenting on private conversations by Musk.

If that's really the problem, it makes a return to flight easier. Just
revert to the 'normal' amount of chilling that they used on previous
flights.



Customers might be less than happy with the idea that their production
launch vehicle is being experimented on, though the contract may allow
for that.


Sylvia, this quite often the case with SpaceX. It's still a young
company and is still optimizing Falcon 9. Unfortunately, when you push
the envelope like this, sometimes an "unknown unknown" bites you in the
ass.

But, look at the usual suspects. ULA has done very little in the way of
innovation related to the EELV's and costs still went up! Why is that?
You'd think if everything was "standardized", costs would come down, but
they didn't.

Orbital ATK is "innovating" a bit, but mostly by seeking out the lowest
bidders for the bits of their liquid fueled stage(es). The rest is
solid stages made in house. I *really* hate solids for launch. Too
much vibration, extremely violent failure modes, can't be economically
reused, and little chance that costs will ever drop by orders of
magnitude. So, on the "solids" side of the house, Orbital ATK isn't
innovating in a way that would ever reduce costs.

The other way to look at this is that if we never innovate, costs will
not come down by the orders of magnitude that is needed for the US to
become a truly space-fairing nation. That's really Musk's long term
goal, to send a truly huge number of people to Mars. This vision is in
stark contrast to NASA's "vision" of sending a handful of NASA
astronauts to Mars (citizens can apply, but will have a snowball's
chance in hell of becoming a NASA astronaut).

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.
  #5  
Old October 18th 16, 01:36 PM posted to sci.space.policy
Jeff Findley[_6_]
external usenet poster
 
Posts: 2,307
Default Latest candidate for SpaceX pad explosion

In article om,
says...

On 2016-10-18 00:23, Fred J. McCall wrote:

freezing point). Some of the super-chilled LOX could have gotten into
the COPV and then frozen. As tank pressure went up, the solid oxygen
could not be squeezed back out of the overwrap and detonated with the
carbon composite wrapping. This breeched the helium pressurization
tank, overpressuring the LOX tank and things go up from there.


Is there a diagram somewhere ?

What is "COPV" ?


Composite overwrapped pressure vessel. Essentially a very thin metal
tank overwrapped by carbon fiber composite to make the tank strong and
light. The carbon fiber gives the tank its strength.

https://en.wikipedia.org/wiki/Compos...ressure_vessel

If something is solid, does it care that pressure around it is
increasing? And while I am at it, are any liquids compressible ?


It does when it's an energetic solid oxidizer (can't get much more
energetic than solid oxygen) right next to a solid fuel (carbon fiber).
You do that and you have what is called a "contact explosive". The
increase in pressure would cause it to literally explode.

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.
  #6  
Old October 18th 16, 04:11 PM posted to sci.space.policy
Fred J. McCall[_3_]
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Posts: 10,018
Default Latest candidate for SpaceX pad explosion

JF Mezei wrote:

On 2016-10-18 00:23, Fred J. McCall wrote:

freezing point). Some of the super-chilled LOX could have gotten into
the COPV and then frozen. As tank pressure went up, the solid oxygen
could not be squeezed back out of the overwrap and detonated with the
carbon composite wrapping. This breeched the helium pressurization
tank, overpressuring the LOX tank and things go up from there.


Is there a diagram somewhere ?


Do you really need one? The helium pressurization tanks, wrapped in
carbon composite, are inside the LOX tanks.


What is "COPV" ?


I said it in the original article and you cut it out. Composite
Overwrapped Pressure Vessel. It's the helium tanks, but the fact that
there is composite overwrapping is important.


If something is solid, does it care that pressure around it is
increasing? And while I am at it, are any liquids compressible ?


TNT is a solid. Does it care about pressure? Yeah, press it and it
makes a really big bang.


H2O is at its densest at 4°C. So when its temprarture drops further it
expands. Does LOX behave the same near its freezing temperature ?


No. Most substances are denser in their solid phases than their
liquid phases. Water, rubber, and a few other things are exceptions
to this rule. It's a good thing water is.


If, when solidifying, LOX expands, I could see this causing structural
strain that could lead to a tank rupturing if it can't take the load.


Oxygen under pressure as a solid being crushed by carbon leads to a
fire. A very fast fire. One might even almost call it an explosion.


What if Helium ruptured, and evaporating helium cooled the LOX into
solid and then the solid expands, breaks the tank ?


Once the helium tank ruptures you don't need any other explanation,
since you just massively overpressured the LOX tank which blows things
up. The question is why did the helium tank rupture?


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #7  
Old October 18th 16, 07:04 PM posted to sci.space.policy
Niels Jørgen Kruse[_2_]
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Posts: 23
Default Latest candidate for SpaceX pad explosion

Fred J. McCall wrote:

While they haven't confirmed it as the cause yet, the current leading
candidate for the cause of the explosion is SOLID oxygen forming in
the composite overwrapped pressure vessel that helium is stored in.

This is how it would work. For this flight SpaceX was apparently
trying to increase the degree of super-cryo chilling on the liquid
oxygen, so they were pumping it even colder than normal (close to
freezing point). Some of the super-chilled LOX could have gotten into
the COPV and then frozen. As tank pressure went up, the solid oxygen
could not be squeezed back out of the overwrap and detonated with the
carbon composite wrapping. This breeched the helium pressurization
tank, overpressuring the LOX tank and things go up from there.

SpaceX has not confirmed that this is their leading theory (or even a
theory). It is being reported as something that came out of a private
conversation with Musk and SpaceX says they have a policy of not
commenting on private conversations by Musk.

If that's really the problem, it makes a return to flight easier. Just
revert to the 'normal' amount of chilling that they used on previous
flights.


They didn't pressurize helium tanks before loading LOX?

--
Mvh./Regards, Niels Jørgen Kruse, Vanløse, Denmark
  #8  
Old October 19th 16, 01:57 AM posted to sci.space.policy
Sylvia Else
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Posts: 1,063
Default Latest candidate for SpaceX pad explosion

On 18/10/2016 11:31 PM, Jeff Findley wrote:
In article ,
ess says...

On 18/10/2016 3:23 PM, Fred J. McCall wrote:
While they haven't confirmed it as the cause yet, the current leading
candidate for the cause of the explosion is SOLID oxygen forming in
the composite overwrapped pressure vessel that helium is stored in.

This is how it would work. For this flight SpaceX was apparently
trying to increase the degree of super-cryo chilling on the liquid
oxygen, so they were pumping it even colder than normal (close to
freezing point). Some of the super-chilled LOX could have gotten into
the COPV and then frozen. As tank pressure went up, the solid oxygen
could not be squeezed back out of the overwrap and detonated with the
carbon composite wrapping. This breeched the helium pressurization
tank, overpressuring the LOX tank and things go up from there.

SpaceX has not confirmed that this is their leading theory (or even a
theory). It is being reported as something that came out of a private
conversation with Musk and SpaceX says they have a policy of not
commenting on private conversations by Musk.

If that's really the problem, it makes a return to flight easier. Just
revert to the 'normal' amount of chilling that they used on previous
flights.



Customers might be less than happy with the idea that their production
launch vehicle is being experimented on, though the contract may allow
for that.


Sylvia, this quite often the case with SpaceX. It's still a young
company and is still optimizing Falcon 9. Unfortunately, when you push
the envelope like this, sometimes an "unknown unknown" bites you in the
ass.


Still, its customers might reasonably expect their satellites to be
launched on proven hardware, operated in the proven way, with
experiments involved with innovation done on hardware that isn't
launching an expensive satellite.

But we don't know what the contract says.

Sylvia.
  #9  
Old October 19th 16, 04:27 AM posted to sci.space.policy
Fred J. McCall[_3_]
external usenet poster
 
Posts: 10,018
Default Latest candidate for SpaceX pad explosion

(Niels Jørgen Kruse) wrote:

Fred J. McCall wrote:

While they haven't confirmed it as the cause yet, the current leading
candidate for the cause of the explosion is SOLID oxygen forming in
the composite overwrapped pressure vessel that helium is stored in.

This is how it would work. For this flight SpaceX was apparently
trying to increase the degree of super-cryo chilling on the liquid
oxygen, so they were pumping it even colder than normal (close to
freezing point). Some of the super-chilled LOX could have gotten into
the COPV and then frozen. As tank pressure went up, the solid oxygen
could not be squeezed back out of the overwrap and detonated with the
carbon composite wrapping. This breeched the helium pressurization
tank, overpressuring the LOX tank and things go up from there.

SpaceX has not confirmed that this is their leading theory (or even a
theory). It is being reported as something that came out of a private
conversation with Musk and SpaceX says they have a policy of not
commenting on private conversations by Musk.

If that's really the problem, it makes a return to flight easier. Just
revert to the 'normal' amount of chilling that they used on previous
flights.


They didn't pressurize helium tanks before loading LOX?


Where the **** did you get that from?

Hint: The pressure in the LOX TANK goes up as you add LOX.


--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
  #10  
Old October 19th 16, 11:23 AM posted to sci.space.policy
Jeff Findley[_6_]
external usenet poster
 
Posts: 2,307
Default Latest candidate for SpaceX pad explosion

In article . com,
says...

On 2016-10-18 08:36, Jeff Findley wrote:

It does when it's an energetic solid oxidizer (can't get much more
energetic than solid oxygen) right next to a solid fuel (carbon fiber).


Ahh. I remember asking early one what could be combusting in the rocket
with LOX leaking and gotten no answer.

I takle it that carbon fibre even when encased in resin is highly
combustible ? is the resin/epoxy also combustible in contact with LOX ?


LOX makes just about anything combustible, but you still need an
ignition source. In this case, the solid oxygen being compressed (with
nowhere to go) inside the composite overwrap is suspected to be the
source of ignition. If it had stayed liquid (i.e. LOX) like on every
other Falcon 9 test firing and flight, it would not have ignited.

(reminder to self: make sure not to spill any LOX on my bicycle :-(


LOX spilled on anything combustible is bad. LOX on clothes will catch
fire. LOX soaked in asphalt is a contact explosive (make your launch
facilities out of concrete!).

Would fibre glass be less explosive or would the resin still provide the
combustible material that would yield the same result ?


Possibly, but fiberglass would be much weaker, and much heavier.

You do that and you have what is called a "contact explosive". The
increase in pressure would cause it to literally explode.



Would it be fair to assume that a breach in the metal coating inside the
tank would have exposed LOX to carbon ?


You're thinking about this all wrong. The helium tank is the COPV. So
the metal bit is containing the helium (else it would leak out of the
composite). The composite overwrap is in contact with the LOX *at all
times*, because the helium tanks are inside the LOX tank. This is
because if your helium tank is inside the LOX tank, it's colder, and can
therefore hold much more helium at its rated pressure than a tank that
is exposed to ambient temperatures (i.e. outside the LOX tank).

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.
 




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