back to article Elon burning to get Falcon back on the launchpad

Only a regulatory sign-off stands between Elon Musk's SpaceX and the restart of its Falcon 9 launch program within a week. With its anomaly investigation complete, the company hopes to launch a Falcon carrying Iridium's NEXT satellite from Vandenberg on January 8. The Elon Musk spaceflight company says the catastrophic …

Oxygen is not flammable

Something is missing from the SpaceX report, or wasn't mentioned in the article. Oxygen is not flammable--it supports the burning of other materials or compounds, but does not by itself burn. Therefore the oxygen in the buckled tank could not have ignited.

7
2
Silver badge

Re: Oxygen is not flammable

While oxygen by itself is not flammable, I'm guessing that something else, like the resin in the composite lining, is flammable when it's in an oxygen-saturated environment. So the friction from the wrap breaking would create enough heat that, coupled with LOX all over, would then ignite the resin, which would turn it all pear-shaped.

9
0

Re: Oxygen is not flammable

But lots of things you don't normally think of as flammable are in a high oxygen atmosphere. The fuel could have been almost anything from the carbon overwrap to the aluminium liner.

14
0

This post has been deleted by its author

Silver badge

Re: Oxygen is not flammable

"I'm guessing that something else, like the resin in the composite lining, is flammable when it's in an oxygen-saturated environment."

True, but saying that the oxygen ignited is sloppy writing although no more so than one might expect from a PR-written press statement.

5
2
Anonymous Coward

Re: Oxygen is not flammable

A bullet from a ULA sniper could also cause liner separation...

4
2

Feeble troll, but anyway...

(1) ordinary rifle bullets have surprisingly poor penetration into water: Mythbusters reported about 1 metre for .50 cal

(2) LOX is rather denser than water

(3) would be high-risk strategy to rely upon video coverage not to show penetration occurring. Much better to use alien death ray from crashed UFO stored at Area 51...

13
0

Re: Oxygen is not flammable

Most everything burns in a 100% oxygen atmosphere, once you have a spark you have a problem with rising pressure and rapid disassembly. The resin and CF composite are likely sources the explanation of breaking fibre in the composite is interesting, though any buckling in a composite would be not good, given the propensity for it to de-laminate if the mechanical stress caused by the buckling was not cater for in the layup.

Lockheed had a problem with its composite tanks back in the X-33 days, but seems using composites for Liquid Helium needs a little work. Most have been using titanium spheres to manage the liquid helium.. Maybe more insulation or rigidity required (likely both).

1
0
Anonymous Coward

Re: Oxygen is not flammable

Back in the mid seventies I remember a fire on board a BAC 111 that the enquiry termed "an oxygen flash fire" (that's if I remember the phrase correctly).

From what I remember being told by people who witnessed the event, an oxygen leak in the cabin caused an excessively rich atmsophere while freight was being loaded. Something in the cabin caused a spark and fire flashed down the down the cabin and burst out through the open freight-loading door.

There was a lot of damage to the internal fittings but the aircraft was returned to the uk and repaired.

Although I'm not sure (as it's quite a while ago now) I believe that I flew in this ac when it came back into service.

I've searched the web for the last hour looking for info about this incident, and although I've found references to the particular aircraft I can't find any mention of the incident.

1
0

This post has been deleted by its author

Silver badge

Re: Oxygen is not flammable

Which is why you generally use a maximum of 70% oxygen for bottled breathing gas - in 100% oxygen almost everything burns rather enthusiastically

2
0

Re: Feeble troll, but anyway...

Only one issue.. LOX is LOX because of a balance of temperature and pressure (as is H20), take one away and it becomes a gas real fast..

While the "magic bullet" wouldn't travel far the sparks on the penetration of the tank would be a possible source..

A good fault analysis considers every possibility no matter how crazy even just to eliminate it as crazy..

2
0

Re: Feeble troll, but anyway...

everybody knows there are no alien death rays at Area 51.

[ they moved them all to Area 52 . . . because nobody looks there ]

4
0
Vic
Silver badge

Re: Oxygen is not flammable

Which is why you generally use a maximum of 70% oxygen for bottled breathing gas

Speak for yourself. Divers frequently use between 80% and 100%[1] O2.

in 100% oxygen almost everything burns rather enthusiastically

There was a move a few years ago to use titanium first stages. Titanium is tricky to ignite, but burns in nitrogen...

Vic.

[1] The appropriate gas to use is a religious argument rather than a technical one :-(

2
3
Bronze badge

Re: Oxygen is not flammable

Pssssst... the clue is in the press release: "COPV consists of an aluminum inner liner with a carbon overwrap".

Carbon is deliciously flammable, especially in an atmosphere that's all oxygen... :-)

1
0
Silver badge

Fuelling the fire[ball]

I don't think we need to look very far, or to unlikely or obscure sources, for the source of the fuel for the fireball; it would have been the kerosene RP-1 propellant.

It would appear that the COPVs used to pressurise the LOX tanks are actually embedded within the tanks but the outer composite wrap was not sealed against penetration by the LOX that surrounded it.

A pressure vessel needs to satisfy two functions: to maintain separation between what's in the vessel and what's outside it, and not to rupture under its rated pressure, and to achieve this Space-X relied upon the impermeability of the aluminium liner to maintain separation and the tensional strength of the outer wrap to withstand and maintain the internal pressure. However, whilst the buckles in the liner may not have significantly reduced the strength of the PV, as that was being provided by the wrap, any buckles in the liner would not have been static as the conditions around it changed; as either the Helium or LOX pressures changed and/or solid LOX formed next to them the buckles in the liner would have been stretched in some areas and compressed in others, eventually resulting in a rupture. As the Helium COPV was at a higher pressure than the LOX, when it ruptured it would have over-pressured the LOX tank in which it was embedded and the resultant failure of the LOX tank would have almost certainly have damaged the rest of the plumbing, including the fuel lines.

Re inflammability of Oxygen: when something burns it is combining with Oxygen in a process that releases heat. The most common example of burning we see in day-to-day life is that of combining Carbon with Oxygen, with rusting probably being the second most common example.

2
0
Anonymous Coward

Re: Oxygen is not flammable

"Speak for yourself. Divers frequently use between 80% and 100%[1] O2."

No they don't you can't use pure oxygen underwater due to oxygen toxicity. Even enriched oxygen products limit the depth you can dive - standard compressed air (the standard recreational scuba kit) only allows you to dive 40-50m but you'd risk nitrogen narcosis at that depth anyway..

The only time you have high purity oxygen in diving is for post-dive medical treatment for decompression sickness (which wouldn't be frequent) or submersible which is mixing its own gas ratios (once again, not common).

High purity oxygen is commonly used in medical situations though - without much risk. People have even been seen to smoke while attached to nasal oxygen supply.

"Which is why you generally use a maximum of 70% oxygen for bottled breathing gas"

Medical oxygen is usually a minimum of 90% and a maximum of 96% pure oxygen.

3
3
Vic
Silver badge

Re: Oxygen is not flammable

Before you get going on this, you might want to read up on the Dunning–Kruger effect.

No they don't

Yes we do.

you can't use pure oxygen underwater due to oxygen toxicity.

You can use pure oxygen underwater despite oxygen toxicity. And we do.

Even enriched oxygen products limit the depth you can dive

Indeed they do. But high-O2 mixes - up to 100% for some people - reduce the time required to decompress from dives. And that is why we use them.

The only time you have high purity oxygen in diving is for post-dive medical treatment for decompression sickness (which wouldn't be frequent) or submersible which is mixing its own gas ratios (once again, not common).

Nonsense on both counts. High-O2 mixes are useful as decompression gases, and there is a whole community of us that carry 100% O2 for continuously mixing our breathing gas underwater. Just because you don't know about something doesn't mean it doesn't exist...

Medical oxygen is usually a minimum of 90% and a maximum of 96% pure oxygen.

Diving Oxygen is better than 99.5% pure, and usually better than 99.9% pure.

Vic.

4
1

Re: Oxygen is not flammable

"Oxygen is not flammable--it supports the burning of other materials or compounds, but does not by itself burn."

Well, it depends on your definition - there are certainly chemicals (fluorine and some of its compounds) out there that will oxidise oxygen. Chemists may frown on calling that "burning" though.

Although these other oxidisers would probably be merrily oxidising any other available chemicals to a greater extent - like nearby fuels, structures, humans, etc. instead of getting a chance to react with the oxygen.

Interestingly, rocketry was one of the fields that had great interest in this area, before deciding it wasn't really worth the bother of working with something that will make a big hole in a concrete floor if you spill it, just for a greater specific impulse.

2
0
Silver badge

Re: Oxygen is not flammable

There was a move a few years ago to use titanium first stages. Titanium is tricky to ignite, but burns in nitrogen...

Titanium has a lower ignition temperature in oxygen than nitrogen. It's not a panacea for handling liquid oxygen.

1
0

This post has been deleted by its author

I&I

Re: Feeble troll, but anyway...

Presumably relates to this Reg. item of last October.

0
0
I&I

Re: Oxygen is not flammable

Presumably relates to this Reg. item of last October.

0
0
Silver badge

Back in business

I look forward to watching another flight next week.

5
0
Anonymous Coward

Re: Back in business

Wonder if they will try for a landing as well?

0
0
Silver badge

Re: Back in business

Why wouldn't they? It's not as if there is any issue with the first stage, this was a second stage failure - and it sounds like they were trying for just a little bit more push (using colder fuels for increased energy density)

0
0

Re: Back in business

They have no plans to not try for a landing every time from now on, with the possible exception of Heavy centre cores. Barge landings for Iridium and Echostar, probable RTLS for CRS-10, and a barge for SES-10 which should also be the first reflight.

0
0
Anonymous Coward

It's an obvious coverup..

.. we all know that the actual cause was the Facebook satellite.

:)

5
0
Silver badge
Coat

reading skills at risk

Aluminium *liner* buckled.

carbon overwrap

(wee baby gap)

possibly solid oxygen (wheeee)

stop load cycle, disconnect, spin up pumps, de-pressurize O tank eeeeever so slightly, solid oxygen jumps state, expands, pops one (or more) carbon strand(s) in overwrap - (sparkie) (carbon goes whooof)(rocket goes boom)

1
0
I&I

Test that it doesn't blow up ?

For the future - what's the logic of performing a potentially wearing-out if not immediately destructive kind of test on a rocket laden with high-consequence (e.g. value) payload ?

ST thought: Maybe that's how the other "Two of Nine" ended up

0
0

POST COMMENT House rules

Not a member of The Register? Create a new account here.

  • Enter your comment

  • Add an icon

Anonymous cowards cannot choose their icon

Forums

Biting the hand that feeds IT © 1998–2018