RuBisCO

Why Fluorine Never made it as rocket fuel

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There was alot of development in fluorine and fluorine/oxygen mixtures (FLOX) as oxidizer for rockets in the 1950/1960's, and a Atlas rocket supposedly once flew on a FLOX mixture, but it never was used again... why? A FLOX (69% LF2) with Kerosene supposedly has 12% more ISP, 17% greater density and 31% great ISP/density. 

Well aside for being more corrosive than LOX, deadly toxic, producing launch pad damaging hot HF gas and corrosive HF pollution, I think the biggest problem was price. 

Liquid fluorine is $6 per kg, compared with Liquid oxygen which is $0.04 per kg, Rocket grade Kerosene is $0.05 per kg and Liquid Hydrogen is $2.6 per kg. Using those numbers for LOX/Kerosene I get $0.043 per kg of propellant, but for FLOX(69%)/Kerosene I get $3.27 per kg! That is a 76 fold more money! Using those numbers it would cost $21,419 to fuel up a 500 ton rocket with LOX/Kerosene, but $1,636,970 for FLOX(69%)/Kerosene. And those are idealized prices (1950's dollars?), we know that Elon Musk claimed it costs roughly $200,000 to fuel up a Falcon 9 with roughly 500,000 kg of propellant, that means the price of LOX/Kerosene is $0.4, or ~10 fold the ideal numbers I linked. A  FLOX(69%)/Kerosene version of the Falcon 9 would end up costing at least 16 million dollars to fuel!  So then the propellant goes from costing 0.3% the launch cost to 26% the launch cost. 

LF/LH2 is not much better, costing 12 fold the cost of LOX/LH2 (0.46 $/kg vs 5.5 $/kg), all for a 5% improvement in ISP and 22% improvement in density and 25% improvement in ISP/density. 

The reason for this is it is very easy to make liquid oxygen, just cryopurify it from air, no need to ship it, just make it on site. Kerosene is refined from oil, Natural gas is cheap, hydrogen is reformed from either then liquified. Fluorine on the other hand has to be manufacture from electrolysis of potassium fluoride, and liquid fluorine is scary to transport. Even N2O4/UDMH is cheap in comparision at 0.42 $/kg, in fact I think there was no oribital rocket that used a propellant that cost more than 1 $/kg in those ideal prices (or 10 $/kg in realistic/today prices). 

So when considering rocket fuels ISP and density it not everything, clearly price is a big factor. 

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Explosions, corrosion and copious amounts of poison just waiting to kill everything in sight.

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It's literally Jeb's wet dream of rocket fuel. Any rocket loaded with that is almost guaranteed to explode spectacularly since it's extremely reactive, poisonous and dangerous. Back then, so many people died while trying to study it that there's a reason they're called "fluorine martyr"

It does makes launching cost lower, but at the same time the risk of catastrophic failure becomes higher, which isn't what you want in an operation like a space program. A safer but pricier option is better than riskier but cheaper option when it comes to launching rocket to space

Edited by ARS

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4 hours ago, RuBisCO said:

Fluorine on the other hand has to be manufacture from electrolysis of potassium fluoride, and liquid fluorine is scary to transport.

Yup.

Hard to obtain and is a PITA to handle.

https://what-if.xkcd.com/40/

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A "PITA to handle" is only scratching the surface IMO. I'd go as far as saying it is The Devil himself.

It is among the strongest oxidizing agents known to man, has the highest electronegativity, and according to literature reacts with all elements except Helium and Neon. Some serious business right there. It is literally the only element that can make direct reactions with the Noble Gases Krypton Xenon and Radon.

Fluorine is no joke.

Under some conditions it forms HF (for example by reaction with Water of Hydrogen), and HF is some crazy stuff too. It would etch/dissolve glass! And can kill people in very nasty ways too.

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I don't think cost was the real issue. Governments have been the major funding source for rockets for decades. A higher propellant cost wouldn't be too much of an issue. The government can afford it.

It likely was the handling issues and the costs and risks associated  with them. And of course the risk of having large amounts of the stuff in a rocket. Heck, having large amounts of lox and lh2 were problem enough as it was.

You can get more than 540 seconds of specific impulse with flourine and lithium with some hydrogen. If it has a high enough thrust to weight, this can allow SSTOs to carry significant payloads. But it's way too hard and dangerous to handle.

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4 minutes ago, Xd the great said:

No rocket scientists are this crazy bruh.

Well, some were crazy enough to think of nukes for propulsion... or at least got on board with the idea. 

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29 minutes ago, Bill Phil said:

Well, some were crazy enough to think of nukes for propulsion... or at least got on board with the idea. 

None of them rode on project orion.

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https://en.wikipedia.org/wiki/Fluorochemical_industry

Quote

The industry was predicted to reach 2.6 million metric tons per year by 2015.

So, they could take a little bit for rockets, and nobody would notice.

Spoiler

"Strange Angel" series.
If they had an idea to build a fluorine rocket and stole it instead of nitric acid and tetraoxide, the world could never see JPL.

 

Edited by kerbiloid

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1 hour ago, kerbiloid said:

https://en.wikipedia.org/wiki/Fluorochemical_industry

So, they could take a little bit for rockets, and nobody would notice.

  Hide contents

"Strange Angel" series.
If they had an idea to build a fluorine rocket and stole it instead of nitric acid and tetraoxide, the world could never see JPL.

 

I agree. Someone should build a fluorine hydrogen rocket.

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1 hour ago, Xd the great said:

None of them rode on project orion.

None have ridden on flourine rockets either.

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1 hour ago, Bill Phil said:

None have ridden on flourine rockets either.

Yeah, but fluorine is so dangerous that handeling them was much harder than dealing with nuclear bombs.

And nuclear bombs are just radioactive,they wont blow you up with safety on.

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41 minutes ago, Xd the great said:

And nuclear bombs are just radioactive,they wont blow you up with safety on.

Well… It happens that such safeties are prone to failure, so they stack them up serially. But yet, there was at least one occurrence of a near accidental explosion. Search for "Broken Arrow" incidents.

The most scary one was the North Carolina one IMHO. All the 7 safeties were improperly engaged, and the thing just didn't blew up because the 7th safety armed but failed to detonate.

http://www.businessinsider.com/nuclear-bomb-accident-goldsboro-nc-swamp-2017-5

 

Edited by Lisias
typo. =/

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10 minutes ago, Lisias said:

Well… It happens that such safeties are prone to failure, so they stack them up serially. But yet, there was at least one occurrence of a near accidental explosion. Search for "Broken Arrow" incidents.

The most scary one was the North Carolina one IMHO. All the 7 safeties were improperly engaged, and the thing just didn't blew up because the 7th safety armed but failed to detonate.

http://www.businessinsider.com/nuclear-bomb-accident-goldsboro-nc-swamp-2017-5

Worrying, but nukes are inherit safe as in they require an precise sequence to go off, you can not set it of with impact or explosion however this will still be an dirty bomb blowing plutonium all over. Again this event shows something was wrong, on an B52 with just two bombs I would want some to enter the bomb bay and pull the safety pins on the bombs in the first place. 

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9 hours ago, Cheif Operations Director said:

Caesium and Flourine as rocket fuel.

Liquid state of course

Meh, how bout caesium as solid and fluorine is pumped inside like a solid booster/liquid engine hybrid

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1 hour ago, Xd the great said:

Meh, how bout caesium as solid and fluorine is pumped inside like a solid booster/liquid engine hybrid

Oh... hehehe

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33 minutes ago, Cheif Operations Director said:

Yes it would be awesome

I feel some explosions.

Jebs gonna love it.

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Near the end of Ignition  it is mentioned that a tri-propellant mixture of fluorine, lithium, and hydrogen was tested to an ISP of 542s, with a relatively low chamber temperature.  The author opined that it would eventually see use as a space stage, especially useful around Jupiter. 

I’m going to guess that the handling issues and complex plumbing (among other things) discouraged anyone from trying to develop a flight unit...

Edited by StrandedonEarth

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