Why Fluorine Never made it as rocket fuel

[Kerbart]

  On 7/21/2018 at 3:26 AM, RuBisCO said:

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.

Expand  

Sane people would point out the disadvantages you're listing. But rocket scientists in general are not sane people. So you're probably right.

[RuBisCO]

Look the reason I started this thread was to try to find other reasons then the obvious "Fluorine is demonic" (which frankly anything that burns on contact with concrete is). I think I hit on a fact that any propellant with a idealize price above $1 never flies, regardless if how hard it is to handle. Red fuming nitric acid and Hydrazine derivatives are corrosive and toxic too, but way cheaper.  

Edited July 23, 2018 by RuBisCO

[kerbiloid]

It's possible to have a look at the launch price from another pov.

(typical launch failure probability) * (cost of launchpad repairing, surroundings cleaning, and health insurance)

I guess this number will make fluorine much more expensive than fluorine market price itself.

[magnemoe]

  On 7/22/2018 at 8:13 PM, RuBisCO said:

Look the reason I started this thread was to try to find other reasons then the obvious "Fluorine is demonic" (which frankly anything the burns on contact with concrete is). I think I hit on a fact that any propellant with a idealize price above $1 never flies, regardless if how hard it is to handle. Red fuming nitric acid and Hydrazine derivatives are corrosive and toxic too, but way cheaper.  

Expand  

Hydrazine is also storable at room temprature who is very nice in many settings. Long term storage is pretty much an requirement for missiles who many orbital rockets derive from. 
Simply having a bit better performance is often not enough if it make handling much harder.
Hydrogen is not standard propellant even if it has best performance simply because low density and very low temperature requirements.  

[Bill Phil]

  On 7/22/2018 at 8:13 PM, RuBisCO said:

Look the reason I started this thread was to try to find other reasons then the obvious "Fluorine is demonic" (which frankly anything the burns on contact with concrete is). I think I hit on a fact that any propellant with a idealize price above $1 never flies, regardless if how hard it is to handle. Red fuming nitric acid and Hydrazine derivatives are corrosive and toxic too, but way cheaper.  

Expand  

Yes. But you have to consider why that price is so high in the first place. 

It's probably hard to create, but storing it and transporting it is also immensely difficult. 

[RuBisCO]

  On 7/23/2018 at 5:28 AM, magnemoe said:

Hydrazine is also storable at room temprature who is very nice in many settings. Long term storage is pretty much an requirement for missiles who many orbital rockets derive from. 
Simply having a bit better performance is often not enough if it make handling much harder.
Hydrogen is not standard propellant even if it has best performance simply because low density and very low temperature requirements.  

Expand  

This could be said of Chlorine tri/pentafluoride, room temp storable, improves performance and density, but the cost of it is too much. 

[kerbiloid]

They were suggesting fluorine upper stages more than once. For Spiral, UR-700, etc.
This is not hundreds tons, usually just a ton or several. This doesn't cost a lot. But was rejected.

So, probably the only reason is  that even more expensive than fluorine itself are the fluorine's consequences.

[Lisias]

  On 7/23/2018 at 2:51 PM, kerbiloid said:

So, probably the only reason is  that even more expensive than fluorine itself are the fluorine's consequences.

Expand  

Just imagine this: 

  Reveal hidden contents

 

or this: 

  Reveal hidden contents

 

And figure out all that fluorine being spilled around...

Edited July 23, 2018 by Lisias
whoops.

[kerbiloid]

That's exactly what I'm saying, but in terms of cost.

[Lilithvia]

You mean F9s could already be flying around the moon with this stuff?

[kerbiloid]

No I mean that fluorine burns launchpad much better.

[Lilithvia]

Excuse me for not knowing much chemistry (I'm a mech engineer, only needed Chem 1200 and chem 1210-1215), but why is fluorine so bad? Doesn't it strengthen teeth?

[kerbiloid]

It strengthens teeth and burns everything in fire.
And it's toxic. And corrosive. And cryogenic.

So, not only that fluorine itself costs much, but if when a rocket bursts, a lot of money would be spent on the launchpad repair.
If it doesn't burst, a lot of money should be spent on precautions.

[Lilithvia]

So it's toxic but yet we use it to strengthen teeth...

???

[kerbiloid]

Chlorine is also toxic but you pour it onto food in salt.

Edited July 23, 2018 by kerbiloid

[Lilithvia]

Well that's different, it's nontoxic when in table/sea salt

I think something to do with ingestion over inhalation plus the molecular bond? I'm not sure

[kerbiloid]

  Reveal hidden contents

Your bones and teeth need fluorine in form of apatite fluoride (?) to be strong and anti-corrosive protected.  Weaker acids can hardly dissolve fluorine compounds.
So, in small amounts fluorine is necessary.

***

About chlorine.

When in water (also in saliva), NaCl dissociates into ions, so you consume the same ions of chlorine.

But no problem, you have enough your own chlorine in stomach liquid, and produce (at the same place) about 1 g of necrotizing venom (pepsin) per day. It's enough to make 50 kg of protein to completely decay.

Just your stomach produces protective slime containing its inhibitor. But in principle nothing has changed since ferns and giant scolopendras..Just you first tear your food apart and push it into your stomach before inject the digestive fluid.

And in fluorine atmosphere burns everything including air.

Edited July 23, 2018 by kerbiloid

[KSK]

  On 7/22/2018 at 8:13 PM, RuBisCO said:

Look the reason I started this thread was to try to find other reasons then the obvious "Fluorine is demonic" (which frankly anything that burns on contact with concrete is). I think I hit on a fact that any propellant with a idealize price above $1 never flies, regardless if how hard it is to handle. Red fuming nitric acid and Hydrazine derivatives are corrosive and toxic too, but way cheaper.  

Expand  

Okay. Lets look at the numbers then.

From this site (feel free to provide an alternative), the Block 2 Falcon 9 contained a total of 174,000 litres of LOX. Liquid fluorine has a density of 1.5 kg/l. So, assuming that the Falcon 9 used 100% fluorine as an oxidiser it would need 261,000 kg of fluorine. From your price of 6$ per kilogram, that works out at $1.56m to fill a Falcon 9. Not cheap by any means but still a single digit percentage of the quoted launch price (whichever launch price you choose to use). And that's with one of the cheapest, if not the cheapest launch vehicle in its class. 

I'm sure price is a factor but it's a fairly insignificant one in the overall scheme of building and flying a launch vehicle. The obvious "Fluorine is demonic" reasons are far more compelling.

[NSEP]

  On 7/23/2018 at 5:14 PM, Lilithvia said:

So it's toxic but yet we use it to strengthen teeth...

???

Expand  

I think you are confusing flourine with flouride?

https://en.m.wikipedia.org/wiki/Fluoride#Cavity_prevention

[RuBisCO]

  On 7/23/2018 at 6:17 PM, KSK said:

Okay. Lets look at the numbers then.

From this site (feel free to provide an alternative), the Block 2 Falcon 9 contained a total of 174,000 litres of LOX. Liquid fluorine has a density of 1.5 kg/l. So, assuming that the Falcon 9 used 100% fluorine as an oxidiser it would need 261,000 kg of fluorine. From your price of 6$ per kilogram, that works out at $1.56m to fill a Falcon 9. Not cheap by any means but still a single digit percentage of the quoted launch price (whichever launch price you choose to use). And that's with one of the cheapest, if not the cheapest launch vehicle in its class. 

I'm sure price is a factor but it's a fairly insignificant one in the overall scheme of building and flying a launch vehicle. The obvious "Fluorine is demonic" reasons are far more compelling.

Expand  

I actually calculated those numbers, on the first post of this thread. 

[Kerbart]

  On 7/23/2018 at 7:33 PM, NSEP said:

I think you are confusing flourine with flouride?

Expand  

Pah! Semantics!

[Bill Phil]

Okay, guys, let's stop the Strangelove talk. 

In any case, flourine isn't likely to be used soon.

Edited July 24, 2018 by Bill Phil

[YNM]

  On 7/23/2018 at 7:33 PM, NSEP said:

I think you are confusing flourine with flouride?

Expand  

Eh, you can whiten your teeth with the exhaust...

[kerbiloid]

Gentlemen, flUOr-, not flOUr.

P.S.
Why not just call it "phthor"...

Edited July 24, 2018 by kerbiloid

[KSK]

  On 7/24/2018 at 1:35 AM, RuBisCO said:

I actually calculated those numbers, on the first post of this thread. 

Expand  

So you did - sorry.

I still don’t think that price is a particularly relevant factor here though. Until fairly recently, rocketry has not been a particularly price sensitive business. If the risks of using fluorine had been outweighed by utility or by pure performance, it would have been used.