RocketSquid

Is it feasible to synthesize RP-1?

Recommended Posts

I was thinking about ISRU, and in attempting to determine the average molecular weight of RP-1 I stumbled on the fact that it was mostly branched or cyclic hydrocarbons. Seeing as the Fischer-Tropsch process, and any other hydrocarbon synthesis processes I could find data on, produce straight-chain hydrocarbons, is synthesis of RP-1 unviable, or is there some way to efficiently produce branched-chain hydrocarbons?

Share this post


Link to post
Share on other sites

Don't know about RP-1, but syntin certainly is synthesized, and is slightly superior to RP-1 in a few ways.

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

I can't find much on kerosene synthesis, but apparently there is a process to make it or something much like it using water and CO2. May be able to synthesize it with syngas as well.

Share this post


Link to post
Share on other sites
1 hour ago, Bill Phil said:

Don't know about RP-1, but syntin certainly is synthesized, and is slightly superior to RP-1 in a few ways.

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

I can't find much on kerosene synthesis, but apparently there is a process to make it or something much like it using water and CO2. May be able to synthesize it with syngas as well.

Fischer-Tropsch can make kerosene, but it’ll still be mostly straight chains.

Share this post


Link to post
Share on other sites
Posted (edited)

ttp://sustainableskies.org/earth-air-water-jet-fire/

https://translate.google.com.tr/translate?sl=ru&tl=en&js=y&prev=_t&hl=ru&ie=UTF-8&u=https://www.gazeta.ru/science/2014/04/30_a_6012781.shtml

Efficiency makes crying.

Quote

 

- What is the efficiency of the process?

- In the process of obtaining syngas using sunlight in a 3 kW reactor, the average efficiency is 1.73%. Peak - 3.53%. The overall efficiency, as the calorific value of the fuel, related to the power of the incident light, is less than 1%. Our goal is to scale the production to the size of the plant to bring efficiency to more than 10%.

Edited by kerbiloid

Share this post


Link to post
Share on other sites
Posted (edited)

Any hydrocarbon can be synthesized. RP-1 is pretty much the same thing as jet A, and jet A can be (and is) synthesized.

Synthetic jet A is different from regular jet A in that it has far fewer aromatics in the fuel, which actually makes it more like RP-1.

However, there is one catch. RP-1 is a fuel standard, not actually a fuel. The fuel standard for Jet A was rewritten several years ago to allow synthetic fuel to be labeled Jet A as long as it meets the other requirements of the standard. Technically, RP-1 is any fuel that meets the RP-1 standard, and the RP-1 standard likely requires it to be refined from crude oil.

Edited by mikegarrison

Share this post


Link to post
Share on other sites
Quote

The propellant shall consist completely of hydrocarbon compounds except as otherwise specified herein.

A quick read-though seems to indicate that nothing in that spec would prevent a synthetic hydrocarbon from meeting it.

Share this post


Link to post
Share on other sites
Posted (edited)

Jet A has 25% aromatics (maximum allowed), while RP-1 allows a maximum of of only 5% aromatics. Synthetic jet fuel has almost no aromatics, so it's probably closer to being "ready to go" RP-1 than it is jet fuel.

(Typically synthetic jet fuel is used in a blend with refined jet fuel because if the aromatic content gets too low, then the seals in the fuel system can start to leak.)

I'm not a chemistry guy, so I don't know all the details. I do know that the main concern with using synthetic fuels is that the specs were originally written assuming natural petroleum. So some aspects of "fit for purpose" (like keeping the seals functional) were not originally part of the spec simply because nobody really imagined that they needed to be specified.

Edited by mikegarrison

Share this post


Link to post
Share on other sites

Totally feasible!

Industrial organic chemistry is like legos up to a point! Where there's a will there's a way. Let's see, for going from methane to specifically aromatics I think the normal answer would be super acid catalysis (normally in a loaded zeolite) to make ethylene, then Pt catalysis to dehydrogenate to benzene. I could probably pull up examples if it's useful, but hopefully this is enough to get started? These chemistries are used on an industrial scale, but the key difficulty is always struggling to maintain high catalyst activity while they're constantly getting covered in coke. That's the main reason you don't see these in laboratories much. The easy approach I learned is to just burn it off, but trying that on a small scale is a bit tricky...

Still, if you had JPL on your side...

Share this post


Link to post
Share on other sites

Diethylcyclohexane is something Rocketdyne proposed using... almost immediately after RP-1 was codified, so nobody was interested.

Share this post


Link to post
Share on other sites
On 4/9/2019 at 6:37 PM, RocketSquid said:

I was thinking about ISRU, and in attempting to determine the average molecular weight of RP-1 I stumbled on the fact that it was mostly branched or cyclic hydrocarbons. Seeing as the Fischer-Tropsch process, and any other hydrocarbon synthesis processes I could find data on, produce straight-chain hydrocarbons, is synthesis of RP-1 unviable, or is there some way to efficiently produce branched-chain hydrocarbons?

You can make synthetic petroleum, Germany did during WW2 and it was interest for it back the oil price was $200 barrel, if that price stayed it would been economical. 
problem is that this uses coal as raw material. 
You can do it from simpler materials but that is way more expensive. 

Hydrogen or methane works better and is easier to manufacture. If you want something who is liquid you can use methanol, ethanol or butane 
RP-1 was selected as JP-1 was very common and cheap and people had lots of experience with it. 
 

Share this post


Link to post
Share on other sites
On 4/12/2019 at 8:00 PM, magnemoe said:

RP-1 was selected as JP-1 was very common and cheap and people had lots of experience with it.

JP-4.

Also, it was too common and the tolerance was set way, way wide, which annoyed the rocket people and there almost-exploding Swiss watches.

Share this post


Link to post
Share on other sites

You can certainly make a complicated hydrocarbon mix. With enough effort put into it, you could probably make something that matches the RP-1 specification. The major question is: why? The RP-1 specification is the way it is because it is (relatively) easy to make it from a feedstock of petroleum. If you don't have access to petroleum, though, it would be needlessly complicated.

There are valid reasons to try to get bigger hydrocarbon chains than methane. More extended chains can be made with more of the easily available CO2 than difficult-to-acquire hydrogen. More likely, however, you're going to see something that isn't RP-1, but a new specification of "a mix that can be readily made from CO2 and hydrogen".

Share this post


Link to post
Share on other sites

As the OP was about ISRU, maybe there is an alternative fuel instead of RP-1/kerosene, appropriatee for jets and rockets?

Maybe not as cheap as kerosene with its 200 years history, but with enough simple technology appropriate for Mars.

There were hydrogen, methane, and propane-buthane experimental aircraft engines, they worked. But they are too volatile.

(Faced this problem when was thinking about KSP ISRU, too, lol).

Share this post


Link to post
Share on other sites

For rockets you can fire methane (SpaceX have a working methalox rocket after all).

I'd think you could make a methane jet engine too given how unfussy turbines are about what they're fired with. Probably little more than an injector change.

Share this post


Link to post
Share on other sites
Posted (edited)
3 hours ago, Flibble said:

For rockets you can fire methane

Rockets are not a problem, they can use various things. I'm mostly about the jets.

The methane jets have been successfully tested, but they require a big airplane and special storage conditions.
While in KSP they mostly use fighter-sized airplanes without cryostats.

Edited by kerbiloid

Share this post


Link to post
Share on other sites
7 minutes ago, kerbiloid said:

Rockets are not a problem, they can use various things. I'm mostly about the jets.

The methane jets have been successfully tested, but they require a big airplane and special storage conditions.
While in KSP they mostly use fighter-sized airplanes without cryostats.

Surviving Mars seems to hint towards magnesium fuel with atmospheric oxidizer, but I haven’t looked into it and the game is guilty of exaggerating Mars’s atmosphere.

Share this post


Link to post
Share on other sites
Posted (edited)
30 minutes ago, DDE said:

Mars’s atmosphere.

Even if leave alone Mars, at least on Earth/Kerbin.

Irl they mine oil, but Kerbal style is ISRU, especially making everything from carbon dioxide and water.
And the jet fuel looks the only resource having no reasonable alternative alternative to oil (for KSP).
So, one can produce rocket fuel and other things right from scratch, but the jet airplanes (and only them) need it.
Irl there are jets using hydrogen, methane, propane-buthane, ethanol (poor fuel, only for local jets).

Also
https://en.wikipedia.org/wiki/Aviation_biofuel

Edited by kerbiloid

Share this post


Link to post
Share on other sites
This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.