Anything can be rocket fuel, if you try hard enough?

[KerikBalm]

add some flourine, and you'll at least get some fireworks!

[Nuke]

I think the answer is simple. Can you burn water (excluding nuclear fusion)? No. Not "anything" can be rocket fuel. Even if you limit yourself to flammable materials, like dried apples, I'm still pretty sure that they would not contain enough energy density to lift anything off the ground. Someone who has finished a chemistry course should probably weigh in, though.

EDIT: However, you can literally use anything with mass as a propellant. Not fuel, though.

there are lots of things you can throw in water to make it react violently.

[Jovus]

Considering that taking off your shoe and throwing it is essentially the same operation as what makes a rocket go, then yes. Anything can be rocket fuel.

[shynung]

add some flourine, and you'll at least get some fireworks!

Why fluorine? It's cryogenic. Try chlorine trifluoride, it boils at much higher temperatures.

Edited October 15, 2015 by shynung

[KerikBalm]

That'll do it too...

Flourine is just simpler for the sake of illustrating the principle that you can "burn" almost anything (at least anything common... I don't think you could possibly burn F-Fr)

[Sanic]

What about some nice, flammable polar bears?

[Guest]

anyway... we digress... it is possible to burn water... the Isp is terrible though, so its not going to be a rocket that gets you to orbit....

Plus... your rocet will be super heavy if you're going to be storing flourine.

You can electrolyze it though.

It becomes H and O which are highly flammable.

[Laie]

I was joking originally, but I wonder if what I said in this post is true: can anything be rocket fuel, if you try hard enough?

I'm not sure if I get the question. Anything can be a propellant, you just need to throw it out forcefully enough. Water rockets are a thing.

If you insist on the energy coming from some chemical reaction of your fuel involved, then yes, there must be a few substances that are totally useless. I expect them to be quite exotic, though. Most everyday stuff can be squeezed for a few BTUs.

[Findthepin1]

Let's use the OP as rocket fuel!

jk

[wumpus]

Let's use the OP as rocket fuel!

jk

Remember, threats are verboten.

Is OP a test engineer? If so he is hypergolic with chlorinetrifloride. Cl3F is famously described by John Clarke as:

"It is, of course, extremely toxic, but that's the least of the problem. It is hypergolic with every known fuel, and so rapidly hypergolic that no ignition delay has ever been measured. It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water  with which it reacts explosively. It can be kept in some of the ordinary structural metals  steel, copper, aluminum, etc.  because of the formation of a thin film of insoluble metal fluoride which protects the bulk of the metal, just as the invisible coat of oxide on aluminum keeps it from burning up in the atmosphere. If, however, this coat is melted or scrubbed off, and has no chance to reform, the operator is confronted with the problem of coping with a metal-fluorine fire. For dealing with this situation, I have always recommended a good pair of running shoes."

PS. According to wiki, John Clarke was not only sufficiently badass to be familiar enough with F3Cl for the above quote, he also influenced the writing career of L. Sprague de Camp (highly recommended) and Fletcher Pratt (who I only really remember from writing the Compleate Enchanter with LSdC). Amazing.

[Dman979]

OP is a budding engineer. I'm stuck in a Creo 3 CAD course, though.

It's ok, I understood him completely.

[Freshmeat]

Then, rephrase the thread to "Anything can be rocket fuel is you're brave enough"?

[wumpus]

Oddly enough, I don't think anyone has managed to use kerbals as rocket fuel. Judging from youtube, it is not for lack of trying.

[Nothalogh]

I was joking originally, but I wonder if what I said in this post is true: can anything be rocket fuel, if you try hard enough?

I think that LOX makes things burn, but is it possible to launch a rocket with, say, leftover mashed potatoes and LOX?

Or to use apples to go suborbital?

A few caveats: "fuels" shouldn't be chemically changed before ignition. So you can't ferment apples, take the alcohol, and burn it. You must burn the apples.

Sure, if you combine said fuel with Chlorine Trifluoride, of course it also tries to eat your rocket

[Yasmy]

Oddly enough, I don't think anyone has managed to use kerbals as rocket fuel. Judging from youtube, it is not for lack of trying.

Well, Kethane has the Kerbal Unreconstitutionator. If you need a tiny bit of fuel more than you need that Kerbal...

[Blackholedestroyer]

What about liquid nitrogen?

[SciMan]

The answer to this thread's title is Yes. However, "trying hard enough" becomes "pushing it out the exhaust nozzle fast enough". And the solution to that is lots and lots of Watts of heat, preferably at extremely high temperatures.

High temperatures ensure complete decomposition of any chemical fed to the engine, and they also ensure a usable exhaust velocity of the resulting (likely ionized) atoms.

Lighter atoms go faster for the same energy input PER ATOM, but heavier atoms give more thrust if you're power limited because you can dump more energy into each atom for the same propellant mass flow (less atoms/second, but heavier atoms = same mass flow). That's why Ion engines use Xenon.

So yes, anything can be a propellant.

Not everything can be a fuel, because fuel is just the energy source. The propellant provides the reaction mass. It just so happens that with chemical rockets, the fuel and propellant are the same thing.

Even light can be a propellant, but you only get one newton for 300 megawatts of directed photons. Might as well not bother unless you're producing those photons as a byproduct anyways.

[sgt_flyer]

if you can propel anything, even directly launching a shoe can act as a reaction mass (and the higher the speed you can impart on it, the higher the ISP of the engine)

Randall wrote about it using golf balls as a rocket fuel, with the engine being simply a golfer stricking the balls

https://what-if.xkcd.com/85/

[GeneralVeers]

Brainstorm!

Silver fulminate cannot be used as rocket fuel. It's extremely unstable, and impossible to store in large quantities because it has a nasty habit of detonating under its own weight (a pile the size of a dime will go off). The stuff would explode instantly if you tried to store it in any kind of fuel tank.