Coke-Propane Rocket Blasts Off Without Ignition

Everyone’s seen the Diet Coke and Mentos “experiment” that ends in a brown eruption. But have you seen the Coke and Propane experiment insanity that results in a rocket launch? As [Itay] pointed out when he sent us the tip, this doesn’t need to be lit. The simple act of turning the bottle upside down starts a powerful reaction without any ignition.

coke-propane-rocket-thumbOf course it’s the how of this that tickles our brains, but let’s finish the setup. This starts with a bottle of Coke which is about 3/4 full. The head space is displaced by spraying propane into the bottle; propane is heavier than air. All that’s left is to turn the bottle upside down and pray it doesn’t smack anyone in the noggin as it takes off.

In trying to find an explanation for this phenomenon we came across a plausible answer on the Chemistry StackExchange. It points to the Mentos phenomenon combined with the temperature differential caused by the very cold propane. The answering user theorizes that tiny ice crystals form and when the bottle is turned upside down the cold propane and micro crystals rise through the warmer soda acting as a much more rapid catalyst than Mentos alone. Of course this is just a theory so please share your own ideas below.

We thought the folks who microwave stuff outside of a microwave enclosure had their fill of danger but this videos is also one of theirs. It should be no surprise that they also tried the experiment with an ignition source. That video is found after the break and should immediately convince you to never try any of this yourself.

84 thoughts on “Coke-Propane Rocket Blasts Off Without Ignition

  1. I am no chemist, but a simple guess would be :

    Each basic Carbon atom has four binding points. Each carbonated beverage contains CO2. Propane is a carbon heavy fluid.

    So, it could be that the double carbon bond that develops upon mixing(between carbon in drink and carbon in propane), frees 2 parts oxygen , which are then free to reconnect at another point in the carbon chain. Which ultimately releases a group of unstable hydrocarbons. Which is why the end result is still flamable.

    1. That… doesn’t really make a great deal of sense. CO2 is already fairly stable – it’s a combustion product, not a fuel. The energy required to liberate oxygen from CO2 is equal to or less than what you get from burning it again.

      1. Was waiting for this response. Like I said in my disclaimer, not a chemist, was just a severely under-educated guess. Didn’t account for the fact that both oxygens are double bonded to a single carbon, I thought these were on single linkages, leaving two open nodes per carbon.

        1. Usually when people say they’re not a chemist they mean they didn’t study it at university, not that they have never studied it at all. Why even comment with this made-up gibberish?

    1. By turning his face away from the exploding bottle, he increases the width of his head, increasing the chance of a random trajectory hitting it. if(when) the bottom of the bottle bursts, there will be one or more direction changes, so the second time it aims for your head, it may be from a random starting point :-)

    1. Pretty sure they called it “insanity” and asserted that you should “… never try any of this yourself”…

      Regardless, it is still taking a conventional item and using it in an unconventional way; i.e. A hack. So, its a fair ball.

  2. I think the explanation is simpler: as liquid propane is less dense than coke, which makes it float on top of the bottle setup. As soon as you turn it upside down, it gets confined. But as you can see in the video, it readily boils at room temperature (boiling point: -42ºC). As a result, the coke gets expelled from the bottle opening, much like combustion gasses are expelled from an ordinary rocket, and by conservation of total momentum, the bottle is launched in the opposite direction.
    My gess is it should work as well with plain water instead of coke.

    1. This. I saw this a while ago and was the conclusion I came too.

      If you look carefully, it’s actually liquid propane sat on the surface of the coke – not a gas. When inverted it boils rapidly taking heat from the coke and becoming confined in the top of the bottle. Thrust is produced as the coke is propelled out the nozzle.

      I’m not sure if the CO2 in the coke has an effect or not. Experiments might be necessary…

      1. How could the propane still be a liquid at room temperature without some phenomenal increase in pressure that would have torn the bottle asunder before the experiment began?

        1. To answer myself:

          OBVIOUSLY, the vicinity around the expanding gas cools, as the injected liquid propane absorbs heat. Which ultimately cools the soda to a point <40C, which results in a comfortable platform upon which liquid propane may float without boiling off.

          (Hates feeling Stoopid)(Loves Learning)

        2. It’s really cold. Not sure if it’s propane or butane, but I’ll use propane in my description. It might even be a mix.

          When it leaves the propane canister a certain quantity of the propane will expand a huge amount. That is accompanied with a drop in pressure. Some of the propane will remain liquid with the temperature drop. This is pretty typical of what happens when emptying one of these bottles – if you’ve got one, or even something that uses propane as a propellant, invert it and squirt a load on a surface. You’ll see it collect as a liquid and boil off as it warms up.

          As the propane has squirted into the bottle of coke a layer of ice has formed. Liquid propane has collected on top of the ice. It won’t stay liquid for long – it’ll boil off as heat is transferred into it from the surroundings.

          However, when inverted the liquid propane is mixed with the warm(er) coke leading to rapid boiling of the propane. The resulting gas is confined in the bottle and forces the liquid coke out of the nozzle.

          At least that’s my take on it….

          1. Ah, I mean drop in temperature. The expansion from exiting the bottle is accompanied by a drop in temperature, not pressure.

            That lunchtime pint is catching up with me…

    2. As you have pointed out, the propane boils off/(sublimates?) at room temperature, so the bulk of its expansion occurs long before the bottle is tipped over. This should result in minimal pressure.

      Good news is, I have plenty of coke bottles, water, and stupid neighbors. Will pickup can of propane and get back to you later. j/k

      1. Hi donkesystripes! As you point out, the propane does boil at room temperature, but the liquid propane that collects after a while of filling the bottle with the decompressing propane gets cold enough as to stay in the liquid form. Then, by inverting the bottle you force a huge heat transfer from the water to the propane, and you get a lot of gas production/pressure from the boiling, as mechanicalsquid described.

        1. Even the liquid spherules that are ejected from the nozzle are subject to the same laws(i.e. They will evaporate at room temperature)….

          Ah hah! Unless the soda is cooled to a point <-40C, where it can liquefy!

          See, that would have been so much easier to say.

          1. Yeah! In fact, the upper layer of the coke gets below – 40ºC, and becomes ice, which helps further insulate the liquid propane from the bulk of the coke. And fortunately, it floats in between both liquids! You always have to remember that this kind of systems is not at equilibrium. So there’s a lot of temperature gradients going on, and it’s not easy to describe.

    3. Hm… anyone want to repeat this with LN2 and water? or LCO2 and water? No fire danger, less mess, and potentially just as impressive :D (oh and fins, fins and a nose cone would make the insanity more predictable)

      1. I wonder if maybe it’s even simpler- liquid propane sitting on the inside surface of the bottle neck, which having low heat capacity will easily cool to below the gas boiling point, until the coke hits it when the bottle is inverted.

    1. amazing how far I had to go down the page to find this. Butane, the bastard gas, not propane nor propane accessories. Might be iso-butane. The walls of the fuel can are not thick enough for propane.

      1. Read Karl Popper’s “poverty of historicism” and the related books to see why the ideas were idiotic. They’re based on a philosophy that borders mysticism, and much of Marx’s work is just applied bullshit (Dialectical materialism).

        Marx had a few good insights about economics and society, but most of it was pseudoscientific dross.

  3. Holy moly is that still shot on the youtube link showing a hole in the smoke where the bottle passed through maximum dynamic pressure (or something) on it’s way out? Couldn’t be passing mach…could it?
    That thing sure accelerated fast so it seems plausible, at least to me.

  4. Second video made me mad. Good way to start a forest fire @#$%&@#$s. I suppose that picnic table belongs to them too, and they swam out and collected all those bottles when they where done wit them? Way to promote banality hackaday.

    1. Have you ever ignited propane? It burns off almost immediately, transferring very little heat to the surface. Note how they’re not screaming and holding horribly burned hands and arms, either.

      Not to say what they’re doing wasn’t extremely dumb, but it’s not likely to have damaged the table or started any forest fires.

      1. Now I’ve been busted for being a lazy speed reader! Really the important question is: who is going to try mixing liquid-O2 and liquid butane for a REALLY fun one? That’s where you get the multiplying effect of 2C4H10 + 9O2 -> 8CO2 + 10H2O, for almost twice as much expansion, plus MOAR FIRE

        1. I remember my chemistry teacher talking about how he mixed acetylene and hydrogen peroxide once when he was young to build a torch because he was unsatisfied with the flame he got from burning acetylene in air. I don’t think he told us how long his hand needed to heal…

  5. I love these guys…

    This would have been my friends and I if we were born 10-15 years later! Instead all our hijinks both went unrecorded and relied only on our own ingenuity, as the internet was not available like it is now.

  6. Shouldn’t people post their hypotheses and not their theories? At least not until the process is understood and proven? Just sayin’. I know it’s pedantic but maybe people in the scientifically literate crowd should be using the right lingo.

  7. Looking at other videos on their English channel, I’m seeing a lot of rapid experiential learning in a bombed-out Ukrainian city with an the absences of available education, electricity, money or laws. These guys might prefer death at their own hands rather than randomly getting blown up by any of the many unexploded missiles around, but what they’re learning might save their community also….. It all looks pretty desperate.

    1. They actually live in a reasonably big city in what used to be (and de jure still is) the most industrialised part of the Ukraine, and the war has been going on for just about two years, so education/educated people aren’t really a scarce resource; this isn’t Somalia. One of these guys actually used to repair electronics for a living. Besides, they started blowing stuff up long before the hostilities began. So my guess is they are doing it for fun, not out of desperation.

  8. I think that there could be more than boiling going on there. There could be a phenomenon known as Rapid Phase Transition (RPT) that is well known to the Liquid Natural Gas (LNG) industry. It is basicly rapid boiling that strips away the boundary layer and makes heat transfer go through the roof. It happens so rapid, that it can produce the same results as an explosion. This is of particular interest in the LNG industry where they are piping cryogenic liquid onto ships and a leak could have really bad results.

    Here is a great vid of RPT in action. Again, the explosions seen in this film are purely due to a phase change. there is not any detonation/deflagration going on here.

  9. I used to work in a “funnel cake” stand at an amusement park managing 15 year olds. At least once a week a kid would throw an ice cube in the fryer. Water being denser than oil, the ice cube sinks to the bottom, melts, and heats up to the boiling point over the course of a minute or so. All at once the water vaporizes into steam, erupting hot oil everywhere. Quite dangerous, but that’s 15 year olds for you!

    Here coke is the oil, butane is the ice/water, and the fryer just happens to be shaped like a rocket. Flipping it upside down spurs the rapid phase change.

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