Episode 55: Steam Cannon

Air Date: July 19, 2006

A cereal box can have more nutritional value than the sugary cereal within.


All tests showed that cereal have superior values of calories, fats, sugars, and proteins compared to cardboard. Furthermore, chemicals within the cardboard may be toxic.

Archimedes was able to build a powerful steam cannon, using technology available at the time.


A flash-boil-powered cannon, built even with modern materials and techniques, was barely able to push a projectile out of the barrel. A more modern pre-boiled, valve-triggered system, like those used in aircraft catapults, was able to project a cannonball a considerable distance, and with far less pressure than the Mythbusters had originally projected required.


  1. jamoecw says:

    i beleive i saw a working replica of the steam cannon on the history channel. don’t know the details unfortunately, i’d bet there is more info on wikipedia about it.

  2. Bruce Fast says:

    Well, wikipedia struck out.

  3. Larry says:

    Re: the ‘busted’ steam cannon – seems the pair don’t remember from one cannon to the next that they have to maintain a gas-tight seal between the barrel and the ball. If the ball could roll out – there wasn’t a sufficient seal (hardly gas-tight).
    Archimedes and DeVinci would’ve used cork or some other flexible material to seal behind the ball.
    Mythbusters IS entertaining but hardly accurate.

  4. tiqq says:

    I´m thinking of a missing part:
    What, if they added oil in the heat chamber and wait till it boils before adding the water?
    Imho this should me more explosive.

  5. Shadow says:

    Archimedes steam cannon..you guys didn’t actually find the cannon ball did you it was a plant right. When Jamie picked it up you could see the imprint int he dirt meaning someone had to drop it there. The crater left behind could not be from the ball rolling there…take a look back guys, cannon ball found BUSTED.

  6. Richard says:

    I agree with Larry’s comment about a gas tight seal.
    I also believe that the (relatively) thin walled SCH80 steel pipe would not have as much mass as a bronze cast cannon for example. The lower mass and hence lower thermal heat capacity of the cannon wall would mean that less thermal energy is available to instantaneously flash the water to steam. The temperature was hot enough but the total energy instantly availbale was not enough. Hence the injection of water would end up cooling the steel pipe rather than being flashed to steam.

  7. Bob says:

    A steam cannon can be made to work by simply adding a diaphragm between the steam chamber and the projectile. When the pressure builds up enough, the diaphragm ruptures and the projectile is shot out the muzzle. The diaphragm just needs to rupture before the barrel does. Why did it take so long to rediscover this application? We didn’t need gun powder!

  8. Nityananda Chandra Das says:

    this cereal story is a story where in cereal was fed to rats and the rats were more interested in the box then the cereal.

  9. Colin Gardner says:

    Re; the steam cannon. Watched a repeat on UK television and I have to say I agree with Richard:
    There was nowhere near enough thermal mass in the flash boiler. The latent heat (energy) needed to create the steam is huge compared to the specific heat capacity of the iron and steel used in the barrel.
    Measuring the temperature of the fire and getting exited is a schoolboy error. It’s the heat not temperature you need to calculate.

  10. Colin Gardner says:

    If they ever get to re-visit it I would like to see the hot end of the barrel stuffed full of cast iron or something to give a lot more thermal mass.

  11. Rob says:

    They should revisit the steam cannon. The biggest problem I no one there has any knowledge of high pressure vessels, HPVs. Calling this a boiler and not a vessel is skewing definition of a boiler. That and 200 psi is beyond what sch80 piping could possibly handle. Bring in a HPV expert. Easy completion with that knowledge

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