There really is no other time of the year quite like Christmas time. Where families can get together and bond over things like, cooking Christmas cookies, singing Christmas carols, going Christmas shopping, and what is now my new favorite Christmas tradition, making a rocket out of the Christmas tree (don’t tell Mom)!

[Youtube=https://www.youtube.com/watch?v=FCjHV63MQ4w]

Thanks to Natalie for the heads up on this movie! Read on to learn more about solid state rocket fuels…

Solid State Rocket Fuel

While a Christmas tree may be an unconventional rocket, these guys use a conventional rocket fuel to get the force necessary to get the tree off the ground. The fuel is Ammonium Perchlorate Composite Propellant (commonly abbreviated APCP), which is basically ammonium perchlorate, aluminum metal, and some iron catalysts all immobilized in a plastic binder material that resembles rubber. Upon ignition the following reaction occurs:

 

The reaction that takes place within ACPC.

The aluminum (Al) is the fuel, which reacts with the Ammonium Perchlorate (NH4ClO4) to produce solid Aluminum Oxide (Al2O3), some Aluminum Chloride (AlCl3), and a bunch of Water and Nitrogen gas. As is common for our explosive reactions, this also releases a ton of energy in the form of heat, causing some rockets to reach internal temperatures of over 5000° F! The energy released by one reaction provides enough energy for the surrounding molecules to undergo the same reaction. The high heat produced inside the rocket causes the water and nitrogen gas that was formed to be rapidly expelled out the nozzle of the rocket, providing the force needed to achieve liftoff!

Rockets Beyond Christmas!

Space shuttle launching, with the two white booster rockets full of ACPC based fuel. The exhaust cloud is mostly aluminum oxide and water vapor. Source: NASA

Rockets can of course be used for launching many other things into the air. This type of chemistry is used in many military propellant applications and is probably most commonly known for it’s use as the booster fuel that launches the space shuttle into orbit.  ACPC can also be found in the “ejector” seats in fighter jets and of course in model rockets. The wide range of uses comes from the ability to tune the specific burning properties, such as burn temperature and burn time, through changing the concentration of ingredients and catalysts mixed in the ACPC.

So I wish you all a Merry (and maybe explosive) Christmas Season!

3 responses »

  1. Pearl says:

    What is ammonium perchlorate is? Aluminum seems like a weird fuel. Is it solid? Why does aluminum work as a fuel? What happens to the solid that is formed as a result of the reaction?

    • Paul Vallett says:

      Aluminum is a strange fuel just because we’re used to liquid, volatile fuels like gasoline, which are easy to make burn and explode. Aluminum conjures images of aluminum foil, which is pretty inert. However, in this case it is a fuel, it just requires a much larger activation energy than a spark, and it requires the ammonium perchlorate as an oxidizer instead of just using the oxygen in the air. The solid just get expelled as particulate matter (see the cloud in the space shuttle photo). Good questions!

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