Tuesday 6 March 2012

DIY Rocket!

Film Canister Rocket
These are super fun to try out and caused much laughter on every occasion I have brought them out.  It draws in crowds of people at the park when we do it as the canisters can really get very high!
I will get a photo for this post very soon.

If you want to try it out yourself it is very simple...
You will need:
  • One empty 35mm plastic film canister and lid. Stores that develop film should have some. I went to Boots and they gave me a bag full!  Apparently the white canisters work much better than the black ones do, I found the black ones worked ok too though!
  • One fizzing antacid tablet (we used a Alka-Seltzer) or a big fizzing vitamin C tablet works just as well.
  • Water
  • Safety goggles (we are silly and never remember to wear any but it is most advisable!)
What to do:

Put on your safety goggles and head outside!  Seriously, when this works, the film canister really flies high! Apparently, if you want to try the indoor version, do not turn the canister upside down in step 5.  (I always go for the outdoor version much more FUN!) 
Break the antacid tablet in half.


Remove the lid from the film canister and put some water into the canister. (you can experiment with a little water and a lot!Do the next 2 steps quickly
Drop the tablet into the canister and snap the cap onto the canister (make sure that it snaps on tightly.
Quickly put the canister on the ground CAP SIDE DOWN and RUN AWAY - I left a at least a 3 metre distance from the ready to pop canister.
It will take only a few seconds usually but can be longer sometimes and then... POP! The film canister will launch into the air!  You have made your very own rocket!
If it does not launch, wait at least a minute (a full 60 seconds) before checking the canister.

So how does it works?
Rocket science is so cool! It certainly made for an exciting ending to our Home Ed group on more than one occasion!  This is how it all works: When you add the water it starts to dissolve the alka-seltzer tablet. This creates a gas; carbon dioxide builds up inside the canister. It releases more and more carbon dioxide until it puts so much pressure inside canister that the cap it blasted down and the rocket is blasted up.
Newton's third law of motion: Every action has an equal and opposite reaction!

This kind of thrust is exactly the same as a real rocket!  It works in exactly the same way in outer space or here in the earth's atmosphere.  There is the difference, of course, that real rockets use rocket fuel not fizzy tablets!

If you want to make this experiment even more fun you can try and control the direction of the rocket by adding fins and a nose cone that you can make out of paper.  Also play around with how much water you use in the film canister; does it make a difference to how high it flies?  Does it make a difference if you change the temperature of the water?  Or in add more than one tablet.  Have fun experimenting!

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