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Cub Scout Activity: Alka-Seltzer Rockets

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Alka-Seltzer Rocket Supplies

10, 9, 8, 7, 6…  This cool Cub Scout activity has all the elements for a fun den meeting or pack meeting:  kids, rockets and explosions!

This Alka-Seltzer rocket activity was such a hit at a Bear den meeting that I decided to do it with all the Cub Scout ranks during our Cub Scout Day Camp.  200 Scouts with 200 rocket explosions was GREAT!

While this Cub Scout activity only fulfills one Adventure requirement, it is a super fun activity for all the Scouts.  You could even make these rockets during your Space Derby.

Webelos/AOL Elective Adventure – Adventures in Science 3d: With adult supervision, build and launch a model rocket. Use the rocket to design a fair test to answer a question about force or motion.

How It Works:

Basically, the gas produced by the Alka-Seltzer and water builds up in the film canister until there is enough pressure to blow the lid off the canister and propel it into the air.  It's Isaac Newton's third law of motion in action: “For every action there is an opposite and equal reaction.”

Supplies Needed:

  • Film Canisters – The ones where the lid fits inside the canister.  The other kind won't work.  Because so many people use digital cameras instead of film cameras, these are getting more difficult to buy.  eBay is probably your best source if you need quite a few.  For just 3 or 4, talk to your local film developing store (Walgreens, CVS, Target, etc.) and ask if they can save some for you.
  • Alka-Seltzer tablets – Generic brands also work well.
  • Water

That's really all you need for the project.  But to make the canister look like a real rocket, you can print and attach the body, fins and cone.

The original designs were taken from this site, but you have to resize the images.  I did that and turned them into printable jpg files for you.  You can pick the color you want or you can print the black and white version for the Scouts to decorate themselves.  Here is an example of the template:

Rocket template red & grey

Downloadable & Printable Templates:

If you decide to use the templates, you'll also need:

  • Scissors
  • Tape
  • Crayons, markers or stickers for decorations

How to Build the Rocket:

  1. To decorate the canister, print off one of the templates and cut it out along the solid lines.  Fold along the dotted lines.
  2. Tape the body around the canister making sure the open part of the canister is pointing down.
  3. Roll the nose into a cone, center it on the canister and tape it down.
  4. Fold the fins so that they form a circle and tape them together. Slide the fins onto the bottom of the canister (open end).

If you are “spatially challenged” like I can be, practice folding the fins and wrapping the body around the canister.  Once you get the hang of it, it's easy, but you'll need to know how to do it so that you can show the Scouts.

This site has illustrated instructions.  There are also directions on how to make and use a launch pad.  We opted to use our driveway for the launch site!

How to Launch:

First, make sure everyone is well away from the launch site except for the Scout whose rocket is about to launch.  Turn the rocket upside down and pour water into the container.

Alka Seltzer Rocket adding water

Drop an Alka-Seltzer into the water and quickly put the lid on.  Make sure the lid snaps completely into the container.  Then RUN!  Seriously, you should move quickly away from the launch site.

Alka Seltzer Rocket ready for launch

Have the Scouts Scoutcount down!

Alka Seltzer Rocket 1

Blast off!  This one went flying!

Alka Seltzer Rocket trail

My camera is a point and shoot, so even in sports mode, I wasn't able to get any shots of the rocket in the air.  But you can see the trail made by the rocket.

Alka Seltzer Rocket not very far

Too much water in this launch for very much height.

A Few Tips:

  • Tape the fins onto the canister well or they'll fly off during the launch.
  • Use only a little bit of water (1/4 to 1/2 full) for the most height.  In the picture above, the canister was about 3/4 full which didn't leave much room for the gas.
  • When you tape the paper onto the canister, make sure the paper doesn't go over the edge of the container.  Leave a little room so that the lid will snap on easily.
  • You can use the Alka-Seltzer a second time.  It will most likely be laying on top of the lid at the launch site.

Hope your den has as much FUN with this activity as we did!

Yours in Scouting,

P.S. If you would like to see a great family movie with some Scouts building rockets, check out my movie and book recommendation.

Thanks to for the inspiration and templates!

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