For every action, there is equal and opposite reaction. If you blow up a balloon and let it go (without tying the end), the air in the balloon goes in one direction and the balloon itself goes the opposite way. Rockets use this same principle. The thrust going out the back end pushes the rocket forward.
The rockets we’re about to build rely on generating enough pressure and releasing that pressure very quickly. You will generate pressure by pumping in air or through chemical reactions (which generate gaseous products).
Let’s get started!
Seltzer Rockets: Place an Alka-Seltzer tablet in a white Fuji film canister (black Kodak canisters won’t work) and fill one-third with water. Working quickly, cap it and invert it on the sidewalk. Stand back… POP! You’ll find there’s an optimal water level for maximum height. If you work fast, you can get about four launches from one tablet. What happens if you try two tablets at once?
Paper Blow-Gun Rockets: Make a very long straw by joining two straws with tape. Roll an 8½x11″ sheet of paper into a long tube and tape shut (younger kids can roll the paper around a dowel to help). Cut triangle fins out of index cards and hot glue onto one end of the rocket. To make the nosecone, cut a circle out of paper. You can trace the inner diameter of masking tape roll to get a good circle. To make a flat circle into a 3D cone, begin to cut the circle in half, but stop cutting when you get to the center. Slide one flap over the other to form a (nose)cone and tape shut. Pile a lot of glue inside the cone and add the long straw and wait to dry. Slip the straw inside the tube and seal the nosecone to the rocket body. When dry, blow into your straw to check for leaks. It should be impossible to blow through. If you have a leak, go back and fix it now. Otherwise, slip over the metal tube and blow hard. If you have one, apply a nozzle from an air tank or compressor to blast these rockets hundred of feet in the air! If your straws come loose, simply cut the rocket body just below the nosecone and rebuild the straw-cone assembly, fastening in place when ready.
Slingshot Rockets Punch a small hole in the bottom of a black Kodak film canister. Chain 5 rubber bands together and push one end of the rubber band chain through the hole from the outside, catching it with a paper clip inside so it can’t slip back through the opening (like a cotter pin). Hot glue the canister into one end of a 6″ piece of ¾” foam pipe insulation and tape the circumference with a few wraps of duct tape. The rubber bands should be hanging out of the foam pipe. Attach triangular foam fins with hot glue to the opposite end. To launch, hook the rubber band over your thumb, pull back, and release!
Puff Rockets: Grab a clean, empty shampoo or lotion bottle. Make sure the bottle you choose gives you a good puff of air out the top cap when you squeeze it. You’ll also need two straws, one slightly smaller than the other. And a small piece of foam. Insert the smaller straw into the hole in the cap. If you have trouble, ream out the hole or just take off the cap and seal the connection with a lump of clay or a lot of hot glue. Insert a small bit of foam into one end of the larger straw. Slide the larger straw (your rocket) onto the smaller straw (your launcher). Squeeze the bottle hard! POOF! Which bottles work best? Does straw length matter? (We had one rocket that cleared 25 feet.)
Micro Paper Rockets: Spiral-wrap a thin strip of paper around and along the length of a wood pencil and tape to secure (You can alternately use a naked straw instead of making your own rocket body from paper, but then you’ll need a slightly smaller launch tube straw.) Hot glue triangular fins made from an index card to one end. Fold the opposite end over twice and secure with a ring of tape to make a nose. Insert straw into the rocket body and blow hard!
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