Safety notes: Either launch a sufficient distance from people or have everyone close by wear safety goggles or both. Never launch at people. If launching by direct blowing, you are responsible for checking whether (a) the project meets your local legal definition of a blowgun and (b) whether blowguns are legal at your location. Children need to be supervised.
Stomp rockets are launched by stomping on a plastic bottle, but they can also be launched by just blowing into a tube.
Ingredients and tools:
Step 1: Rocket: Tube
1. Cut a colorful page from a magazine. Make sure the edges don't have rips. You can use a utility knife and a rule to cut a lot of them at once.
2. Roll page around CPVC pipe. Make sure it's loose but not too loose. It needs to slide very smoothly, but if you leave too much of a gap, air will escape. You can experiment and see what works best.
3. Glue the outside edge in place. Make sure none of the outside edge is loose, and don't get glue on the pipe as it'll impede movement.
Step 2: Rocket: Cone
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Update: I have since found that it's better to make a styrofoam nose cone. I may eventually make a new Instructable for that version or just update this one. A styrofoam nose cone can be blunter which is (a) safer, (b) more durable and (c) more aerodynamic at subsonic speeds. I basically turned them on my drill press using this method.
1. Fold a magazine page in half, with a sharp horizontal crease. Sharpness of crease matters, precision of halfness doesn't.
2. Start to roll a cone, with tip in the middle of the crease. Put a finger or two inside as your roll it, and make the tip sharp. The cone will be much longer than you need.
3. When you get fairly close to the end, put glue on the paper you're rolling onto the cone. Make sure the tip is airtight, putting a glob of glue on as needed.
4. Stick the cone into the rocket tube, tip first (!), to see how much of the cone you need. Then cut off the cone so that 3/4" of it sticks out of the tube.
5. Keeping the cone still inside the tube tube-first, cut four slits lengthwise along the part of the cone that sticks out. The slits should almost reach the tube. This will make four flaps that you will use to glue the cone inside the tube. You may also want to glue the layers of the flaps to each other, but it's not absolutely necessary.
6. Put glue on the flaps and stuff the flaps inside the tube. Try to make the cone fit as neatly as possible, with the connection air-tight (put a bead of glue as needed) and the cone pointed correctly.
Step 3: Rocket: Fins
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1. Take a piece of thin cardstock. A magazine mail-in insert is perfect. Choose a colorful one.
2. Fold it in half, and then in half again.
3. Cut out fins, of your favorite shape, leaving a 1/4" wide flap for gluing onto tube, cutting through all four layers.
4. Fold the flaps for gluing onto tube.
5. Now, you need to mark where the four fins go. The simplest method is just to gently flatten the bottom 3/4" of the tube, making sure the creases are not sharp but visible. Then unfold the tube, making it round again, and flatten the tube again, but this time making sure the creases you just made are opposite each other. Then unfold the tube, and the bottom of the tube has a square cross-section. The pipe will round it back out once you glue fins. If you don't like creasing your rocket tube, you can instead make a paper sleeve that fits snugly over the bottom of the rocket, and do the folding trick with it, and use it to mark where the fins go.
6. Glue the fin flaps to the rocket, as symmetrically as you can. You might want to insert the pipe so you can apply pressure without damaging the tube.
7. After the fins are stuck (wait ten minutes or so), straighten them nicely.
The rocket is done!
Step 4: Launching: Blowpipe style
Place rocket on a tube somewhat longer than the rocket (no need to waste breath on a longer tube). Breathe deeply in. Point upwards. Blow hard into tube. Doing the blowing with an explosive sound, like "pfu!", may help to get more pressure quickly into the rocket.
Step 5: Launching: Stomp style
There are many ways of doing this. I went for a simple one. I had a plastic bottle, some bicycle inner tube, and a three-foot CPVC pipe (that we also use as a blowgun). I worked the inner tube over the neck of the bottle. Eventually, I tied it on with some shoelaces because it was slipping off. I then put the other end over the tube and attached it with rubber bands.
Then one puts the bottle on the ground, puts the rocket on top of the pipe. makes sure that one's face isn't near the flight path--and safety goggles are a great idea--and stomps. If all goes well, the rocket will fly two or three stories up.
Step 6: Educational content
Try having kids brainstorm how to measure the height the rocket goes up to. (Advanced method: Quadrant--or app on phone--and trigonometry. Simpler method: See how far the shadow goes from the launch point, and then see how long the shadow of an object--like the launch tube--whose length you can measure is.)
Then see what effect different parameters have on how high the rocket goes: