At Home Experiment 4: Stomp-Bottle Rockets
In the woolly wilds of Oregon, Spring has sprung! The sun is shining, bees are buzzing, and if your covered wagon turns over while fording the river, you might not die of hypothermia. (That was an Oregon Trail joke.) What better way to usher in the season and enjoy the outdoors than building your own stomp-bottle rocket launcher? Safe and easy, you can welcome back the songbirds with a barrage of air-propelled science! (Explosions Inc. does not condone firing rockets at living creatures. Not even birds. Not even if they totally pooped on you and your fancy new pants completely on purpose while you were minding your own business. Stupid birds.)
For the launcher:
- 1 ten-foot length of PVC pipe (1/2 inch diameter)
- A PVC cutter or other cutting tool
- An adult to do the cutting
- 1 PVC elbow joint (also ½ inch diameter)
- Duct tape
- Empty 2-liter soda bottle
For the rocket:
- Glossy magazine pages
- Thin cereal box cardboard
- Clear tape
Cut the PVC pipe into 1 four-foot piece, 2 two-foot pieces, and 2 one-foot pieces. Attach the four-foot piece to one of the two-foot pieces with the elbow joint, forming a large “L” shape. Attach the one-foot pieces to the four-foot piece with duct tape so the two-foot piece is standing upright. Using duct tape, attach the empty soda bottle to the open end of the four-foot piece of PVC.
To build the rocket we will use the left over two-foot piece of PVC as a frame. Take one or two pages of the glossy magazine and wrap it around the PVC pipe. Attach the seams together with tape and slide the rocket body off of the PVC pipe.
Using the clear tape seal one end of the rocket. Make sure it is airtight. Use the scissors to cut fin shapes from the cardboard and attach them with tape to the open end of the rocket. Experiment with different shapes and numbers of fins
To launch your rocket slide it over the upright end of the launcher. Stomp on the soda bottle and watch your rocket fly into the air! To un-crush the bottle, simply blow air into the open end of the launcher.
Why it works:
Most rockets work on Newton’s Third Law that states that for every action there is an equal and opposite reaction. Fuel exits the bottom of the rocket and the rocket itself launches upwards. In this
circumstance, we are utilizing air pressure to propel the rocket. The volume of air in the soda bottle is forced into the PVC pipe when you stomp on it and, since the PVC pipe has less space for the air, it forces the rocket (which is capping the end of the PVC pipe) into the air. To be fair to Newton, his third law still applies. The air presses against the rocket, the rocket presses back, but the rockets relatively low mass means it is taking a trip to the skies.