Rockets are devices that use force to move an object forward. Chinese people invented the first rockets to launch fireworks in the 1200s. Today, not only are rockets used for fireworks but they are also used to send objects (and even people!) into space (Encyclopedia Brittanica, 2022). Model rockets are a great way to explore and learn about the physics and engineering that go into creating real-world rockets.
Teachers, are you looking for a ready-to-go bottle rocket science project?
The Physics of Model Rockets
How does a bottle rocket science project work?
Three main forces affect the upward motion of a model rocket: weight, thrust, and drag (NASA, 2021).
- The downward pull on the mass of the rocket caused by gravity is weight. A rocket with more mass will have more weight.
- The upward force caused by the force of the “fuel” (more on this later) exiting the body of the rocket is thrust. As stated by Newton’s third law of motion, for every action, there is an equal and opposite reaction. The force of the fuel pushing down causes an equal and opposite force on the rocket in the upward direction.
- Drag is the air resistance the model rocket experiences as it launches into space. Drag works against thrust. A model rocket with less air resistance will experience less drag and launch further into the air.
If you want to launch your model rocket off the ground, you must create an unbalanced force. The thrust force must be greater than the weight and drag acting in the opposite direction. If you want your rocket to go as far as possible, you should plan to maximize the thrust and minimize the weight and drag forces acting on the rocket.
Thrust and Model Rocket Fuel
Usually, trapping a build-up of gas generates thrust for a bottle rocket. Then, as the gas releases downward, the rocket shoots upward.
How does a water bottle rocket work?
Water and air pumps are one way to achieve thrust. First, fill the bottle rocket partway with water. Then seal the bottle with a special cork that has an air pump needle inserted through the middle. Next, place the bottle in the launch position and use the air pump to force more air into the bottle and increase the pressure inside. When the force of the air inside the bottle is great enough it will push out the cork. The water will shoot out of the bottle and lift the rocket into the air.
How does a baking soda and vinegar bottle rocket work?
Chemical reactions that release gas as a product are another way to generate thrust in model rockets. For example, a baking soda and vinegar reaction can launch model rockets. When the reactants mix, they create water, a salt, and carbon dioxide (National Center for Families Learning, 2022). The carbon dioxide trapped inside the rocket generates a build up of pressure.
To use a chemical reaction as model rocket “fuel” you must add the reactants to the bottle. Then seal off the opening of the bottle with a cork. Next, place the bottle in the launch position and wait for the buildup of carbon dioxide to force the cork from the opening of the bottle and cause rocket to launch into the air. Sometimes, bottle rocket engineers prefer to slow down the mixing of the reactants, so more gas is trapped inside the rocket. To do this, one reactant can be wrapped inside an absorbent material and then placed in the bottle.
Now that you know how a bottle rocket science project works, it’s time to design and build your own model rocket! What will you use as fuel? How will you get your rocket to fly high in the sky? Tell us in the comments below.