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A rocket is simply a chamber filled with pressurized gas. A small opening called a nozzle allows the air to escape, causing thrust that propels the rocket. You can demonstrate this when you blow up a balloon and let it go without tying it off. The balloon will fly through the air as all the air inside escapes.
>> Watch our video to see a balloon rocket in action!
Sir Isaac Newton laid the foundation for the modern science of rocketry near the end of the 17th century. Newton's Laws of Motion are essential to rocket flight. Here are two of them:
The principles of rocketry apply to more than flying rockets - with this project you can make a 'rocket car' that is powered by pressurized gas (air in a balloon!). Adult supervision recommended.
The water bottle forms the chassis, or body, of your balloon car. You can start by mounting the wheels on this body.
The air in the balloon is gas under pressure. The air pushes against the balloon, causing it to expand, but the balloon is also pushing back on the air. The pressure of the balloon pushes the air right out through the nozzle, which creates thrust that propels the car forward.
Keep track of how long the car rolls and how far it goes. Try it several times, then try changing the design to see if you can get it to go farther or faster. How will it work if you only use three straws for the nozzle? What if you use a bigger or smaller balloon? Does the car go farther on linoleum or the sidewalk? Why do you think this might be? Will the car go farther if you start it at the top of a ramp?
Decorate your car and have races with siblings or friends. Try to figure out why one car goes faster or farther than another, and keep experimenting to make your design better!
Unlike a balloon rocket, most rockets create the gas they need for thrust via a chemical reaction. A fuel (like liquid hydrogen) is mixed with a source of oxygen (often liquid oxygen) and burned in a chemical reaction that produces a lot of gas! In this project you can make a simple rocket and fuel it by a chemical reaction that produces carbon dioxide. Make sure you launch this messy rocket outside!
The Alka-Seltzer reacts with water to produce carbon dioxide. When enough carbon dioxide is produced to create pressure on the inside of the canister, it will force the lid to pop off so the gas can escape. As the gas escapes the rocket is propelled upward.
Try to measure how high your rocket goes compared to a nearby fence or a tree. Try it several times; do you get the same results each time? Does the rocket go higher if you add more or less water? Why do you think this is? What happens if you change the design of your fins or nose cone?
Now try it again with a different type of fuel. When vinegar and baking soda are mixed together, they produce carbon dioxide. Experiment to see how much baking soda and vinegar will launch the rocket the highest. (Some tips: You can either pack the baking soda in the lid with a damp thumb so that the reaction doesn't start until you turn the rocket over, or you can wrap it in some tissue paper or toilet paper to delay the reaction starting and give you time to set the rocket right-side-up.)
- In order to launch a rocket through earth's atmosphere, the mass of the different parts must be very carefully distributed. The ideal rocket mass is 91% propellant, 3% tanks, engines, fins, etc., and 6% 'payload.' The payload includes astronauts, satellites, or spacecraft. What does this mean? Rockets need a LOT of fuel!
- In the 16th century the primitive rockets of the time were used more for fireworks than for warfare. A German fireworks maker, Johann Schmidlap, invented a 'step rocket' to take his fireworks to higher altitudes. He sent up a small rocket on top of a big one, and when the big rocket burned out the smaller one continued to take the fireworks higher before they exploded. Schmidlap's idea of rocket stages is now used on all rockets fired into outer space.
Watch this short PBS Kids episode to see how 3 kids designed a model rocket that could reach an altitude of 1600 feet.
Dive into rocketry with the Beginner's Guide to Model Rockets from NASA.
Build a tiny balloon-powered nanorover like the one NASA built to explore an asteroid.