This is a recording of a recent live teleclass I did with thousands of kids from all over the world. I’ve included it here so you can participate and learn, too!

Blast your imagination with this super-popular class on rocketry! Kids learn about fin design, hybrid and solid-state rocketry, and how rockets make it into space without falling out of orbit. This class is taught by a real live rocket scientist (me!). We’ll launch rockets during the class, too!

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Materials:

• straw
• paperclip
• rubber band
• index card
• popsicle stick
• scissors
• masking tape
• water
• alka-seltzer tablets (generic brands work fine)
• film canister or small container with tight-fitting lid
• OPTIONAL: Small toy car

Below you will find an older version of the same teleclass. We are making a different experiment during class, so the materials you will need are a little different:

Materials:

• 2L soda bottle
• 1/2″ PVC pipe
• duct tape
• pen or pencil
• index cards
• sheets of paper
• bicycle inner tube

Key Concepts

A rocket has a few parts different from an airplane. One of the main differences is the absence of wings. Rockets utilize fins, which help steer the rocket, while airplanes use wings to generate lift. Rocket fins are more like the rudder of an airplane than the wings.

Another difference is the how rockets get their speed. Airplanes generate thrust from a rotating blade, whereas rockets get their movement by squeezing down a high-energy gaseous flow and squeezing it out a tiny exit hole. If you’ve ever used a garden hose, you already know how to make the water stream out faster by placing your thumb over the end of the hose. You’re decreasing the amount of area the water has to exit the hose, but there’s still the same amount of water flowing out, so the water compensates by increasing its velocity. This is the secret to rocket nozzles – squeeze the flow down and out a small exit hole to increase velocity.

The rockets we’re about to build get their thrust by generating enough pressure and releasing that pressure very quickly. You will generate pressure both by pumping and by chemical reaction, which generates gaseous products.

What’s Going On?

For every action, there is equal and opposite reaction. If flames shoot out of the rocket downwards, the rocket itself will soar upwards. It’s the same thing if you blow up a balloon and let it go-the air inside the balloon goes to the left, and the balloon zips off to the right (at least, initially).

Your rocket generates a high pressure by squeezing the air into a very small space and using Bernoulli’s Principles in action! As you stomp on the rocket, the air pressure leaves the bottle pretty quickly, pushing the paper rocket out of the way as it zooms out of the tube. By narrowing the exit diameter, you allow the air to speed up as it exits, creating a higher launch for your rocket.

You can modify your rocket body design. Add more fins, tilt the fins at a angle, or try no fins at all! You can add a more steeply slanted  nose. You can cut the rocket body in half or make it twice as long.  There’s so many things you can test out, change, or modify with this simple activity! You can also add canards (glider-type wings) to either side of the rocket body right under the nose and turn it into a glider when it starts to fall back to Earth!

Questions to Ask

1. Does it matter how many fins you use?
2. What happens if there’s an air leak in the system?
3. How can you make the rocket fly even higher? Name three different ways.
4. Is the center of pressure before or aft of the center of gravity on your rocket?
5. For stable flight, how many fins do you ideally need?
6. How can you make the rocket spin as it launches?

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