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Objective Kids love going fast and blowing things skyward. This set of experiments should satisfy both needs. The goal is to not only provide them with a safe set of activities that will keep their eyebrows intact, but also to get them really excited about aerodynamics and rocket design by building projects that really work. Most rockets will require a certain amount of tweaking (like the Flying Machines experiments did) in order to fly straight. This is an excellent time to hone their observation skills and get them into the habit of changing and testing only one thing at a time.
We’re going to continue learning about pressure as we generate high pressure through both bicycle pumps as well as chemical reactions. The first thing to do is watch the video on the Rocketry website page, and then dive into the experiments.
Main Ideas While the kids are playing with the experiments see if you can get them to notice these important ideas. When they can explain these concepts back to you (in their own words or with demonstrations), you’ll know that they’ve mastered the lesson.
- For every action, there is an equal and opposite reaction.
- The position of the center of pressure relative to the center of gravity of a rocket determines how stable the flight will be.
About the Experiments The experiments in this section vary from small indoor flights to rockets that go over a football field in distance. All rockets move by a quick release in pressure. Once your rocket takes flight, take a clear look (or better, a video so you can watch it a few times over) at how it flies when it’s up there. By launching at an angle instead of straight up, you’ll get a better view… just be sure your launch area is clear.
Stability of Flight: A rocket has two key points (CP & CG, covered in the Flying Machines experiments) that you need to know in order to have stable flight. Here’s how you find and adjust them:
- Finding the Center of Pressure: You can find center of pressure by tying a string around the rocket body and swinging it around your head. The balance point is your center of pressure. Mark the point as CP.
- Finding the Center of Gravity: Balance your rocket on a pencil tip. Mark the point as CG. Note if this is forward or aft of your CP.
- To adjust the CG/CP: It’s easier to adjust the CG – add weight to the nose or more fins to the tail section. Re-measure your CG when you’re done.
- Read more about rocket stability here.
The How and Why Explanation Rockets shoot skyward with massive amounts of thrust, produced by chemical reaction or air pressure. Scientists create the thrust force by shoving a lot of gas (either air itself, or the gas left over from the combustion of a propellant) out small exit nozzles.
According to the universal laws of motion, 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, until the balloon neck turns into a thrust-vectored nozzle, but don’t be concerned about that just now).
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 converging 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. Let’s get started!
Questions to Ask When you’ve worked through most of the experiments ask your kids these questions and see how they do:
- If you inflate a balloon (don’t tie the end), which direction does the air in the balloon and the balloon itself travel? (a) both the same way (b) in opposite directions (c) nothing happens
- When you drop an effervescent tablet into water, what happens? (a) bubbles foam up (b) it burps (c) carbon dioxide gas is released (d) it produces a chemical reaction that can propel a rocket skyward
- Puff Rockets use which of the following propellants? (a) air pressure (b) chemical reactions (c) both (d) neither
- The most dangerous parts of the Water Rocket experiment is are: (a) working with high pressure (b) that you’ve stripped out the threads that normally secure the cap in place, and now it’s easier to accidentally release the rocket and shoot someone’s eyeballs out (c) reusing the bottles over and over causes fissures and cracks to form in the bottle, increasing the chances of bursting if you don’t replace the bottle after every 7-10 launches (d) all of the above and more
- The most important things to remember when launching water rockets are: (a) safety goggles or face shield (b) 70 psi maximum air pressure (c) always hold the valve-side down when holding the bottle (d) only use soda bottles that are build to hold pressure (e) never water bottles, juice bottles, sports drink bottles, or any others that don’t say pssssst! when you first open them
- To get the multi-staging rockets to work correctly, where does the trigger need to be? (a) inside the first balloon (b) on the string (c) in the straw (d) squished between the first balloon and the cup
- How does a Slingshot Rocket work? Where does the thrust come from?
- If your Blow Gun Rocket straw rips loose, what can you do to quickly repair it without rebuilding the entire rocket?
How many of these items do you already have? We’ve tried to keep it simple for you by making the majority of the items things most people have within reach (both physically and budget-wise).
You do not need to do ALL the experiments – just pick the ones you want to do! Look over the experiments and note which items are needed, and off you go!
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Materials
- 10 sheets of 8×11” paper
- 5 index cards
- 7-9” latex balloon
- 15 large straws
- 5 small straws (make sure these slide easily into the larger straws)
- wooden spring-type clothespin
- 4 popsicle sticks (any size)
- 5 skewers
- 8 milk jug lids, film tops, or other small, plastic lids that are round for wheels
- 6” long piece of 3/4” foam pipe insulation
- foam sheet from a craft store
- 4 Fuji film canisters or plastic M&M containers (check recycle bin at a photo developing store)
- 2 small paper clips
- 8 rubber bands
- effervescent tablets (generic alka seltzer works great)
- clean, empty shampoo or lotion bottle
- small piece of squishy foam or packing peanut
- wood skewer (should fit inside straws)
- bike pump
- needle valve
- neoprene stopper that fits a 2L soda bottle
- empty 2-liter soda bottles
Tools
- duct tape
- scissors
- tape
- hot glue gun
Optional Materials: These rockets go a lot further, but also require adult help to create or are more expensive to build. Watch the video first before starting these projects!
- razor blade
- vice or vice grips
- drill with ½” drill bit (spade bit is best)
- air compressor and/or air tank
- spray-nozzle for compressor/tank
- 3 foot piece of metal tubing that fits just inside the larger straws (listed above)
- car tire valve (find this at a tire repair shop)
- 2 to 5 empty 2-liter soda bottles with caps
- 5 ball bearings , ½” diameter
- 4 neodymium (super-strong) magnets (1/2″ cube)
- paper towel tube
- 1 inch wide bike tube (at least 3 feet long)
- 12” long x 1/2” diameter PVC pipe
Simple rockets are not only fun to launch, but teach kids the basics of fin design (how many fins are best?), projectile motion(does launch angle matter for furthest distance), and basic construction (can you really make fins from just tape itself?). Let your kid's imagination soar with this easy and fun project.
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You get to not only build as many rockets as you want, but also the launcher to go with it! Although the launcher takes about 20 minutes to assemble, it will serve you for thousands of rocket launches, and doesn’t require an air compressor or even a bike pump! You’re going to make your own single-piston air pump using everyday hardware store parts. You can opt to include the protractor if you want to be more precise in your measurements. You can use this experiment in more advanced projects, like science fairs. See tips below for more information.
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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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This is a faster, easier project than the Linear Accelerator, and builds on the ideas from both Unit 11: Magnetism and Unit 2: Motion (in the momentum section).
Have you ever shot a billiard ball toward another on a pool table and watched the first one stop while the second goes flying? This has to do with a concept known as momentum.
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Newton's Third Law states that all forces come in pairs. When you push against the wall, the wall pushes back against you with an equal amount of force (or push). When a rocket fires, the rocket moves forward as the exhaust gases move in the opposite direction. An inflated balloon will zip through the air as the air escapes. For every action there is an equal and opposite reaction.
If you were to fart in space, what do you think would happen (before it froze)? You would move in the opposite direction!
This rocket car uses high pressure on the inside to blow a weight out the back (the neoprene stopper) and propel itself forward.
These rockets use air pressure to launch your lightweight rocket skyward. Using simple materials, you'll be able to make your launcher in minutes and as many rockets as you want. The first time I flew these, they got stuck on the roof, so be prepared with a few extras just in case.
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You'll see these in toy stores, but why not design your own version? You can add weight to the nose, widen the fins, and lengthen the slingshot part to figure out how to get to to soar further.
Materials:
- foam tube (I used a piece of foam from 3/4" pipe insulation, but you can also use a paper towel tube)
- foam sheet
- film canister or other small container to hold the rubber band in place (or tape the rubber bands to the outside using duct tape)
- paper clip
- 5 to 8 rubber bands
- scissors
- hot glue gun
- duct tape
This is the kind of thing I wish I had back in grade school. I could have launched these across the room without anyone being the wiser. Be sure to fold the nose down securely, or you'll have air leaks (and no launch!) This is a smaller version of the Rocketships experiment.
Materials:
All you need is a
- sheet of paper
- a straw
- tape
- scissors
If you don't have access to an air compressor or air tank with a spray-nozzle, you can either make your own rocket launcher (watch second video below), or make the blow-gun rockets. Either way, you're going to be launching sky-high in no time!
Materials:
- Two straws each in two different sizes
- two sheets
- index cards
- scissors
- tape
- hot glue gun
- air compressor or air tank with spray-nozzle
- metal tubing that fits just inside the larger straws
Here are a few ideas for making a mini-stomp rocket called a PUFF ROCKET that uses something other than your lungs to get your rocket launched.
When you do this experiment, think about which kind of bottles will work the best. And does straw length matter? In our testing, we had one rocket that cleared 25 feet!
- clean lotion bottle or shampoo bottle
- larger straw that fits onto a smaller straw
- small piece of foam that fits snugly into the straws
- hot glue gun
Rockets shoot skyward with massive amounts of thrust, produced by chemical reaction or air pressure. Scientists create the thrust force by shoving a lot of gas (either air itself, or the gas left over from the combustion of a propellant) out small exit holes out the back of the nozzles.
Here are two videos of real rockets being tested. The second video uses a special type of photography to see the shock waves (you will learn more about how that's done in Unit 9).
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. They both follow Newton's Third Law: for every action, there is an equal and opposite reaction.
What you're looking at in the video below is exactly the kind of work I did as a graduate student in college when I was 21. The end of a rocket nozzle is on the right side, and you're looking at supersonic air (made visible by a special type of photography called 'Schlieren') as a rushes past from right to left. The thick white lines are shock waves, which are lines where the pressure drop is huge. When the flow is fast enough (around Mach 2 and up), you'll see nicely shaped 'Mach Diamonds' form.
Scientists use these images to tell how well the engines will perform at high-speed flight. One of the greatest aeronautical engineers, Kelly Johnson, who founded Skunkworks at Lockheed, said the greatest compliment he ever received was when a friend commented: "It's amazing... he can actually see airflow." This is what Johnson could visualize in his mind simply because he understood the fundamentals of aerodynamics:
This project is simple, yet highly satisfying. The current record distance traveled is 74 feet... can you beat that? Make sure you launch these UP, not horizontally! You only need three items, all of which are in your house right now! First, you need a piece of...
This project is simple, yet highly satisfying. The current record distance traveled is 74 feet... can you beat that? Make sure you launch these UP, not horizontally! You only need three items, all of which are in your house right now! First, you need a piece of...
Rockets shoot skyward with massive amounts of thrust, produced by chemical reaction or air pressure. Scientists create the thrust force by shoving a lot of gas (either air itself, or the gas left over from the combustion of a propellant) out small exit nozzles.
According to the universal laws of motion, 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, until the balloon neck turns into a thrust-vectored nozzle, but don’t be concerned about that just now).
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 converging rocket nozzles—squeeze the flow down and out a small exit hole to increase velocity.
There comes a point, however, when you can’t get any more speed out of the gas, no matter how much you squeeze it down. This is called “choking” the flow. When you get to this point, the gas is traveling at the speed of sound (around 700 mph, or Mach 1). Scientists found that if they gradually un-squeeze the flow in this choked state, the flow speed actually continues to increase. This is how we get rockets to move at supersonic speeds or above Mach 1.
The image shown here is a real picture of an aircraft as it breaks the sound barrier. This aircraft is passing the speed at which sounds travel. The white cloud you see in the photo is related to the shock waves that are forming around the craft as it moves into supersonic speeds. Because the aircraft is moving through air, which is a gas, the gas can compress and results in a shock wave.
You can think of a shock wave as big pressure front. In this photo, the pressure is condensing water vapor in the air, hence the cloud. There are lots of things on earth that break the sound barrier – bullets and bullwhips, for example. The loud crack from a whip is the tip zipping faster than the speed of sound.
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. Let's get started!
For this experiment, you will need:
We’re going to experiment with Newton’s Third law by blowing up balloons and letting them rocket, race, and zoom all over the place. When you first blow up a balloon, you’re pressurizing the inside of the balloon by adding more air (from your lungs) into the balloon. Because the balloon is made of stretchy rubber (like a rubber band), the balloon wants to snap back into the smallest shape possible as soon as it gets the chance (which usually happens when the air escapes through the nozzle area). And you know what happens next – the air inside the balloon flows in one direction while the balloon zips off in the other.
Question: why does the balloon race all over the room? The answer is because of something called ‘thrust vectoring’, which means you can change the course of the balloon by angling the nozzle around. Think of the kick you’d feel if you tried to angle around a fire hose operating at full blast. That kick is what propels balloons and fighter aircraft into their aerobatic tricks.
We’re going to perform several experiments here, each time watching what’s happening so you get the feel for the Third Law. You will need to find:
- balloons
- string
- wood skewer
- two straws
- four caps (like the tops of milk jugs, film canisters, or anything else round and plastic about the size of a quarter)
- wooden clothespin
- a piece of stiff cardboard (or four popsicle sticks)
- hot glue gun
First, let’s experiment with the balloon. Here’s what you can do:
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