You only need a few simple supplies for this easy STEM activity, and it’s a great way to observe action and reaction. This hands-on activity is a lot of fun, so grab a friend and get ready for take off!
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How do balloon rockets work?
Newton’s 3rd law of motion says that for every action there is an equal and opposite reaction. As the air escapes the balloon through the straw, the rubber of the balloon contracts and the air gets pushed out backwards. This propels the balloon in the opposite direction, moving it forward. The straw and the fishing line keep your balloon flying straight. But you can also try setting your rocket off from the ground without a string. The balloon’s path is a little unpredictable without the string, but it will generally spin in a few circles as it rises into the air.
Why is my balloon rocket spinning in circles?
It’s normal for the balloon to spin in a few circles once it gets half way deflated. Adding fins and flames to the end of your balloon will help keep it weighted down so it spins less, but you won’t be able to get rid of all spinning.
What to do if my balloon rocket bounces and gets caught on the line?
Make sure your fishing line is as tight as possible. If the line is floppy, the straw will get caught on the line as it moves across. This will cause the balloon to bounce up and down and fly more slowly. We also found that cutting a slit and taping the ends of the guiding straw to make them smaller really helped to keep our rocket from getting caught on the line. The balloon’s tendency is to rise up as it flies. So making the ends of the guiding straw small helps prevents the balloon from pushing up on the straw and stalling the movement.
Do I need 2 different straw sizes to make this balloon rocket?
No, you can use a regular sized straw to inflate your balloon rocket instead of using a smoothie straw. However, since less air is released through the smaller straw opening, your balloon rocket will fly quite a bit slower than with the smoothie straw. On the other hand, the energy will last longer so your rocket will actually fly farther.
What kind of string is best for making a balloon rocket?
It’s best to use a smooth string like fishing line, beading thread, or nylon kite string. These cords allow the balloon rocket to fly smoothly. If you don’t have any of those options you can also use baker’s twine, a thin yarn, or even thread. But any string with texture will cause friction and make it more difficult for your rocket to move. If you have both kinds of string, compare the smooth fishing line to the more textured yarn. Do you notice a difference in how the balloon rocket travels?
Where is the best place to set up my balloon rocket?
We played with our balloon rocket outside, tying the fishing line around two trees. You can also tie the strings to anything stationary indoors, like table legs, chairs, doorknobs, or cupboard handles. Wherever you set up your rocket balloon, make sure that you tie each side of the string at the same height, and give the balloon a good distance to fly, at least 10 or 15 feet apart. Make sure the line is as tight as possible – if the string is too loose the balloon won’t travel properly. If you don’t have a good place to tie the string, you can make little handles at the ends of the string and have 2 friends hold each end tightly!
How many times can I use my balloon rocket?
You should be able to use your rocket balloon over and over again. Just remember that balloons are a bit unpredictable – so be prepared for it to pop at some point if you’re using it many times. To re-use the balloon rocket, simply blow into the straw at the end of the balloon to inflate it again. Then re-tape it to the small straw. If you’re careful you can even use the same tape multiple times.
See scientific principles in action as you use air power to send your rocket balloon flying! You could even try different sizes and shapes of balloons and compare how well they fly. Grab a friend or two and have a race with your balloon rockets!
Here’s even more fun STEM ideas:
Balloon Car
Paper Airplane Launcher
Popsicle Stick Catapult
Our book Low-Mess Crafts for Kids is loaded with 72 fun and simple craft ideas for kids! The projects are fun, easy and most importantly low-mess, so the clean up is simple!
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