A balloon rocket is a balloon filled with air. To launch the rocket, a person releases the opening of the balloon. The balloon rocket is then propelled by the escape of the air which creates thrust. The flight altitude amounts to some meters. The balloon rocket is not by any means a technical machine, and can be used easily as a cheap and harmless way to demonstrate simple physics, namely law of reciprocal actions.

A common variant of the balloon rocket uses a length of string, a drinking straw and adhesive tape. The string is threaded through the straw as is attached at both ends to objects of some kind, such as a doorknob on one end and a chair on the other. The straw is then taped to the top of the air-filled balloon, with the open end of the balloon touching one of the objects. When the balloon is released, the thrust from the opening propells it along the length of the string.

The balloon can also be filled with gases other than air, with similar results.

Balloons | Rockets and missiles

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