A balloon rocket is a rubber balloon filled with

air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing f ...

or other gases. Besides being simple toys, balloon rockets are a widely used as a teaching device to demonstrate basic physics.

How it works

To launch a simple

rocket A rocket (from it, rocchetto, , bobbin/spool) is a vehicle that uses jet propulsion to accelerate without using the surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely fr ...

, the untied opening of an inflated balloon is released. The elasticity of the balloon contracts the air out through the opening with sufficient force and the resulting pressure creates a

thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that sys ...

which propels the balloon forward as it deflates. It is usual for the balloon to be propelled somewhat uncontrollably (or fly in and unstable

centre of mass In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force may ...

), as well as turbulence that occur in the opening as the air escapes, causing it to flap rapidly and disperses air outwards in random direction. Near the end of its deflation, the balloon may suddenly shoot quickly in the air shortly before it drops down, due to the rubber rapidly squeezes out the remaining air inside as it reaches the inclination to return to its uninflated size. The flight altitude only amounts to some metres, with larger or lighter balloons often achieving longer flights. In addition, a cylindrical-shaped (or "airship") balloon may have a more stable flight when released. If the balloon is inflated with

helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

or other

lighter than air A lifting gas or lighter-than-air gas is a gas that has a density lower than normal atmospheric gases and rises above them as a result. It is required for aerostats to create buoyancy, particularly in lighter-than-air aircraft, which include free ...

gases, it tends to fly in an inclined trajectory (usually going upwards), due to the light nature of the gas.

In physics

The balloon rocket can be used easily to demonstrate simple

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...

, namely Newton’s third law of motion. A common experiment with a balloon rocket consists in adding other objects such as a string or fishing line, a

drinking straw A drinking straw is a utensil that is intended to carry the contents of a beverage to one's mouth. Straws are commonly made from plastics but environmental concerns and new regulation have led to rise in reusable and biodegradable straws. These ...

and adhesive tape to the balloon itself. The string is threaded through the straw and is attached at both ends to fixed objects. The straw is then taped to the side of the inflated balloon, with the mouth of the balloon touching the object it is pointed. When the balloon is released, it propels itself along the length of the string. Alternatively, a balloon

rocket car A rocket car is a land vehicle propelled by a rocket engine. A rocket dragster is a rocket car used for competing in drag racing, and this type holds the unofficial world record for the 1/4 mile. Fritz von Opel was instrumental in popularizing ...

can be built.Summer Science Newsletter: Building a balloon rocket car
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Rocket balloon

There is also dedicated toy known as a rocket balloon, usually tubular-shaped and inflated with a special pump (pictured). These balloons, when released, propel in a more stable direction because of a steadier thrust of air and elongated shape, unlike ordinary round balloons which often launch uncontrollably. Aside from the shape, rocket balloons are also characterized by their distinctive loud buzzing or screaming noises due to the tight, reed-like opening designed to make noise as the air rushes through. They are also known as noisemaker balloons, due to the aforementioned noise

As cartoon gags

The fact that an untied toy balloon flies away when released sometimes has become a staple recurring gag and comedic effect in most cartoons. For instance, when an object or a character is comically being " inflated" and then deflates, it flies away uncontrollably, in a similar fashion to a balloon itself. In addition, the noises that a balloon creates when deflating is sometimes used in conjunction with this comedic effect.

References

External links

NasaQuest: Teacher Information on balloon rockets

Balloon Rocket Video
{{DEFAULTSORT:Balloon Rocket Balloons (entertainment) Inflatable manufactured goods