# Student Corner: Practical Applications of Air Balloons

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All children are fond of playing different games with air-filled balloons and air bubbles. This article discusses applications of balloons, some of which were developed by students.

A technical definition of an air balloon is a toy with fabric panels that forms a shape with an open interior space when filled. The fabric can be closed at the top when the balloon reaches it correct size and shape. Air balloons are different from other types of balloons, which may be formed without panels.

Air-filled balloons can be useful for solving practical problems in addition to play. A creativity class filled with young students was shown a picture of a cat with an injured paw and asked to help the cat with its injury. To give the students a helping hand, the instructors showed them air balloons. Figure 1 shows the results of their efforts.

 Figure 1: Using Balloons Practically

Courtesy of Merle and Kelly Cunningham

A misery Cat. It can't walk on its fours.
A misery Cat. It started to cry.
To cure my pet, balloons I should buy.
Astonished crowd: in accordance with laws
A misery Cat. It has cut one of the paws.
Attired by different kinds of festoons,
My cat partly walks along a road on paws,
And partly is flying … is flying with the help of balloons

– Written in Russian by Irina Tokmakova, translated to English by Nikolay Rudenko

What other practical uses are there for balloons besides those for entertainment? Focus on the properties of the balloon; it is a bag and the volume of the bag can be changed by filling it with a gas, where the volume depends on the gas pressure.

Imagine that you are in a place with low temperatures at wintertime. An underground water pipeline has been built in this area; the water could freeze at such low temperatures. While freezing, water expands and could break the pipeline. How can such a breakdown be prevented with the use of air balloons? An inventor advised to insert a set of balloons filled with air in a pipeline. When temperatures reach freezing levels, ice will expand, but the air will balance this extra volume of space (Russian Patent #2,004,109,831).

The next example of balloons' practical application is also from the construction industry. For testing the density of compacted soil, which contains big particles, a method was invented that includes the following operations: dig a pit, weigh all soil extracted from the pit and measure the volume of the pit. The weighing operation is simple, but how to determine the volume? Technological instructions recommended putting a flexible membrane inside the pit and filling it with water – the amount of water in the completely filled pit will be equal to the volume of the pit.

To use such a method it is necessary to have a lot of water in field conditions. Moreover, operations with water, especially in winter conditions, are complicated because of the potential of water to freeze. An air balloon could help, but how?

What is around in any place? Air. How to operate with air, how to put it in a small pit? Use air placed in a balloon! The idea is simple – put an air balloon in a pit, level the upper "boundaries" of the balloon with the soil level, extract the balloon from the pit, put it in a box with a known volume (like a bucket), and, using Boyle's Law (see below), calculate the volume of the pit.

It is necessary to measure is the pressure of the air inside the balloon in both cases – in the pit and in the bucket. Boyle's Law helps provide a balance equation:

P1 x Vx = P2 x V2

from which the volume of the pit can be calculated:

Vx = (P2 x V2)/P1

Where
V2
: volume of a box and
P1 and P2: air pressure in a soil pit and in standard capacity, respectively

This sounds great, but when the balloon was placed in the pit and air was pumped inside, the air balloon from the pit was unable to be extracted without tearing the balloon. What to do?

There was a contradiction – from one side the balloon has to fill the internal space of the pit with air, but from the other side it has to be easily extracted. This is a clear example of a TRIZ physical contradiction, "I want the balloon to be big (when measuring) and I want the balloon to be small (when inserting and extracting it)." The solution came later – use a balloon of a size much bigger than the pit's volume. When putting it in the pit, the balloon will be pressurized to the walls of the pit – making it possible to measure the volume of air inside such a "box." Then the balloon can be extracted easily; after opening the pit by taking off its lid the balloon will spread its shell and the pressure inside the balloon will reduce. Then the balloon can be placed in a box and its air pressure can be measured. Using a large balloon and folding it before it was placed in the pit resolved the problem/contradiction.

 Figure 2: Applying an Air Balloon Underground

SU Patent # 1,462,089

In some areas people extract natural resources from underground spaces (e.g., coal or stones for buildings). After extraction there would be an empty space underground. If in the future people would decide to build in such areas, they would need to investigate the underground space to find how much emptiness exists. How can this be done? Students from Ukraine proposed using an air balloon.

The general scheme of this method is shown in Figure 2. The idea is: install inside a balloon a vertical stick, and put several bobbins with wound thread on this stick and on the axle, and connect the ends of each thread with the internal surface of the balloon. Now imagine what would happen if air is pumped inside the balloon? The balloon would expand until it reaches the walls of the underground emptiness. By the length of the unwound thread the diameters of the emptiness on all its depths can be determined.

If readers can develop their own practical uses for air balloons, please share with other TRIZ Journal readers.

Happy inventing!