Sally Sager, age 10, of Louisville, Ky., for her question:
HOW ARE BALLOONS USED?
Three principal gases are used in balloons: hydrogen, helium and coal gas. Hydrogen is the lightest and has the greatest lifting power, but it is very explosive when mixed with air. Helium is heavier than hydrogen, but it is much safer because it will not explode or catch fire. Coal gas is cheap, but its lifting power is weak. Hot air is also used in some balloons.
A balloon is an airtight bag able to rise in the air because it is filled with light gases. At the bottom of the scale is the toy rubber balloon filled with air or light gases. You go up to sophisticated blimps and observation balloons.
Balloons have many uses. One is the scientific exploration of the stratosphere. A first ascension of this type was made by a Swiss professor named Auguste Piccard and his assistant, Charles Kipfer, in 1931. They went up 51,961 feet over Angsburg, Germany. Official record for the highest balloon flight is 113,739.9 feet set in 1961 over the Gulf of Mexico by Cmdr. Malcolm Ross and the late Lt. Cmdr. Victor Prather of the U.S. Navy.
Balloons which carry only instruments can rise much higher. An experimental weather balloon rose to about 150,000 feet over Ft. Monmouth, N.J., in 1959.. The National Weather Service uses sounding balloons to collect facts which help in weather forecasting. Instruments attached to balloons record the temperature and humidity of the atmosphere as well as changes in atmospheric pressure at various altitudes. Information is sent from the balloons back to earth through small radio sets.
Pilot balloons are released at many airports. Measuring about three feet in diameter, the balloons are observed from the ground. Speed and direction of the wind can be determined from the behavior of the balloons.
Cosmic ray experiments are made using balloons similar to those used by weathermen.
Early balloon bags were made of cotton or silk cloth that was coated with rubber to make it airtight. Today the bags are made of plastic.
A stratosphere balloon is not inflated to full capacity when the flight starts. The gas inside the balloon expands and fills out the bag when it reaches the thinner air of the stratosphere.
Balloons are filled with gas lighter than air but at a pressure the same as or slightly greater than the surrounding air. If more light gases were pumped into the balloons, and pressure were increased without making the balloons larger, the lifting power of the balloons would be less. This is because the increase in the amount of gas in the balloon increases the overall weight of the balloon.