Balloon

Balloons and the exploration of the unknown

Resources

A balloon is a nonsteerable aircraft consisting of a thin envelope inflated with any gas lighter than the surrounding air. The balloon rises from the ground similar to a gas bubble in a glass of soda. The physical principle underlying this ability to ascend is Archimedes’ law, according to which any immersed body is pushed upward by a force equal to the weight of the displaced fluid. If this force is greater than the weight of the body itself, the body rises. The lighter the balloon is in comparison with air of the same volume, the more load (envelope, people, instruments) it can lift. The approximate lifting capacity of some lighter-than-air gases in a 1,000 cubic meters (1,308 cubic yards) balloon at 32°F (0°C) is shown below (in pounds):

For example, a balloon filled with nitrogen possesses only about 1/30 of the lifting capacity of the same balloon filled with hydrogen. As a matter of fact, only hydrogen, helium, and hot air are of practical importance. Hydrogen, the lightest existing gas, would be ideal for the balloon inflation if it had not one serious demerit: inflammability. Helium is 7% less efficient than hydrogen, and is absolutely safe in usage, however, but it is not easily available and production is not cheap. Hot air is safe and easy to obtain, making it the most often used for common manned flights. But to get lifting power equal to even 40% of helium it must be heated to about 570°F (299°C).

There is always an element of uncertainty in a balloon flight. The ascensional force of a hot-air balloon is difficult to control, since it is very unstable, sharply reacting to any variations of the inside air temperature. Once airborne, it floats freely in air currents, giving its pilot the ability to regulate only vertical direction.

From the first flight of a smoke-filled bag launched by the Montgolfier brothers in Paris in 1783 until the first practical powered airplane in 1905, balloons and their later modifications, airships, remained the only means of aerial navigation. This period was full of exciting achievements of courageous aeronauts. The crossing of the English Channel (1785, by Blanchard, France, and Jeffries, USA), parachute descent from a balloon (1797, by Garnerin, France), the crossing of the Irish Sea (1817, by Windham Sadler, England), and the long-distance flight from London to Weilburg, Germany (1836, by Green, England), are a few of the milestones in the balloon’s early history.

The suitability of balloons for observation, espcially of inaccessible areas, was soon recognized. The first air force in the world was created by France in 1794, and by the end of the nineteenth century balloon corps, whose main function was reconnaissance, were common in European and American armies. With the introduction of a heavier-than-air craft military interest in balloons faded. However, the most challenging pioneering and scouting missions via balloons were yet to come.

Balloons and the exploration of the unknown

In 1863, the first truly high-altitude ascent was made by Glaisher and Coxwell in England. The flight was purely scientific, intended to observe and record the properties of the upper atmosphere. The explorers rose to over 33,000 feet (10,000 m), an altitude that almost cost them their lives. This outstanding attempt was followed by many others, and high-altitude scientific ascents continued until the early 1960s.

A specific layer of the atmosphere between 35,000 and 130,000 feet (11,000 and 40,000 m)—the stratosphere—became a particular challenge to human spirit and engineering. The mark of 72,395 feet (22,066 m), achieved by Stevens and Anderson in 1935, was not surpassed until twenty years later, when the United States resumed the manned stratosphere ballooning. The last flight in the series was made by Ross and Prather, who attained the altitude of 113,740 feet (34,467 m) in 1961. Technology that allowed human survival in extreme conditions became a germ of future space life-support systems.

The introduction of new lightweight and very strong plastic materials made it possible to build extremely big balloons able to take aloft huge pay-loads. Loaded with sophisticated instruments, such balloons began to carry out complex studies of the atmosphere, biomedical and geographical research, and astronomical observations.

Each day, thousands of balloons measure all possible characteristics of the atmosphere around the entire globe, contributing to the worldwide meteorological database. This information is needed to understand the laws of air-mass movement and for accurate weather forecasting.

Balloon astronomy makes observations in the clarity of the upper air, away from dust, water vapor, and smoke. Telescopes with a diameter of up to 3.3 feet (1 m) are placed on platforms, which are supported by mammoth balloons, as high as an eight-story building, at elevations of up to 66,000-120,000 feet (20,000-35,000 m).

The Russian mission to Venus in 1985 used two helium balloons to examine the motion of the Venutian atmosphere. For 46 hours, they floated above Venus with an attached package of scientific equipment that analyzed the environment and transmitted the information directly to Earth. In comparison, a landing module functioned for only 21 minutes.

See also Aerodynamics; Buoyancy, principle of.

Resources

BOOKS

The Cambridge Encyclopedia of Space. Cambridge University Press, 2002.

Curtis, A. R. Space Almanac. Arcsoft Publishers, 1990.

DeVorkin, D. H. Race to the Stratosphere. Springer-Verlag, 1989.

Jackson, D. D. The Aeronauts. Time-Life Books, Inc., 1980.

OTHER

Prints George. “Flights of Fancy” <http://www.printsgeorge.com/ArtEccles_Aeronauts3.htm> (accessed October 30, 2006).

U.S. Centennial of Flight Commission. “Balloons in the American Civil War” <http://www.centennialofflight.gov/essay/Lighter_than_air/Civil_War_balloons/LTA5.htm> (accessed October 30, 2006).

Elena V. Ryzhov