Baloon and Airship

 All Europe was excited in June 1783. The Montgolfier brothers of Annonay, France, had sent a large paper bag sailing upward 6,000 feet (1,800 meters) into the air. They had filled it with hot smoke from a straw fire. To most people of that day, the soaring bag seemed a miracle. Yet within 50 years inventors had developed most of the principles and devices used in ballooning today.

Airships, or dirigibles, were developed from principles of ballooning. Airships, however, carry engines with propellers to drive them through the air and rudders to steer them. Some airships have a rigid outer fabric, while others are nonrigid and are commonly called blimps. Balloons and airships are classed as lighter-than-air craft to distinguish them from airplanes, gliders, and helicopters, which are heavier than air and have to keep moving and which require power generated from an engine to stay aloft.

Why a Balloon Rises

A balloon rises because it is filled with a gas that is lighter than air. The total weight of the gas, the balloon bag, and the load it carries must be less than the weight of the air that would occupy the same space (the displaced air). Suppose, for example, that a balloon 30 feet (9 meters) in diameter occupies with its load 14,300 cubic feet (405 cubic meters) of space. At sea level and at a standard temperature of 59° F (15° C), 14,300 cubic feet of air weighs about 1,100 pounds (500 kilograms) . In order to rise, the balloon must weigh less than this, so it must be filled with hot air or gases that are lighter than air.
The lifting power, or buoyant force, of a gas is the difference in weight between equal volumes of the gas and air, measured under the same conditions. At 32° F (0° C) and standard sea-level pressure, the buoyant force of 100 cubic feet (3 cubic meters) of hydrogen is about 120 ounces (3.4 kilograms), helium about 111 ounces (3.1 kilograms), and coal gas from about 34 to 88 ounces (1.0 to 2.5 kilograms). Hydrogen, the lightest gas, catches fire and explodes easily. Coal gas is cheaper, but it is heavier than hydrogen and burns just as easily. Helium, with 93 percent of the lifting power of hydrogen, cannot burn . Although scarce and expensive, it is the ideal balloon gas. The main supply is found in the United States, and its use is government-controlled.
When a toy balloon is blown up by mouth, it falls to the ground. This is because the weight of the rubber and the compressed air in it make it heavier than the same volume of air. But if it is placed on a radiator so that the air in it becomes hot (not too hot, or it will burst), the balloon expands. It will rise and stay on the ceiling until the air in it cools off. A toy balloon that floats up is filled with helium. It rises until it bursts.
In principle, the round passenger balloon resembles this gas-filled toy. If it is fastened to the ground with a cable, it is called a captive balloon.
When it is released to soar and drift with the wind, it is a free balloon. The up-and-down motion of a free balloon can be controlled but not its horizontal direction.

Navigating a Free Round Balloon

The free passenger balloon is nearly always spherical or pear-shaped. The huge bag is made of cloth coated with rubber or some other substance to make it leakproof. It is filled through a sleevelike opening at the bottom, called the neck or appendix. The entire bag is enclosed in a strong net to which the passenger basket is attached. At the top of the bag is a valve for releasing gas. This is connected to a cord that usually runs through the envelope and out the appendix, hanging within a balloonist's reach. Bags of sand are hung around the basket for ballast.
When the balloonist is ready to take off, the cables are unhooked, and the balloon rises gently. It is now the winds that control flight direction. But the balloonist can change altitude by throwing ballast overboard or by releasing gas. So fine is the balance between gas and weight that a second's escape of gas or a pound of sand thrown overboard can cause a sharp change in altitude.
As the balloon rises, the lesser pressure of the upper air permits the gas to expand. The balloon tends to go higher and higher. If the expanding bag threatens to burst, the balloonist releases gas. To come down, the balloonist lets gas escape gradually until the balloon becomes somewhat heavier than air. But as it descends into air with higher pressure, the balloon tends to contract and drop faster and faster. The balloonist must throw out ballast to slow down.
The free balloon is not a practical means of transportation. Great distances have been covered in it, however. One of the longest trips was made in 1914 by Hans Berliner, who sailed from Germany to the Ural Mountains in Russia—a distance of 1,897 miles (3,053 kilometers).
The free balloon reached the stratosphere before the airplane, with an altitude of 72,395 feet (22,066 meters) in 1935. Since then there have been numerous manned balloon flights into the stratosphere. New record heights are reached almost annually. The stratosphere balloon is equipped with oxygen tanks and made airtight so that the pressure inside can be maintained despite the thin atmosphere outside. Valuable information for weather forecasts and on radio and cosmic rays has been obtained from stratosphere flights.
The advent of the modern sport balloon in the early 1960s led to a rebirth of ballooning in the United States. These craft feature envelopes constructed of synthetic materials and filled with hot air that is produced by propane burners. Much easier and less expensive to operate than gas balloons, the hot-air craft do not require ballast or gas valves. Altitude is controlled by varying the temperature of the air in the balloon 

Captive Balloons and Airships

During World War II thin steel cables held aloft by barrage balloons were used to defend troops and cities against strafing and bombing attacks by low-flying planes. The cables also held the balloons captive. Facing probable destruction if they flew into a cable, enemy planes had to climb above the balloons or turn back. Barrage balloons were shaped like thick kites. Tail fins held them steady and pointed their noses upward and into the wind. Round balloons were unsatisfactory because they were unsteady and could be blown to the ground.
The free balloon travels with the wind. The airship can choose its course. The buoyant gas in its long envelope keeps the craft aloft, while engines drive the propellers that push or pull it through the air. The pilots operate rudders and elevators on the stern of the ship to guide its flight.
Blimps were used by the British during the first World War to scout for submarines. The name blimp came from their classification—Type B-limp. Early blimps had long cigar-shaped bags that creased when gas was released and often bent or buckled in storms or when turned rapidly. They could not be made large enough to carry heavy loads, since larger bags increased the danger of folding.

The German Zeppelins

To overcome these difficulties Germany developed a rigid type of airship. It was named Zeppelin for its inventor, Count Ferdinand von Zeppelin. The rigid skeleton of the gas bag consisted of circular girders and cross braces from side to side and ribs that ran from end to end. The skeleton was made of a light alloy. The fabric of the bag was painted with aluminum to reflect the sun's rays and prevent excessive heating and expansion of the lifting gas. The gas was kept in separate cells to minimize leakage. Catwalks inside the envelope permitted the crew to reach all sections. The engines burned nonexplosive Blau gas. A Zeppelin could travel 80 miles (130 kilometers) an hour in calm air.
The rigid frame made it possible to construct airships of tremendous size. The Hindenburg, the biggest Zeppelin, was 804 feet (245 meters) long and 135 feet (41 meters) in its largest diameter. The huge craft could lift a total weight of about 235 tons (215 metric tons). It carried 50 passengers and a crew of 60, besides baggage, mail cargo, and its heavy load of fuel. It was renowned not only for its size but for its luxurious two-deck passenger accommodations. Since hydrogen was used, these quarters were tightly sealed off in an effort to prevent fire.
The very size of these huge ships was, however, a disadvantage. Air currents tossed and twisted them, and the framework was unable to withstand the stresses imposed by violent storms.
A third type of airship is semirigid. It has a metal cone to stiffen the nose and a metal keel that extends the length of the ship. The car is attached to the keel. The so-called blimps used by the United States Navy in World War II were actually of the semirigid classification of airship.

Fast Naval Dirigibles

Improved nonrigid airships using helium as the lifting gas were developed during the mid-1930s and were produced when the war started. In World War II they were used for patrolling, hunting submarines, and escorting convoys. They were huge targets, but almost none were shot down. After the war blimps were used as flying radar stations for the coastal defense system. The use of helium and technical improvements, such as radar, insured safe operation of nonrigid airships.
Increasing use of the helicopter and the great expense of building and maintaining blimps eventually doomed the Navy's Lighter-Than-Air (LTA) program. The last blimps were retired from service in 1962; only a few remain in war-reserve storage. From World War II until their retirement the Navy used six types of nonrigid airships. The older designations G, K, M, and N were replaced by Z for lighter-than-air craft, P for patrol, W for aircraft early warning, and G for Goodyear.

The Hardy Blimp

The fabric pressure-type airship (nonrigid) is not readily damaged by momentary strain, such as that produced by a strong wind. Fabric envelopes may wrinkle or buckle under gusty conditions, but they will recover completely when the strain-causing forces are removed.
The airship is able to land and to stop its forward motion by means of aerodynamic lift and reversible propellers . Only a few people are needed to operate vehicles known as mules, which take over the handling lines and guide the airship to its mooring mast. Therefore large ground crews are not required.

Airship Fuel Requirements

When traveling at cruising speeds airships use little fuel. A United States Navy airship established an aircraft endurance record of 264 hours without refueling in flight while traveling across the Atlantic and back in March 1957. If refueled in flight, an airship may remain aloft indefinitely.
An airship grows lighter as it uses up its fuel. For this reason, airships tend to climb higher unless gas is discharged or some form of ballast is taken aboard. Because the gas used is costly helium, it is rarely released. Instead, water ballast is taken on. This is accomplished by reducing forward speed and bringing the ship close to the ocean's surface. A large fabric bag is lowered into the ocean. When more power is given to the airship's engines, the craft climbs, lifting the bag of water with it. A suction pump transfers the water from the bag into a ballast tank.

Weather Balloons

A floating free balloon is carried by wind currents. Ground observers study the speed and direction of wind currents at various altitudes by means of telescopes. At night these weather balloons are fitted with small electric lights for easier observation.
The need of weather observers for more detailed data on conditions in the upper air led to the development of radiosonde in the late 1930s. This approximately 3¹/₂-pound (1.6-kilogram) device consists of units that are sensitive to pressure, temperature, and relative humidity changes. A small radio and battery are also included. As the balloon rises, the sensitive elements record changes. These are transmitted to ground receivers by radio. On attaining altitudes of 50,000 to 100,000 feet (15,000 to 30,000 meters), the balloon bursts. The box of instruments is carried to the ground by parachute. When recovered, these instruments may be used again.

HISTORY OF BALLOONING

Joseph-Michel and Jacques-Étienne Montgolfier built other hot-air balloons after the success of their first model, described at the start of this article. These were named montgolfières in their honor. On Sept. 19, 1783, Louis XVI and his family witnessed the first balloon flight to carry living passengers. The balloon, 72 feet (22 meters) long, carried a duck, a rooster, and a sheep. On Oct. 15, 1783, Jean-François Pilâtre de Rozier unofficially became the first human being to ascend in a balloon. (He and François Laurent made the first official manned flight in a Montgolfier balloon on Nov. 21, 1783.)
Hydrogen, which was discovered in 1766, was first used in a balloon on Aug. 27, 1783 Professor J.-A.-C. Charles, a French physicist, sent up a varnished silk bag that measured 13 feet (4 meters) in diameter. He launched it in Paris. After rising 3,000 feet (900 meters), it returned to Earth as the gas leaked away. The balloon landed about 15 miles (24 kilome- ters) outside of Paris. In the same year, Professor Charles and a man named Roberts stayed aloft for two hours. Their balloon was built by public subscription and contained many features of modern round balloons. For example, it had a valve at the top and sand ballast in the basket.
Interest in ballooning spread. Two men crossed the English Channel in 1785. To prevent falling into the sea, they were forced to throw equipment and even clothing overboard. Pilâtre de Rozier was killed in 1785 in an attempted channel crossing when his balloon caught fire.
Captive balloons were used for military observation during the Civil War and later in European wars. In the Franco-Prussian War (1870–71), 65 balloons of the Balloon Poste carried 164 passengers and 20,000 pounds (9,000 kilograms) of mail high over the German lines and out of besieged Paris.

Development of the Dirigible

Until the mid-1800s airborne balloons could not be steered. Once aloft, the balloon merely drifted along. The first attempt to equip a balloon with a steering apparatus involved the use of simple sails. Later, lightweight oars made of cloth stretched over a wood frame were tried. In 1852 Henri Giffard installed a small steam engine in the car of a spindle-shaped balloon. This engine turned a propeller that pulled the airship through the air at a speed of 5 miles (8 kilometers) an hour against the wind. Steam power, however, proved both cumbersome and too dangerous to use in balloons.
In 1898 Alberto Santos-Dumont, a wealthy Brazilian residing in Paris, began to experiment with gasoline engines as a power source for balloons. On Oct. 19, 1901, he steered his cigar-shaped balloon over a seven-mile (11-kilometer) course above Paris. For this journey, which took half an hour, Santos-Dumont received the coveted Henri Deutsch prize of 125,000 francs.

German Air Supremacy

Germany was the first nation to recognize the military possibilities of a powered airship that could be navigated. Supremacy in air navigation passed from France to Germany, largely through the efforts of Count Ferdinand von Zeppelin. As a young military attaché in Washington during the Civil War, Zeppelin had noted the usefulness of observation balloons. Beginning in 1891, he worked intensively on designs for aircraft that were to bear his name.
The first Zeppelin had a capacity equal to that of 112 standard boxcars. Tested in 1900, the craft achieved a speed of 18 miles (29 kilometers) an hour for a short distance. By 1910 the Zeppelin Company was operating the first commercial air transport service. In a three-year period the company carried more than 14,000 passengers a total distance of 100,000 miles (161,000 kilometers) without accident.
During World War I the Germans used Zeppelins to bomb London. However, once the defending British pursuit planes were able to climb to the airships' cruising altitude, the slow and cumbersome Zeppelins proved easy targets. After the war German Zeppelins were turned over to Allied countries as indemnity. Because Germany did not have enough Zeppelins when the war ended, it was forced to build one—the Los Angeles—for the United States.

A Grim Record of Disasters

The first successful airship crossing of the Atlantic was made in 1919 by the British R-34. In 1921, however, a wave of airship disasters began. The R-34 was wrecked at its mooring. The Roma, built in 1922 by Italy for the United States, exploded over Hampton Roads, Va. A French Zeppelin obtained from Germany, the Dixmude, was lost in the Mediterranean in 1923. In 1925 the United States Shenandoah was destroyed by violent winds. The United States Navy built two more airships. These were the Akron, destroyed in 1933, and the Macon, which crashed in 1935.
Although other nations discontinued building Zeppelins, Germany continued to make them. In 1929 the Graf Zeppelin flew around the world in less than 21 days. The Hindenburg made ten round trips between Germany and the United States. In 1937 the Hindenburg caught fire as it approached its Lakehurst, N.J., mooring, killing 35 of the 97 persons aboard.
When World War II began, the rigid dirigibles had vanished from the skies. During the war, however, nonrigid airships were built and used effectively.

Free Balloons Reach the Stratosphere

Much knowledge concerning upper-air conditions has been gained through the use of balloons. As early as 1784, pioneer balloonists took instruments aloft to measure air pressure, temperature, and moisture at various levels. Samples of air were taken at different altitudes and brought to Earth for study.
As balloons became larger, they were able to ascend into regions where the intense cold and thin atmosphere caused some passengers to die. In 1898 the French physicist Teisserenc de Bort found that when a balloon reached an altitude of 6 to 8 miles (10 to 13 kilometers) it entered a belt where the temperature no longer dropped. He named this region the stratosphere.
In 1901 in Berlin Prof. A. Berson and Dr. R.J. Süring rose to a 35,440-foot (10,802-meter) altitude. Although they carried oxygen tanks, the men were unconscious during the highest part of the flight. Capt. Hawthorne C. Gray of the United States Army soared to 28,500 feet (8,680 meters) on March 9, 1927. This was an American record. On May 4 he reached 40,000 feet (12,190 meters) but was forced to parachute during his descent. For this reason the record was not officially accepted. On Nov. 4, 1927, Captain Gray rose to 42,470 feet (12,945 meters), but he died when his oxygen supply failed.

Some History-Making Ascensions

When Prof. Auguste Piccard of Brussels University began exploring the stratosphere, he devised an airtight, ball-shaped, aluminum cabin equipped with oxygen tanks. In 1932 he reached an altitude of 53,153 feet (16,201 meters). Using similar equipment, United States Army Captains Albert W. Stevens and Orvil A. Anderson reached 72,395 feet (22,066 meters) on Nov. 11, 1935. This team's ascension was made from Rapid City, S.D.
On Aug. 19, 1957, Air Force Maj. David G. Simons set a new record. Starting from an open-pit mine at Crosby, Minn., he rose to about 102,000 feet (31,100 meters) over Wahpeton, N.D. Major Simons' altitude was 6,000 feet (1,830 meters) higher than the record set in June 1957 by Capt. Joseph Kittinger, who rose 96,000 feet (29,260 meters) in a test of the equipment used by Major Simons. These flights brought back valuable information about cosmic rays and other phenomena.
Captain Kittinger, on Aug. 16, 1960, set four world's records in one flight. He ascended at least 102,800 feet (31,330 meters) in an open-gondola balloon, thus setting height records both for open gondolas and for manned balloons of any type. He also made the highest parachute jump and set a free-fall record of 85,300 feet (26,000 meters). On May 4, 1961, Lieut. Comdr. Victor Prather and Comdr. Malcolm Ross soared to a record 113,740 feet (34,668 meters). Prather was killed when he fell from the hoist of a helicopter while being picked up after the flight.
The largest balloons ever launched were sent aloft in 1960 by the United States Navy and the National Science Foundation. They were 40-story-high cosmic-ray research balloons with gondolas weighing 2,500 pounds (1,135 kilograms).
The first passive communications satellite, Echo I, was sent into space by a Thor-Delta rocket on Aug. 12, 1960. It was an aluminum-coated plastic balloon used to reflect radio signals. In a successful test for setting up manned astronomical balloon observatories, the United States Air Force launched a balloon with special stabilization equipment on March 12, 1962. The Star- Gazer balloon carried two men and a 12-inch (30-centimeter) telescope to almost 100,000 feet (30,500 meters) where, with more than 90 percent of the atmosphere below the balloon, unusually clear studies of the stars and planets could be made.
One of the great events in the history of ballooning began on Aug. 11, 1978. On that day, Ben Abruzzo, Max Anderson, and Larry Newman lifted off in the Double Eagle II and attempted to cross the Atlantic Ocean. Since 1958 thirteen teams had attempted the flight without success. Five days, 17 hours, and 6 minutes after takeoff from Presque Isle, Me., Double Eagle II touched down in a field near Miserey, France, having traveled 3,120 miles (5,021 kilometers).
In 1981 Abruzzo, Newman, Ron Clark, and Rocky Aoki became the first group of balloonists to cross the Pacific Ocean. In Double Eagle V the group flew 5,208 miles (8,381 kilometers) from Nagashima, Japan, to the coast of northern California in 84 hours and 31 minutes.
The first solo balloon crossing of the Atlantic was made in 1984 by Joseph Kittinger. Nearly 84 hours after takeoff from Caribou, Me., he was forced to crash-land his Rosie O'Grady's near Savona, Italy. His 3,535-mile (5,689-kilometer) trip also set a new world distance solo record. In 1995 Steve Fossett became the first person to fly a balloon solo across the Pacific Ocean. He covered more than 5,400 miles (8,690 kilometers), setting a new distance record.
In 1992 the first transatlantic balloon race in history, which included gas balloons from Belgium, the United States, The Netherlands, and Germany, was won by the Belgian team. They flew from Bangor, Me., to Peque, Spain, in 114 hours and 27 minutes and covered a distance of more than 2,580 miles (4,150 kilometers). During this race, the American team of Richard Abruzzo and Troy Bradley completed the longest balloon flight up to then (146 hours) and inadvertently made the first balloon flight from the United States to Africa when high winds blew them off their intended course toward Europe.
Steve Fossett, a 52-year-old securities broker from Colorado, navigated the longest hot-air-balloon flight to date in January 1997. After lifting off from St. Louis, Mo., Fossett floated across the eastern United States, crossed the Atlantic Ocean, passed over the southernmost point of the Iberian peninsula, and traversed Africa and much of Central Asia before landing abruptly on January 20 in the easternmost region of India. The 9,672-mile (15,565-kilometer) trip lasted for 146 hours and 54 minutes. Fossett obliterated his own previous record for balloon-flight distance, which had stood at 5,438 miles (8,751 kilometers), and broke the old duration mark by 2 hours and 40 minutes. Nevertheless, Fossett fell well short of his intended goal of circumnavigating the world by hot-air balloon. He stated that he would try to accomplish the goal in the future. Balloonists have attempted to circumnavigate the world during each year since 1991. Fossett, who came the closest, fell short by approximately 15,000 miles (24,140 kilometers).