Airship Gases - Helium
The two lifting gases historically used in airships are hydrogen and helium. Hydrogen is less dense so it has slightly more lift, about 70 pounds per 1000 cubic feet of gas versus 65 for helium. It is also considerably less expensive. Because hydrogen is highly flammable all contemporary airships use helium. The reason the German airships of the twenties and thirties used hydrogen is because at the time the United States had the only useful supply of helium in the world and was unwilling to sell it to Germany because it was considered a war resource. American airships of the same period all used helium.
In a nonrigid airship the hull structure consists of both the outer envelope of the ship-which serves double duty as the gas envelope - and the lifting gas itself, which is slightly pressurized to between 1/4 and 1/2 pound per square inch to give the envelope rigidity. To paraphrase a contemporary airship design engineer, "I like helium because it is a great structural material that also happens to lift itself plus more. It allows us to build these hugely large vehicles relatively inexpensively and as a bonus they don't weigh nearly as much as they would if constructed conventionally."
Helium is extensively used for filling balloons as it is a much safer gas than hydrogen. The hydrogen used to inflate dirigibles and observation balloons being highly inflammable and explosive, the balloons were easy to destroy with bullets. There is no balloon fabric that is absolutely gas-tight. The German machines were formed of a rigid shell divided into compartments in which the gas-bags are placed. In the space between the bags and their containers there is bound to be an accumulation of gas which mixes with the air and needs only a spark to touch it off. Under the balloon are the gasoline engines, which were quite liable to discharge flaming gases from their exhaust-pipes. To avoid the danger of fire these engines must be suspended well below the gas-bags and their exhaust-pipes must be carefully screened. Another danger lies in the fabric of the balloon itself. It is liable to become highly electrified and under certain conditions will emit sparks which may cause the balloon to explode.
Helium being non-inflammable and non-explosive, and, next, to hydrogen, the lightest of gases, would have been an ideal substitute. Its lifting power is only 8 percent, less than that of hydrogen. Hydrogen is so light that it passes through the walls of the gas bag and escapes at a far more rapid rate than helium. The daily loss of hydrogen from a 37,000 cu. ft. balloon may run as high as 5000 cu. ft. Experiments with other non-inflammable gases proved unsuccessful because of their too great weight. With helium the design of the airship may be improved materially. The passenger and engine cars can be attached directly to the balloon proper. The engines can even be placed within the balloon, thus cutting down head resistance and bringing the propellers on the center line of the airship, where they can exert a more direct pull. With the fire risk removed there are so many advantages of the airship over the airplane for big loads and long-distance travel.
Helium has a unique combination of properties that make it very special. It is odorless, colorless, and tasteless. Like argon, it refuses to combine with any other substance, and must therefore be classed with the group of chemically inert gases. Helium has the lowest melting point of any element and is widely used in cryogenic research because its boiling point is close to absolute zero. Helium has other peculiar properties: It is the only liquid that cannot be solidified by lowering the temperature. It remains liquid down to absolute zero at ordinary pressures, but will readily solidify by increasing the pressure. Solid 3He and 4He are unusual in that both can be changed in volume by more than 30% by applying pressure.
Helium was one of the rare gases. Its cost per cubic foot ranged from fifteen hundred dollars to six thousand dollars. To fill a large Zeppelin with helium at even the lowest market price would have cost three billion dollars. But then there was not that much helium in captivity. No laboratory in the country could boast of more than five cubic feet. One of the reasons for the scarcity of helium lay in its apparent uselessness.
The French astronomer Pierre Janssen obtained the first evidence of helium during the solar eclipse of 1868 when he detected a new line in the solar spectrum. They observed in the spectrum of the sun's chromosphere a bright yellow line, which could not be identified with that of any known terrestrial substance. Lockyer and Frankland suggested the name helium (Gr. helios, the sun) for the new element. In 1895 Ramsay discovered helium in the uranium mineral cleveite while it was independently discovered in cleveite by the Swedish chemists Cleve and Langlet at about the same time. Rutherford and Royds in 1907 demonstrated that alpha particles are helium nuclei.
Except for hydrogen, helium is the most abundant element found in the universe. It was discovered in natural gas in 1905. In fact, all natural gas contains at least trace quantities of helium. A rise from the position of a laboratory curiosity, of such rarity as to cost $1,700 a cubic foot, to that of a commodity producible at 5.22 cents a cubic foot, in quantities to meet a great demand for both industry and science, is the record of the new element helium since 1918. Up to that year, not more than three or four cubic yards of the new element had been collected, fifty years after its (astronomical) discovery. The cost of helium fell from $2500/ft3 in 1915 to 1.5 cents /ft3 in 1940. The U.S. Bureau of Mines set the price of Grade A helium at $37.50/1000 ft3 in 1986.
After the wreck of a Zeppelin in 1910, a German proposed that helium be used to avoid similar accidents in the future. British and United States experts also joined in urging the importance of helium as a munition of war.
When Great Britain entered the war there was found to be great need of helium and no means of getting it. Equally unsuccessful at the time were the British efforts to separate helium from the mine gases in the United Kingdom and from the natural gas issuing from certain wells in Canada. On the proposal of Sir Richard Threlfall, the Admiralty Board of Invention and Research sent Professor McLennan, in 1915, to determine the helium contents of the natural gases in Alberta and New Brunswick, and to devise methods of extracting and purifying them.
The United States government became interested in helium during World War I. The Army valued it as a safe, noncombustible alternative to hydrogen for use in buoyant aircraft. Assistant Secretary Roosevelt, of the Navy, has summed up these advantages in his statement that "with the fire risk eliminated, the rigid airship, or Zeppelin, will be one of the most powerful weapons known." The Federal Government's involvement in Helium production had its origins in 1917 with attempts to develop uses for this lighter-than-air element. Helium separation technology sponsored by the Bureau of Mines and War Department was put into use at the first experimental plant built near Ft. Worth, Texas, in 1918. Both the Bureau of Mines and private companies collaborated to improve separation technologies and develop helium as a lifting gas for observational blimps. During this time for security reasons, Helium was referred to as Gas X or even Argon so as to deflect attentions from the military uses.
The war came to a close before the helium-filled airship had been produced. Some helium had been manufactured, enough to fill some American observation balloons "on the other side" in France. When the armistice was signed preparations were under way to build a fleet of helium airships to conduct bombing raids over Germany. If the war had lasted until the spring of 1919, the British and American Governments would have sent helium-filled rigid airships over strategic points in Germany, each capable of dropping a 'total of 10 tons or more of high explosive either in a single tremendous discharge or in a number of smaller ones during its passage over a fortress or city. These airships would have carried batteries amply sufficient to repel airplane attack. These airships would not feel the sting of the battle-plane's incendiary bullets. Had the Germans continued the fight, the Zeppelin raids on London would have been amply avenged.
The first successful use of helium as a substitute for hydrogen gas occurred on Dec. 1, 1921, when the U. S. Navy non-rigid airship C-7 was successfully inflated and made two successful trips from the naval air station at Hampton Roads, Va., which were repeated on the following day and subsequently. This large blimp, which had a capacity of 181,000 cubic feet, was filled with gas made at the U. S. Government plant at Fort Worth, Texas.
The United States was the only country in the world having a supply of helium adequate for an ambitious airship program. In 1919 helium was found to constitute 2 to 5 percent, of the natural gas in the wells of Kansas, Texas and elsewhere. Helium is an element that occurs in only a few locations in quantities sufficient for extraction on a commercial scale. But in the Kansas, Oklahoma, and Texas fields the helium gas occurs only in a certain group of geologic formations, and that in the strata above and below this group the helium content is very low. Means had been devised to reduce the cost of production to 39 cents a cubic foot in the plant at Petrolia, Texas. Another plant, constructed by the Navy Department at Fort Worth, produced helium at a cost of 5.22 cents a cubic foot.
No other countries had any commercial supplies of helium. Great Britain, however, was thoroughly searched for helium gases during the war without success. In France there were some mineral springs which emit gas rich in helium, but the total volume per year is insignificant. Far larger volumes of helium are contained in the "fire-damp" of French and Belgium coal mines, but the proportions are so small that there is little hope of extracting the helium commercially. The return of Alsace puts France in possession of an oil field in which some gas is produced, but the normal variety contains only a trace of helium. A deep test-hole near Pechelbronn, however, found in the older formations a little gas which carries 0.4 percent. In Italy some gas is produced on the northern flank of the Apennines, but two analyses of this gas showed only very minute quantities of helium. Germany produced a little gas near Hamburg, but the helium content was only 0.014 percent, and the Austrian gas produced near Wels contains even less. The only gas field in Europe which compares in size with the American fields was located in Transylvania, and several analyses of this gas show less than 0.002 per cent helium. The Roumanian and Galician oil fields on the Carpathian front yielded very little gas, and the Baku fields of Russia were also primarily oil producers. In 1925 Congress created a Federal Helium Program to ensure that helium would be available to the government for defense needs. As the Ft. Worth field reserves began to run out, new sources of helium were identified near Amarillo, Texas. The Bureau of Mines retained the rights to the Cliffside field. The Bureau of Mines constructed and operated a large helium extraction and purification plant just north of Amarillo, Texas, that went into operation in 1929. From 1929 to 1960 the federal government was the only domestic producer of helium. Production continued at the Amarillo plant between the world wars.
When wartime demands increased dramatically the bureau of mines built four new plants, the Exell plant in Texas, the Otis plant in Kansas, the Cunningham plant also in Kansas, and the Navajo plant located in New Mexico. This increased the supply that was need to do meet in the creasing wartime demands primarily air ship patrols.
During and after World War II the demand for helium increased. In response, Congress passed amendments to the Helium Act in 1960. The amendments provided incentives for private natural gas producers to strip helium from natural gas and sell it to the government. The Secretary of the Interior was given authority to borrow money from the U.S. Treasury to buy helium. Some of this helium was used for research, NASA's space program, and other applications, but most was injected into a storage facility known as the Federal Helium Reserve. The 1960 amendments required the Bureau of Mines to set prices on the helium it sold that would cover all of the helium program's costs and repay its debts.
Federal demand for helium did not live up to post-war expectations, and by the 1990s private demand for helium far exceeded federal demand. The 1996 Helium Privatization Act redefined the government's role in helium production. The Bureau of Land Management was made responsible for operating the Federal Helium Reserve and providing enriched crude helium to private refiners.
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