While wonderful success has attended the development of the dirigible
(steerable) balloon the most ardent advocates of this form of aerial
navigation admit that it has serious drawbacks. Some of these may be
described as follows:
Expense and Other Items.
Great Initial Expense.--The modern dirigible balloon costs a fortune.
The Zeppelin, for instance, costs more than $100,000 (these are official
figures).
Expense of Inflation.--Gas evaporates rapidly, and a balloon must
be re-inflated, or partially re-inflated, every time it is used. The
Zeppelin holds 460,000 cubic feet of gas which, even at $1 per thousand,
would cost $460.
Difficulty of Obtaining Gas.--If a balloon suddenly becomes deflated, by
accident or atmospheric conditions, far from a source of gas supply, it
is practically worthless. Gas must be piped to it, or the balloon carted
to the gas house--an expensive proceeding in either event.
Lack of Speed and Control.
Lack of Speed.--Under the most favorable conditions the maximum speed
of a balloon is 30 miles an hour. Its great bulk makes the high speed
attained by flying machines impossible.
Difficulty of Control.--While the modern dirigible balloon is readily
handled in calm or light winds, its bulk makes it difficult to control
in heavy winds.
The Element of Danger.--Numerous balloons have been destroyed by
lightning and similar causes. One of the largest of the Zeppelins was
thus lost at Stuttgart in 1908.
Some Balloon Performances.
It is only a matter of fairness to state that, under favorable
conditions, some very creditable records have been made with modern
balloons, viz:
November 23d, 1907, the French dirigible Patrie, travelled 187 miles in
6 hours and 45 minutes against a light wind. This was a little over 28
miles an hour.
The Clement-Bayard, another French machine, sold to the Russian
government, made a trip of 125 miles at a rate of 27 miles an hour.
Zeppelin No. 3, carrying eight passengers, and having a total lifting
capacity of 5,500 pounds of ballast in addition to passengers, weight
of equipment, etc., was tested in October, 1906, and made 67 miles in 2
hours and 17 minutes, about 30 miles an hour.
These are the best balloon trips on record, and show forcefully the
limitations of speed, the greatest being not over 30 miles an hour.
Speed of Flying Machines.
Opposed to the balloon performances we have flying machine trips (of
authentic records) as follows:
Bleriot--monoplane--in 1908--52 miles an hour.
Delagrange--June 22, 1908--10 1/2 miles in 16 minutes, approximately 42
miles an hour.
Wrights--October, 1905--the machine was then in its infancy--24 miles
in 38 minutes, approximately 44 miles an hour. On December 31, 1908, the
Wrights made 77 miles in 2 hours and 20 minutes.
Lambert, a pupil of the Wrights, and using a Wright biplane, on October
18, 1909, covered 29.82 miles in 49 minutes and 39 seconds, being at
the rate of 36 miles an hour. This flight was made at a height of 1,312
feet.
Latham--October 21, 1909--made a short flight, about 11 minutes, in
the teeth of a 40 mile gale, at Blackpool, Eng. He used an Antoniette
monoplane, and the official report says: "This exhibition of nerve,
daring and ability is unparalled in the history of aviation."
Farman--October 20, 1909--was in the air for 1 hour, 32 min., 16
seconds, travelling 47 miles, 1,184 yards, a duration record for
England.
Paulhan--January 18, 1901--47 1/2 miles at the rate of 45 miles an hour,
maintaining an altitude of from 1,000 to 2,000 feet.
Expense of Producing Gas.
Gas is indispensable in the operation of dirigible balloons, and gas
is expensive. Besides this it is not always possible to obtain it in
sufficient quantities even in large cities, as the supply on hand is
generally needed for regular customers. Such as can be had is either
water or coal gas, neither of which is as efficient in lifting power as
hydrogen.
Hydrogen is the lightest and consequently the most buoyant of all known
gases. It is secured commercially by treating zinc or iron with dilute
sulphuric or hydrochloric acid. The average cost may be safely placed
at $10 per 1,000 feet so that, to inflate a balloon of the size of the
Zeppelin, holding 460,000 cubic feet, would cost $4,600.
Proportions of Materials Required.
In making hydrogen gas it is customary to allow 20 per cent for loss
between the generation and the introduction of the gas into the balloon.
Thus, while the formula calls for iron 28 times heavier than the weight
of the hydrogen required, and acid 49 times heavier, the real quantities
are 20 per cent greater. Hydrogen weighs about 0.09 ounce to the cubic
foot. Consequently if we need say 450,000 cubic feet of gas we must have
2,531.25 pounds in weight. To produce this, allowing for the 20 percent
loss, we must have 35 times its weight in iron, or over 44 tons. Of acid
it would take 60 times the weight of the gas, or nearly 76 tons.
In Time of Emergency.
These figures are appalling, and under ordinary conditions would be
prohibitive, but there are times when the balloon operator, unable to
obtain water or coal gas, must foot the bills. In military maneuvers,
where the field of operation is fixed, it is possible to furnish
supplies of hydrogen gas in portable cylinders, but on long trips
where sudden leakage or other cause makes descent in an unexpected spot
unavoidable, it becomes a question of making your own hydrogen gas or
deserting the balloon. And when this occurs the balloonist is up against
another serious proposition--can he find the necessary zinc or iron? Can
he get the acid?
Balloons for Commercial Use.
Despite all this the balloon has its uses. If there is to be such a
thing as aerial navigation in a commercial way--the carrying of freight
and passengers--it will come through the employment of such monster
balloons as Count Zeppelin is building. But even then the carrying
capacity must of necessity be limited. The latest Zeppelin creation,
a monster in size, is 450 feet long, and 42 1/2 feet in diameter. The
dimensions are such as to make all other balloons look like pigmies;
even many ocean-going steamers are much smaller, and yet its passenger
capacity is very small. On its 36-hour flight in May, 1909, the
Zeppelin, carried only eight passengers. The speed, however, was quite
respectable, 850 miles being covered in the 36 hours, a trifle over 23
miles an hour. The reserve buoyancy, that is the total lifting capacity
aside from the weight of the airship and its equipment, is estimated at
three tons.