Dirigible Balloons

by Charles B. Hayward

CAPTIVE BALLOONS

Military Value. As an aid to military operations, the use of the captive balloon dates back many years. It was extensively employed in the Civil war and more recently in the Boer war, but with the advent of both the dirigible and the aeroplane, it was generally considered outside of Germany that its reason for existence had passed away. The German military plans included a large number of balloons for artillery observation purposes and they were used right from the start. It was only when the fighting settled down to trench warfare, however, that they came into prominence and the aid that they rendered the German batteries put their opponents at a serious disadvantage. Like the bayonet, which was also generally considered to have been relegated to military operations of the past, the captive balloon is now playing a very important role, particularly on the western front. In favorable weather, anywhere from ten to forty of these aerial observation posts will be visible from a single point on the line.

Spherical Type Defective. The captive balloon of the present day, however, bears no resemblance to its predecessors. From a sphere, it has been developed into a form that more nearly resembles the dirigible and at the same time, it embodies some of the features of the aeroplane. The old spherical balloon was always at the mercy of the wind, which not only governed the altitude to which the balloon would rise but also made things extremely uncomfortable as well as dangerous for the observers. With 1,000 feet of cable out, such a balloon rises to an equivalent height on a perfectly, calm day. But even a light wind cuts this height down by 100 or 200 feet, while if a strong wind is blowing, the balloon is held down to within a few hundred feet of the ground regardless of the length of cable paid out. Every strong gust beats it over at a perilous angle and the resulting shocks to the basket are so severe that its occupants can have little thought for anything but their own safety. Strong cross gusts set both the bag and basket to spinning and jumping in a manner that would make the results of the severest storm at sea seem mild by comparison, since the movements of the basket are executed with such rapidity that they seem to be in almost every plane simultaneously. As a result, the old type of captive balloon was available for service only in the calmest weather.

Modern Kite Balloon. It should not be supposed that the improved type of observation balloon now in use in such large numbers provides any unusual amount of ease or comfort, since it is also prey to the wind and does a great deal of swinging about as well as jerking when the wind is more than 15 or 20 miles an hour. But it has been improved to a point where the wind not only serves to elevate, instead of depressing it, but also to steady it. The new type. Fig. 25, is technically known as a kite balloon, because, in addition to the appendages attached to the bag itself for steadying purposes, it is equipped with a tail to assist in keeping it heading into the wind. This consists of a number of bucket-shaped pieces of heavy canvas attached to the tail cable by bridles so as to catch the wind and hold it, thus placing a heavy strain on the cable and preventing the balloon from swinging violently. As is the case with practically everything used at the front, the technical name of the new type of balloon is prominent by its absence. It is a Drache (kite) to the Germans and a "blimp" to Tommy Atkins. Both its shape and attitude when aloft bear a close resemblance to a huge sausage, so that the term "sausage" is used by all the belligerents in common to a large extent. A side view of an American type is shown in Fig. 26.

Fig. 25. Head-On View of Modern Kite Balloon, Showing Details of Tail Buckets
Copyright by Central News Service, New York City

It will be noted from Figs. 25 and 26 that the suspension of the basket and the appendages attached to the balloon at the rear hold it in a position which is roughly the equivalent on a large scale of the curve of an aeroplane wing. It has both camber and an angle of incidence, so that the wind serves to elevate it instead of beating it down. This lifting effect is further increased by tubes of large diameter, open at the forward end only and curving around the end of the gas bag at the rear. (It is also equipped with an air balloonet, the same as a dirigible.) The wind enters the lower end of this tubular member, which is in a line with the longitudinal axis of the balloon, but it must pass around the curve at the end of the gas bag before it can fully inflate it, so that it performs the double function of increasing the lift and steadying the balloon, though the latter is its chief purpose. The basket is suspended quite a distance below the gas bag and has accommodation for two observers. Like scores of other inventions that the Germans were the first to utilize on a large scale in the present war, the kite balloon was not a German creation but was originally developed in France.

Fig. 26. American Kite Balloon of Latest Type Ascending
Copyright by Committee on Public Information, Washington, D C.

Methods of Inflation. The average capacity of the kite balloons used for observation purposes is 28,000 cubic feet. They are inflated with hydrogen either from a portable generating plant forming part of the equipment of the balloon company or from a supply carried under high pressure in heavy steel "bottles" similar to those used for transporting oxygen or carbonic acid gas intended for industrial use. Since the balloon companies are stationed about 4 miles back of the firing line, the use of the portable plant is practical, but it has been found more economical and more convenient to generate the gas on a large scale at special establishments in France and England and send it to the front in containers. With a portable plant, several hours are necessary to inflate the gas bag, whereas with a large supply of the gas at hand under high pressure, the operation may be carried out in less than an hour.