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.

The balloon naturally works under the same difficulties as all lighter-than-air craft, that is, there is a constant leakage of the hydrogen through the fabric in addition to that lost by the expansion of the gas on warm days when the summer sun beats down directly on the gas bag. Where a field generating plant is employed, quick inflation of a new balloon or replacement of loss is accomplished by the used of several "nurses", Fig. 27. These are simply large gas bags which are kept replenished by the gas plant working constantly, in other words, they are storage tanks, and when it is necessary to inflate the balloon quickly, their contents are simply transferred to it.

Fig. 27. Landing Big Kite Balloon at Training Station "Somewhere in England." "Nurse" in Background
Copyright by Underwood and Underwood, New York

Balloon Company. Though aeronautical in character, the kite balloon service is actually a branch of the artillery, to which it is directly attached. A balloon company accordingly consists of twelve to twenty artillery officers of varying ranks and about 120 to 130 men. Of the officers, six to eight are artillery lieutenants or captains and go aloft as observers, this number being necessary because the strain of watching constantly is very great and the observers must be relieved at frequent intervals, the balloon otherwise being kept up continuously, both day and night. There are also a number of sergeants, each of whom is in charge of a different branch of the work, such as the inflation, transport, telephone service, and winding machine. No less than fifteen 3-ton to 5-ton motor trucks are necessary for each balloon company besides two or more motorcycle messengers, the care of the machines usually being entrusted to the corporals of the company. The remainder of the company are practically laborers, whose chief duties are to attach the ballast bags to the ropes when it is intended to hold the balloon on the ground for any length of time and to utilize their own weight for the same purpose when the balloon is about to go aloft or is only on the ground temporarily. In addition, every company has its surgeon and assistants, quartermaster, cooks, company clerk, and other attaches necessary to complete its organization, since a balloon company serves as an independent unit.

Equipment. The paraphernalia required is quite as elaborate as that necessary to keep several aeroplanes aloft, though naturally of a different nature. It must all be readily portable, for a balloon company has to change camp more or less frequently, or as often as the enemy artillery happens to discover its range. To secure mobility is the purpose of the great number of motor trucks employed. One of these is equipped with a hoisting winch and a large drum capable of holding 3,000 or 4,000 feet of about 3/8-inch steel cable. The winch is driven by the same engine that propels the truck, and in case of emergency the engine may be applied to the two purposes alternately within a short space of time. For instance, in case of attack either by shrapnel from an enemy battery or by a hostile aviator, it may be used to quickly haul in or let out cable to change the altitude of the balloon, or it may be employed to drive the truck to another and more favorable location with the balloon in tow.

Another truck houses a complete telephone exchange, since the observers in the balloon may wish to communicate with any one of a number of batteries which they are serving. Telephone communication is established by means of an insulated wire which forms the core of the cable, while the steel cable itself acts as the return wire to complete the circuit. In some cases, a separate copper cable is employed, using the steel cable as the return half of the circuit. In addition there is a truck for transporting the balloons, for the company must always have duplicate equipment at hand in case of the destruction of the balloon it is using or, as more frequently happens, damage of a nature that requires hours or days to repair. In addition to the balloon itself, there are covers and the ground cloth, as in inflating a balloon no part of its fabric must be allowed to touch the ground because of the danger of stones or sticks tearing rents in it. The balloon proper and its immediate accessories utilize at least one and sometimes two motor trucks.

To hold the balloon on the ground when out of service, there are eighty sacks of sand weighing 25 pounds each, or an aggregate of 1 ton of ballast, in addition to which there are necessary a large number of steel screw stakes, spare ropes and parts, ladders and the like, besides the basket and its equipment. The stakes are employed to hold the balloon down in a heavy wind by "pegging" it in the same manner as a tent. Three or four trucks are required to carry the large supply of hydrogen necessary, which entails the transportation of 130 to 150 containers. Each container holds several thousand cubic feet of gas under high pressure, which is released through a reducing valve. Some of the other transportation units required are the "cook wagon," quartermaster’s stores truck, truck for carrying tents, blankets, and other impediments for the men, and the "doctor’s wagon" (ambulance).

Advantages of Kite Balloon. It became a necessity to resurrect the captive balloon and bring it up to date, not simply because the Germans were employing it in numbers, but because experience demonstrated that it possessed numerous advantages over the aeroplane for artillery observation. The observer in an aeroplane is carried back and forth over and around the location he wishes to watch, at high speed and at a constantly varying altitude. He must communicate by means of either signals or wireless, and it is not always possible for him in either case to know whether his signals have been received and understood, since it is possible to transmit messages by wireless from an aeroplane but a very difficult matter to receive. The observers in a kite balloon, on the other hand, have the advantage of being able to scrutinize a certain sector constantly with the aid of powerful glasses. With a few weeks of experience in observing a given terrain they become so familiar with it that any changes or the movements of troops or supplies are quickly distinguished. The greatest advantage, however, is that the information thus acquired may be instantly transmitted not merely to one but to any one or all of a group of batteries extending over a mile or two of front in either direction, the balloons being stationed 4 to 6 miles apart. The observers are fitted with portable head sets so that they speak directly into their telephones without the necessity of removing the glasses from their eyes, which enables them to watch the fall of the shells and tell the battery attendant in the dugout alongside the gun whether a shell fell "short", "over," "left," or "right," and the amount of correction needed before the smoke from the explosion has cleared away. With the aid of close corrections of this nature the battery commander is in a position to get the range exactly without the great expenditure of ammunition that firing entirely by map or with the assistance of aeroplane observers entails. Instances are recorded in which a 9.5-inch shell has been landed right in a concrete "pill-box" not over 15 feet square from a distance of 3 miles after six trial shots had been fired to obtain the range. Such a shot is reported back to the battery by the balloon observer as a "direct hit," and it is only necessary to fire the gun at the same range and direction to score as often as necessary.

Duties of Balloon Crew. Each kite balloon carries aloft two observers, Fig. 28, both of whom can concentrate their entire attention on the work of "spotting," since they have nothing to do with the control of the balloon itself, except to give orders. Their chief duties consist of "counter-battery" observation, that is, spotting the location of enemy batteries, and being constantly alert to detect any suspicious movements back of the enemy’s lines, such as movements of troops, ammunition, or supplies. The batteries controlled from observation balloons are the "heavies," which are located 1 mile or more back of the front line trenches and to the gunners of which the objects they are firing at are never visible. Some of the heaviest guns mounted on specially constructed railway trucks are often fired from points 5 miles or more back of the lines. In fact, when balked in their attempt to take Calais, the Germans bombarded the town with the aid of long-range naval guns from a distance of over 15 miles and every shot dropped into either some part of the city or its outskirts. Buildings, hills, or specially constructed and concealed observation towers are frequently utilized in conjunction with captive balloons to serve as auxiliary observation posts, so that the base line connecting the two may be used to triangulate distances and thus calculate them more accurately than is possible by direct observation from a single point.

Fig. 28. French Kite Balloon Observers about to Ascend
Copyright by Committee on Public Information, Washington, D.C.

Risks Incurred. Enemy Fire. While the observers in a kite balloon are not subjected to all the risks that the aviator must encounter when he goes aloft or, at least, not to the same extent, their lot is far from being free from danger. One of the duties of the reconnoitering aviator is to destroy observation balloons by means of incendiary bombs equipped with fishhooks which catch in the fabric or by the use of his machine gun. Enemy batteries may also succeed in getting the range of the balloon and fire at it with large caliber shrapnel, which spreads its fragments over an area 100 yards or more in diameter when it bursts. So many of the German balloons were downed by French and British aviators in the early part of the war—and the Germans retaliated in kind—that a battle plane is now always detailed to keep watch above the balloon to ward off attacks by aeroplanes.

Escape of Balloon. In addition to the risk of being shot down, there is the ever-present danger of the balloon being wrecked by a sudden squall or of its breaking away from its windlass through the parting of the cable and floating over the enemy lines. Balloons have been lost through both causes in a number of instances. Each of the two observers wears a heavy harness to which is attached a parachute suspended by a light cord from the rigging of the balloon, so that in case of emergency they may save themselves by jumping without having to make any preparations for their sudden drop.

In case of the breakage of the cable, which usually results from a strong wind coming up suddenly and putting a terrific strain on the steel line by jerking it, the observers are guided in their actions by the direction in which the balloon moves. When it is carrying them back over their own territory, they navigate in the same manner as a free balloon, coming to the ground as soon as a favorable landing place can be reached. Instruction in free ballooning is accordingly an important part of the curriculum that the kite balloon observers must go through. Should the wind be in the opposite direction, however, as only too often proves to be the case, all instruments, papers, and maps are immediately thrown over the side and the observers promptly follow suit in their parachutes, abandoning the balloon to its fate. As the balloon travels with the speed of the wind, once it is released, and the parachute of the descending observer is carried in the same direction, prompt action is vital to prevent coming to the ground in the enemy’s territory. In a 30-mile wind, for example, only eight minutes would elapse from the moment that the balloon broke away until it traversed the 4 miles intervening between its station and the enemy’s lines. On some occasions, kite balloons which were not fit for further service have been loaded with explosives and released from a height that would cause them to land well within the enemy’s territory with disastrous results to the men detailed to capture them.

Marine Service. The kite balloon was first used by the British naval forces in their operations against the Dardanelles and proved so valuable that they have since been employed in fleet expeditions in the North Sea as well as for anti-submarine work. In the latter form of service, they have the same superiority over the aeroplane for observation that they possess in land operations. The ship naturally cannot run the risk of remaining stationary, but as the speed of the balloon is the same as that of the ship towing it, the observers do not pass over a given area with anything like the velocity of an aeroplane, while their elevated position affords the same advantages for detecting the presence of the submerged submarine or the approach of enemy vessels.

EXAMINATION PAPER

DIRIGIBLE BALLOONS

Read Carefully: Place your name and full address at the head of the paper. Any cheap, light paper like the sample previously sent you may be used. Do not crowd your work, but arrange it neatly and legibly. Do not copy the answers from the Instruction Paper; use your own words, so that we may be sure you understand the subject.

What essential features of design did Meusnier’s first dirigible incorporate?
Describe the difference between rigid, semi-rigid, and flexible types of dirigibles.
State the laws governing the increase of resistance with speed, the increase of power necessary for a given increase of speed, and the ratio in which the volume and area of the gas bag increase with increased dimensions.
What provides the lifting power of the dirigible and how is this lifting power utilized? Why should this lifting power be so much less at night than in the daytime? What is net lifting power?
What are air balloonets? How and for what purpose are they used?
What is the most efficient form of envelope for the dirigible, and why?
Why cannot the ordinary spherical balloon be propelled as a dirigible?
Is the form of the stern as important as the bow?
What is longitudinal stability and how is it obtained?
How is stability of direction obtained? What are stabilizing planes?
Why must a form of suspension for the car that cannot be accidentally displaced with relation to the balloon be provided?

12. Theoretically, where should the propulsive effort be applied to a dirigible? What factors affect the placing of the propeller and what has been proved to be the most practical solution of the problem?

Discuss the advantages of the kite balloon over the aeroplane for observation.
What is the effect of the wind on a modern kite balloon?
What is the difference between "pounds per horsepower" and "pounds per horsepower hour" as applied to the motor of a dirigible? Which is more important?

Sketch and explain the Astra-Torres suspension.

What differences exist between a Zeppelin and a Schutte-Lanz dirigible?
Describe the "L-49", discussing power plant and control.
Define static and dynamic equilibrium as applied to the dirigible.
Is the Zeppelin effective? Discuss fully.

After completing the work, add and sign the following statement:

I hereby certify that the above work is entirely my own.

(Signed)

*** END OF THIS PROJECT GUTENBERG EBOOK DIRIGIBLE BALLOONS ***