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.

  1. What essential features of design did Meusnier’s first dirigible incorporate?
  2. Describe the difference between rigid, semi-rigid, and flexible types of dirigibles.
  3. 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.
  4. 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?
  5. What are air balloonets? How and for what purpose are they used?
  6. What is the most efficient form of envelope for the dirigible, and why?
  7. Why cannot the ordinary spherical balloon be propelled as a dirigible?
  8. Is the form of the stern as important as the bow?
  9. What is longitudinal stability and how is it obtained?
  10. How is stability of direction obtained? What are stabilizing planes?
  11. 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?