The German general staff so strongly appreciated the work of the allied kite balloons that in its system of rating aviators it ranked a balloon brought down as the equal of one and one-half planes.
The average life of a kite balloon on an active sector of the western front was estimated to be about 15 days. Some of them lived only a few minutes. One American balloon passed unscathed through the whole period of American activity on a busy sector. While ordinarily five or six months of nonwar service will deteriorate the balloon fabric, there are many cases of useful service longer than this.
When the war broke out Germany is said to have had about 100 balloons of the kite type. France and England had few of them. The German balloon was known as the Drachen. Its gas cylinder of rubberized cotton cloth was approximately 65 feet long and 27 feet in diameter, the ends being rounded. To give it a kite-like stability in the air a lobe, which was a tube of rubberized fabric, of a diameter approximately one-third of the diameter of the main balloon, was attached to the underbody of the gas bag as a sort of rudder, which curved up around the end of the balloon. This lobe was not filled with gas, but the forward end of it was open so that when the balloon rose the breeze filled the lobe with air. The inflated rudder then held the Drachen in line. The lobe automatically met the emergency. In calm, windless weather the balloon needed no steadying and the lobe was limp. Let the gale blow, and the lobe inflated and held the nose of the Drachen into the wind. As a further stabilizer three tailcups, with mouths open to the breeze, were attached 10 feet apart on a line descending from the rear of the balloon. In a strong wind these helped to keep the contrivance from swinging.
The tail-cup was made of rubberized fabric, circular in shape, about 4 feet in diameter, and about 2 feet deep when inflated by the breeze. It looked like an inverted umbrella, and was attached to the tail end of the balloon for exactly the same purpose and with the same effect as the tail attached to a kite.
The Drachen type of balloon was still in the experimental stage here and in France and England when the Germans swept over Belgium. The Drachen balloon was clumsy and relatively unstable in high winds, yet its importance to the Artillery could not be ignored by the allies. The results of its work daily became more apparent. The first effort of the allies was to improve the Drachen to give it greater stability and permit it to go to higher altitudes. While this work was going on, Capt. Caquot, of the French Army, produced a kite balloon so superior that it quickly superseded what had been in use. Germany clung to the Drachen for a time, but finally abandoned it for the Caquot principles of design.
The earlier balloons of the sausage type had been merely cylinders with hemispherical ends. Now for the first time, in the Caquot model, appeared a captive that was sharply stream lined. Stream lines are lines so curved as to offer the least possible resistance to the medium through which a mobile object, such as a yacht, an automobile, or an airship, moves. The Caquot gas bag was 93 feet long, as compared with the Drachen's 65 feet of length, yet its largest diameter was only 28 feet, being but a foot thicker than the pioneer German type. The Caquot, as all balloons developed in the war, was made of rubberized cotton cloth. Its capacity of 37,500 cubic feet of hydrogen gas lifted the mooring cable, the basket, two observers, and the mass of necessary equipment, and in good weather the balloon could ascend to a maximum altitude of over 5,000 feet.
The principal innovation in the design of the Caquot balloon was the location of the balloonette or air chamber within the main body of the gas envelope. This chamber was in the forward instead of the rear part of the bag and along the bottom of the envelope. It was separated from the gas chamber by a diaphragm of rubberized cotton cloth, which was sewn, cemented, and taped to the inner envelope somewhat below the "equator" or median line from the nose to the tail of the gas bag.
CAQUOT, TYPE R, CAPTIVE OBSERVATION BALLOON.
This balloon is 93 feet long and 28 feet in diameter. Its gross lifting power is 2,600 pounds.