For nearly a century after the invention of the Montgolfier and Charlier balloons there was not much progress made in the science of aeronautics.True, inventors such as Charles Green suggested and carried out new methods of inflating balloons, and scientific observations of great importance were made by balloonists both in Britain and on the Continent.But in the all-important work of steering the huge craft, progress was for many years practically at a standstill.All that the balloonist could do in controlling his balloon was to make it ascend or descend at will; he could not guide its direction of flight.No doubt pioneers of aeronautics early turned their attention to the problem of providing some apparatus, or some method, of steering their craft.One inventor suggested the hoisting of a huge sail at the side of the envelope; but when this was done the balloon simply turned round with the sail to the front.It had no effect on the direction of flight of the balloon."Would not a rudder be of use?" someone asked.This plan was also tried, but was equally unsuccessful.
Perhaps some of us may wonder how it is that a rudder is not as serviceable on a balloon as it is on the stern of a boat.Have you ever found yourself in a boat on a calm day, drifting idly down stream, and going just as fast as the stream goes? Work the rudder how you may, you will not alter the boat's course.But supposing your boat moves faster than the stream, or by some means or other is made to travel slower than the current, then your rudder will act, and you may take what direction you will.
It was soon seen that if some method could be adopted whereby the balloon moved through the air faster or slower than the wind, then the aeronaut would be able to steer it.Nowadays a balloon's pace can be accelerated by means of a powerful motor-engine, but the invention of the petrol-engine is very recent.Indeed, the cause of the long delay in the construction of a steerable balloon was that a suitable engine could not be found.A steam-engine, with a boiler of sufficient power to propel aballoon, is so heavy that it would require a balloon of impossible size to lift it.
One of the first serious attempts to steer a balloon by means of engine power was that made by M.Giffard in 1852.Giffard's balloon was about 100 feet long and 40 feet in diameter, and resembled in shape an elongated cigar.A 3-horse-power steam-engine, weighing nearly 500 pounds, was provided to work a propeller, but the enormous weight was so great in proportion to the lifting power of the balloon that for a time the aeronaut could not leave the ground.After several experiments the inventor succeeded in ascending, when he obtained a speed against the wind of about 6 miles an hour.
A balloon of great historical interest was that invented by Dtipuy du Lonie, in the year 1872.Instead of using steam he employed a number of men to propel the craft, and with this air-ship he hoped to communicate with the besieged city of Paris.
His greatest speed against a moderate breeze was only about 5 miles an hour, and the endurance of the men did not allow of even this speed being kept up for long at a time.
Dupuy foreshadowed the construction of the modern dirigible air-ship by inventing a system of suspension links which connected the car to the envelope; and he also used an internal ballonet similar to those described in Chapter X.
In the year 1883 Tissandier invented a steerable balloon which was fitted with an electric motor of 1 1/2 horse-power.This motor drove a propeller, and a speed of about 8 miles an hour was attained.It is interesting to contrast the power obtained from this engine with that of recent Zeppelin air-ships, each of which is fitted with three or four engines, capable of producing over 800 horse-power.
The first instance on record of an air-ship being steered back to its starting-point was that of La France.This air-craft was the invention of two French army captains, Reynard and Krebs.By special and much- improved electric motors a speed of about 14 miles an hour was attained.
Thus, step by step, progress was made; but notwithstanding the promising results it was quite evident that the engines were far too heavyin proportion to the power they supplied.At length, however, the internal- combustion engine, such as is used in motor-cars, arrived, and it became at last possible to solve the great problem of constructing a really-serviceable, steerable balloon.
