Hot air balloon

“ We now have two aerial craft competing for popular favour: the Montgolfier hot-air balloon and the "Charlier" or gas-inflated balloon. About four months after the first trial trip of the latter the inventors decided to ascend in a specially-constructed hydrogen-inflated craft. This balloon, which was 27 feet in diameter, contained nearly all the features of the modern balloon. Thus there was a valve at the top by means of which the gas could be let out as desired; a cord net covered the whole fabric, and from the loop which it formed below the neck of the balloon a car was suspended ”

“ Fourthly, by an octahedron of glass, heated by the sun, and of which the lower part should be allowed to penetrate the dense cold air, which, pressing up against the rarefied hot air, would raise the balloon. Fifthly, by a car of iron and a ball of magnetised iron, which the aeronaut would keep throwing up in the air, and which would attract and draw up the balloon. The wiseacre who invented these modes of flying in the air seems, some would say, to have been more in want of very strict confinement on the earth than of the freedom of the skies. ”

“ Their first balloon took fire and went up as smoke. But they were rich paper manufacturers, and soon had another balloon 33of 700 cubic feet capacity. This rose from the fire to a height of 1,000 feet, carrying no fuel with it. Thus two practical [6] men had made fire lift a paper sac; let the Academy explain how. The baby Aërostation was born.
How fortuitous the primal steps of science! Galvanism from the twitch of a frog’s leg; aërostation from the puff of a petticoat! There had been no year in thirty centuries when people could not easily have built a hot-air balloon. ”

“ I have plenty of silk in the Palace, so it will be no trouble to make the balloon. But in all this country there is no gas to fill the balloon with, to make it float."
"If it won't float," remarked Dorothy, "it will be of no use to us."
"True," answered Oz. "But there is another way to make it float, which is to fill it with hot air. Hot air isn't as good as gas, for if the air should get cold the balloon would come down in the desert, and we should be lost." ”

“ Balloons that really go up are always attractive but by thoughtful planning they can be made much more beautiful. A nice white balloon against a blue sky is very pleasing, but most boys like more color. The hot air balloons are made of tissue paper, and consist of an inverted bag with a light piece of reed at the bottom to keep the mouth open. The most successful shape is shown by Fig. ”

“ There was always a possibility of the balloon catching fire while it was being filled, and on landing there was further danger from the hot pan which kept up the supply of hot air on the voyage—the collapsing balloon fell on the pan, inevitably. ”

“ You can fill a balloon with common air so as to make it fly up like the gas balloon; but the air must be heated to do this. A boy can make such a balloon very easily out of thin paper. He pastes the paper together so as to shape it like a balloon, leaving one end open. It can be filled with hot air by holding it over something burning, with its open end down. It is sometimes done in another way. A sponge wet in turpentine or alcohol is fixed under the opening of the balloon by a little frame-work, as represented here ”

“ We should not need the fire-basket you speak of. That is only required, when you design to keep your balloon some length of time in the air. If you only wish to make a short ascent, once filling the bag with hot air is sufficient ”

“ In the race for actual accomplishment the balloonists, the advocates of lighter-than-air machines, took the lead at first. It is customary and reasonable to discard as fanciful the various devices and theories put forward by the experimenters in the Middle Ages and fix the beginning of practical aeronautical devices with the invention of hot-air balloons by the Montgolfiers, of Paris, in 1783. ”

“ Directly the balloon rises expansion takes place, owing to the rarefied state of the atmosphere, and the higher it ascends the more rarefied the air becomes, and consequently the less atmospheric pressure is there upon the balloon, the natural result being that the gas expands, and makes its way by degrees out of the neck. If there were no such escape, the balloon would burst. When the neck is wide open, those in the car can see into the middle of the balloon, which has a very curious appearance. ”

“ The balloon then rises high into the air, where the weight of atmosphere pressing upon it is much diminished. The higher it rises the less the pressure becomes, and the gas it holds soon expands so much that, unless a vent is provided for it, the balloon will burst. At the present day the neck of a balloon is always left wide open when the balloon is in the air, to allow of the escape of the gas during the ascent. ”

“ The balloon is never entirely filled, for the atmospheric pressure diminishing as it ascends, allows the hydrogen gas to dilate, in virtue of its expansive force, and, unless there is space for this expansion, the balloon is sure to explode in the air.
An ordinary balloon, with a lifting power sufficient to carry up three persons, with necessary ballast and materiel, is about fifty feet high, thirty-five feet in diameter’ and 2,250 cubic feet in capacity. ”

“ The air in the balloon is heated by the fire and becomes lighter than the cold air outside, and the balloon rises like a bubble in water, and it floats up in the air until it reaches atmosphere so rare as to be lighter than the heated air. ”

“ 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. ”

“ After a time, when gas is lost, one of the smaller ones could be emptied into the others, and the exhausted envelope discharged as ballast; the smaller balloons would be easier to transport by porters than one big one, and they could be more easily secured on the earth during contrary winds. Over the main balloon a light awning might be rigged to neutralise, as far as possible, the changes of temperature. A lightning conductor to the top of the balloon might be desirable. ”

“ The gas was renewed by Roziers, and the balloon again rising, extricated itself from among the branches, and soared majestically into the air, followed by the acclamations of the public. This second ascent was very instructive, for it had been often asserted that if ever a balloon fell upon a forest it would be destroyed, and would place those who travelled in it in the greatest peril. This experiment proved that the balloon does not FALL it DESCENDS; that it does not overturn; that it does not destroy itself on trees; that it neither causes death, nor even damage, to its passengers ”

“ The balloon is made of long strips of silk, sewn together, and rendered air-tight by means of a coating of caoutchouc. A valve is fitted to the top, and by means of it the aeronaut can descend to the earth at will, by allowing some quantity of the gas to escape. The car in which he sits is suspended to the balloon by a network, which covers the whole structure. ”

“ Striking as the fact is, it would be still more surprising if it were otherwise; for, having once entered a current of air, and surrendered our machine to its guidance, we become, as it were, part of the medium in which we are immersed. The balloon has no longer any will of its own, or of its occupants, except for purposes of ascent or descent. It glides along with the stream, and, coming athwart no obstructions, it knows none of the bumpings to which more grovelling vehicles are exposed. ”

“ Monsieur Nadar, as the reader already knows, scouts the idea of steering balloons.
In reference to this he states with truth that, “a balloon which presents to the action of the atmosphere a volume of from 22,000 to 42,000 (cubic) feet of a gas from ten to fifteen times lighter than air, is, by its very nature, smitten with incapacity to struggle against the slightest current, no matter what may be the resisting motive force which may be imparted to it. Both by its constitution, and by the medium which drives it hither and thither at the pleasure of the winds, it can never become a vessel. ”

“ The balloon, because of its vast size and from its being lighter than the air, is completely at the mercy of the wind. It forms an integral part, so to speak, of the wind for the time being, and the direction of the wind in every instance determines the horizontal motion of the balloon. The force required to propel a balloon against even a moderate breeze would result in its destruction. The balloon cannot be transferred with any degree of certainty from one point of the earth’s surface to another, and hence the chief danger in its employment. ”

“ The air-balloon, as now constructed, is a bag of silk of large dimensions, usually cut in gores, and is, when expanded by gas, of a pear-shape. It ascends in the atmosphere because its whole bulk is much lighter than the air would be in the space it occupies. It is, in fact, a vessel filled with a fluid which will float on another fluid lighter than itself. ”

“ They placed themselves in the car, and, when thrown off from the fastenings, they rose through the air with the speed of an arrow. The height to which the balloon reached made it suddenly dilate, and the network, which was much too small, was stretched to the utmost. The balloon was forced down upon them by the dilation, and one of them, in the endeavour to work the valve, made a rent in the lower part of the globe, from which the gas escaping almost over the heads of the travellers, nearly choked them. ”

“ A balloon is an apparatus with an envelope filled with gas, the specific gravity of which is less than that of the atmosphere near the surface of the earth. It is practically at the mercy of air-currents. The science of balloon aeronautics dates definitely from 1783, when the Montgolfier brothers at Angonay in France constructed their first balloons. ”

“ Before the invention of the balloon men were quite unaware of the nature of the air even a short distance above their heads. In those days high mountain climbing had not come into fashion, and when Pilâtre de Rozier made the first ascent, it was considered very doubtful whether he might be able to exist in the strange atmosphere aloft. Charles and Roberts were the first to make scientific observations from a balloon, for they took up a thermometer and barometer, and made certain rough records, as also did other early aeronauts. ”

“ The very strong wind which arose immediately before our departure, had driven us down to tee ground many times, making us fear for the safety of our oars, &c., when we resolved to throw over as much ballast as would enable us to rise against the wind. The ballast, including from 70 to 80 lbs. of provisions, was thrown over, and then we rose so rapidly that all the objects around were instantly passed and were very soon lost to view. The swelling form of our balloon told us that the gas inside had expanded under the heat of the sun and the lessening density of the surrounding air. ”

“ The rapid climb of the first balloon could be attributed to a vertical air current, or to an air layer of variable density, or both. A balloon often develops leaks at high altitudes and then descends to an intermediate altitude where the loss of gas and the denser atmosphere cause it to hover. ”

“ A free balloon is completely at the mercy of the wind, and simply drifts where the wind takes it. Balloons are usually constructed of cotton fabric, though occasionally of gold-beater's skin, in which case they are commonly filled with hydrogen in place of coal-gas. ”

“ When all is prepared let some one hold the balloon from its top by means of a stick, while you dip the cotton in spirits of wine till it is thoroughly saturated, place it under the balloon and set fire to it, but be very careful you do not set fire to the balloon. When the air is sufficiently heated within, the balloon will indicate a desire to rise, and when it pulls very hard, let it go, and it will ascend to a great height in the air, and at night present a very beautiful appearance. ”

“ It is absurd to talk of guiding balloons. How will you set about it? How is it possible that a balloon—say, for instance, like the Flesselles, whose diameter measures 120 feet—can resist and manoeuvre against opposing winds or currents of air? It would require a power equal to 400 horses for the sails of a ship to struggle on equal terms with the wind. ”

“ On the 16th of the same month the Count d’Albon threw off from his gardens at Franconville a balloon inflated with gas, and made of silk, rendered air-tight by a solution of gum-arabic. It was oblong, and measured twenty-five feet in height, and seventeen feet in diameter. To this balloon a cage, containing two guinea-pigs and a rabbit, was suspended. The cords were cut, and the inflated globe rose to an enormous height with the greatest rapidity. ”

“ It is all-important that the envelope of a navigable balloon should not lose its shape—that it should be kept distended with sufficient tautness, so that it may be driven through the air with considerable velocity. On this account the non-rigid type depends entirely on the ballonet system, which consists of having one or more small balloons inside the outer envelope, into which air can be pumped by means of a mechanically driven fan or ventilator to compensate for the loss of gas from any cause. ”