Ballonet

“ Ballonets are internal balloons or air compartments fitted inside the main envelope, and were originally filled with air by a blower driven either by the main engines or an auxiliary motor. These blowers were a continual source of trouble, and at the present day it has been arranged to collect air from the slip-stream of the propeller through a metal air scoop or blower-pipe and discharge it into an air duct which distributes it to the ballonets.
The following example will explain their functions:
An airship ascends from the ground full to 1,000 feet. ”

“ Every man on board was holding on like grim death. With the floor as steep as the roof of a house there was nothing to be done but hold on. The ballonets were practically empty save the four or five for'ard ones. The propellers were now virtually helices--whirling screws that strove valiantly but unavailingly to lift the huge bulk of the airship in an almost vertical direction. Should the motors fail to function, then the "Golden Hind" would drop like a stone. ”

“ The ascent of this balloon deserves to be regarded with special interest, because, besides being the first hydrogen balloon which carried up human beings, it was the first in which scientific observations were made and recorded. Monsieur Charles was a lecturer on natural philosophy, and, like our own great aeronaut, Mr Glaisher, does not seem to have been content to produce merely a spectacle, but went up to the realms of ether with an intelligent and scientific eye; for we read of him recording the indications of the thermometer and barometer at different heights and under various conditions. ”

“ His balloon was of the ordinary spherical shape, made of the best oiled silk, about 520 yards of which were used in its construction. It was filled with hydrogen gas, and provided with car, oars, and wings. The car consisted simply of a wooden platform surrounded by a breast high railing, and the oars and wings were intended, the one to check, by a vertical motion, the rapidity of descent, and the other to act as sails when becalmed in the upper regions of cloudland. ”

“ A few minutes after midnight, when the last little sacks of sand ballast had been hung out over the edge of our wicker-basket, when a final glance had been given to the ropes, the net, the valve, etc.,—with a careless au revoir from the foreman of the gas-works, and a parting joke from the cocher who had driven us there,—the dark forms, whose hands were holding us down, silently stepped back, and with a gentle and graceful swing the “Rolla” started off on its sixth ascension.
Had we taken with us another small sack of ballast, our balloon could not have left the earth. ”

“ Montgolfier, Thirion, and Saint Felix were near me. The balloon descended so rapidly that it gave us the vertigo. The air, which we had left so calm above, became a violent wind as we neared the earth. ‘We are going to throw down the anchors,’ said Godard, ‘hold tight!’ Ah! the car struck the earth with tremendous violence. I cannot imagine how it was that my arms were not broken. After the first terrible shock the balloon went up again, but the safety-valve was opened—it again fell—and we suffered a second shock, if not more violent, at least more painful to us than the first. ”

“ His simple yet complete invention was that of the valve which gives escape to the hydrogen gas, and thus renders the descent of the balloon gentle and gradual; the car that carries the travellers; the ballast of sand, by which the ascent is regulated and the fall is moderated; the coating of caoutchouc, by means of which the material of the balloon is rendered airtight and prevents loss of gas; and, finally, the use of the barometer, which marks at every instant, by the elevation or the depression of the mercury, the position in which the aeronaut finds himself in the atmosphere. ”

“ This kite system is like fitting a gigantic sail to a lilliputian boat, d’ye see?”
“I see, father. But I wish it had been a balloon. It would have been greater fun to have gone to the Pole in a balloon!”
“A balloon will never go there, nor anywhere else, Benjy, except where the wind carries it, for a balloon cannot be steered. It’s impossible in the nature of things—as much so as that dream of the visionary, perpetual motion.” ”

“ The bold aeronauts, on this occasion, were the naturalist Rozier and the Marquis d’Arlandes, a major of infantry. From the gardens of the Château of Muetta they ascended on the 21st November 1783.
In the car there was a quantity of ballast, and a provision of straw to feed the fire. The balloon mounted at first with a majestic steady motion, gazed at in breathless wonder by thousands of spectators, who assembled not only in the neighbourhood of the Château, but clustered on every point of vantage in Paris. ”

“ If the balloon had dragged us through the town we should, inevitably, have been cut to pieces. But fortunately it rose a little and then bumped against the ground again with as much violence as before. Every one of these shocks wrenched our limbs; to complete our misfortunes the rope of the safety-valve got loose from us, and the safety-valve shutting up we lost all hope of the balloon emptying itself. It went on by bounds of twenty-five, thirty, and forty metres from the earth, and continued to fall upon its head. Everything that stood in the way of the car was dashed to pieces. ”

“ 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. ”

“ A rustling of the silk of our balloon made us look upwards; the monster, under the influence of the sun, now very hot, was palpably swelling. As it would have been supremely ridiculous, after having made such a first-rate journey, to have treated the inhabitants of Nienburg with the spectacle of seeing us blown up—to say nothing of the consequences of such a catastrophe to our own limbs—we resolved to come down. The remaining bags of ballast were got in order, the ropes and the anchors prepared, and Godard opened the safety-valve. ‘The monster is disgorging!’ exclaimed Thirion. ”

“ No sound ever reaches the ear a second time. But though the sound from the closing of the valve in those silent regions is striking, it is also cheering,—it is reassuring; it proves all to be right, that the balloon is sound, that the colder regions have not frozen tight the outlet for gas, and that we are so far safe. We have descended a mile, and our feelings improve with the increase of air and warmth. ”

“ He clambered up into the netting, the shocks of which were so terrible that three times he fell on my head. At length he reached the cord of the valve, opened it, and the gas having a way of escape the monster ceased to rise but it still shot along in a horizontal line with prodigious rapidity. There were we squatting down upon the frail osier car. ‘Take care!’ we cried, when a tree was in the way. We turned from it, and the tree was broken; but the balloon was discharging its gas, and if the immense plain we were crossing had yet a few leagues, we were saved. ”

“ He says, ‘I have decided upon opening the large upper valve,’ and carefully explains why. ‘The tension,’ he says, ‘in the balloon is not greater than it would bear with safety in a warm stratum of air; but now that we are three miles up with a chilled balloon, it is better to allow some to escape at top, as well as a good deal from the neck.’ At once I see the force of the argument, and inwardly infer that I am in no way dependent upon chance, and not likely to suffer from carelessness with Mr Coxwell. We are now far beyond all ordinary sounds from the earth ”

“ Unhappily, the balloon, like the fancied inspiration of the poet, goes where the wind guides it; this every one knows; while the steam-engine, like prose, goes straight upon its road. Green and his balloon were soon overlooking Paris and all its horizon; long trails of sand, ballast that he threw over to raise himself higher, streaked the heavens with their white tracks, proving, by the time it took them to descend to the earth, the hight to which the intrepid aeronaut had mounted in a few minutes. ”

“ Up rose the balloon, until it climbed to about five hundred feet, but with its ballast gone it was like a kite without a tail—a wild balloon at the mercy of the wind. That was a sight you did not soon forget! All hands were on deck staring up with bated breath—a few tried to shout advice, but the gale drowned out their voices and the boy in the basket was far too busy hanging on for his life to heed us. ”

“ The Duke de Chartres ascended in it along with Robert and two others to a considerable height, and in five hours performed a voyage of 135 miles. This machine was furnished with a helm and four oars, for men still laboured under the erroneous belief that it was possible to direct the course of a balloon.
One of the most interesting balloon voyages of the last century was that of Monsieur Testu. He ascended from Paris on the 18th June 1786 in a balloon of glazed tiffany, 29 feet in diameter, which was constructed by himself. It was filled with hydrogen, and had wings as well as oars! ”

“ Delighted to find the balloon is thus checked, as it is favourable to good readings of the several instruments at this elevation, I work as quickly as I can, noticing also the landscape below; rich mounds of green foliage, fields of various shades of green, like a tessellated pavement in motion; with roads, rivers, rivulets, and the undulatory nature of the ground varying the scene every instant. Should our passage be over a town, it is like a model in motion; and all is seen with a distinctness superior to that from the earth; the line of sight is through a purer and less dense medium ”

“ 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. ”

“ Joe and Kennedy at once went to work, and soon had an immense pile of dried grass heaped up near the baobab.
In the mean time, the doctor had enlarged the orifice of the balloon by cutting it open at the lower end. He then was very careful to expel the last remnant of hydrogen through the valve, after which he heaped up a quantity of grass under the balloon, and set fire to it.
It takes but a little while to inflate a balloon with hot air. A head of one hundred and eighty degrees is sufficient to diminish the weight of the air it contains to the extent of one-half, by rarefying it. ”

“ Our longing gaze followed it behind the dark clouds in the horizon, whose edges it tipped with a glorious purple. Its last rays shone on us, and then came a bluish-grey twilight. Suddenly we are enveloped in a dense fog. We look around, above us. Everything has disappeared in the mist. The balloon itself is no longer visible. We can see nothing except the ropes which suspend us, and these are only visible for a few feet above our heads, when they lose themselves in the fog. We are alone with our wickerwork house in an unfathomable vault. ”

“ Up we went again; the balloon dragged its anchors. Several times we thought we should be thrown out. ‘The anchors are broken,’ exclaimed Godard. The balloon beat the ground with its head, like a kite when it falls down. It was horrible. On we went towards Nienburg, at the rate of ten leagues an hour. Three large trees were cut through by the car, as clean as if by a woodman’s hatchet. ”

“ In France, each one following his own notions, made out for himself special benefits to flow from the discovery of balloons. Every discovery then appeared to be only the precursor of other and greater discoveries, and nothing after that time seemed to be impossible to him who attempted the conquest of the atmosphere. This idea clothed itself in every form. The young embraced it with enthusiasm, the old made it the subject of endless regrets. ”

“ Beneath the centre of the Balloon, and about two-thirds of its length, is a frame of light wood, answering to the hoop of an ordinary Balloon; to which are attached the cords of the net which encloses the suspending vessel, and which serves to distribute the pressure of the appended weight equally over its whole surface, as well as to form an intermediate means of attachment for the rest of the apparatus. This consists of a car or basket in the centre; at one end the rudder, and at the other the Archimedean Screw. ”

“ 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. ”