My Airships/Chapter 4
MY "BRAZIL"—SMALLEST OF SPHERICAL BALLOONS
I LIKED ballooning so much that, coming back from my first trip with M. Machuron, I told him that I wanted a balloon built for myself. He liked the idea. He thought that I wanted an ordinary-sized spherical balloon, between 500 and 2000 cubic metres in volume. No one would think of making one smaller.
It is only a short time ago, but it is curious how constructors still clung to heavy materials. The smallest balloon basket had to weigh 30 kilogrammes (66 lbs.). Nothing was light—neither envelope, rigging, nor accessories.
I gave M. Machuron my ideas. He cried out against it when I told him I wanted a balloon of the lightest and toughest Japanese silk, 100 cubic metres (about 3500 cubic feet) in volume. At the works both he and M. Lachambre tried to prove to me that the thing was impossible.How often have things been proved to me
SMALLEST OF SPHERICAL BALLOONS
They showed me that for a balloon to have "stability" it must have a certain weight. Again, a balloon of 100 cubic metres, they said, would be affected by the movements of the aeronaut in his basket much more than a large balloon of regulation size.
With a large balloon the centre of gravity
in the weight of the aeronaut is as in Fig. 1, a. When the aeronaut moves, say, to the right in his basket, Fig. 1, b, the centre of gravity of the whole system is not shifted appreciably.
In a very small balloon the centre of gravity, Fig. 2, a, is undisturbed only so long as the aeronaut sits straight in the centre of his basket. When he moves to the right the centre of gravity, Fig. 2, b, is shifted beyond the vertical line of the balloon's circumference, causing the balloon to swing in the same direction.
Therefore, they said, your necessary movements in the basket will cause your little balloon to roll and swing continually.
"We shall make the suspension tackle longer in proportion," I replied. It was done, and the "Brazil" proved remarkably stable.
When I brought my light Japanese silk to M. Lachambre he looked at it and said: "It will be too weak." But when we came to try it with the dynamometer it surprised us. Tested thus, Chinese silk stands over 1000 kilogrammes (or 2200 lbs.) strain to the linear metre (3*3 feet). The thin Japanese silk stood a strain of 700 kilogrammes (1540 lbs.)—that is, it proved to be thirty times stronger than necessary according to the theory of strains. This is astonishing when you consider that it weighs only 30 grammes (a little more than one ounce) per square metre. To show how experts may be mistaken in their merely off-hand judgments I have been building my air-ship balloons of this same material; yet the inside pressure they have to stand is enormous, while all spherical balloons have a great hole in the bottom to relieve it.
As the proportions finally adopted for the "Brazil" were 113 cubic metres (4104 cubic feet), corresponding to about 113 square metres (135 square yards) of silk surface, the whole envelope weighed scarcely 3 kilogrammes (less than 8 lbs.). But the weight of the varnish, three coats, brought it up to 14 kilogrammes (about 31 lbs.). The net, which often weighs into the hundreds of lbs., weighed 1800 grammes, or nearly 4 lbs. The basket, which usually weighs 30 kilogrammes (66 lbs.) at a minimum, weighed 6 kilogrammes (13 lbs.); the basket which I now have with my little "No. 9" weighs less than 5 kilogrammes (11 lbs.). My guide rope, small, but very long—100 yards — weighed at most 8 kilogrammes (17 lbs.); its length gave the "Brazil" a good spring. Instead of an anchor I put in a little grappling-iron of 3 kilogrammes (6 lbs.).
Making everything light in this way I found that, in spite of the smallness of the balloon, it would have ascensional force to take up my own weight of 50 kilogrammes (110 lbs.) and 30 kilogrammes (66 lbs.) of ballast. As a fact, I took up that amount on my first trip. On another occasion, when a French Cabinet Minister was present, anxious to see the smallest spherical balloon ever made, I had practically no ballast at all, only 4 or 5 kilogrammes (10 or 11 lbs.). Nevertheless, causing the balloon to be weighed, I went up, and made a good ascent.
The "Brazil" was very handy in the air—easy to control. It was easy to pack also on descending, and the story that I carried it in a valise is true.
Before starting out in my little "Brazil" I made from twenty-five to thirty ascents in ordinary spherical balloons, quite alone, as my own captain and sole passenger. M. Lachambre had many public ascents, and allowed me to do some of them for him. Thus I made ascents in many parts of France and Belgium. As I got the pleasure and the experience, and as I saved him the labour and paid all my own expenses and damages, it was a mutually advantageous arrangement.
I do not believe that, without such previous study and experience with a spherical balloon, a man can be capable of succeeding with an elongated dirigible balloon, whose handling is so much more delicate. Before attempting to direct an air-ship it is necessary to have learned in an ordinary balloon the conditions of the atmospheric medium, to have become acquainted with the caprices of the wind, and to have gone thoroughly into the difficulties of the ballast problem from the triple point of view of starting, of equilibrium in the air, and of landing at the end of the trip.
To have been oneself the captain of an ordinary balloon at the very least a dozen times seems to me an indispensable preliminary to acquiring an exact notion of the requisites for constructing and handling an elongated balloon furnished with its motor and propeller.
Naturally, I am filled with amazement when I see inventors, who have never set a foot in the basket, drawing up on paper—and even executing in whole or in part—fantastic air-ships, whose balloons are to have a capacity of thousands of cubic metres, loaded down with enormous motors which they do not succeed in raising from the ground, and furnished with machinery so complicated that nothing works! Such inventors are afraid of nothing, because they have no idea of the difficulties of the problem. Had they previously journeyed through the air at the wind's will, and amid all the disturbing influences of atmospheric phenomena, they would understand that a dirigible balloon, to be practical, requires first of all to have the utmost extreme of simplicity in all its mechanism.
Some of the unhappy constructors who have paid with their lives the forfeit of their rashness had never made a single responsible ascent as captain of a spherical balloon! And the majority of their emulators, now so devotedly labouring, are in the same inexperienced condition. This is my explanation of their lack of success. They are in the condition in which the first-comer would find himself were he to agree to build and steer a transatlantic liner without having ever quitted land or set foot in a boat!