My Airships Part 7

There could be no doubt about it--there was less vibration in this light-weight tricycle hanging in the air than I had regularly felt while travelling on the ground. It was my first triumph in the air!

I will say frankly that as I rose in the air on my first trip I had no fear of fire. What I feared was that the balloon might burst by reason of its interior pressure. I still fear it.

Before going up I had minutely tried the valves. I still try them minutely before each of my trips. The danger, of course, was that the valves might not work adequately, in which case the expanding of the gas as the balloon rose would cause the dreaded explosion. Here is the great difference between spherical and dirigible balloons. The spherical balloon is always open. When it is taut with gas it is shaped like an apple; when it has lost part of its gas it takes the shape of a pear; but in each case there is a great hole in the bottom of the spherical balloon where the stem of the apple or the pear would be, and it is through this hole that the gas has opportunity to ease itself in the constant alternations of condensation and dilatation. Having such a free vent, the spherical balloon runs no risk of bursting in the air; but the price paid for this immunity is great loss of gas and, consequently, a fatal shortening of the spherical balloon's stay in the air. Some day a spherical balloonist will close up that hole; indeed, they already talk of doing it.

I was obliged to do it in my air-ship balloon, whose cylindrical form must be preserved at all cost. For me there must be no transformations as from apple to pear. Interior pressure only could guarantee me this.

The valves to which I refer have since my first experiments been of all kinds--some very ingeniously interacting, others of extreme simplicity.

But their object in each case has always been the same: to hold the gas tight in the balloon up to a certain pressure and then let only enough out to relieve dangerous interior pressure. It is easy to realise, therefore, that should these valves refuse to act adequately the danger of bursting would be there.

This possible danger I acknowledged to myself, but it had nothing to do with fire from the explosive motor. Yet during all my preparations, and up to the moment of calling: "Let go all!" the professional aeronauts, completely overlooking this weak point of the air-ship, continued to warn me against fire, of which I had no fear at all!

"Do we dare strike matches in the basket of a spherical balloon?" they asked.

"Do we even permit ourselves the solace of a cigarette on trips that last for many hours?"

To me the cases did not seem the same. In the first place, why should one not light a match in the basket of a spherical balloon? If it be only because the mind vaguely connects the ideas of gas and flame the danger remains as ideal. If it be because of a real possibility of igniting gas that has escaped from the free hole in the stem of the spherical balloon it would not apply to me. My balloon, hermetically closed, except when excessive pressure should let either air or a very little gas escape through one of the automatic valves, might for a moment leave a little trail of gas _behind_ it as it moved on horizontally or diagonally, but there would be none in front where the motor was. (See Fig. 4.)

[Ill.u.s.tration: Fig. 4]

In this first air-ship I had placed the gas escape valves even farther from the motor than I place them to-day. The suspension cords being very long I hung in my basket far below the balloon. Therefore I asked myself:

"How could this motor, so far below the balloon, and so far in front of its escape valves, set fire to the gas enclosed in it when such gas is not inflammable until mixed with air?"

On this first trial, as in most since, I used hydrogen gas. Undoubtedly when mixed with air it is tremendously inflammable--but it must first mix with air. All my little balloon models are kept filled with hydrogen, and, so filled, I have more than once amused myself by burning _inside them_, not their hydrogen, but its mixture with the oxygen of the atmosphere. All one has to do is to insert in the balloon model a little tube to furnish a jet of the room's atmosphere from an air pump and light it with the electric spark. Similarly, should a pin-p.r.i.c.k have made ever so slight a vent in my air-ship balloon, the interior pressure would have sent out into the atmosphere a long thin stream of hydrogen that _might_ have ignited had there been any flame near enough to do it.

But there was none.

This was the problem. My motor did undoubtedly send out flames for, say, half-a-yard round about it. They were, however, mere flames, not still-burning products of incomplete combustion like the sparks of a coal-burning steam-engine. This admitted, how was the fact that I had a ma.s.s of hydrogen unmixed with air and well secured in a tight envelope so high above the motor to prove dangerous?

Turning the matter over and over in my mind I could see but one dangerous possibility from fire. This was the possibility of the petroleum reservoir itself taking fire by a _retour de flamme_ from the motor. During five years, I may here say in pa.s.sing, I enjoyed complete immunity from the _retour de flamme_ (sucking back of the flame). Then, in the same week in which Mr Vanderbilt burned himself so severely, 6th July 1903, the same accident overtook me in my little "No. 9" runabout air-ship just as I was crossing the Seine to land on the Ile de Puteaux.

I promptly extinguished the flame with my Panama hat ... without other incident.

[Ill.u.s.tration: "No. 9" CATCHES FIRE OVER THE ILE DE PUTEAUX]

For reasons like these I went up on my first air-ship trip without fear of fire, but not without doubt of a possible explosion due to insufficient working of my balloon's escape valves. Should such a "cold"

explosion occur, the flame-spitting motor would probably ignite the ma.s.s of mixed hydrogen and air that would surround me; but it would have no decisive influence on the result. The "cold" explosion itself would doubtless be sufficient....

Now, after five years of experience, and in spite of the _retour de flamme_ above the Ile de Puteaux, I continue to regard the danger from fire as practically _nil_; but the possibility of a "cold" explosion remains always with me, and I must continue to purchase immunity from it at the cost of vigilant attention to my gas escape valves. Indeed, the possibility of the thing is greater technically now than in the early days which I describe. My first air-ship was not built for speed--consequently, it needed very little interior pressure to preserve the shape of its balloon. Now that I have great speed, as in my "No. 7," I must have enormous interior pressure to withstand the exterior pressure of the atmosphere in front of the balloon as I drive against it.

CHAPTER X

I GO IN FOR AIRSHIP BUILDING

In the early spring of 1899 I built another air-ship, which the Paris public at once called "The Santos-Dumont No. 2." It had the same length and, at first sight, the same form as the "No. 1"; but its greater diameter brought its volume up to 200 cubic metres--over 7000 cubic feet--and gave me 20 kilogrammes (44 lbs.) more ascensional force. I had taken account of the insufficiency of the air pump that had all but killed me, and had added a little aluminium ventilator to make sure of permanency in the form of the balloon.

[Ill.u.s.tration: ACCIDENT TO "No. 2," MAY 11, 1899

(FIRST PHASE)]

This ventilator was a rotary fan, worked by the motor, to send air into the little interior air balloon, which was sewed inside to the bottom of the great balloon like a kind of closed pocket. In Fig. 5, _G_ is the great balloon filled with hydrogen gas, _A_ the interior air balloon, _VV_ the automatic gas valves, _AV_ the latter's air valve, and _TV_ the tube by which the rotary ventilator fed the interior air balloon.

[Ill.u.s.tration: Fig. 5]

The air valve _AV_ was an exhaust valve similar to the two gas valves _VV_ in the great balloon, with the one exception that it was weaker.

In this way, when there happened to be too much fluid (_i.e._ gas or air, or both) distending the great balloon, all the air would leave the interior balloon before any of the gas would leave the great balloon.

The first trial of my "No. 2" was set for 11th May 1899. Unfortunately, the weather, which had been fine in the morning, grew steadily rainy in the afternoon. In those days I had no balloon house of my own. All the morning the balloon had been slowly filling with hydrogen gas at the captive balloon station of the Jardin d'Acclimatation. As there was no shed there for me the work had to be done in the open, and it was done vexatiously, with a hundred delays, surprises, and excuses.

When the rain came on, it wetted the balloon. What was to be done? I must either empty it and lose the hydrogen and all my time and trouble, or go on under the disadvantage of a rain-soaked balloon envelope, heavier than it ought to be.

I chose to go up in the rain. No sooner had I risen than the weather caused a great contraction of the hydrogen, so that the long cylindrical balloon shrunk visibly. Then before the air pump could remedy the fault, a strong wind gust of the rainstorm doubled it up worse than the "No.

1," and tossed it into the neighbouring trees.

My friends began at me again, saying:

"This time you have learned your lesson. You must understand that it is impossible to keep the shape of your cylindrical balloon rigid. You must not again risk your life by taking a petroleum motor up beneath it."

I said to myself:

"What has the rigidity of the balloon's form to do with danger from a petroleum motor? Errors do not count. I have learned my lesson, but it is not that lesson."

[Ill.u.s.tration: ACCIDENT TO "No. 2," MAY 11, 1899

(SECOND PHASE)]

Accordingly I immediately set to work on a "No. 3," with a shorter and very much thicker balloon, 20 metres (66 feet) long and 750 metres (25 feet) at its greatest diameter (Fig. 6). Its much greater gas capacity--500 cubic metres (17,650 cubic feet)--would give it, with hydrogen, three times the lifting power of my first, and twice that of my second air-ship. This permitted me to use common illuminating gas, whose lifting power is about half that of hydrogen. The hydrogen plant of the Jardin d'Acclimatation had always served me badly. With illuminating gas I should be free to start from the establishment of my balloon constructor or elsewhere as I desired.

[Ill.u.s.tration: Fig. 6]

It will be seen that I was getting far away from the cylindrical shapes of my first two balloons. In the future I told myself that I would at least avoid doubling up. The rounder form of this balloon also made it possible to dispense with the interior air balloon and its feeding air pump that had twice refused to work adequately at the critical moment.

Should this shorter and thicker balloon need aid to keep its form rigid I relied on the stiffening effect of a 10-metre (33-foot) bamboo pole (Fig. 6) fixed lengthwise to the suspension cords above my head and directly beneath the balloon.

While not yet a true keel, this pole keel supported basket and guide rope and brought my shifting weights into much more effectual play.

On November 13th, 1899, I started in the "Santos-Dumont No. 3," from the establishment of Vaugirard, on the most successful flight that I had yet made.

[Ill.u.s.tration: ACCIDENT TO "No. 2," MAY 11, 1899

(THIRD PHASE)]

From Vaugirard I went directly to the Champ de Mars, which I had chosen for its clear, open s.p.a.ce. There I was able to practise aerial navigation to my heart's content--circling, driving ahead in straight courses, forcing the air-ship diagonally onward and upward, and shooting diagonally downward, by propeller force, and thus acquiring mastery of my shifting weights. These, because of the greater distance they were now set apart at the extremities of the pole keel (Fig. 6), worked with an effectiveness that astonished even myself. This proved my greatest triumph, for it was already clear to me that the central truth of dirigible ballooning must be ever: "To descend without sacrificing gas and to mount without sacrificing ballast."

During these first evolutions over the Champ de Mars I had no particular thought of the Eiffel Tower. At most it seemed a monument worth going round, and so I circled round it at a prudent distance again and again.

Then--still without any dream of what the future had in store for me--I made a straight course for the Parc des Princes, _over almost the exact line that, two years later, was to mark the Deutsch prize route_.

I steered to the Parc des Princes because it was another fine open s.p.a.ce. Once there, however, I was loth to descend, so, making a hook, I navigated to the manoeuvre grounds of Bagatelle, where I finally landed, in souvenir of my fall of the year previous. It was almost at the exact spot where the kite-flying boys had pulled on my guide rope and saved me from a bad shaking-up. At this time, remember, neither the Aero Club nor myself possessed a balloon park or shed from which to start and to which to return.