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.
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.
Fig. 5