THE BUILDING OF MY "NO. 6"
On the very evening of my fall to the roof of the Trocadero hotels I
gave out the specifications of a "Santos-Dumont, No. 6," and after
twenty-two days of continuous labour it was finished and inflated.
[Illustration: Fig. 10]
The new balloon had the shape of an elongated ellipsoid (Fig. 10), 33
metres (110 feet) by its great axis and 6 metres (20 feet) by its small
axis, terminated fore and aft by cones.
[Illustration: "No. 6." FIRST TRIP]
I now gave more care than ever to the devices on which I depended
to maintain the balloon's rigidity of form. I had fallen to the
roof of the Trocadero hotels by the fault of the smallest and most
insignificant-looking piece of mechanism of the entire system--a
weakened valve that let out the balloon's hydrogen. In very much the
same way the fall of the first of all my air-ships had been occasioned
by the failure of a little air-pump.
In all my constructions, except the big-bellied balloon of the "No.
3," I had depended much on the interior compensating air balloon
(Fig. 5, page 119) fed by air pump or rotary ventilator. Sewed like a
closed patch pocket to the inside bottom of the great balloon, this
compensating air balloon would remain flat and empty so long as the
great balloon remained distended with its gas. Then, as hydrogen might
be condensed from time to time by changes of altitude and temperature,
the air pump or ventilator worked by the motor would begin to fill the
compensating air balloon, make it take up more room inside the great
balloon, and so keep the latter distended.
Inside the balloon of my "No. 6" I now sewed such a compensating
balloon, capable of holding 60 cubic metres (2118 cubic feet). The
ventilator that was to feed it formed practically a part of the motor
itself. Revolving continually while the motor worked, it would serve air
continually to the compensating balloon whether or not the latter would
be able to hold it. What air it could not hold would escape through a
comparatively weak valve ("Air Valve," Fig. 10) communicating with the
outer atmosphere through the bottom of the air balloon, which was also
the bottom of the great outer balloon.
To relieve the great balloon of its dilated hydrogen when necessary I
supplied it with two of the best valves I could make ("Gas Valves,"
Fig. 10). These also communicated with the outer atmosphere. Imagine,
now, that after a certain condensation of my hydrogen the interior
compensating balloon should have filled up in part with air from the
ventilator and so maintained the form of the great balloon rigid.
Shortly after, by a change of temperature or altitude, the hydrogen
would begin to dilate again. Something would have to give way, or the
balloon would burst in a "cold explosion." What ought to give way first?
Evidently the weaker air valve ("Air Valve," Fig. 10). Letting out
part or all of the air in the interior balloon, it would relieve the
tension of the swelling hydrogen; and only afterwards, should this not
be sufficient, would the stronger gas valves (Fig. 10) let out precious
hydrogen.
All three valves were automatic, opening outward on a given pressure
from within. One of the hypotheses to account for the terrible accident
to the unhappy Severo's dirigible "Pax"[A] is concerned with this
all-important problem of valves. The "Pax," as originally constructed,
had two. M. Severo, who was not a practical aeronaut, stopped up one of
them with wax before starting on his first and last voyage. In view of
the decreasing pressure of the atmosphere as one goes higher the ascent
of a dirigible should always be slow and never great, for gas will
expand on the rise of a few yards. It is quite different from the case
of the spherical balloon, which has no interior pressure to withstand. A
dirigible whose envelope is distended by great pressure depends on its
valves not to burst. With one of its valves stopped with wax the "Pax"
was allowed to shoot up from the earth, and immediately its occupants
seem to have lost their heads. Instead of checking their rapid rise
one of them threw out ballast--a handful of which will send up a great
spherical balloon perceptibly. The mechanician of Severo is said to have
been last seen throwing out a whole bag in his excitement. Up shot the
"Pax" higher and higher, and the expansion, the explosion, and the awful
fall came as a chain of consequences.
[A] In the early morning of 12th May 1902 M. Augusto Severo,
accompanied by his mechanician, Sachet, started from Paris
on a first trial with the "Pax," the invention and
construction of M. Severo. The "Pax" rose at once to a
height almost double that of the Eiffel Tower, when, for
reasons not precisely known, it exploded, and came crashing
to earth with its two passengers. The fall took eight
seconds to accomplish, and the luckless experimenters were
picked up broken and shapeless masses.
The tonnage of my new balloon was 630 cubic metres (22,239 cubic feet),
affording an absolute lifting power of 690 kilogrammes (1518 lbs.),
but the increased weight of the new motor and machinery, nevertheless,
put my disposable ballast at 110 kilogrammes (242 lbs.). It was a
four-cylinder motor of 12 horse-power, cooled automatically by the
circulation of water round the top of the piston (culasse). While the
water cooler brought extra weight, I was glad to have it, for the
arrangement would permit me to utilise, without fear of overheating or
jamming _en route_, the full power of the motor, which was able to
communicate to the propeller a traction effort of 66 kilogrammes (145
lbs.).
[Illustration: AN ACCIDENT TO "No. 6"]
My daily practice with the new air-ship ended, 6th September 1901, in a
slight accident. The balloon was reinflated by 15th September, but four
days later it crashed against a tree in making a too sudden turn. Such
accidents I have always taken philosophically, looking on them as a kind
of insurance against more terrible ones. Were I to give a single word of
caution to all dirigible balloonists, it would be: "Keep close to earth."
The place of the air-ship is not in high altitudes, and it is better to
catch in the tops of trees, as I used to do in the Bois de Boulogne,
than to risk the perils of the upper air without the slightest practical
advantage.