BALLOONS: HOW TO OPERATE.
Preliminary
inspection--Instruments--Accessories--Ballast--Inflating--Attaching
the car--The ascension--Controls--Landing--Some things to be
considered--After landing--Precautions.
The actual operation of a balloon is always entrusted to an experienced
pilot, or “captain” as he is often called, because he is in command,
and his authority must be recognized instantly whenever an order
is given. Nevertheless, it is often of great importance that every
passenger shall understand the details of managing the balloon in case
of need; and a well-informed passenger is greatly to be preferred to an
ignorant one.
It is ordinarily one of the duties of the captain to inspect the
balloon thoroughly; to see that there are no holes in the gas-bag, that
the valve is in perfect working order, and particularly that the valve
rope and the ripping cord are not tangled. He should also gather the
instruments and equipment to be carried.
The instruments are usually an aneroid barometer, and perhaps a mercury
barometer, a barograph (recording barometer), a psychrometer (recording
thermometer), a clock, a compass, and an outfit of maps of the country
over which it is possible that the balloon may float. Telegraph blanks,
railroad time tables, etc., may be found of great service. A camera
with a supply of plates will be indispensable almost, and the camera
should be provided with a yellow screen for photographing clouds or
distant objects.
The ballast should be inspected, to be sure that it is of dry sand,
free from stones; or if water is used for ballast, it should have the
proper admixture of glycerine to prevent freezing.
It is essential that the inflating be properly done, and the captain
should be competent to direct this process in detail, if necessary.
What is called the “circular method” is the simplest, and is entirely
satisfactory unless the balloon is being filled with pure hydrogen for
a very high ascent, in which case it will doubtless be in the hands of
experts.
When inflating with coal-gas, the supply is usually taken from a
large pipe adapted for the purpose. At a convenient distance from the
gas-main the ground is made smooth, and the ground cloths are spread
out and pegged down to keep them in place.
The folded balloon is laid out on the cloths with the neck opening
toward the gas-pipe. The balloon is then unfolded, and so disposed that
the valve will be uppermost, and in the centre of a circle embracing
the upper half of the sphere of the balloon, the opening of the neck
projecting a few inches beyond the rim of the circle. The hose from the
gas-main may then be connected with the socket in the neck.
[Illustration: Balloon laid out in the circular method, ready for
inflation. The valve is seen at the centre. The neck is at the right.]
Having made sure that the ripping cord and the valve rope are free from
each other, and properly connected with their active parts, and that
the valve is fastened in place, the net is laid over the whole, and
spread out symmetrically. A few bags of ballast are hooked into the net
around the circumference of the balloon as it lies, and the assistants
distributed around it. It should be the duty of one man to hold the
neck of the balloon, and not to leave it for any purpose whatever. The
gas may then be turned on, and, as the balloon fills, more bags of
ballast are hung symmetrically around the net; and all are continually
moved downward as the balloon rises.
Constant watching is necessary during the inflation, so that the
material of the balloon opens fully without creases, and the net
preserves its correct position. When the inflation is finished the hoop
and car are to be hooked in place. The car should be fitted up and hung
with an abundance of ballast. Disconnect the gas hose and tie the neck
of the balloon in such fashion that it may be opened with a pull of the
cord when the ascent begins.
The ballast is then transferred to the hoop, or ring, and the balloon
allowed to rise until this is clear of the ground. The car is then
moved underneath, and the ballast moved down from the ring into it. The
trail-rope should be made fast to the car directly under the ripping
panel, the object being to retard that side of the balloon in landing,
so that the gas may escape freely when the panel is torn open, and not
underneath the balloon, as would happen if the balloon came to earth
with the ripping panel underneath.
The balloon is now ready to start, and the captain and passengers
take their places in the car. The neck of the balloon is opened, and
a glance upward will determine if the valve rope hangs freely through
it. The lower end of this should be tied to one of the car ropes. The
cord to the ripping panel should be tied in a different place, and in
such fashion that no mistake can be made between them. The assistants
stand around the edge of the basket, holding it so that it shall not
rise until the word is given. The captain then adjusts the load of
ballast, throwing off sufficient to allow the balloon to pull upward
lightly against the men who are holding it. A little more ballast is
then thrown off, and the word given to let go. The trail-rope should be
in charge of some one who will see that it lifts freely from the ground.
The balloon rises into the air to an altitude where a bulk of the
higher and therefore lighter air equal to the bulk of the balloon has
exactly the same weight. This is ordinarily about 2,000 feet. If the
sun should be shining the gas in the balloon will be expanded by the
heat, and some of it will be forced out through the neck. This explains
the importance of the open neck. In some of the early ascensions no
such provision for the expansion of the gas was made, and the balloons
burst with disastrous consequences.
[Illustration: Inflating a military balloon. The net is being adjusted
smoothly as the balloon rises. The bags of ballast surround the balloon
ready to be attached as soon as the buoyancy of the gas lifts it from
the earth.]
When some of the gas has been driven out by the heat, there is less
_weight_ of gas in the balloon, though it occupies the same space. It
therefore has a tendency to rise still higher. On the other hand, if
it passes into a cloud, or the sun is otherwise obscured, the volume
of the gas will contract; it will become denser, and the balloon will
descend. To check the descent the load carried by the balloon must
be lightened, and this is accomplished by throwing out some ballast;
generally, a few handfuls is enough.
There is always more or less leakage of gas through the envelope as
well as from the neck, and this also lessens the lifting power. To
restore the balance, more ballast must be thrown out, and in this way
an approximate level is kept during the journey.
When the ballast is nearly exhausted it will be necessary to come down,
for a comfortable landing cannot be made without the use of ballast.
A good landing place having been selected, the valve is opened, and
the balloon brought down within a few yards of the ground. The ripping
cord is then pulled and ballast thrown out so that the basket will
touch as lightly as possible. Some aeronauts use a small anchor or
grapnel to assist in making a landing, but on a windy day, when the car
is liable to do some bumping before coming to rest, the grapnel often
makes matters much worse for the passengers by a series of holdings and
slippings, and sometimes causes a destructive strain upon the balloon.
In making an ascent with a balloon full of gas there is certain to be a
waste of gas as it expands. This expansion is due not only to the heat
of the sun, but also to the lighter pressure of the air in the upper
altitudes. It is therefore the custom with some aeronauts to ascend
with a partially filled balloon, allowing the expansion to completely
fill it. This process is particularly advised if a very high altitude
is sought. When it is desired to make a long voyage it is wise to make
the start at twilight, and so avoid the heat of the sun. The balloon
will then float along on an almost unchanging level without expenditure
of ballast. Rain and even the moisture from clouds will sometimes wet
the balloon so that it will cause a much greater loss of ballast than
would have been required to be thrown out to rise above the cloud or
storm. Such details in the handling of a balloon during a voyage will
demand the skilled judgment of the captain.
[Illustration: A balloon ready for ascent. Notice that the neck is
still tied.]
The trail-rope is a valuable adjunct when the balloon is travelling
near the ground. The longer the part of the trail-rope that is dragging
on the ground the less weight the balloon is carrying. And at night,
when it is impossible to tell the direction in which one is travelling
in any other way, the line of the trailing rope will show the direction
from which the wind is blowing, and hence the drift of the balloon.
The care of the balloon and its instruments upon landing falls upon
the captain, for he is not likely to find assistants at hand competent
to relieve him of any part of the necessary work. The car and the ring
are first detached. The ropes are laid out free and clear, and the
valve is unscrewed and taken off. The material of the balloon is folded
smoothly, gore by gore. The ballast bags are emptied. After all is
bundled up it should be packed in the car, the covering cloth bound on
with ropes, and definite instructions affixed for transportation to the
starting-point.
It is apparent that the whole of the gas is lost at the end of the
journey. The cost of this is the largest expense of ballooning. For a
small balloon of about 50,000 cubic feet, the coal-gas for inflating
will cost about $35 to $40. If hydrogen is used, it will cost probably
ten times as much.
In important voyages it is customary to send up pilot balloons, to
discover the direction of the wind currents at the different levels,
so that the level which promises the best may be selected before the
balloon leaves the ground. A study of the weather conditions throughout
the surrounding country is a wise precaution, and no start should
be made if a storm is imminent. The extent of control possible in
ballooning being so limited, all risks should be scrupulously avoided,
both before and during the voyage, and nothing left to haphazard.