captive balloon and bring it up to date, not simply because the Germans
were employing it in numbers, but because experience demonstrated that
it possessed numerous advantages over the aeroplane for artillery
observation. The observer in an aeroplane is carried back and forth over
and around the location he wishes to watch, at high speed and at a
constantly varying altitude. He must communicate by means of either
signals or wireless, and it is not always possible for him in either
case to know whether his signals have been received and understood,
since it is possible to transmit messages by wireless from an aeroplane
but a very difficult matter to receive. The observers in a kite balloon,
on the other hand, have the advantage of being able to scrutinize a
certain sector constantly with the aid of powerful glasses. With a few
weeks of experience in observing a given terrain they become so familiar
with it that any changes or the movements of troops or supplies are
quickly distinguished. The greatest advantage, however, is that the
information thus acquired may be instantly transmitted not merely to one
but to any one or all of a group of batteries extending over a mile or
two of front in either direction, the balloons being stationed 4 to 6
miles apart. The observers are fitted with portable head sets so that
they speak directly into their telephones without the necessity of
removing the glasses from their eyes, which enables them to watch the
fall of the shells and tell the battery attendant in the dugout
alongside the gun whether a shell fell "short", "over," "left," or
"right," and the amount of correction needed before the smoke from the
explosion has cleared away. With the aid of close corrections of this
nature the battery commander is in a position to get the range exactly
without the great expenditure of ammunition that firing entirely by map
or with the assistance of aeroplane observers entails. Instances are
recorded in which a 9.5-inch shell has been landed right in a concrete
"pill-box" not over 15 feet square from a distance of 3 miles after six
trial shots had been fired to obtain the range. Such a shot is reported
back to the battery by the balloon observer as a "direct hit," and it is
only necessary to fire the gun at the same range and direction to score
as often as necessary.
*Duties of Balloon Crew.* Each kite balloon carries aloft two observers,
Fig. 28, both of whom can concentrate their entire attention on the work
of "spotting," since they have nothing to do with the control of the
balloon itself, except to give orders. Their chief duties consist of
"counter-battery" observation, that is, spotting the location of enemy
batteries, and being constantly alert to detect any suspicious movements
back of the enemy’s lines, such as movements of troops, ammunition, or
supplies. The batteries controlled from observation balloons are the
"heavies," which are located 1 mile or more back of the front line
trenches and to the gunners of which the objects they are firing at are
never visible. Some of the heaviest guns mounted on specially
constructed railway trucks are often fired from points 5 miles or more
back of the lines. In fact, when balked in their attempt to take Calais,
the Germans bombarded the town with the aid of long-range naval guns
from a distance of over 15 miles and every shot dropped into either some
part of the city or its outskirts. Buildings, hills, or specially
constructed and concealed observation towers are frequently utilized in
conjunction with captive balloons to serve as auxiliary observation
posts, so that the base line connecting the two may be used to
triangulate distances and thus calculate them more accurately than is
possible by direct observation from a single point.
[Illustration: Fig. 28. French Kite Balloon Observers about to Ascend
_Copyright by Committee on Public Information, Washington, D.C._]
*Risks Incurred.* _Enemy Fire._ While the observers in a kite balloon
are not subjected to all the risks that the aviator must encounter when
he goes aloft or, at least, not to the same extent, their lot is far
from being free from danger. One of the duties of the reconnoitering
aviator is to destroy observation balloons by means of incendiary bombs
equipped with fishhooks which catch in the fabric or by the use of his
machine gun. Enemy batteries may also succeed in getting the range of
the balloon and fire at it with large caliber shrapnel, which spreads
its fragments over an area 100 yards or more in diameter when it bursts.
So many of the German balloons were downed by French and British
aviators in the early part of the war—and the Germans retaliated in
kind—that a battle plane is now always detailed to keep watch above the
balloon to ward off attacks by aeroplanes.
_Escape of Balloon._ In addition to the risk of being shot down, there
is the ever-present danger of the balloon being wrecked by a sudden
squall or of its breaking away from its windlass through the parting of
the cable and floating over the enemy lines. Balloons have been lost
through both causes in a number of instances. Each of the two observers
wears a heavy harness to which is attached a parachute suspended by a
light cord from the rigging of the balloon, so that in case of emergency
they may save themselves by jumping without having to make any
preparations for their sudden drop.
In case of the breakage of the cable, which usually results from a
strong wind coming up suddenly and putting a terrific strain on the
steel line by jerking it, the observers are guided in their actions by
the direction in which the balloon moves. When it is carrying them back
over their own territory, they navigate in the same manner as a free
balloon, coming to the ground as soon as a favorable landing place can
be reached. Instruction in free ballooning is accordingly an important
part of the curriculum that the kite balloon observers must go through.
Should the wind be in the opposite direction, however, as only too often
proves to be the case, all instruments, papers, and maps are immediately
thrown over the side and the observers promptly follow suit in their
parachutes, abandoning the balloon to its fate. As the balloon travels
with the speed of the wind, once it is released, and the parachute of
the descending observer is carried in the same direction, prompt action
is vital to prevent coming to the ground in the enemy’s territory. In a
30-mile wind, for example, only eight minutes would elapse from the
moment that the balloon broke away until it traversed the 4 miles
intervening between its station and the enemy’s lines. On some
occasions, kite balloons which were not fit for further service have
been loaded with explosives and released from a height that would cause
them to land well within the enemy’s territory with disastrous results
to the men detailed to capture them.
*Marine Service.* The kite balloon was first used by the British naval
forces in their operations against the Dardanelles and proved so
valuable that they have since been employed in fleet expeditions in the
North Sea as well as for anti-submarine work. In the latter form of
service, they have the same superiority over the aeroplane for
observation that they possess in land operations. The ship naturally
cannot run the risk of remaining stationary, but as the speed of the
balloon is the same as that of the ship towing it, the observers do not
pass over a given area with anything like the velocity of an aeroplane,
while their elevated position affords the same advantages for detecting
the presence of the submerged submarine or the approach of enemy
vessels.
EXAMINATION PAPER
DIRIGIBLE BALLOONS
*Read Carefully:* Place your name and full address at the head of the
paper. Any cheap, light paper like the sample previously sent you may be
used. Do not crowd your work, but arrange it neatly and legibly. _Do not
copy the answers from the Instruction Paper; use your own words, so that
we may be sure you understand the subject._
1. What essential features of design did Meusnier’s first dirigible
incorporate?
2. Describe the difference between rigid, semi-rigid, and flexible
types of dirigibles.
3. State the laws governing the increase of resistance with speed,
the increase of power necessary for a given increase of speed, and
the ratio in which the volume and area of the gas bag increase
with increased dimensions.
4. What provides the lifting power of the dirigible and how is this
lifting power utilized? Why should this lifting power be so much
less at night than in the daytime? What is net lifting power?
5. What are air balloonets? How and for what purpose are they used?
6. What is the most efficient form of envelope for the dirigible, and
why?
7. Why cannot the ordinary spherical balloon be propelled as a
dirigible?
8. Is the form of the stern as important as the bow?
9. What is longitudinal stability and how is it obtained?
10. How is stability of direction obtained? What are stabilizing
planes?
11. Why must a form of suspension for the car that cannot be
accidentally displaced with relation to the balloon be provided?
12. Theoretically, where should the propulsive effort be applied to a
dirigible? What factors affect the placing of the propeller and what has
been proved to be the most practical solution of the problem?
13. Discuss the advantages of the kite balloon over the aeroplane for
observation.
14. What is the effect of the wind on a modern kite balloon?
15. What is the difference between "pounds per horsepower" and "pounds
per horsepower hour" as applied to the motor of a dirigible? Which
is more important?
10. Sketch and explain the Astra-Torres suspension.
17. What differences exist between a Zeppelin and a Schutte-Lanz
dirigible?
18. Describe the "L-49", discussing power plant and control.
19. Define static and dynamic equilibrium as applied to the dirigible.
20. Is the Zeppelin effective? Discuss fully.
*After completing the work, add and sign the following statement:*
I hereby certify that the above work is entirely my own.
(Signed)