The Story of the Airship 6

The Story of the Airship 6

Since this is an airship story, we should first make clear the

difference between the airship and the airplane.

 

The French hit on an apt phrase to distinguish them, dividing aircraft

into those which are lighter than the air, such as airships, and those

which are heavier than the air, like airplanes.

 

Airships are literally lighter than air. So are all free balloons, used

for training and racing, and all anchored balloons, such as the

observation balloon widely used in the last war and the barrage balloons

of the present war.

 

The airship goes up and stays up because the buoyancy given by its

lifting gas makes it actually lighter than the air it displaces, and

even with the load of motors, fuel, equipment and passengers, must still

use ballast to hold it in equilibrium.

 

The airplane, on the other hand, is heavier than the air. Even the

lightest plane can stay up only if it is moving fast enough to get a

lifting effect from the movement of air along the wings, similar to that

which makes a kite stay up. A kite may be flown in calm weather only if

the one who holds the cord keeps running. On a windy day, the kite may

be anchored on the ground, and the movement of the wind alone will have

sufficient lifting effect. So powerful are these air forces that a plane

weighing 20 tons may climb to an altitude of 10,000 feet if its speed is

great enough, and its area of wing surface broad enough to produce this

kiting effect.

 

But an airplane can remain aloft only as long as it is moving faster

than a certain minimum speed. Cut the motors, or even throttle down

below this stalling speed, and the plane will start earthward.

 

The airship needs its motors only to propel it forward. It can cut its

speed, even stop its engines, and nothing happens. It retains its

buoyancy, continues to float. The airplane’s lift is dynamic, that of

the airship is static.

 

The airship has some dynamic lift, also, because its horizontal fins or

rudders, and the body of the airship have some kiting effect in flight.

The blimp pilot, starting on a long trip, will fill up his tanks with

all the fuel the ship can lift statically, then take on another 2,000

pounds, taxi across the airport till he gets flying speed and so get

under way with many more miles added to his cruising speed.

 

This dynamic lift however, while useful in certain operations is still

incidental. Primarily the airship gets its lift from the fact that the

gas in the envelope is much lighter than the air.

 

Hydrogen is only one-fifteenth the weight of air, helium, the

non-inflammable American gas, is a little heavier, about one-seventh.

The practical lift is 68 pounds to the thousand cubic feet of hydrogen,

63 pounds in the case of helium.

 

Lighter-than-air ships are of three classes, rigid, semi-rigid and

non-rigid. The rigid airship has a complete metal skeleton, which gives

the ship strength and shape. Into the metal frame of the rigid airship

are built quarters, shops, communication ways, even engine rooms in the

case of the Akron and Macon, with only the control car, fins, and

propellers projecting outside the symmetrical hull. The lifting gas is

carried in a dozen or more separate gas cells, nested within the bays of

the ship.

 

The non-rigid airship has no such internal support. The bag keeps its

taut shape only from the gas and air pressure maintained within. Release

the gas and the bag becomes merely a flabby mass of fabric on the hangar

floor. Ship crews do not live in the balloon section, but in the control

car below.

 

The British, apt at nicknames, differentiated between the two types of

airships by calling them “rigid” and “limp” types, and since an early

“Type B” was widely used in the first World War, quickly contracted “B,

limp” into the handier word “Blimp.”

 

The third type, semi-rigid, has a metal keel extending the length of the

ship, to which control surfaces and the car are attached, and with a

metal cone to stiffen the bow section.

 

The rigid ship is of German origin. Developed by Count Zeppelin, retired

army officer, and largely used by that nation during the war of 1914-18,

it was taken up after the war started, by the British and Americans, and

to a small extent later by France and Italy.

 

Non-rigid ships were widely used by the British and French, to a less

extent by Italy and United States.

 

The intermediate semi-rigid was largely Italian and French in war use,

though United States bought one ship after the war from the Italians,

built one itself. The Germans also built smaller Parseval semi-rigids.

 

The rigid airships are the largest, the non-rigids smallest. The rigid

has to be large to hold enough gas to lift its metal frame along with

the load of fuel, oil, crew, supplies, passengers and cargo. The blimps

can be much smaller.

 

The Army’s first airship, built by Major Tom Baldwin, old time

balloonist, had 19,500 cubic feet capacity. Goodyear’s pioneer helium

ship “Pilgrim” had 51,000 cubic feet. These contrast with the seven

million feet capacity of the Hindenburg, and the ten million cubic feet

of ships projected for the future.

 

The following table will show the range of sizes:

 

Rigid Airships: Hindenburg (German) 7,070,000 cubic feet

Akron-Macon (U. S.) 6,500,000 cubic feet

R-100, 101 (British) 5,000,000 cubic feet

Graf Zeppelin (German) 3,700,000 cubic feet

Los Angeles (U. S.) 2,500,000 cubic feet

R-34 (British) 2,000,000 cubic feet

Semi-Rigids: Norge (Italian) 670,000 cubic feet

RS-1 (U. S.) 719,000 cubic feet

Non-Rigids: Navy K type (Patrol) 416,000 cubic feet

Navy G type (Advanced Training) 180,000 cubic feet

Navy L type (Trainer) 123,000 cubic feet

Goodyear (Passenger) 123,000 cubic feet

Pilgrim (Goodyear) 51,000 cubic feet

 

The Akron and Macon were 785 feet in length, the K type non-rigid, 250

feet long, the Navy “L’s” 150 feet long.

 

Let’s cut back now to the Montgolfiers. Progress was disappointingly

slow. The simple balloon would only go up and down, and in the direction

of the wind. Before it could be practical, men must be able to drive it

wherever they liked, make it dirigible, or directable.

 

Ingenious men, Meusnier, Giffard, Tissandier, Renard, Krebs, many others

worked over that problem through the entire nineteenth century. They

devised ballonets or air compartments to keep the pressure up. They

built airships of cylinder shape, spindle shape, torpedo shape, airships

shaped like a cigar, like a string bean, like a whale. But the stumbling

block remained, the need of an efficient power plant.

 

The steam engine was dependable, but once you had installed firebox,

boiler and cord wood aboard, there was little if any lift remaining for

crew or cargo. Giffard in 1852 built an ingenious small engine using

steam but it still weighed 100 pounds per horsepower, drove the ship at

a speed of only three miles an hour. Automobile engines today weigh as

little as six pounds per horsepower, modern airplane engines one pound

per horsepower.

 

Man experimented with feather-bladed oars, with a screw propeller,

turned by hand, using a crew of eight men. Haenlein, German, built a

motor that would use the lifting gas from the ship—coal gas or hydrogen.

Rennard in 1884 built an electric motor, taking power from a storage

battery.

 

But real progress would have to wait for the discovery of petroleum in

Pennsylvania and the invention of the internal combustion engine. When

the gasoline engine came in, in the 90’s, the dirigible builders saw the

long sought key to their problem.

 

While Count Zeppelin was experimenting with his big ships in Germany,

Lebaudy, Juliot, Clement Bayard in France and most conspicuously the

young Brazilian, Santos Dumont, were working with the smaller

dirigibles. Santos Dumont built 14 airships in the first decade of the

century, brought the attention of the world to this project. He won a

100,000 franc prize in 1901 for flying across Paris to circle Eiffel

Tower and return to his starting point—and gave the money to the Paris

poor.

 

The Wright Brothers made their historic flight at Kitty Hawk, in 1903,

opening a different field of experiment. France pushed both lines of

research. After Santos Dumont’s dirigible flight, Bleriot started from

the little town of Toury in an airplane, flew to the next town and back,

a distance of 17 miles, making only two en route stops,—and the town

erected a monument to him.

 

In 1909, Bleriot flew a plane across the English Channel and in the

following year the airship Clement Bayard II duplicated the feat,

carrying a crew of seven, made the 242 miles to London in six hours.

 

The year 1910 was a momentous one for all aircraft, with France as the

world center. Bleriot and Farman, Frenchmen, Latham, British, the

Wrights and Curtiss, Americans, broke records almost daily at a big meet

in August that year, while at longer range the French and English

dirigibles and the Parsevals of Germany, and still more important the

great Zeppelins at Lake Constance droned the news of a new epoch.

 

A young American engineer, P. W. Litchfield, attended the Paris meet,

saw these wonders, made notes. He stopped in Scotland on his way back,

bought a machine for spreading rubber on fabric, hired the two men

tending it (those men, Ferguson and Aikman, were still at their posts in

Akron thirty odd years later), hired two young technical graduates on

his return, tied in the fortunes of his struggling company with what he

believed was a coming industry.

 

The next five years would see the nations of the world bending their

efforts toward perfecting these vehicles of flight,—little realizing

they were building a combat weapon which would revolutionize warfare.