Read Ebook: British Airships Past Present and Future by Whale George

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To stabilize the ship in flight, fins or planes are fitted to the after end of the envelope or hull. Without the horizontal planes the ship will continually pitch up and down, and without the vertical planes it will be found impossible to keep the ship on a straight course. The planes are composed of a framework covered with fabric and are attached to the envelope by means of stay wires fixed to suitable points, in the case of non-rigid ships skids being employed to prevent the edge of the plane forcing its way through the surface of the fabric. The rudder and elevator flaps in modern practice are hinged to the after edges of the planes.

The airship car contains all instruments and controls required for navigating the ship and also provides a housing for the engines. In the early days swivelling propellers were considered a great adjunct, as with their upward and downward thrust they proved of great value in landing. Nowadays, owing to greater experience, landing does not possess the same difficulty as in the past, and swivelling propellers have been abandoned except in rigid airships, and even in the later types of these they have been dispensed with.

Owing to the great range of an airship a thoroughly reliable engine is a paramount necessity. The main requirements are--firstly, that it must be capable of running for long periods without a breakdown; secondly, that it must be so arranged that minor repairs can be effected in the air; and thirdly, that economy of oil and fuel is of far greater importance to an airship than the initial weight of the engine itself.

HANDLING AND FLYING OF AIRSHIPS

The arrangements made for handling airships on the ground and while landing, and also for moving them in the open, provide scope for great ingenuity. An airship when about to land is brought over the aerodrome and is "ballasted up" so that she becomes considerably lighter than the air which she displaces. The handling party needs considerable training, as in gusty weather the safety of the ship depends to a great extent upon its skill in handling her. The ship approaches the handling party head to wind and the trail rope is dropped; it is taken by the handling party and led through a block secured to the ground and the ship is slowly hauled down. When near the ground the handling party seize the guys which are attached to the ship at suitable points, other detachments also support the car or cars, as the case may be, and the ship can then be taken into the shed.

In the case of large airships the size of the handling party has to be increased and mechanical traction is also at times employed.

As long as the airship is kept head to wind, handling on the ground presents little difficulty; on many occasions, however, unless the shed is revolving, as is the case on certain stations in Germany, the wind will be found to be blowing across the entrance to the shed. The ship will then have to be turned, and during this operation, unless great discretion is used, serious trouble may be experienced.

Many experiments have been and are still being conducted to determine the best method of mooring airships in the open. These will be described and discussed at some length in the chapter devoted to the airship of the future.

During flight certain details require attention, and carelessness on the pilot's part, even on the calmest of days, may lead to disaster. The valves and especially the gas valves should be continually tested, as on occasions they have been known to jam, and the loss of gas has not been discovered until the ship had become unduly heavy.

Pressure should be kept as constant as possible. Most airships work up to 30 millimetres as a maximum and 15 millimetres as a minimum flying pressure. During a descent the pressure should be watched continuously, as it may fall so low as to cause the nose to blow in. This will right itself when the speed is reduced or the pressure is raised, but there is always the danger of the envelope becoming punctured by the bow stiffeners when this occurs.

HOUSING ACCOMMODATION FOR AIRSHIPS, ETC.

During the early days of the war, when stations were being equipped, the small type of airship was the only one we possessed. The sheds to accommodate them were constructed of wood both for cheapness and speed of construction and erection. These early sheds were all of very similar design, and were composed of trestles with some ordinary form of roof-truss. They were covered externally with corrugated sheeting. The doors have always been a source of difficulty, as they are compelled to open for the full width of the shed and have to stand alone without support. They are fitted with wheels which run on guide rails, and are opened by means of winches and winding gear.

The later sheds built to accommodate the rigid airship are of much greater dimensions, and are constructed of steel, but otherwise are of much the same design.

The sheds are always constructed with sliding doors at either end, to enable the ship to be taken out of the lee end according to the direction of the wind.

It has been the practice in this country to erect windscreens in order to break the force of the wind at the mouth of the shed. These screens are covered with corrugated sheeting, but it is a debatable point as to whether the comparative shelter found at the actual opening of the shed is compensated for by the eddies and air currents which are found between the screens themselves. Experiments have been carried out to reduce these disturbances, in some cases by removing alternate bays of the sheeting and in other cases by substituting expanded metal for the original corrugated sheets.

It must be acknowledged that where this has been done, the airships have been found easier to handle.

At the outbreak of war, with the exception of a silicol plant at Kingsnorth, now of obsolete type, and a small electrolytic plant at Farnborough, there was no facility for the production of hydrogen in this country for the airship service.

When the new stations were being equipped, small portable silicol plants were supplied capable of a small output of hydrogen. These were replaced at a later date by larger plants of a fixed type, and a permanent gas plant, complete with gasholders and high pressure storage tanks was erected at each station, the capacity being 5,000 or 10,000 cubic feet per hour according to the needs of the station.

With the development of the rigid building programme, and the consequent large requirements of gas, it was necessary to reconsider the whole hydrogen situation, and after preliminary experimental work it was decided to adopt the water gas contact process, and plants of this kind with a large capacity of production were erected at most of the larger stations. At others electrolytic plants were put down. Hydrogen was also found to be the bye-product of certain industries, and considerable supplies were obtained from commercial firms, the hydrogen being compressed into steel cylinders and dispatched to the various stations.

Before concluding this chapter, certain words must be written on parachutes. A considerable controversy raged in the press and elsewhere a few months before the cessation of hostilities on the subject of equipping the aeroplane with parachutes as a life-saving device. In the airship service this had been done for two years. The best type of parachute available was selected, and these were fitted according to circumstances in each type of ship. The usual method is to insert the parachute, properly folded for use, in a containing case which is fastened either in the car or on the side of the envelope as is most convenient. In a small ship the crew are all the time attached to their parachutes and in the event of the ship catching fire have only to jump overboard and possess an excellent chance of being saved. In rigid airships where members of the crew have to move from one end of the ship to the other, the harness is worn and parachutes are disposed in the keel and cars as are lifebuoys in seagoing vessels. Should an emergency arise, the nearest parachute can be attached to the harness by means of a spring hook, which is the work of a second, and a descent can be made.

It is worthy of note that there has never been a fatal accident or any case of a parachute failing to open properly with a man attached.

The material embodied in this chapter, brief and inadequate as it is, should enable the process of the development of the airship to be easily followed. Much has been omitted that ought by right to have been included, but, on the other hand, intricate calculations are apt to be tedious except to mathematicians, and these have been avoided as far as possible in the following pages.

EARLY AIRSHIPS AND THEIR DEVELOPMENT TO THE PRESENT DAY

The science of ballooning had reached quite an advanced stage by the middle of the eighteenth century, but the construction of an airship was at that time beyond the range of possibility. Discussions had taken place at various times as to the practicability of rendering a balloon navigable, but no attempts had been made to put these points of argument to a practical test.

Airship history may be said to date from January 24th, 1784. On that day Brisson, a member of the Academy in Paris, read before that Society a paper on airships and the methods to be utilized in propelling them. He stated that the balloon, or envelope as it is now called, must be cylindrical in shape with conical ends, the ratio of diameter to length should be one to five or one to six and that the smallest cross-sectional area should face the wind. He proposed that the method of propulsion should be by oars, although he appeared to be by no means sanguine if human strength would be sufficient to move them. Finally, he referred to the use of different currents of the atmosphere lying one above the other.

This paper caused a great amount of interest to be taken in aeronautics, with the result that various Frenchmen turned their attention to airship design and production. To France must be due the acknowledgment that she was the pioneer in airship construction and to her belongs the chief credit for early experiments.

At a later date Germany entered the lists and tackled the problems presented with that thoroughness so characteristic of the nation. It is just twenty-one years ago since Count Zeppelin, regardless of public ridicule, commenced building his rigid airships, and in that time such enormous strides were made that Germany, at the outbreak of the war, was ahead of any other country in building the large airship.

In 1908 Italy joined the pioneers, and as regards the semi-rigid is in that type still pre-eminent. Great Britain, it is rather sad to say, adopted the policy of "wait and see," and, with the exception of a few small ships described in the two succeeding chapters, had produced nothing worthy of mention before the outbreak of the great European war. She then bestirred herself, and we shall see later that she has produced the largest fleet of airships built by any country and, while pre-eminent with the non-rigid, is seriously challenging Germany for the right to say that she has now built the finest rigid airship.

FRANCE

To revert to early history, in the same year in which Brisson read his paper before the Academy, the Duke of Chartres gave the order for an airship to the brothers Robert, who were mechanics in Paris. This ship was shaped like a fish, on the supposition that an airship would swim through the air like a fish through water. The gas-chamber was provided with a double envelope, in order that it might travel for a long distance without loss of gas.

The airship was built in St. Cloud Park; in length it was 52 feet with a diameter of 82 feet, and was ellipsoidal in shape with a capacity of 30,000 cubic feet. Oars were provided to propel it through the air, experiments having proved that with two oars of six feet diameter a back pressure of 90 lb. was obtained and with four oars 140 lb.

On July 6th in the same year the first ascent was made from St. Cloud. The passengers were the Duke of Chartres, the two brothers Robert and Colin-Hulin. No valves having been fitted, there was no outlet for the expansion of gas and the envelope was on the point of bursting, when the Duke of Chartres, with great presence of mind, seized a pole and forced an opening through both the envelopes. The ship descended in the Park of Meudon.

On September 19th the airship made a second ascent with the same passengers as before, with the exception of the Duke. According to the report of the brothers Robert, they succeeded in completing an ellipse and then travelled further in the direction of the wind without using the oars or steering arrangements. They then deviated their course somewhat by the use of these implements and landed at Bethune, about 180 miles distant from Paris.

In those days it was considered possible that a balloon could be rendered navigable by oars, wings, millwheels, etc., and it was not until the last decades of the nineteenth century, when light and powerful motors had been constructed, that the problem became really practical of solution.

In 1834 the Compte de Lennox built an airship of 98,700 cubic feet capacity. It was cylindrical in form with conical ends, and is of interest because a small balloon or ballonet, 7,050 cubic feet contents, was placed inside the larger one for an air filling. A car 66 feet in length was rigged beneath the envelope by means of ropes eighteen inches long. Above the car the envelope was provided with a long air cushion in connection with a valve. The intention was by compression of the air in the cushion and the inner balloon, to alter the height of the airship, in order to travel with the most favourable air currents. The motive power was 20 oar propellers worked by men.

This airship proved to be too heavy on completion to lift its own weight, and was destroyed by the onlookers.

The next airship, the Dupuy de Lome, is of interest because the experiments were carried out at the cost of the State by the French Government. This ship consisted of a spindle-shaped balloon with a length of 112 feet, diameter of 48 1/2 feet and a volume of 121,800 cubic feet. An inner air balloon of 6,000 cubic feet volume was contained in the envelope. The method of suspension was by means of diagonal ropes with a net covering. A rudder in the form of a triangular sail was fitted beneath the envelope and at the after part of the ship. The motive power was double-winged screws 29 feet 6 inches diameter, to be worked by four to eight men.

On her trials the ship became practically a free balloon, an independent velocity of about six miles per hour being achieved and deviation from the direction of the wind of ten degrees.

At the close of the nineteenth century Santos-Dumont turned his attention to airships. The experiments which he carried out marked a new epoch and there arose the nucleus of the airship as we know it to-day. Between the years 1898 and 1905 he had in all built fourteen airships, and they were continually improved as each succeeding one made its appearance. In the last one he made a circular flight; starting from the aerodrome of the aero club, he flew round the Eiffel Tower and back to the starting point in thirty-one minutes on October 19th, 1902. For this feat the Deutsch prize was awarded to him.

The envelopes he used were in design much nearer approach to a streamline form than those previously adopted, but tapered to an extremely fine point both at the both and stem. For rigging he employed a long nacelle, in the centre of which was supported the car, and unusually long suspensions distributed the weight throughout practically the entire length of the envelope. To the name of Santos-Dumont much credit is due. He may be regarded as the originator of the airship for pleasure purposes, and by his success did much to popularize them. He also was responsible to a large extent for the development and expansion of the airship industry in Paris.

At a little later date, in 1902 to be precise, the Lebaudy brothers, in conjunction with Julliot, an engineer, and Surcoup, an aeronaut, commenced building an airship of a new type. This ship was a semirigid and was of a new shape, the envelope resembling in external appearance a cigar. In length it was 178 feet with a diameter of 30 feet and the total capacity was 64,800 cubic feet. This envelope was attached to a rigid elliptical keel-shaped girder made of steel tubes, which was about a third of the length of the ship. The girder was covered with a shirting and intended to prevent the ship pitching and rolling while in flight. A horizontal rudder was attached to the under side of this girder, while right aft a large vertical rudder was fixed.

A small car was suspended by steel rods at a distance of 17 feet 9 inches from the girder, with a framework built up underneath to absorb the shock on landing.

A 35 horse-power Daimler-Mercedes motor, weighing some 800 lb. without cooling water and fuel, drove two twin-bladed propellers on either side of the car.

In the year 1903 a number of experimental flights were made with this ship and various details in the construction were continually introduced. The longest flight was 2 hours 46 minutes. Towards the end of that year, while a voyage was being made from Paris to Chalais Meudon, the airship came in contact with a tree and the envelope was badly torn.

In the following year it was rebuilt, and the volume was slightly increased with fixed and movable planes added to increase the stability. After several trips had been made, the airship again on landing came in contact with a tree and was burst.

The ship was rebuilt and after carrying out trials was purchased by the French Army. The Lebaudy airship had at that time been a distinct success, and in 1910 one was purchased for the British Government by the readers of the Morning Post.

In the ten-ton Lebaudy the length of the keel framework was greatly extended, and ran for very nearly the full length of the envelope. The disadvantage of this ship was its slowness, considering its size and power, and was due to the enormous resistance offered by the framework and rigging.

Airships known as the "Clement-Bayard" were also built about this time. They were manufactured by the Astra Company in conjunction with Monsieur Clement, a motor engineer.

In later days vessels were built by the Astra Company of the peculiar design introduced by Senor Torres. These ships, some of which were of considerable size, were highly successful, and we became purchasers at a later date of several.

The Zodiac Company also constructed a number of small ships which were utilized during the war for anti-submarine patrol. It cannot be said, however, that the French have fulfilled their early promise as airship designers, the chief reason for this being that the airship is peculiarly suitable for work at sea and the French relied on us to maintain the commerce routes on the high seas and concentrated their main efforts on defeating the Germans in the field, in which as all the world acknowledges they were singularly successful and hold us under an eternal obligation.

GERMANY

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