The great difference, of course, between the airplane and the airship is that the former sustains itself as a heavier-than-air vessel by the lifting power of the air in relation to a body driven hard against it by its powerful engines, while the latter sustains itself as a lighter-than-air body because of the large amount of air displaced by a huge envelop loaded with gas much lighter than the air itself. The contrast is obvious; one vessel is small, agile, and very fast; the other is slow and clumsy. The airship cannot attain anything like the speed of the airplane, nor can it go so high or maneuver so quickly, but on the other hand, at least for the immediate present, it can stay afloat very much longer and carry much greater weight.
Moreover, the airship has certain other easily perceptible advantages over the airplane. Ordinarily an airship need not fly at much more than a thousand feet, which not only makes far less cold traveling than at higher altitudes, but also allows the passengers to enjoy the view far better than from an airplane, whence the world below looks like a dull contour map. An airship also flies on an even keel; it does not bank as an airplane does nor does it climb or descend so quickly.
At present airship travel gives a greater feeling of comfort and security. Sleeping is a calm experience; moving about comparatively simple. Also there is less noise than in an airplane where the engines beat incessantly and the wind rushes through the wires and struts. An airship has no wires and can at the same time slow down and even shut off its engine, so that it need be no more noisy than a motor-car. Engine failure also is not so serious as in an airplane, for the gas-bag will always keep the ship up until there has been a chance for repairs.
Up to the present, too, the airship is less of a fair-weather flier than the airplane. A surprising record has been attained in the war by British airships, as is shown by the fact that in 1918, a year of execrable weather, there where only nine days during which their vessels were not up. This is, of course, in considerable contrast to airplanes as at present developed, but it may reasonably be expected that the latter will very soon develop to the same point of independence of the weather.
Of course, the great difficulty of airships has been their ungainly size and the difficulty of housing them. The sheds, particularly those for the Zeppelins, have been most costly, but the British have recently developed a system of mooring masts which make much of this expense unnecessary. If such a device can be successfully put into every-day use it will enormously increase the ease of loading and unloading passengers, which now makes for considerable discomfort and loss of time.
Some of the plans for future airships are unbelievable to one who has not followed their development carefully. Already there is planned in England a monster ship known as the "ten million," for the reason that it will have a gas capacity of ten million cubic feet, over four times that of the largest Zeppelin. The length is placed at 1,100 feet, the speed at 95 miles an hour, the cruising range 20,000 miles, and the cost at about $1,000,000. As a matter of actual practice, however, the best division of the space and lifting power of this airship would be for it to carry a crew of about 20, a useful load of 200 passengers or 150 tons of merchandise, and 50 tons of petrol, which would give it a non-stop run of about 5,000 miles.
Airship travel would undoubtedly be expensive. The gas alone to maintain such a vessel as described is expected to cost about $30 an hour, which, added to the original investment for the ship and its house and the wages of the crew and the 200 or more skilled men at each station, would come up to a high figure. At the same time, the airship would not afford the element of very high speed which is so certain to justify any expense which may have to be put into the airplane. Nevertheless, with the improvements that are sure to come, with the ability to reach places not touched by other methods of travel, the freedom from all the delays, inconveniences, and expense of trans-shipment, this preliminary charge will be largely compensated for.
Those who sponsor the airship urge that it will be used almost exclusively for long-distance flights beyond the range of the ordinary airplane and very little for short local flights. For transatlantic travel, for instance, it is being particularly pressed, as ships even of to-day have all the capacity for such a voyage, without the dangers which might surround an airplane if its sustaining engine power were to give out.
There are several records which would easily justify it. Besides the flight across the Atlantic by the R-34 and the four-day trip of the German airship from Bulgaria to Africa and back, a British airship during the war stayed up for 50 hours and 55 minutes, and another, just after the armistice, stayed up for 61 hours. An American naval dirigible a short time after the armistice made a flight from New York to Key West, 1,200 miles, at 40 miles an hour, for 29-1/2 hours, with one stop at Hampton Roads. As an example of some of the difficulties of airship travel, this landing was possible only after the ship had circled the town and dropped a message asking the people to go to a large field near by and catch the dirigible drag-net when it approached the ground. Even at that, however, the time of less than a day and a quarter for what is usually a very arduous train trip from New York down the coast to Florida gives some indication of the possibilities of this method of travel when properly developed.
Practically all the new airships contemplated look to a much greater speed than the pre-war speed of about 40 miles an hour. It is not at all uncertain that they will not run up as high as 100 miles, though at the present time that figure is extreme. But granted that they no more than double the pre-war speed and reach the actual figure contemplated of about 75 miles an hour, they still would triple the best passenger-steamer speed, which would make them a matter of the utmost importance in all long ocean voyages.