第一次世界大战中AIRSHIP的背景知识
By the start of the Great War the airship had been developed into two main types - rigid and non-rigid (technically, the latter is more accurately described as pressure-rigid). Cylindrical in cross-section, both were given buoyancy by gas and motion by engine-driven propellers and were controlled by vertical rudders and horizontal elevators.
In the rigid type, a solid framework, which might be likened to a skeleton, supports an external covering of fabric called the envelope (a very few experimental types had a metallic covering). Within the framework are contained bags of gas called balloonets. In the non-rigid, the envelope''s shape is maintained by the pressure of the gas that fills it; there is no framework. The rigid''s control car and engines are suspended from the framework; in the non-rigid they are attached directly to or suspended directly from the envelope. (In some later rigids the engines were mounted internally, driving thepropellers by transmission belts.)
There was an intermediate type, now long vanished, called the semi-rigid. It had a pressure-rigid envelope but a solid keel.
The rigid airship, employed so extensively by Germany during the Great War, was perfected soon after the turn of the century by a former Wurttenberg army cavalry officer, Ferdinand Adolf August Heinrich Graf von Zeppelin, who had been inspired by a balloon ascent he had made in the United States on 19-Aug-1863. 2 His craft were, naturally , known as Zeppelins. "Zeppelin" is a proprietary, or trade, name (such as Kodak, Ferris Wheel and Autogiro), and is applied properly only to craft constructed by Luftshiffbau Zeppelin G.m.b.H. or firms licensed to use its patents. It should thus be spelled with a capital Z; modern writers who spell it in lower case are mistaken in their apparent belief that it is generic. 3
It has become customary to refer to all German rigid airships of the Great War as Zeppelins, but in fact not all were. Some were constructed by a rival firm, Luftschiffbau Schutte-Lanz G.m.b.H., which employed a framework of laminated plywood instead of the aluminum alloy used in Zeppelins. 4
The vast amount of literature devoted to German airships can easily, and has, led to the belief that these were the dominant LTA craft of the Great War. Actually, the British navy was the greatest exponent of the airship, receiving more than 200 non-rigids during 1915-1918 for anti-submarine patrolling. This type was also used, although in far fewer numbers, by the U.S. Navy and the French and Italian armies and navies. The German army and navy also had a handful.
The rigid airship no longer exists; none has been built since the 1930s. 5 The demise is usually blamed on the Hindenburg disaster 6 although that had been preceded by the loss of a number of American, British, French and Italian rigids. All airships flying today are non-rigid types, popularly known as blimps.
飞艇按其结构可分为软式、半硬式、硬式。
(1)软式飞艇艇体由主气囊和前后副气囊组成。气囊不仅要求密封，还要有相当强度能承受一定的压强。气囊上装有安全活门，压强超过规定值时能自动放气保证气囊不被胀破。主气囊内充浮升气体，副气囊内充空气。副气囊的作用是在不排放主气囊内气体的条件下，保持主气囊内外压强差为定值。当飞艇爬高，外界大气压强降低时，副气囊放气使主气囊增大容积，从而保持主气囊原来的内外压强差。当外界大气压强增大时，向副气囊内充气使它膨胀，从而压缩主气囊的容积，使主气囊的压强仍能保持略高于外界大气压强。设置前后副气囊还可调节浮力中心的位置。仅向后副气囊充气时，重心后移，飞艇产生抬头力矩;反之，产生低头力矩。
(2)半硬式飞艇气囊构造与软式飞艇相似，但在气囊下部增加刚性的龙骨架，组成半硬式飞艇的艇体。
(3)硬式飞艇艇体由刚性骨架外罩蒙布或薄铝皮构成整个艇体不密封，主要起维持流线型和连接各部分的作用。艇体内部由隔框分割成许多小气室，每个小气室内放有密封的小气囊，内充比空气轻的气体。在地面时，小气囊没有完全胀满气室。随着飞行高度增加，外界大气压强降低，囊内气体随之膨胀，在达到规定高度时，气囊恰好胀满气室。众多小气囊可提高飞艇的抗损性和安全性。部分小气囊受损，整个飞艇的浮力不会完全丧失。
第一艘飞艇是法国的H·吉法尔于1852年制成的。1900年德国的齐柏林公司开始制造大型硬式飞艇，在第一次世界大战期间，曾多次用飞艇进行远程轰炸。
