Airship

Airships are vehicles based on absolute levitation devices. The advantage of this over the relative levitation devices used in hoverships and hovercarts is that absolute levitation is insensitive to topography, and can operate equally well at any elevation. Thus, an airship is ideal for crossing mountainous terrain that low-altitude levitating vehicles would find difficult or even impassable.

The drawback of airships is that they cannot make effective use of lateral force devices or hoverkeels, as a hovership would. Because hoverkeels are limited by torque rather than force, applying a significant keel force at high altitude would require an immensely powerful, and therefore immensely expensive and heavy, hoverkeel. Without the use of a hoverkeel, an airship cannot harness wind power. If unpowered, an airship will simply drift in the wind, quickly settling to zero air speed. Under such conditions, sails are obviously useless.

Because of this drawback, airships must rely on alternate sources of power to drive a propeller. In some cases, air oars are used instead. These are basically movable vanes attached to long levers; the vane is turned parallel to its motion when moved one way, then turned perpendicular to its motion when moved the other way, thus providing net thrust in one direction. However, air oars are mechanically complicated compared to propellers and are therefore generally used only when the ultimate source of energy is human muscle power.

Muscle power in the form of treadmills or animal power is a common way to drive airships. However, this is usually only practical on smaller airships, where the amount of power needed to gain altitude is not too great. For larger airships, some form of heat engine is used. Most heat engines are inefficient and unreliable, being prone to magical jamming. One design that compensates for this is the steam tower. Heat engines for airship use are generally powered by summoned heat, such as from magma. It is also possible for an airship to be powered electrically, as electricity can be summoned from the ionosphere by a principle similar to the arc lantern. However, such methods are not as well developed.

Airships are generally quite slow compared to other levitating vehicles, particularly hoverships. They are also easily outmaneuvered by wingknights. When placed in military use, airships commonly compensate for this through raw size and armor, creating a target that is difficult to destroy at long range; its altitude then provides it with defense against deadly melee weapons such as melting swords.

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