Glossary of Dirigible Terms

Aerodynamic Flight – Heavier-than-air craft like airplanes and helicopters use propulsion and control surfaces (wings, rotors, etc.) to actively force their flight into the air.

Aerostatic Flight – Lighter-than-air craft such as blimps and other airships use a lifting gas that is lighter than air to become buoyant and passively rise into the air.

Ballast – This is typically a heavy fluid material such as sand or water that adds additional weight which can be dumped in order to increase the upward lift or buoyancy of an airship.

Ballonet – This is a separate gas impermeable containment cell within an airship (most modern blimps) used to collect external air as weight and pressure against the internal lifting gas. This helps to control an airship’s buoyancy.

Blimp – A blimp is a non-rigid airship because it relies upon the pressure of the lifting gas to hold its shape. The story goes that it got its name from a World War I era Lieutenant who mimicked the sound made when thumping on the side of the airship.

Buoyancy – This is the relative amount of lift an airship has compared to the surrounding air. Positive net buoyancy means that an airship will rise, while negative means it will fall. Most airships strive for neutral buoyancy or a slight negative buoyancy that can then be controlled aerodynamically.

Control Car – This is often a separate compartment that hangs below an airship where the airship’s controls are located and where the airship’s piloting crew operates.

Dirigible – Is derived from a French word that means ‘to steer’. A dirigible is essentially any lighter than air craft that can be steered or controlled.

Elevator – The elevator of a dirigible is the horizontal tail fin that controls pitch. Pitch is the up or down angle that an airship takes through the air.

Envelope – The envelope is the external covering of the airship that encloses the lifting gas.

Gold Beater’s Skin – Many old airships used gold beater’s skin to create the gas impermeable cells that contained the lifting gas. Gold beater’s skin was made from specially treated cow intestines and was originally used by gold beaters who used it to beat and thus shape gold into thin sheets.

Gas Impermeable – This applies to material which gas cannot permeate or pass through.

Gondola – This is a compartment that holds passengers, crew, and/or equipment and is located beneath a balloon or airship.

Helium – Helium is the second lightest gas after hydrogen. It is one of the noble gases due to its inherent stability. This is the primary gas used in most blimps today.

Hydrogen – Hydrogen is the lightest gas of all. It is highly flammable.  Many airships of the past used hydrogen as a lifting gas, however today it is more likely to be used in liquid form as rocket fuel.

Lifting Gas – Typical lifting gasses are hydrogen, helium, methane, ammonia and hot air due to the fact that they are less dense than the surrounding air and thus tend to rise. When harnessed within the envelope of an airship these gasses become lifting gasses for the purpose of lifting the airship.

Mooring Lines – These lines were dropped from the nose section of large airships and used to help reel them in toward their mooring mast.

Mooring Mast – The mooring mast is a tower-like structure whose mast connects to the nose cone of airships that have landed.

Pressure Height – The pressure height is the maximum altitude an airship can rise before the internal lifting gas begins to expand beyond the containment of the gas envelope. If an airship rises too high it may become necessary to valve excess lifting gas to prevent the gas cells from bursting.

Rudder – The rudder is the vertical tail fin that controls the directional heading of the airship.

Sub-cloud Car – During World War I German zeppelins used these one man contraptions to lower hundreds of feet below the zeppelin so that a spotter could find targets while the rest of the airship remained safely hidden above the clouds. They are said to have not been very effective.

Zeppelin – Named after its inventor, Count von Zeppelin, this dirigible is a rigid style airship typically of very large size and has not been in use since the late 1930s following the Hindenburg disaster.

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