Continuing the series on Airships:
Some basic comments on airship technical design. I'll be referring to Goodyear's web pages on flying their blimp.
The basic components of the airship are the envelope (outer covering), gondola, fins or aerodynamic controls, engines, and the balloonets.
Lift for the airship is provided by a combination of static (buoyancy) lift provided by the lifting gas - usually helium - and dynamic lift provided by the air moving over the aerodynamic shape of the airship and the thrust provided by the engines. Airships are boyant, like any balloon, by being less dense than the surrounding air. To be specific, the airship weighs less than the amount of air volume it displaces. This difference provides lift. If an airship weighs exactly the same as the air it displaces, then it is neutrally buoyant and will neither rise nor sink. The problem with this is that as you ascend into the atmosphere, the air becomes less dense. Airships are normally trimmed with ballast (added weight) to be slightly heavy at ground level - and to use dynamic lift provided by forward motion to climb.
