The word aerostat was originally French and is derived from the Greek aer (air) + statos (standing). An aerostat is a lighter than air object that can stay stationary in the air. Aerostats include free balloons, airships, moored balloons and tethered Helikites. An aerostat's main structural component is its envelope, a lightweight skin containing a lifting gas to provide buoyancy, to which other components are attached. Technically, aerostats are capable of providing "aerostatic" lift in that the force upwards arises without movement through the surrounding air mass. This contrasts with aerodynamic lift which requires the movement of at least some part of the aircraft through the surrounding air mass. However, in reality most aerostats (except spherical balloons) obtain lift from both aerodynamic lift and pure gas lift at some time or other. Aerostats are generally tethered lighter-than-air objects. Types of tethered aerostat include spherical balloons, blimps and Helikites. Helikites are probably the most commonly used worldwide at present, with thousands produced each year.

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