Ballast refers to a weight carried aboard a lighter-than-air vehicle to offset the buoyancy of its lifting gas.
Gas balloons commonly use sand, while blimps often carry metal shot in small canvas bags. Water has been the traditional ballast in rigid airships. Ballast is often expendable, being anything with weight that can be jettisoned from the vehicle. Ballast may be dropped by an airship to compensate for lost lifting gas or to ascend more quickly.
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Ballast tamper (Ballast tamper is described as a power-operated ...)
List of books: Ballast