is the carrying capacity
of an aircraft or launch
vehicle, usually measured in terms of weight. Depending on the nature of the flight or mission, the payload of a vehicle may include cargo
, passengers, flight crew, munitions, scientific instruments or experiments, or other equipment. Extra
fuel, when optionally carried, is also considered part of the payload. In a commercial context (i.e., an airline or air freight
carrier), payload may refer only to revenue-generating cargo or paying passengers.
For a rocket, the payload can be a satellite, space probe, or spacecraft carrying humans, animals, or cargo. For a ballistic missile, the payload is one or more warheads and related systems; the total weight of these systems is referred to as the throw-weight.
of payload to the total liftoff weight of the air or spacecraft is known as the "payload fraction". When the weight of the payload and fuel are considered together, it is known as the "useful load
fraction". In spacecraft, "mass fraction" is normally used, which is the ratio of payload to everything else, including the rocket structure.