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| Topics in Astrodynamics [edit] |
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In aerospace engineering, payload fraction is a common term used to characterize the efficiency of a particular design. Payload fraction is calculated by dividing the weight of the payload by the weight of the otherwise empty aircraft when fully fueled. Fuel represents a considerable amount of the overall takeoff weight, and for shorter trips it is quite common to load less fuel in order to carry a heavier load. For this reason the useful load fraction calculates a similar number, but based on the combined weight of the payload and fuel together.
Propeller-driven airliners had useful load fractions on the order of 25-35%. Modern jet-powered airliners have considerably higher useful load fractions, on the order of 45-55%.
For spacecraft the payload fraction is often less than 1%, while the useful load fraction is perhaps 90%. In this case the useful load fraction is not a useful term, because spacecraft typically can't reach orbit without a full fuel load. For this reason the related term mass fraction, is used instead. However, if the latter is large, the payload can only be small.
Examples
| Vehicle | Takeoff Mass | Final Mass | Mass ratio | Payload fraction |
|---|---|---|---|---|
| Ariane 5 (vehicle + payload) | 746,000 kg [1] (~1,645,000 lb) | 2,700 kg + 16,000 kg[1] (~6,000 lb + ~35,300 lb) | 39.9 | 0.975 |
| Titan 23G first stage | 117,020 kg (258,000 lb) | 4,760 kg (10,500 lb) | 24.6 | 0.959 |
| Saturn V | 3,038,500 kg[2] (~6,700,000 lb) | 13,300 kg + 118,000 kg[2] (~29,320 lb + ~260,150 lb) | 23.1 | 0.957 |
| Space Shuttle (vehicle + payload) | 2,040,000 kg (~4,500,000 lb) | 104,000 kg + 28,800 kg (~230,000 lb + ~63,500 lb) | 15.4 | 0.935 |
| Saturn 1B (stage only) | 448,648 kg[3] (989,100 lb) | 41,594 kg[3] (91,700 lb) | 10.7 | 0.907 |
| Virgin Atlantic GlobalFlyer | 10,024.39 kg (22,100 lb) | 1,678.3 kg (3,700 lb) | 6.0 | 0.83 |
| V2 | 13,000 kg (~28,660 lb) (12.8 ton) | 3.85 | 0.74 [4] | |
| X-15 | 15,420 kg (34,000 lb) | 6,620 kg (14,600 lb) | 2.3 | 0.57[5] |
| Concorde | ~181,000 kg (400,000 lb [5]) | 2 | 0.5[5] | |
| Boeing 747 | ~363,000 kg (800,000 lb[5]) | 2 | 0.5[5] |
References
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