Payload fraction

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 takeoff weight of aircraft. 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 lighter 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 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 propellant 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 Mass 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
V-2 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]

Note: the above table may incorrectly include the mass of the empty upper stage or stages.

See also

References

  1. 1 2 Astronautix- Ariane 5g
  2. 1 2 Astronautix - Saturn V
  3. 1 2 Astronautix- Saturn IB
  4. ↑ Astronautix-V-2
  5. 1 2 3 4 5 AIAA2001-4619 RLVs
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