In aerospace engineering, payload fraction is a common term used to characterize the efficiency of a particular design. The payload fraction is the quotient of the payload mass and the total vehicle mass at the start of its journey. It is a function of specific impulse, propellant mass fraction and the structural coefficient. In aircraft, loading less than full fuel for shorter trips is standard practice to reduce weight and fuel consumption. For this reason, the useful load fraction calculates a similar number, but it is based on the combined weight of the payload and fuel together in relation to the total weight.
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 orbital rockets the payload fraction is between 1% and 5%, while the useful load fraction is perhaps 90%.
| Vehicle | Liftoff Mass | Payload Mass to LEO | Mass ratio | Payload fraction | |
|---|---|---|---|---|---|
| Falcon 9 Block 5 | 549,054 kg + 22,800 kg | 22,800 kg | 25.1 | 3.99% | |
| Proton-M | 705,000 kg + 23,000 kg | 23,000 kg | 31.7 | 3.16% | |
| Long March 3B/E | 458,970 kg + 11,500 kg | 11,500 kg | 40.9 | 2.44% | |
| Ariane 6 | 860,000 kg + 21,500 kg | 21,500 kg | 41.0 | 2.44% | |
| Electron | 13,000 kg + 300 kg | 300 kg | 44.3 | 2.26% | |
| SpaceX Starship | 200,000 kg + 5,000,000 kg | 200,000 kg[1] | 26 | 3.85% | |
| Soyuz-2.1b[2] | 312,000 kg + 8,200 kg | 8,200 kg | 40.0 | 2.50% | |
| Space Shuttle | 2,030,000 kg | 27,500 kg | 73.8 | 1.35% | |
| Apollo 17 Saturn V[3] | 2,961,860 kg | 48,609 kg to TLI | 60.9 | 1.64% | |
| Apollo 17 Lunar Module Descent stage | 36,362 lb | 10,542.8 lb (LLO to Moon) | 3.45 | 29.0% | |
| Apollo 17 Lunar Module Ascent stage | 10,542.8 lb | 552.1 lb (Moon to LLO) | 19.1 | 5.24% | |
| V-2[4] | 12,805 kg | 1,000 kg (320 km distance suborbital) | 12.8 | 7.81% |
For payload fractions and fuel fractions in aviation, see Fuel Fraction.