Payload fraction

Inaerospace engineering,payload fractionis 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 ofspecific impulse,propellant mass fractionand thestructural coefficient.In aircraft, it is standard practice to load less than full fuel for shorter trips to reduce weight and fuel consumption. For this reason theuseful load fractioncalculates a similar number, but based on the combined weight of the payload and fuel together in relation to the total weight.

Propeller-drivenairlinershad useful load fractions on the order of 25–35%. Modernjet airlinershave considerably higher useful load fractions, on the order of 45–55%.

Fororbital rocketsthe payload fraction is between 1% and 5%, while the useful load fraction is perhaps 90%.

Examples

Vehicle	Liftoff Mass	Payload Mass toLEO	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	26	3.85%
Soyuz-2.1b	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 17Saturn V	2,961,860 kg	48,609 kg toTLI	60.9	1.64%
Apollo 17Lunar ModuleDescent stage	36,362 lb	10,542.8 lb (LLOtoMoon)	3.45	29.0%
Apollo 17Lunar ModuleAscent stage	10,542.8 lb	552.1 lb (Moon to LLO)	19.1	5.24%
V-2	12,805 kg	1,000 kg (320 km distancesuborbital)	12.8	7.81%

For payload fractions and fuel fractions in aviation, seeFuel Fraction.

See also

• Tsiolkovsky rocket equation