What explains the relation between how much a launcher weights on the launch pad, and how much mass it can lift to orbit?
I had expected that more payload requires more fuel to be launched and that a launcher is built around that fuel mass. I'm surprised to see that these two measures are just weakly correlated. The data I use here is indeed sloppy but it can't be that much off, or can it? (I'm getting suspicious). I can understand that Falcon 9 v1.1 is much heavier than v1.0 because it is supposed to be more robust and have fuel enough to be reusable. I note that the (older style) Russian and Chinese launchers are the least efficient according to this simple ratio, but with Ariane 5 a bit worse than Proton. I'm surprised to realize that Atlas V 551 and Ariane 5 both lift about the same mass to orbit, but that Ariane 5 is well more than twice as heavy on the launch pad! Is it because of the large solid fuel boosters? What other factors explain this lack of general relation?
Below are figures I took from Wikipedia about eleven different launchers. I've picked values for the maximum LEO capacity configuration. The four columns are:
- Mass of the launcher on the launch pad (tons).
- Mass payload the launcher can put in low Earth orbit (tons).
- The ratio between the two above (tons on pad / tons in LEO).
The difference between that ratio and the average ratio in this sample, which is 33 tons on the launch pad per ton payload to LEO, ranging hugely from 21 (Saturn V) to 55 (Long March 2F).
Pad, LEO, Ratio, Deviation from average ratio [tons]
240 6.0 40 7 Antares (not in the chart)
308 6.5 47 15 Soyuz
333 13.0 26 −7 Falcon 9 v1.0
334 19.0 18 −15 Atlas V
464 8.5 55 22 Long March 2F
506 13.0 39 6 Falcon 9 v1.1
531 19.0 28 −5 H-IIB, Japan
694 21.0 33 0 Proton
733 29.0 25 −8 Delta IV Heavy
777 21.0 37 4 Ariane 5
3000 140.0 21 −11 Saturn V (not in the chart)
Chart: Tons payload to LEO versus tons of rocket on the launch pad.