Re: Something doesn't add up
"ie over 3.3 times the thrust for less than 1.6 times the payload. Why so little increase in payload? are the figures wrong?"
The figures don't greatly surprise me, to be honest. The payload is the smallest part of the package.
If you want to carry more payload you need more engine. And then you need more fuel for both the bigger payload and the bigger engine.
Then you need more fuel to carry the fuel. And more fuel to carry *that* fuel. And more fuel to...
You get the idea - it's turtles all the way down. Eventually somebody round up a decimal point and it becomes enough. But even small increases in payload mass can have a remarkably distorted effect on launch mass.