How much kinetic energy does a given launch give its payload?
Could all launches be fairly lined up according to one single scalar representing how much kinetic energy they have actually delivered to their payloads? From launch pad to whatever trajectory the payload ends up in.
Popularly, mass to low Earth orbit or mass to geosynchronous orbit are used to classify rockets. But those figures depend on many assumptions and circumstances that vary since no payloads or orbits or launch sites or launcher configurations and on and on are all ever the same. Is there any simple measure of much kinetic energy a launch event in the end actually has transferred to its payload? (Or any better idea on the same line). Rocketry is like all other shipping about only three things. Relocation relocation relocation. But what's the bottom line?
I don't think you can avoid the specifics and still end up with a better metric than 'mass to low Earth orbit or mass to geosynchronous orbit'.
For one, launcher performance depends on orbit. See for instance this question that compares a few launchers. The difference in payload changes a lot depending on the target orbit. So the orbit has to be part your metric.