system
Given the following post, respond as if you're commenting on Reddit:
human
What is the trade-off that requires astronauts to be able to withstand several Gs during launch?

I know about escape velocity, but in my mind it doesn't help much in knowing about the acceleration during launch, especially why the acceleration couldn't be made less. As a side question, how much as far as Gs during launch does it matter if we are headed to LEO or headed to the moon or beyond?
gpt
It's a matter of efficiency. Consider the following thought experiment: What if you have a rocket that can just barely accelerate under gravity (it provides enough thrust to fight gravity, and just a little more)?  After 10 seconds, it has only picked up a few m/s of velocity, but it has spent 10 seconds worth of fuel fighting gravity. By the time you reach orbital velocity (or escape velocity, or whatever velocity you want), you will have to have spent a great deal of fuel just resisting gravity.

Now consider a high-g acceleration rocket. If it accelerates at 4G, then 1G goes to countering gravity and 3G goes to increasing velocity. It needs less time to reach the desired velocity, so it doesn't have to fight gravity for as long (once you are in orbit, you don't need to fight gravity any more).

A high acceleration rocket is much more efficient for liftoff. Once you're in orbit, it doesn't matter as much (for reasons I'll skip for the time being), so there are other factors that determine efficiency in orbit. But for liftoff, higher accelerations are more efficient (until you reach the point where atmospheric friction becomes significant, but that's another problem), regardless of final destination.