Hi, So I recently started to wonder two things: 1. If the Oberth effect causes your burns to be more effective at higher speeds, why does everyone burn at apogee, when the speed is lowest? Wouldn't burning when you're lower/deeper in the gravity well be more effective? 2. Why does a rocket with one engine go farther than a rocket with three engines? I tested this just now. I put a rocket with one engine and a rocket with one engine on a rocket that would carry it to an altitude of 70km (to avoid the atmospheric drag getting in the way). To my surprise, the rocket with three engines (tricoupler -> three aerospikes) got to ~2 million meters, while the rocket with one engine escaped kerbin's gravity! I guess what I'm trying to ask is, why does the three-engine rocket have a lower dV than the rocket with a single engine? Thanks!
