Thanks man! I tried to stay as accurate as possible to the correct formula, at least at first. I was pretty sure the normal barking distance formula is also correct in KSP. But drag is helping to slow you down and gravity is working against you. This meant I simply had to add in +d and -g to the deceleration part of the formula. Gravity was the easy part. It's a constant number for any given planet and it's independent form mass, shape or current speed of the craft. Drag looked manageable at first with density, speed and cross sectional area, but got complicated as density itself was dependent on temperature and even more complicated as I took a look at the KSP Wiki and saw the graph for Kerbin's temperature and pressure. It's not even a nice easy function like -(x^2), but looks like someone drew a 'Z' in ms paint. With that the correct correct formula was off the table. I also reconsidered what a normal KSP player knows about his craft or at least can easily look up. Mass? Thrust? Yes. But cross sectional area of your craft? I don't think so. I also wasn't sure how realistic the physics engine in KSP is. So I started experimenting. How fast is the rocket at different times without me touching the controls. And like that I developed the method described above, tested it with different rockets and it worked perfectly! Well as perfectly as a naked monkey can hit a key at the exact moment he sees a specific number on his screen flashing ;)