Pretty sure Continuum just uses a simple linear interpolation... When someone lags out (or goes through a jump gate in Hyperspace), the ship just continues to float at a constant speed, whether or not you were thrusting in a direction. And emm... This is extrapolation, btw, not interpolation The tricky part, in my opinion, is to consider the future ship bounces in the extrapolation, so you don't predict someone will go through a wall.