What kinds of Guidance Systems have been tried? Does anything work besides fins?
Guidance, Active vs Passive All hobby rockets, with the exception of the experimental ones described later, are passively stable. They achieve this by the simple expedient of placing the CP behind the CG, which is almost always done with fins. Passive fins are placed at the back of a rocket because that’s where they are needed to provide negative feedback. As much as this sounds bad to the touchie- feelie crowd, negative feedback is simply an engineering term which means that any disturbing forces are fed back into the system in the opposite direction. Thus any force which causes, say, a positive pitch will make the fins generate a negative pitch force to help put it back right. Positive feedback, conversely, causes continued motion in the *same* direction, exemplified by the tight spirals of an unstable rocket where the fins push it further in the direction of the error. I say that passive fins ‘help’ put it back right because, being a passive system, it has no way of knowing which wa
