The RCS system as it stands has also been, umm, sugaring me to tears... My biggest annoyance is that it doesn't seem to have any concept of zero-torque translations - attach a tiny tug to one end of a big, dumb long thing (e.g. a stack o' big fuel tanks), and thrust "up", and it just sets you tumbling. Various tutorials suggest placing your thrusters symmetrically about the centre of mass, but no, just NO. - this is SPACE, and that's just silly in this context. Leverage - it's not rocket science (well...), it's primary school science... This scenario: V 10N |------------------------------| |--------------0---------------| |------------------------------| ------/\ 20 N yields 10N in the upwards direction, and no torque. You'd think this would be what happens when you're in docking mode and press shift for 'up', but apparently 'up' actually just means 'fire all thrusters that point down', which is, as previously noted, just silly. Looking at the MechJeb 2 source, they have code for an 'RCS balancer', which sets RCS throttles individually - so, it's not too hard to do. The algorithm implemented, however, is currently pretty poor though - better can be done. On the question of quaternions - yes, they can be used to model either a change in direction only or a change in direction and roll. I'm going to try putting together a better 'balancer', which allows angular control with or without net linear effects, and linear control without angular effects (as per the lever above). Other things I'd like to do / have in an RCS system: - Angular velocity limiter - all that wasted monoprop trying to swing a ship around as fast as mechanically possible makes my inner dolphin cry. - better handling of rate and direction when performing a large maneuver, e.g. a PID for movement along the shortest path, and a damper (just the 'D' of a PID) for movement perpendicular, so the perpendicular error can damp out early, leaving the ship headed towards the right direction. Currently it appears to be treated as a single-axis system, just thrusting 'towards' or 'away from' the target, resulting in some nasty seeking behaviour (e.g. spiralling around the target). One thing which I'm not sure about either is getting the moment of inertia (not that it matters for my immediate purposes) - the Vessel class (in Assembly-CSharp.dll) has a "Vector3 MOI", but I don't see the principal axes anywhere - they could just be using moments about the x, y, and z axes, but that's not just wrong, it's wronggitty wronggity wrong - I choose to think better of the devs, but I'm not sure where to look.
