Curious question : Why do we use the concept of effectors for thrusters, etc? Why can't that also be just a module + message?

[ephraim71]

Say thruster module sends a torque/force message to spacecraft object. And spacecraft object considers that to affect 6DOF.
So the whole simulation basically would just be modules and messages. Right now there is this concept of effectors, what are the advantages that provides over just using messages?