I am not really solving an exercise for homework so hopefully this general forum is OK for my question. For my thesis, what is attitude control of a flying object with a reaction wheel, I am learning the basics from this NASA Technical Report: http://www.hot.ee/ronn/design_glob_anal_spacecraft_att_control.pdf [Broken] (I mirrored it because currently NASA website publishing this is down) Things are quite clear to me until eq (22) in PDF page 20, where the 3rd term is "gyroscopic coupling". I am unfamiliar with this phenomenon and can not grasp it from the equation. Could someone please explain me the meaning of this term? I do not see how can change of angular velocity depend only in the current velocity. Is it somehow the same thing as precession?