Kirk's
My question: Is the simplification

--Joel

___Optimal Control Theory___(amazon.com/dp/0136380980) includes some practice examples involving spacecraft control, "neglecting the change in mass resulting from fuel consumption" for simplicity. (To be fair, in a later section -- after introducing inequality constraints on state & control -- he does treat the full lunar soft-landing problem, including the changing system mass.)***ever***reasonable? Are there classes of rocket engines where the consumed fuel comprises so small a fraction of vehicle mass that it can be (to low order) ignored? Nuclear-thermal rockets? Ion drives?--Joel