Maybe i should pose this query in a different area, but since it involves basic physical laws of motion... Space flight? I know this should be obvious enough but i was wondering how a shuttle is capable of maneuvering once in an area with which gravity and atmosphere play too little a part on its movements.. Pressurized propellants such as oxygen have been sighted but there are some issues that need resolved before this is plausible. If the pressurized oxygen, (or anything), being released from a container is allowed to expand at the rate of its release or more, does it then act upon the vessel in such a way as to create momentum? And does the loss of mass from a vessel create a thrust in an opposite direction of the loss if there is no possitive point of inertia to equate to the vessel? These are two questions i seem to have trouble finding an answer that seems plausible.