A momentum management system for attitude control of a spacecraft includes a housing to be fixed to the spacecraft and a momentum wheel rotor in the housing for storing angular momentum. In some examples, data may be categorized as frequently used and stored at an information technology system testing system. With the present invention, the user’s message interaction preferences are determined, and the current message can be replied automatically, thereby enhancing user experience. ACF generation and use can be specified by the programmer. Accessing of data from the data file includes the controller executing an internal application. Providing precise control of liquid depth over the vertically stationary platform as well as focusing of a laser beam for curing the liquid at the varying surface levels thereof relative to the vertically stationary platform is effected using a laser range finder system controlled by a computer used to control the stereolithographic process in a closed loop fashion.