a next step is to write altitude specifications

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Unformatted text preview: e such that there are always at least TBD days to reentry," "collision avoidance maneuvers shall always increase the altitude," "reboost only after resupply flights that have brought fuel," "rotate the crew every TBD days." • A next step is to write altitude specifications. These choices might consist of replacing the TBDs (values to be determined) in the altitude strategy with explicit numbers. • Monthly operations plans are eventually part of the complete system design. These would include scheduled reboost burns based on predictions of the accumulated effect of drag and the details of on-board microgravity experiments. • Actual firing decisions are based on determinations of the orbit which results from the momentum actually added by previous firings, the atmospheric density variations actually encountered, and so on. Note that decisions at every step require that the capabilities offered by available technology be considered—often at levels of design that are more detailed than seems necessary at first. pabilities definition spiral moving in the opposite direction. The concepts can never be created from whole cloth. Rather, they result from the synthesis of potential capabilities offered by the continually changing state of technology. This process of design concept development by the integration of lower-level elements is a part of the systems engineering process. In fact, there is always a danger that the top-down process cannot keep up with the bottom-up process. There is often an early need to resolve the issues (such as the system architecture) enough so that the system can be modeled with sufficient realism to do reliable trade studies. When resources are expended toward the implementation of one of several design options, the resources required to complete the implementation of that design decrease (of course), while there is usually little or no change in the resources that would be required by unselected alternatives. Selected alternatives thereby become ev...
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This document was uploaded on 02/26/2014 for the course E 515 at University of Louisiana at Lafayette.

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