Fractionation enables responsive space systems and potentially increased value delivery in life cycle of the space systems in face of various uncertainties such as component failure, vulnerability to external and environmental risks such as meteorite impact and object collision, irregular radiation etc. Fractionation also creates the potential of upgradability of the spacecraft payloads in operational lifecycle by replacing one or more fraction(s). The redesign cost of a fraction and its potential value for the fractionated space system is subject of this paper. In this research, we provide a model to examine the upgradability value associated with different fractionation types. Our approach is based on using the Design Structure Matrix (DSM) and a measure of module complexity. The cost of upgrading a module (or fraction) depends on the redesign effort of the replacement module, and deployment cost. The redesign cost of a module is proportional to the functional complexity of the unit, and the level of fraction's coupling to other fractions in the system. We present a fractionation design decision tool for upgradability and evolvability optimization of space systems. We examine the sensitivity of the model to stakeholders requirements uncertainty and have observed that fractionation (and modularization of general systems) is recommended to be done with extreme caution. In short this paper is an attempt to uncover the simple rules governing Fractionation of the systems to deliver and optimal evolvability value.
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