SYSTEMS ENGINEERING THROUGH THE SYSTEM LIFE CYCLE
Modern engineered systems come into being in response to societal needs or because of new opportunities offered by advancing technology, or both. The evolution of a particular new system from the time when a need for it is recognized and a feasible technical approach is identiﬁed, through its development and introduction into operational use, is a complex effort, which will be referred to as the system development process. This chapter is devoted to describing the basic system development process and how systems engineering is applied at each step of this process.
A typical major system development exhibits the following ...view middle of the document...
we follow the structure of the system life cycle, so as to more clearly relate systems engineering functions to their roles in specific periods during the life of the system.
DEVELOPMENT OF A SYSTEMS ENGINEERING LIFE CYCLE MODEL
System life cycle models have evolved significantly over the past two decades.
Furthermore, the number of models has grown as additional unique and custom applications were explored. Additionally, software engineering has spawned a significant number of development models that have been adopted by the systems community. The end result is that there is no single life cycle model that is
(1) Accepted worldwide and
(2) Fits every possible situation.
Various standards organizations, government agencies, and engineering communities have published their particular models or frameworks that can be used to construct a model. Therefore, adopting one model to serve as an appropriate framework was simply not prudent.
Fortunately, all life cycle models subdivide the system life into a set of basic steps that separate major decision milestones. Therefore, the derivation of a life cycle model to serve as an appropriate framework for this book had to meet two primary objectives.
First, the steps in the life cycle had to correspond to the progressive transitions in the principal systems engineering activities. Second, these steps had to be capable of being mapped into the principal life cycle models in use by the systems engineering community. The derived model will be referred to as the “ systems engineering life cycle,”
D o D Acquisition Management Model.
In the second half of the twentieth century, the United States was in the forefront of developing large - scale complex military systems such as warships, airplanes, tanks, and command and control systems. To manage the risks in the application of advanced technology, and to minimize costly technical or management failures, the DoD has evolved comprehensive system acquisition guidelines, which are contained in the DoD 5000 series of directives. The fall 2008 version of the DoD life cycle model, which reflects the acquisition guidelines, is displayed in Figure below.
It consists of five phases: material solution analysis, technology development, engineering and manufacturing development, production and deployment, and operations and support. The two activities of user need determination and technology opportunities and resources are considered to be part of the process but are not included in the formal portion of the acquisition cycle.
The DoD model is tailored toward managing large, complex system development efforts where reviews and decisions are needed at key events throughout the life cycle.
The major reviews are referred to as milestones and are given letter designations: A,
B, and C. Each of the three major milestones is defined with respect to entry and exit conditions. For example, at milestone A, a requirements document needs to be approved by a military oversight...