p.24 A systems engineer should have a creative bent and must like
to solve practical problems... The following characteristics are commonly found in successful systems engineers.
They
1. Enjoy learning new things and solving problems
2. Like a challenge
3. Are skeptical of unproven assertions
4. Are open minded to new ideas
5. Have a solid background in science and engineering
6. Have demonstrated technical achievement in a specialty area
7. Are knowledgeable in several engineering areas
8. Pick up new ideas and information quickly
9. Have good interpersonal and communications skills
p.25 a systems engineer does not need to spend a lifetime becoming
an expert in associated disciplines, but rather can accumulate a working knowledge of related fields through selected readings,
and more particularly, discussion with colleagues knowledgeable in each field. The important thing is to know which
principles, relationships, acronyms, and the like are important at the system level and which are details. The power
of multidisciplinary knowledge is so great that to a systems engineer the effort required to accumulate it is well worth the
learning time.
The Power of Approximate Calculation
The practice of systems engineering requires another talent besides multidisciplinary knowledge. The ability
to carry out "back of the envelope" calculations to obtain a "sanity check" on the result of a complex calculation or
test is of inestimable value to the systems engineer... Most systems engineers have the ability, using first principles,
to apply basic relationships, such as the communications equation or other simple calculation, to derive
an order of magnitude result to serve as a check.
p.27 A system is a set of interrelated components working together toward a common objective.
A complex engineered system (as defined in this book) is:
Composed of a multiplicity of intricately interrelated diverse elements.
Requires systems engineering to lead its development.
p.32 the technique of modeling is one of the basic tools of systems engineering,
especially in circumstances where unambiguous and quantitative facts are not readily available.
p.47 System building block models can be useful in:
Identifying actions capable of achieving operational outcomes
p.50 A typical major system development exhibits the following characteristics:
- It is a complex effort
- It meets an important need
- It usually requires several years to complete
- It is made up of many interrelated tasks
- It involves several different disciplines
- It is usually performed by several organizations
- It has a specific schedule and budget
p.57-58 The needs analysis phase defines the need for a new system. It addresses the questions:
"Is there a valid need for a new system?" and "Is there a practical approach to satisfying such a need?" These questions require
a critical examination of the degree to which current and perceived future needs cannot be satisfied by physical or operational
modification of available means, as well as whether or not available technology is likely to support the increased capability
desired.
p.58 Concept Exploration Phase This phase examines potential system concepts in answering the questions: "What
performance is required of the new system to meet the perceived need?" and "Is there at least one feasible approach to
achieving such performance at an affordable cost?"
p.58 Concept Definition Phase The concept definition phase selects the preferred concept.
It answers the question: "What are the key characteristics of a system concept that would achieve the most beneficial balance
between capability, operational life, and cost?" To answer this question a number of alternative concepts must be
considered and their relative performance, operational utility, development risk, and cost must be compared.
p.83 When a new design approach is undertaken it is unwise to wait until the design is fully
implemented before determining whether or not the approach is sound. Instead, testing should first be done on a theoretical
or experimental model of the design element, which can be created quickly and at minimum cost.
p.135 The principal objective of the concept exploration phase, as defined here, is to convert the operationally
oriented view of the system derived in the needs analysis phase into an engineering-oriented view required in the concept
definition and subsequent phases of development. This conversion is necessary to provide an explicit and quantifiable basis
for selecting an acceptable functional and physical system concept, and then guiding its evolution into a physical model of
the system... As in the case of operational requirements, the derivation of system performance requirements must also simultaneously
consider system concepts that could meet them. However, to ensure that the performance requirements are sufficiently
broad to avoid unintentionally restricting the range of possible system configurations, it is necessary to conceive not one,
but to explore a variety of candidate concepts.
p.145 Guidelines for Defining Alternative Concepts [section title] As noted
in the next section, conceiving new candidate approaches to satisfying a set of requirements is an inductive process,
and hence requires a leap of the imagination. For such a process it is helpful to postulate some guidelines for selecting
alternatives:
1. Start with the existing (predecessor) system as a baseline
2. Partition the system into its major subsystems
3. Postulate alternatives that replace one or more of the subsystems essential to the mission with an advanced,
less costly, or otherwise superior version
4. Vary the chosen subsystems [or superior system] singly or in combination
5. Consider modified architectures, if appropriate
6. Continue until you have a total of four to six meaningful alternatives.
p.154 the objective of exploring implementation concepts is to consider a sufficient variety of
approaches to support the definition of a set of system performance requirements that are feasible of realization
in practice and do not inadvertently preclude the application of an otherwise desirable concept. To that end the exploration
of system concepts needs to be broadly based.
Alternative Implementation Concepts
The predecessor system, where one exists, forms one end of the spectrum to be explored. Given the operational
deficiencies of the predecessor system to meet projected needs, modifications to the current system concept should first be
explored with a view to eliminating these deficiencies. Such concepts have the advantage of being relatively easier to assess
from the standpoint of performance, development, risk, and cost than are radically different approaches... The other end of
the spectrum is represented by innovative technical approaches featuring advanced technology.
p.409 Another powerful strategy for dealing with decisions in the face of complexity and uncertainty is
the use of modeling throughout the system development process. In broad terms, modeling is used to focus on particular key
attributes of a complex system and to illuminate their behavior and relationships apart from less important system characteristics.
The objective is to reveal critical system issues by stripping away properties that are not immediately concerned with the
issue under consideration. Simulation is the modeling of dynamic behavior. Trade-off analysis is the modeling of decisions
among alternatives.
p.419 Approximate calculations represent the use of mathematical models, which are abstract representations
of selected functional characteristics of the system element being studied. Such models capture the dominant
variables that determine the main features of the outcome, omitting higher-order effects that would unduly complicate
the mathematics. Thus, they facilitate the understanding of the primary functionality of the system element.
