Unformatted text preview: quot;wrapped" (multiplied by a factor greater than one) to
cover the costs of integration and test, program
management systems engineering, etc. These additional
costs are NASA Systems Engineering Handbook
Systems Analysis and Modeling Issues
called systemlevel costs, and are often calculated as
percentages of the direct costs.
Using Parametric Cost Models. A number of
parametric cost models are available for costing NASA
systems. Some of these are shown in Table 5.
Unfortunately, none alone is sufficient to estimate
lifecycle cost. Assembling an estimate of lifecycle cost
often requires that several different models (along with
the other two techniques) be used together. To integrate
the costs being estimated by these different models, the
system engineer should ensure that the inputs to and
assumptions of the models are consistent, that all
relevant lifecycle cost components are covered, and
that the timing of costs is correct.
The system engineer may sometimes find it
necessary to make some adjustments to model results
to achieve
Learning Curve Theory
The learning curve (also known as the progress or
experience curve) is the timehonored way of
dealing with the empirical observation that the unit
of fabricating multiple units of complex systems like
aircraft and spacecraft tends to decline as the
number increases. In its usual form, the theory
states that as the total quantity produced doubles,
the cost per unit decreases by a constant
percentage. The cost per unit may be either the
average cost over the number produced, or the cost
of the last unit produced. In the first case, the curve
is generally known as the cumulative average
learning curve; in the second case, it is known as
the unit learning curve. Both formulations have
essentially the same rate of learning.
Let C(1) be the unit cost of the first production
unit, and C(Q) be the unit cost of the Qth production
unit, then learning curve theory states there is a
number, b, such that
C(Q) = C(1) Qb
The number b is specified by the rate of learning. A
90 percent learning rate means that the unit cost of
t...
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 Spring '13
 Mr.Kau
 Systems Engineering, The American, ... ...

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