16.842
Fundamentals
of
Systems
Engineering
Master
Solution
Mid­Term
Exam
Olivier
de
Weck
10/16/2009
10/16/2009
1. Please provide a succinct definition of Systems Engineering (in your own words):
Systems
Engineering
is
a
disciplined
approach
for
turning
customer
requirements
into
functioning
products
and
systems
that
meet
or
exceed
these
requirements.
This
approach
consists
of
a
coherent
set
of
methods
and
tools
that
map
functionality
to
components
of
form,
while
carefully
managing
interfaces
between
parts.
Systems
engineering
should
place
particular
emphasis
on
human
factors
and
safety.
2. The following activities are included as part of Systems Engineering (multiple
correct answers, check all that you think are correct)
Managing
the
interfaces
between
various
components
Analyzing
test
data
to
diagnose
a
complex
vibration
problem
Ensuring
that
the
displays
in
the
cockpit
are
user
friendly
Tracking
the
gross
takeoff
weight
(GTOW)
of
an
aircraft
during
design
Identifying
potential
failure
modes
of
the
system
3. You are asked to select from the following set of concepts that are characterized
by two performance metrics J1 and J2. We will use the notation "X(2.1,3.2)" to
indicate that concept X performs at a level of 2.1 for J1 and 3.2 for J2. Assume that
we want to maximize both J1 and J2. The concepts are as follows: A(1.5, 2.2),
B(1.6, 1.5), C(2.0, 1.0), D(3.0, 0.2), E(1.6,1.0), F(1.0, 1.0), G(0.5, 2.0), H(0,2.5).
Which of these concepts are strongly dominated?
F
G
4. Which of the concepts are weakly dominated?
E
F
G
5. Note: the following 5 questions are taken from the 2003 Vehicle Design
and Performance doctoral qualifying exam at MIT Aero Astro Caution: There is not a single correct answer to this question. - Be as quantitative as
you can. - Be brief and succinct. Don't spend more than 45 minutes. It is
more important to answer all questions somewhat, than to dwell extensively
one only one or two. - Demonstrate your ability to think like a vehicle
designer or systems engineer. - - - Imagine a Mars surface mission rover
(see here for an image: http://www-robotics.jpl.nasa.gov/images/mslRover540.jpg) that carries a research laboratory to a variety of sites and
communicates scientific measurements back to Earth. 1) Perform a firstlevel functional decomposition of this system.
Sensing
Data
Processing
Communicating
Navigating
Transporting
Self‐Testing
2) List subsystems that are important in the design, clearly rank their relative
importance in determining performance and cost and briefly explain why.
Instruments
Power
Source
Avionics
Software
Antenna
Camera
Mast
Robotic
Arm
Body
Suspension
Wheels
These
10
subsystems
are
a
rough
decomposition
of
the
rover
by
form.
They
are
listed
in
rough
order
of
importance,
even
though
this
cannot
really
be
done
since
all
these
subsystems
are
essential
and
the
failure
of
any
one
of
them
can
lead
to
total
mission
failure.
The
key
to
delivering
value
though
is
the
flow
of
information
from
the
scientific
instruments
to
the
avionics/software
and
back
to
Earth
through
the
antenna
system.
All
of
the
subsystems
contribute
to
cost
in
various
amounts.
The
flight
software
has
become
a
major
cost
driver
and
can
make
up
>20%
of
mission
cost.
The
instruments
are
also
a
major
cost
driver.
3) Map the functions you determined in 1) to the subsystems from 2). Which
subsystem carries out what functions?
Sensing
>
requires
>
instruments,
avionics,
power
source,
camera
mast,
body
Data
Processing
>
requires
>
avionics,
power
source,
software
Communicating
>
requires
>
avionics,
power
source,
antenna
Navigating
>
requires
>
antenna
mast,
avionics,
power
source,
software
Transporting
>
requires>
wheels,
suspension,
body,
power
source
avionics
Self‐Testing
>
requires
>
avionics,
power
source
Clearly
this
is
only
a
partial
mapping,
but
it
hints
at
the
complexity
of
this
system.
4) Define a set of quantitative metrics that can be used to formulate requirements.
Science
data
bandwidth
(bits/sec)
Spatial
and
spectral
sampling
rate
(1/sec,
1/m)
Range
(m)
Terrain
features,
e.g.
max
slope
(deg)
Lifetime
(sols)
5) From among two or three sub-systems listed in 2) define a trade-off situation.
What is the most important tradable parameter and how do cost, performance, and
your metrics in 4) change as this parameter is varied?
There
is
a
tradeoff
between
science
bandwidth
(amount
of
data
collected)
and
range.
Collecting
more
science
data
will
require
more
capable
and
therefore
heavier
and
power‐intensive
instruments.
The
larger
the
instruments,
the
less
range
will
be
available
for
a
given
total
rover
mass,
since
motors,
wheels
and
the
power
will
have
to
be
sized
smaller
to
fit
within
the
overall
mass
constraint.
Thus
one
could
build
a
quasi‐static
rover
with
very
capable
instruments
or
a
sprinter/long‐range
rover
optimized
for
mobility
with
simpler
instruments.
The
exact
tradeoff
requires
a
more
detailed
rover
model.
Given
such
a
model
one
could
tradeoff
1km
of
range
versus
X
GBytes
of
science
return.
6. Enter your analysis of the JPL image below.
Spirit
has
been
stuck
in
a
sand
dune
at
Mars
since
May
2009.
The
image
shows
a
web
URL:
http://www.jpl.nasa.gov/freespirit/
During
its
first
90
day
mission
the
rover
was
operated
within
its
requirements/design
envelope.
Then
during
the
extended
operations
the
team
became
more
aggressive
and
started
operating
the
rover
outside
the
guaranteed
(conservative)
operating
envelope
in
terms
of
slope
(the
slope
here
is
about
11
degrees
which
exceeds
the
requirement
of
10
degrees),
soil
properties
etc...
This
is
not
a
failure
of
system
engineering
since
the
primary
mission
objectives
were
met,
but
shows
the
challenges
of
operating
a
vehicle
outside
its
design
envelope
as
defined
by
the
requirements.
7. What are the main flaws in Figure 4.4-2 of the NASA Systems Engineering
Handbook (p. 56) compared to a standard view of the spiral development process?
The
process
should
start
inside
and
spiral
outwards,
indicating
successively
larger
effort
with
each
iteration
There
should
be
specific
milestones
shown
as
the
radial
lines
8. Read the following article about the Future Imaging Architecture (FIA) program to
replace aging intelligence ('spy') satellites for the National Reconnaissance Office
(NRO). This program has been called by some the greatest failure of systems
engineering in the last decade. Do you agree? List the two most problematic parts of
the FIA program based on what you have learned about systems engineering in
16.842 (16.899) so far. Keep your answer to 200 words.
http://www.globalsecurity.org/intell/systems/fia.htm
The
two
main
problems
with
FIA
from
a
systems
engineering
perspective
were:
1.
The
requirements
for
the
new
system
were
too
aggressive
(>
10x
improvement)
compared
to
the
current
state
of
the
art.
Rather
than
evolving
the
system
based
on
current
capabilities,
a
utopian
system
was
required
that
no
one
knew
how
to
build
within
cost
and
budget
constraints.
2.
Stakeholder
alignment
and
conflicts
of
interest.
The
main
contractor
(Boeing)
might
have
been
quite
aware
early
on
that
this
was
an
infeasible
project,
but
proceeded
with
the
project
anyway
to
ensure
a
flow
of
work
and
increasing
contractual
scope,
despite
the
high
levels
of
technical
and
programmatic
risk.
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16.842 Fundamentals of Systems Engineering
Fall 2009
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