Schedule Module Space Systems Engineering, version 1.0

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Schedule Module Space Systems Engineering,
version 1.0

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Module Purpose Schedule

• To understand the different types of schedules
  Gantt chart, milestone chart, network schedules.
  To recognize their advantages and disadvantages.
• To introduce the key concepts of critical path
  and float as applied to network scheduling.
• To show how to prepare a schedule and estimate
  activity durations.
• To introduce schedule margin recommendations.
• To discuss example schedule performance measures
  and reporting formats.

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The When Project Schedule

• Provides a framework of time-phased and
  coordinated activities which represent the plan
  for completing the project within established
  constraints.
• Used
• To integrate all elements of a project as a
  function of time and flow
• As a communication tool across the project team
• As a basis for assessing project status
• For project management control
• Key inputs
• The work breakdown structure (WBS)
• External constraints (such as imposed launch
  date)
• Required milestones (such as technical reviews)
• Major deliverables
• Imposed funding profiles (can only get so much
  done for X)

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Scheduling Approaches

• Gantt chart A graphic portrayal of a project
  which shows the activities to be completed and
  the time to complete represented by horizontal
  lines drawn in proportion to the duration of the
  activity.
• Milestone chart A graphic portrayal of a project
  that shows the events to be completed on a
  timeline.
• Network scheduling
• Critical Path Method (CPM) A graphical technique
  that aids understanding of the dependency of
  events in a project and the time required to
  complete them.
• Program Evaluation and Review Technique (PERT) A
  technique based on constructing a network model
  of integrated activities and events. Difference
  from CPM uses statistical theory and probability
  to make a determination of duration time for each
  task and the likelihood of an event being on
  schedule.

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Gantt Chart Formataka Bar Charts
Gantt and milestone charts are best used for
displaying the planned activities and events of a
project and the progress in meeting them. This
makes them very useful for presenting schedule
and program status information in a concise
simple format at such things as program or
activity reviews. Because of its simplicity and
ease of interpretation, it is a particularly good
tool for communicating to higher management when
information must be presented quickly and
efficiently.
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Example Milestone Chart
Pre-formulation
0 Complete
Phase A
100 Complete
Phase B
FY05
FY06
FY07
FY08
FY09
FY10
FY11
FY12
FY13
Flight Test/Mission Milestones
ISS-2
UCM-1
RRF-2
ISS-1
RRF-3
RRF-1
PC-1
PC-2
ISS-3
Program Integration
Pre-NAR Kickoff
Pre-NAR Complete
PDR Complete
CDR Complete
NAR
L1 Req Baseline Review
L2 SRR Complete
L2 SDR
CEV SRR
ATP
SDR
PDR
CDR
CEV
Contractor 12 SRR
Del for RRF-1
Del for RRF-3
Del for ISS-1
Del for PC-1
Del for LAS-1
Del for LAS-2
Del for LAS-2
Del for LAS-3
Delivery of Crew Service Module
Unpressurized payload structure
Del for RRF-2
Del for LAS-4
Del for RRF-1
Del for RRF-3
Del for RRF-2
Del for ISS-1
Delivery of Launch Abort System
Del for LAS-4
CLV
Govt Lead
SRR
CDR
PDR
System Engineering Integration
Jul
Feb
Jun
Del for RRF3
Del for RRF-1
ATP
SRR
PDR
CDR
First Stage
Del ISS1 to KSC
Del for RRF2
Del for RRF3
Govt Lead
SRR
PDR
CDR
MPTA
Del for US ISS-1 to KSC
Upper Stage
Fab, Integ Test
Del for RRF2
Jul
Nov
Apr
Dev Eng Needed
Del for RRF3
CDR
MPTA
ATP
SRR
PDR
Del for ISS-1
Upper Stage Engine (RS-25d/e)
Del for RRF2
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Milestone or Event Charts

• Key features
• Displays activity milestones against time.
• Lines represent duration of a single activity
  with appropriate start and stop milestones.
• Open triangles indicate milestones planned.
• Closed triangles indicate milestones completed.

Example Symbols Used on Milestone Charts
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Gantt Milestone Charts

• ADVANTAGES
• Simple to prepare and update,
• Information portrayed in easily understood
  format,
• Relatively inexpensive to prepare using software
  tools,
• Relate activities and calendar dates,
• Easy to roll up information into summary form,
• Useful first step for preparation of more complex
  type schedules
• Reliable estimates can be developed when the work
  is repetitive and when the product is easy to
  measure quantitatively.

• DISADVANTAGES
• Difficult to use for detailed schedule analysis
• Do not show the effects of late or early activity
  starts,
• Do not represent dependencies among activities as
  well as other scheduling methods
• Do not reflect the uncertainty in the planned
  activity duration or event date
• Only as reliable as the estimates on which they
  are based looking at the chart doesnt indicate
  which estimates are the most reliable
• Do not allow quick or easy exploration of the
  consequences of alternative actions.

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Example Network Schedule for Computer
Installation Program

• Network schedule data consists of
• Activities
• Dependencies between activities
• Milestones that occur as a result of one or more
  activities
• Duration of each activity

• Activity Legend
• A - Build raised floor
• B - Build air conditioning vents
• C - Bring special power source to computer room
• D - Install wiring and connect to power source
• E - Install air conditioning
• F - Await delivery of computer
• G - Install computer

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Example Critical Path and Float

• Critical Path is the sequence of activities that
  will take the longest to accomplish. Any delay on
  this path will delay the project.
• Example 14 days,
• Activities that are not on the critical path have
  a certain amount of time that they can be delayed
  until they, too are on the critical path. This
  time is called float (or slack).
• Example, Path 1 9 days gt 5 days of float
• Example, Path 2 13 days gt 1 day of float

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Time Estimates Used in PERT
Using PERT, it is possible to determine an
expected time for completion of a project and the
likelihood (probability) that this expected
completion time will be met. Projects best suited
for PERT are one-of-a-kind complex programs that
involve new technology or processes and research
and development.

• Three estimates are required
• Most Likely, m
• Optimistic, a
• Pessimistic, b
• Expected completion time, or mean time
• te a4mb
• 6

b
m
a
Beta Probability Distribution
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Network Schedules

• ADVANTAGES
• Provide graphical portrayal of project activities
  and relationships/constraints
• Force communications among team members in
  identifying activities
• Organize what would otherwise be confusing
  material, making it easier for managers to make
  tradeoffs and develop alternative plans
• Give managers more control over activities/events
  and schedules
• Facilitate what if exercises
• Provide the basis for Gantt and milestone chart
  information

• DISADVANTAGES
• Network construction can be difficult and time
  consuming.
• Only as sound as the activity time and resource
  estimates.
• Sometimes difficult to portray graphicallytoo
  many lines, nodes and intersections.
• Not particularly good for conveying information
  in briefings/reviews.
• Complex networks, once sketched out on a large
  wall chart, tend to become the focus of
  management attention when, in fact, a manager
  should be paying attention to factors not on the
  chart, such as management/ labor relations.

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Schedule Preparation

• A five-step process for schedule preparation that
  is commonly used in project management includes
• Activity definition - what has to be
  accomplished?
• Activity sequencing - what has to occur first,
  second?
• Activity duration estimation - how long does
  activity take?
• Schedule development - what are realistic start
  finish dates?
• Schedule control - how to manage changes
  track performance?
• Risk is inherent in all programs, and scheduling
  is one element of risk. Uncertainty introduced
  in estimating the duration of each activity
  causes most schedule risk. Project managers must
  assess the likelihood of failing to meet schedule
  plans and the impact of that failure.
  Probabilistic techniques have proven to be very
  useful in conducting these assessments.

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Activity Duration Estimating

• Activity duration estimating is the determination
  of the time required to complete the activities
  that make up the project.
• This is one of the most difficult aspects of
  schedule development and should be performed by
  people who are most familiar with the activity.
• Two key inputs to the estimation process
• the resources/workforce required and assigned for
  the activity
• the capabilities of the resources assigned.
• The following techniques are commonly used in
  estimating activity durations
• Expert judgment guided by historical information,
  
• Analogous estimating based on experience of
  similar programs,
• Parametric estimating based on formulas
  describing relationships among project parameters
  and time, and
• Use of simulation to develop distributions of
  probable duration of each activity.
• Note If probability distributions not used,
  then estimates should include a range of possible
  values, e.g., 3 weeks 1 week, and a clear
  statement of the assumptions made in the
  estimation process.

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Schedule Margin
Definitions Total Schedule Critical Path
(i.e., Planned Activities) Schedule
Margin Schedule Margin No Planned Activities,
but Funded Schedule Schedule Margin Rate
Schedule Margin/(Planned Activity Schedule
Margin)
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Additional Schedule Materials

• Next few slides
• Technical Performance Measures
• Schedule examples for James Webb Space Telescope
  (JWST)
• Resource Loaded Schedules

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(No Transcript)
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PROJECT TREND ANALYSIS


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Resource Loaded Schedules

• Important to do
• Assure no resource conflicts
• Staff being assigned efficiently
• Minimize gaps for engineering personnel (EPs)

Months
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Schedule
C
Project Complete
Resources Required
1) Eng EPs -- Act A -- Act B
-- Act C -- Act D -- Act E --
Act F -- Act G -- Act H 2) Mfg/Test
EPs -- Act A -- Act B -- Act C
-- Act D -- Act E -- Act F
-- Act G -- Act H 3) Test Facilities
-- Act A -- Act B -- Act C --
Act D -- Act E -- Act F -- Act
G -- Act H
3 3 - - - - - - - 1 1 - - - - - - - - - - - - -
- - -
3 3 - - - - - - - 1 1 - - - - - - - - - - - - -
- - -
5 - 3 - - - 2 - - 2 - 1 - - - 1 - - - - - - - -
- - -
5 -3 - - - 2 - - 2 - 1 - - - 1 - - - - - - - - -
- -
3 - - 2 - - - 1 - 12 - - 7 - - - 5 - - - - - - -
- - -
3 - - 2 - - - 1 - 12 - - 7 - - - 5 - - - - - - -
- - -
3 - - 2 - - - - 1 10 - - 7 - - - - 3 1 - - - - -
- - 1
2 -- - 1 - - - 1 7 - - - 4 - - - 3 2 - - - 1 - -
- 1
1 -- - 1 - - - - 4 - - - 4 - - - - 1 - - - 1 - -
- -
1 -- - 1 - - - - 4 - - - 4 - - - - 1 - - - 1 - -
- -
1 -- - - 1 - - - 4 - - - - 4 - - - 1 - - - - 1 -
- -
1 -- - - 1 - - - 4 - - - - 4 - - - 1 - - - - 1 -
- -
- -- - - - - - - - - - - - - - - - - - - - - - -
- -
- -- - - - - - - - - - - - - - - - - - - - - - -
- -
- -- - - - - - - - - - - - - - - - - - - - - - -
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- -- - - - - - - - - - - - - - - - - - - - - - -
- -
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Module Summary Schedule

• There are different methods for displaying
  project schedule information.
• Gantt and Milestone charts relate activities to
  calendar dates in an easily understood format.
• Network schedules show the dependencies between
  activities in a graphical portrayal with activity
  durations.
• Critical Path is the sequence of activities that
  will take the longest to accomplish. Any delay on
  this path will delay the project. Activities that
  are not on the critical path have a certain
  amount of time that they can be delayed until
  they, too are on the critical path. This time is
  called float (or slack).
• There is inherent risk in developing schedules.
  Probabilistic techniques can be used to assess
  the risk.
• For space missions, guidelines exist for
  determining schedule margin.
• Schedule information, such as the accomplishment
  of milestones or the amount of schedule slack,
  can be used to report project status/progress (as
  a form of technical performance measures).

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Backup Slidesfor Schedule Module
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Additional Schedule Topics

• Additional topics if you are interested in adding
  to the lecture
• Earned Value Management (EVM)
• A tool for measuring and assessing project
  performance through the integration of technical
  scope with schedule and cost objectives during
  the execution of the project. EVM provides
  quantification of technical progress, enabling
  management to gain insight into project status
  and project completion costs and schedules. Two
  essential characteristics of successful EVM are
  EVM system data integrity and carefully targeted
  monthly EVM data analyses (i.e., risky WBS
  elements).
• One can dedicate an entire lecture just on EVM.
  Note that many contractors and government
  agencies have entire courses devoted to teaching
  EVM.
• Schedule Software Tools, such as
• Microsoft Project
• Primavera

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Network Schedule Example
In this example, the lines represent project
activities A through H the nodes represent the
events associated with the beginning and end of
the activities. The network shows the following
constraints among the activities activity A must
be completed before activities B, C, or D can
begin B must be completed before E can begin F
cannot begin until D is completed G cannot begin
until C and E are done, and H cannot begin until
F and G are completed. In addition to showing
this type of sequencing constraints, network
schedules can also show the time and resources
planned for each activity and thus provide
managers with a mechanism to monitor and control
the project.
H

• Network schedule data consists of
• Activities
• Dependencies between activities
• Milestones that occur as a result of one or more
  activities
• Duration of each activity

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Example Milestone Chart