NASA Technical Reports Server (NTRS) 19930015492: What is a system? NASA's phased project description

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WHAT ISA SYSTEM?
WHAT IS A SYSTEM? NASA's PHASED PROJECT / 7,3
DESCRIPTION
From the MSFC Systems Engineering Handbook (1991) _ -_ / _J
Systems engineering is defined in MIL-STD- • Many hardware and software systems in
499A as concurrent development
• . . the process(es) required to trans- • Complex operational and logistic support
form an operational need into a requirements
description of system performance • Constrained development time
parameters and a system configuration • High level of advanced technology
through the use of an iterative process (Systems Engineering Management
of definition, synthesis, analysis, de- Guide, U.S. Government Printing Office,
sign, test and evaluation. It includes 1986).
the integration of related technical
parameters and ensures compatibility There are many definitions of a system. Two
of all physical, functional, and program of these are listed below:
interfaces in a manner that optimizes
the total system definition and design. A system is a set of interrelated compo-
In addition, systems engineering nents working together toward some com-
integrates reliability, maintainability, mon objective. (Blanchard, Benjamin S.
safety, survivability, and other such and Fabrycky, Wolter J., Systems Engi-
efforts into the total engineering effort neering and Analysis, Prentice Hall, Inc.,
to meet cost, schedule and technical 1990)
performance objectives. (Engineering A system is a grouping of parts that
Management, May 1, 1974) operate together for a common purpose.
Systems engineering is a continuous, For example, an automobile is a system of
iterative process that has a built-in feedback components that work together to provide
mechanism. It is used throughout a project transportation. An autopilot and an
or program's life cycle to arrive at the best airplane form a system for flying at a
system architecture and design possible. specified altitude. (Forrester, Jay W.,
Just when systems engineering began to be Principles of Systems, Wright-Allen Press
practiced as a separate discipline is open to Inc., 1968).
debate, but there seems to be general agree-
ment that formal recognition and definition Systems engineering is a cyclical process as
of the process started after World War II. depicted in Figure 1. The terms shown in
Large, complex post-war development this figure are explained in the following
projects such as the first U.S. ballistic paragraphs.
missiles and NASA's Apollo program exhib- 1. Project and Mission Requirements/
ited the characteristics which created the Need Definition can also be termed as "cus-
need for systems engineers. tomer engineering." It is the process by
Among these project characteristics are: which the needs of the customer (the princi-
pal investigator or other significant parties,
• Large design teams with many highly such as Congress or other budgetary author-
specialized designers ity) are determined. This allows the systems
• Many contractors involved, widely sepa- engineer to define requirements for a system
rated geographically, complicating com- that will meet the needs of the customer.
munications
2,A
READINGINSSYSTEMENSGINEERING
1.ProjecatndMissionRequirements/NeDeedfinition
9. Verification and Validation
2. Risk Analysis/Management
8.Technical 3. Systems Analysis
Oversight
7. Configuration 4. Concept
Management Development
5. Derived Requirements Definition
6. Implementation Planning and
Systems Integration
Figure 1 Systems Engineering Cycle
2. Risk Analysis(cid:0)Management is a 5. Derived Requirements Definition is
continuing process to identify and assess the the process of translating mission and func,
risks involved with the development and tionai=anaiysis resuits, system =operational
operation of the system. These include tech- concepts, and the selected system architec-
nical, schedule, cost and organizational ture into a set of system performance and
risks. Following the identification of the interface requirements. At this level, the
risks involved, the system engineer then de- requirements must specify either functional
velops an implementation plan to control or interface criteria only, without presenting
and, if possible, reduce risks. design solutions. This gives: the detail
3. Systems Analysis involves under- designers the flexibility needed to arrive at
standing how the key mission and system design solutions that meet the requirements.
functional elements interact. The mission 6. Implementation Planning and Sys-
analysis translates the users' needs into tems integration is a complex activity
functional/performance requirements and resulting in a coherent, integrated set of
design constraints. A functional analysis implementation tasks and responsibilities
takes these requirements and breaks them for the design, development, fabrication, ver-
d0_wn ip_t9 specific tasks. ification and operation of the required
4. Concept Development is the process of system. It requires negotiation between the
making informed trade-offs among the var- system requirements definition personnel
ious options to select the one that best meets and the system implementation (develop-
the requirements and design constraints. ment) personnel. The plan must also consid-
Preliminary design and performance re- er the project constraints of schedule and
quirements and implementation architec- budget while avoiding unnecessary risk.
ture are the results.
24
WHAT ISA SYSTEM?
7. Configuration Management activities systems engineer should view these changes
ensure that controlled definition of all as a normal part of the design process. Avoid
engieering documentation is maintained and the tendency to view the Systems Require-
correct information is distributed to all ments Specification as something, once base-
appropriate parties in a timely manner. This lined, that is final and unchangeable.
is one of the most important responsibilities 9. During the Verification and Valida-
of the systems engineering organization. On tion portion of the development activity, the
larger programs that have large numbers of characteristics and performance of the sys-
people involved, this process becomes even tem are compared to the requirements and
more critical. This activity is also the mecha- specifications. Tests, analyses and demon-
nism by which the system development strations are performed to verify that the
process is documented (i.e., design knowl- hardware and software satisfactorily meet
edge capture). the performance requirements of the system
Configuration Management establishes specifications.
the system to control the requirements and
configuration of hardware and software, NASA PHASED PROJECT DESCRIPTION
evaluate changes, and maintain the defini-
tion of the configuration via baselined docu- In the planning of major projects, critical
mentation and released drawings. requirements must be well defined and the
8. Technical Oversight serves two func- necessary technology must be available. If
tions. First, it ensures that all the subsys- these criteria are met, there will be an ac-
tems work together. Second, it implements ceptable level of risk in meeting technical
mechanisms to guarantee that the developed goals with reasonable cost and schedule.
and documented architectural concept is not To ensure that the program is at a proper
inadvertently changed during the develop- level of maturity when Congress approves
ment process. This allows the developer to major funding for design and development,
certify that the system, which is ultimately projects go through various phases of analy-
tested, will meet the customer's require- sis and definition. There are five phases in
ments. Technical oversight consists of the the life cycle of a typical successful project:
technical reviews and audits that gather pre-Phase A (concept study), Phase A
consensus from all parties involved to ascer- (preliminary analysis), Phase B (definition),
tain that the effort at any given time is Phase C (design) and Phase D (development/
correct and adequately planned for the operations). Depending on the complexity of
continuance of the work. the system, funding availability and launch
A specific task for the systems engineer schedules, a project may combine phases or
to perform is assuring that the systems re- add intermediate phases. Common
quirements are understood and correctly variations would include combining pre-
implemented by the design organizations. Phase A and Phase A, adding an advanced
This responsibility requires the systems development phase between Phase B and
engineer to work closely with the design Phase C, combining Phase C and Phase D
organizations throughout the program. At into Phase C/D, or moving operations out of
the same time, the systems engineer must Phase D into a separate phase. As a further
recognize that the initial set of systems example, the Space Shuttle program had
requirements will not be perfect. During both a Phase B' (B prime) and Phase B" (B
design evolution or because of the inability of Double-prime) in order to further refine the
a subsystem to meet its intended functional definition and requirements of the system
requirements, changes in the systems before proceeding into Phase C. Figure 2
requirements will be necessary, and the depicts a typical phased project flow in which
2_
READINGS IN SYSTEMS ENGINEERING
MAJOR MANAGEMENT DECISIONS
PRE-PHASE A/
PHASE D
PHASE A PHASE B PHASE C
DEVELOPMENT/
PRELIMINARY DESIGN DESIGN
ANALYSIS OPERATIONS
• Develop Project • Refine Selected • Develop Detail of • Develop and Test
Objectives Alternative Concepts Selected Concept • Manufacture
• Assess Feasibility • Conduct Systems • Develop Specific • Checkout
• Identify Research and Analysis Requirements and • Operate
Advanced Technology • Develop Preliminary Design Specifications • Evaluate
Requirements Requirement and Design • Develop Plans for
• DistributeResults
• Identify Support Specifications Manufacturing, Testing,
Requirements Areas $ Define Support Operations, Supporting
• Develop Gross Plans for Requirements Systems, Facilities, etc.
Implementation • Assess Preliminary • Initiate Required
• Perform Trade-Off Manufacturing and Test Long Lead Advance
Analysis Requirements Development and Define
Plan for Supporting
• IdentifyFavorable and • IdentifyAdvanced
Development
Unfavorable Factors Technology and
• Define Relationships to Advanced Development • Develop Schedules and
Requirements Estimates of Costs
Programs
• Assess Costsand • Refine Management and
• Perform CostAnalysis
Schedules Procurement Plans
• Define Management
and Procurement
Approaches
• Perform Trade-off
Analysis
• Perform Operation
• Feasible ProjectConcepts for • Preliminary Design and • ProjectDesign and • Completed Project
Detailed Study Specifications Specificationincluding
Manufacture Testand
• Preliminary Schedule,
Resource and Management Operation Plans
Plans • Schedule Resources
• WBS Management and
Procurement Plans
(1)Missionneedstatementapproved
(2)Missionneedstatementreaffirmed Source: MM7120.21 Project Management Handbook
Figure 2 NASA Program Phases
pre-Phase A has been combined with decision points. Note that this description
Phase A. pertains to the typical program, in which
Safety is a critical systems engineering NASA contracts with industry to do the
function that must be considered during all Phase C/D activity. Other types of programs
program phases and in all studies and analy- include small, contracted efforts, as well as
ses. In short, although safety is organization- both large and small in-house programs
ally the responsibility of S&MA, it is a where NASA may retain all or part of the
responsibility of all program participants design and development responsibility.
and should be a primary consideration The typical program review phasing
throughout the systems engineering process. includes many more activities and formal
Figure 2 shows the major activities in reviews than are shown in Figure 2. For
each phase, as well as the outputs and major completeness, these are introduced here and
26
WHAT ISA SYSTEM?
PRTR PDR CDR AR
T
Preliminary Definition
Analysis Phase B Design Development/Operation
Phase A Phase C Phase D
Post Refiight
Concept Requirements ,?eliminary [ Final
Definition Generation Fabrication VerificationIIntegration Operation
__Design, [ Design nalysis
Launch/Vehicle/Payloads I
I
I
!
I
v
IPL IPL IPL IPL IPL IPL
ATP RR PDR CDR GOR FOR mR
N-7 _ _:7 v7 V'7 _
TDe Mission
Interface Final Verification & Ground &
Definition Design Integration Flight
finition Operations
Space System Carrier
Notes: PRR -Preliminary Requirements Review RR- Requirements Review
PDR- Preliminary Design Review GOR- Ground Operations Review
CDR -CriticalDesign Review FOR- FlightOperations Review
AR -Acceptance Review IRR- IntegratedReadiness Review
ATP -Authority toProceed FRR -FlightReadiness Review
IPL -Integrated Payload
Figure3 TypicalProgram ReviewPhasing
shown in Figure 3.This figure alsoserves to year period is used to execute the definition
relate the major reviews to the project phase (Phase B) and prepare the request for
phases and to show the more detailed inte- proposal (RFP) for Phase C/D. The new start
gration activitiesassociated with attached approval process includes a definition review
payloads and Spacelab-kinds ofexperiments. or non-advocate review (NAR) generally con-
At MSFC, the Program Development ducted during the Phase B activity at a time
(PD) Directorate isresponsible fornurturing when the project manager, Center manage-
new projectsfrom idea conception through ment, and Headquarters program office
concept definition supporting preliminary deem appropriate. Results of the NAR are
design. Systems engineering is emphasized factored into the Phase C/D RFP, as well as
and utilizedthroughout thisprocess,both in- the budget approval process. Note that this
house and during contracted studies. Typi- timeline pertains principally to large pro-
cally,concepts that have matured through grams which include in-house and contract-
this process and gained Congressional new ed efforts. The timeframe could be much
startapproval tobecome officialprojectsare shorter for smaller projects such as experi-
then moved into project offices.The new ments. Figure 4 shows the overall systems
startreview and approval process begins ap- engineering process flow in Program Devel-
proximately two years in advance of Phase opment (PD).
C/D authority to proceed (ATP) at which In the course of developing the pre-
point funds are applied to begin a major liminary systems requirements and the
design and development effort.That two- conceptual design, PD uses many of the same
READINGS IN SYSTEMS ENGINEERING
Planning Missainodn AnaPllyasninsing Operatainodns AnalyPsliaenmng [
II
il
Planning Systems Analysis Applicatinns
Space Technologies _l
Feasibility and Definition
i PPlraongnrianmg i and Implementations Studies I
Manpower Planning
and Analysis c...,.otoo°.,oonitio .
Program Control
i
lit ] Preliminary Systems
I
--4_[ PrRogerqaumir/eSmcieenntcse Requirements _i PreliDmeisniagrny
Analysis &Tradea
la I AdvanceRdequireDmeevneltospment I
iI Sys_me4Subsy otems III
Cost Modeling&
E_timating
1_ I Supporting/AadnvdancTedechnolngy Research i
Headquarters Approval Lead to
Program Initiation Agreement
Figure 4 Systems Engineering Process Flow in Program Development
analysis tools and techniques that are em- further study can come from a variety of
ployed by Science & Engineering (S&E) in sources: industry, the scientific community,
later program phases. The principal differ- university and research centers, MSFC con-
ences in thebutputs of the two 0rganiza_i_ns tractors and associateSl :or: evenfrom wlth_n
are the quantity, format and maturity of the MSFC itself. Typically, such ideas receive a
documentation and the level of detail in the top-level examination by cognizant
analyses. In summary, the analyses and MSFC/PD personnel. A quick assessment of
trade studies by S&E are to refine, not re- objectives, requirements and the total mis-
peat, the concepts developed by PD in sup- sion concept is performed. Often, new ideas
port of design implementation. PD develops are shared with colleagues through propos-
the conceptual approach and S&E develops als (eithe r inresponse to an RFP_unsolicit-
the designimp]ementation. ed),technical papers at professional society
meetings, or "white papers" propounding the
PRE-PHASE A (CONCEPT STUDY) new idea/concept.From an MSFC in-house
weeding out process,concepts are identified
A pre-Phase A study may be accomplished forfurther (Phase A) study.
within the engineering capability of Pro- System functional concept trades are per-
g)-am DeveI0pme-fit-orcontracted with formed during the pre'Phase A period,
funding from one of the major NASA Head- generally at a fairly cursory level of detail.
quarters offices. Successful results from this This process eliminates architectures that
study would provide justification to initiate a are too costly or time-consuming to develop.
Phase A study or additional pre-Phase A They are conducted at a level sufficient to
studies. The genesis of new ideas requiring support the definition of the top-level system
28
WHAT ISA SYSTEM?
requirements. Architectural options are the database discussed above. The has access to
result. Some of the primary sources for this several cost estimating systems, both
identification of concepts include brain- government and commercial. One example is
storming, past experience, examination of the GE/RCA Price Model. Each model is
other systems and intuition. unique with special capabilities and limita-
Cost estimates are developed in pre- tions. Complexity factors and Cost Estimat-
Phase A and are usually at a very prelimi- ing Relationships are applied to the
nary level due to the lack of detailed systems estimatinK software using system weight as
definition. These estimates are based pri- the independent variable. A factor is applied
marily on parametrics adjusted for the new to the hardware/software costs to account for
program, taking into account differences in wraparounds such as project management,
mission, size, complexity and other factors. test and verification, percent new design,
operational complexity, hardware complex-
PHASE A (PRELIMINARY ANALYSIS) ity, similarity to other projects or develop-
ment activities and others. As each system is
A Phase A study is the preliminary analysis defined in more detail and the system weight
of a space concept. These concepts could have is further refined, the cost estimates become
come from a pre-Phase A study or from other more realistic and provide a higher confi-
sources within or external to NASA. The ma- dence level in the results.
jority of concepts that are studied at MSFC A cost/risk analysis and assessment is
are assigned by NASA Headquarters and usually completed near the end of each
funded accordingly. Documentation in this Phase A study. The analysis is accomplished
Phase usually consists of study reports and with special software that uses statistical
briefing charts. techniques, including a Monte Carlo simula-
Schedules are developed during Phase A tion. The results predict the probability of
studies by Program Development in conjunc- completing the program within the estimat-
tion with the organization performing the ed cost. A risk assessment, which follows the
study (contractor, PD, S&E). The schedules analysis, should identify areas of high risk
include an overall program schedule pro- that require further cost analysis or possibly
vided by MSFC and a detailed technical further trade studies to look at alternate sys-
schedule developed by the contractor. tems that would lower the potential costs
The overall program schedule depicts im- without sacrificing technical capability.
portant milestones that establish the start As part of the study activity, the contrac-
and finish dates of each study phase, includ- tor provides a detailed risk analysis and
ing design, development, launch, and oper- assessment to establish a high level of confi-
ations. Programmatic milestones are also dence for the program cost. The cost estimate
shown. These are dependent on the federal established during this phase will provide
budget cycle plus proposal preparation and NASA Headquarters with the funding
evaluation time. The contractor schedule requirements to be approved by Congress
depicts the major activities and phasing before the development program can begin.
required to develop the hardware in time to The processes occurring during Phase A
meet the scheduled launch date. Since this is include:
a concept study, the detail schedule is still at
a relatively high level and would not show • Development of project objectives
activity below the system level. • Assessment of project feasibility
Cost estimates developed during Phase A • Identification of research and advanced
are generated using a parametric cost technology requirements
analysis system in conjunction with the cost
29
READINGS IN SYSTEMS ENGINEERING
• Identification ofsupportrequirements are Level I (NASA Headquarters) require-
areas ments from preliminary activities.
• Performance of trade-off analyses Level I requirements are broad mission
• Identification of favorable and unfavor-
needs and objectives. Occasionally, there
able factors
may be some Level H (project office level) re-
• Definition of relationships to other quirements at this time.
programs The mission need determination is the
• Selection of systems concepts first step in a multifaceted preliminary con-
• Identification of maintenance, technology cept definition activity. This is the step that
insertion, and disposal concepts of is first performed at a NASA Headquarters
payload and orbital debris or Center level (or industry, university, etc.)
• Environmental Impact Analysis. and is the precursor to concept development.
The mission need determination is that part
The outputs from Phase A, which become the of early mission planning that identifies a
inputs to Phase B, are in the form of reports scientific knowledge need or gap that could
or annotated briefing charts and include in- be met with some kind of NASA sponsored
formation on:
activity. A set of Level I requirements is gen-
erally developed during or just prior to the
• Concept definition activities described in the following para-
• Preliminary system requirements graphs.
• Preliminary configuration layouts A feasibility analysis is conducted to de-
• Point designs termine the viability of the project. The
• Preliminary implementation plans study report usually includes requirements,
• Preliminary schedules objectives, problems, opportunities and costs.
• Preliminary cost estimates A utility analysis is then conducted to de-
• Environmental impact. termine the value of a project. The following
criteria may be considered during this study:
PHASE B (DEFINITION AND the needs met, the scientific knowledge ac-
PRELIMINARY DESIGN) quired, the political benefits, or potential
spinoffs and applications.
This phase of the project consists of the re- Certain satellites and/or instruments are
finement of preliminary requirements, cost selected for a more detailed level of design.
estimates, schedules and risk assessments The Preliminary Design Office of Program
prior to starting final design and develop- Development performs these studies. This
ment. office is a miniature replication of the capa-
Once the feasibility of an idea is estab- bilities of the laboratories at MSFC: Propul-
lished, the concept definition phase is begun sion, Guidance, Navigation and Control,
to explore alternatives to meet the docu- Electrical Power, Avionics, Structures,
mented mission need. Competition and inno- Operations, etc. One difference is the empha-
vation should be employed to ensure that a sis by Program Development in developing
wide variety of alternatives are identified credible cost estimates. Cost is an important
and examined. Modeling and computer ana- differential, but often other factors, such as L
lysis are required to assess the best concepts. mission risk or incompatibility with other
The goal of a concept definition activity is instruments that may be grouped on a com-
to determine the best and most feasible mon satellite, may predominate.
concept(s) that will satisfy the mission and Throughout the Phase B period the con-
science requirements. Generally, the re- cepts that were developed during Phase A
quirements available at this point in time are iteratively reviewed and analyzed. Using
3O
WHAT ISA SYSTEM?
trade study techniques, the concepts' capa- the Phase A overall program schedules. In
bilities are compared to the system require- addition, other schedules are developed that
ments. Those concepts that consistently include Phase C and D procurement strate-
satisfy the requirements are identified and gies, cost phasing and project manning
refined. Any concepts that do not meet requirements. The study contractor sched-
performance and other requirements are ules are expanded to lower levels of the work
scrutinized very closely for possible elimina- breakdown structure (WBS) to include
tion. Following the examination of those subsystem development, program manage-
that do not perform well, assessments are ment, manufacturing, verification, logistics
made regarding their augmentation to dis- planning, operations planning and other
cover the degree of change necessary to bring technical areas. The schedule detail would
their performance into scope. The concepts show the phasing of all major activities
that have to change too much or would through launch and the follow-on operations.
experience severe budgetary and/or schedule As in Phase A, the typical documentation
impacts are deleted from the concept defini- of this phase consists of reports and briefing
tion and analysis cycle. This allows the ana- charts.
lysts' energies to be focused on those concepts The processes occurring during Phase B
that are valid and workable. include:
These trade studies provide a more de-
tailed look at the architectural concepts and • Refinement of selected alternative
result in a narrowing of the field of candi- concepts
dates. Trades performed during this time • Performance of trade-off analyses
consider such things as cost, schedule, life- • Performance of system analyses and
time and safety. The evaluation criteria used simulations
to assess alternative concepts are developed • Definition of preliminary system and
to a finer level of detail than for earlier sys- support requirements
tem trades. • Definition and assessment of preliminary
Cost estimates from Phase A are refined manufacturing and test requirements
as further detailed requirements are identi- • Identification of advanced technology and
fied during Phase B. The cost estimating advanced development requirements for
process is still dependent on parametric ana- focused funding
lysis. The Program Development cost office • Refinement of preliminary schedules
works closely with the study contractor in • Refinement of preliminary cost estimate
evaluating costing methodology and continu- and trade study results which support
ously compares government cost estimates selection of baseline for cost estimate
with those of the study contractor. Should a • Assessment of technical, cost, and sched-
large discrepancy occur, the assumptions ule risks
and schedule inputs of the study contractor • Assessment and refinement of the Mis-
are examined. If this examination yields val- sion Need Statement.
id assumptions and schedules, the NASA
estimates are adjusted. The cost estimation The outputs from Phase B, which become the
process goes through continuous iterations inputs to Phase C, may include (in the form
during the study to reflect the evolution of of study reports and annotated briefing
detail resulting from trade studies. charts) information related to:
Schedules are developed during Phase B
by the task team program control personnel • Preliminary WBS
and by the study contractors. Schedules de- • System requirements
veloped by the task team are expanded from • Preliminary interface requirements
READINGS IN SYSTEMS ENGINEERING
PHASE A PHASE B PHASE C PHASE D
Preliminary Development]
Analysis Definition Design Operations
PROGRAM pDO ........
DEVELOPMENT TASK TEAM
PROGRAM/PROJECT OFFICES
s_s _SS
SCIENCE & ENGINEERING In-depth Technical Support
A
J
INSTITUTIONAL &PROGRAM SUPPORT Support &Services
l I I
Source: PD Lead Engineer's Guide
Figure 5 MSFC Support Relationships in Project Phases
• Management and procurement ap- chief engineer is often the deputy to the task
proaches team manager and is usually the first Sci-
• Program Implementation Plans ence and Engineering representative sub-
• Request for Proposal (RFP) inputs, where stantially involved in the process. The chief
applicable. engineer's office has personnel resources
available to support the project as needed
Phase B is normally the final phase of during the study. Additional engineering
activity within Program Development. A support from S&E may be used at the discre-
=
separate core of people is selected to form a tion of the chief engineer. The chief engineer
task team to manage the Phase B contract. plays a key role in determining the state of
At the beginning of Phase B, a chief engineer technical maturity of the project for starting
is appointed to the task team (or project the design and development phase.
office) to provide consultation to the task At the conclusion of Phase B, the task
team manager on all related engineering team is converted to a project office, and it is
matters. The chief engineer also helps no longer under the direction of program
ensure that the study contractor uses accept- development. On large projects, such as
able engineering practices and sound Space Station, a project office might be
judgment during the course of the study. The created prior to Phase B; in that case,
32