Fellowship activities were directed towards the identification of opportunities for application of the Multiple Criteria Decision Making (MCDM) techniques in the Space Exploration Initiative (SEI) domain. I identified several application possibilities and proposed demonstration application in these three areas: evaluation and ranking of SEI architectures, space mission planning and selection, and space system design. Here, only the first problem is discussed. The most meaningful result of the analysis is the wide separation between the two top ranked architectures, indicating a significant preference difference between them. It must also be noted that the final ranking reflects, to some extent, the biases of the evaluators and their understanding of the architecture

Masud, Abu S. M.

English

NASA Technical Reports Server

N92-13847
APPLICATION OF MULTIPLE CRITERIA DECISION METHODS IN
SPACE EXPLORATION INITIATIVE DESIGN AND PLANNING
Abu S. M. Masud, Ph.D., P.E.
Industrial Engineering Department
The Wichita State University
Wichita, Kansas 67208
My 1991 NASA/ASEE Summer Faculty Fellowship activities at the Langley Research Center
(LaRC) were directed towards the identification of the opportunities for application of
Multiple Criteria Decision Making (MCDM) techniques in the Space Exploration Initiative
(SEI) domain. I identified several application possibilities and proposed demonstration
application in these three areas: (1) evaluation and ranking of SEI architectures, (2) space
mission planning and selection, and (3) space system design. Due to page limitations, this
report describes only the results of my research efforts directed towards the first problem. A
more detailed report about all three problems would be issued later.
SEI Architectures
SEI represents the focused efforts by NASA in meeting President Bush's challenge to the
American's, made on the 20th anniversary of first manned Moon landing, to go "..back to the
Moon.. (and this time) to stay.., and a manned mission to Mars." Accordingly, several studies
have been conducted to define strategies about how this can be accomplished. One of the
first detailed report discussing scenarios (called "architectures") for Mars missions is the "90-
day Study" report by NASAl1 l; and, the most recent one is the report of the "Synthesis
Group" set up by Vice-President Quayle[2l. NASA would now be conducting additional
technical studies to arrive at a baseline SEI architecture. My research was aimed towards
demonstrating that MCDM methods can assist in this. The following five architectures were
chosen for evaluation and ranking:
A : Architecture I (Mars Exploration) of the Synthesis Group Report.
B : Architecture 11 (Science Emphasis for the Moon and Mars) of the Synthesis Group
Report.
C : Architecture III (Moon to Stay and Mars Exploration) of the Synthesis Group Report.
D : Architecture IV (Space Resource Utilization) of the Synthesis Group Report.
E • Modified Reference Architecture of the 90-Day Study Report.
Evaluation Criteria
Several researchers from the SEI Office at LaRC participated in the development of a two-
level, hierarchically structured set of general evaluation criteria. Specific, technical criteria
were not deemed to be relevant at this early stage of architectural concepts. Table 1 shows
the developed criteria set.
134
https://ntrs.nasa.gov/search.jsp?R=19920004629 2020-03-17T13:45:02+00:00Z
Relative Importance of the Evaluation Criteria
Many approaches for the development of relative importance weights are. availab!e|3]. We
h_v,. used th,- rnn_'ept proposed by e ....... ^-_,...:_
.......... o,_,,,y for ' ': .... "- "" "''"..... rtnnatytiu ,,,c, atC.y Process t,'_nr). Using the
scale shown in Table 2, SEI researchers first made pairwise comparisons of the major criteria.
Weights for these major criteria were then computed from these comparisons; see column 2
of Table 3. Next, they made pairwise comparisons of the sub-criteria under each major
criterion. Weights from these comparisons and the weights of the major criteria computed
previously were used to determine the absolute weights of each sub-criterion. Finally, sub-
criteria with only marginal effects were combined, to reduce the set of the evaluation criteria.
Table 3 shows the resultant reduced set of evaluation criteria and the corresponding weights.
Evaluation of the Architectures
Each of the five architectures were then evaluated by the SEI researchers with respect to each
the sub-criterion. The scale in Table 4 was used in these evaluations, and the results are
shown in Table 5.
Rank Ordering of the Architectures
Different rank ordering methods, such as Simple Additive Weighing, ELECTRE and TOPSIS,
are available. We have used TOPSIS by Hwang and Yoon[3]. TOPSIS uses the Euclidian
distance of each alternative from an "Ideal Solution" (constructed from the best achieved •
value with respect to each criterion by any of the alternatives under consideration) and a
"Negative Ideal Solution" (constructed from the worst criteria values of all the alternatives) to
compute a closeness measure, Co. The closeness measure for an alternative equals 1 when it
coincides with the "Ideal Solution" and the measure equals 0 when the alternative coincides
with the "Negative Ideal Solution." Table 6 shows the computed closeness measure values
for all five of the architectures, and their final ranking.
Concluding Remarks
The most meaningful result from this analysis is the wide separation between the top two
ranked architectures, indicating a significant preference difference between them. It must also
be noted that the final ranking reflects, to some extent, the biases of the evaluators and their
understanding of the architectures.
REFERENCES
1. Report of the 90-Day Study on Human Exploration of the Moon and Mars. NASA
Internal Report, Johnson Space Center (Aaron Cohen, Study Leader), November, 1989.
2. America at the Threshold : America's Space Exploration Initiative. Final report of the
Synthesis Group (Thomas Stafford, Group Leader), May, 1991.
3. Hwang, C.L. and K. Yoon, Multiple Attribute Decision Making : Methods and
Applications. Springer-Verlag, New York, 1981.
,i
135
Table 1. Evaluation Criteria
Criterion Sub-criterion Explanation
Maximize the following criteria (i.e., the more the better)
1. Utility/Benefit
1.1 Economical
1.2 Technological
1.3 Educational
1.4 Scientific
1.5 Commercial
1.6 Synergy
1.7 Visibility
1.8 International
Cooperation
1.9 Political
Potential national economic payoffs
Technological Payoffs/spinoffs
Impact on national education system
Impact on scientific knowledge
Potential for commercial payoffs
Positive (synergistic) effect on other SEl/Civilian space projects
Public visibility and appeal
Degree of International cooperation that
may be achieved
Political appeal and attractiveness
2. Feasibility
2.1 Technical
2.2 Schedule
2.3 Political
Soundness and reasonableness of the technological state-of-the-art
assumptions
Functionality and reas(mableness of the schedule
Potential for public/congress support
3. Flexibility
3.1 Launch Date
3.2 Budget
3.3 Schedule
3.4 Mission
3.5 Design
Flexibility in launch date
Flexibility in the required budget
Flexibility in the overall schedule (resiliency in the schedule)
Adaptability to changes in the mission goal, focus, etc.
Robustness of the architectural design
4. Manageability
4.1 Developmental
4.2 Operational
Degree of difficulty in the management of the development efforts
Degree of difficulty in the management of the mission operations
Minimize file following criteria (i.e. 1 the less the better)
5. Risk/Uncertainty
5.1 Crew Safety
5.2 Technological
5.3 Economical
5.4 Schedule
5.5 Performance
Potential risk in crew safety and health
Risk that the expected technology would not be developed at all or in a
timely manner
Economic risk/uncertainty (potential, and degree thereof, for the budget
to increase)
Robustness of the schedule (level of uncertainty in the schedule)
Potential uncertainty about achieving the expected performance
6. Cost
6.1 Life Cycle Cost
6.2 Conflict
Total developmental and operating cost
Potential for detrimental effect on other SEl/Civilian space projects?
136
Table 2. Pairwise Preference Measurement Scale
?
Intensity of
Importance of
criterion C: over
criterion C7
2,4,6,8
Definition
Equal importance
Weak importance
Essential or strong
importance
Demonstrated importance
Absolute importance
Intermediate values
Explanation
C1 and C_ are equally important
Experience & judgement slightly favor C 1 over Ca
Experience & judgement strongly favor C I over Ca
CI is strongly favored & its dominance is demonstrated in
practice
The evidence favoring C_ over Ca is of the highest
possible order of affirmation
When compromise is needed between two adjacent judgements
137
Table 3 Final Weights of Evaluation Criteria
Criterion
Utility/Benefit
Feasibility
Weight Sub-criterion
0.0754
Economical/
Technological/
Educational
.......................
Scientific
Visibility
Political
0.3179
Weight
.... Reiative--[--Absolute
0.2279
0.2314
0.2511
0.2896
0.0172
0.0175
0.0189
0.0218
Flexibility
Manageability
Schedule 0.4600
Political 0.3190
0.0774
...........................................
Launch Date/ 0.2192
Schedule
.....................................
Mission 0.6095
Design 0.1713
Risk/Uncertainty
O.O331
0.3610
Technical 0.221 ! 0.0703
0.1462
0.1014
Technological/
Performance
Economical/
Schedule
Life Cycle Cost 0.9000
0.0170
0.0471
0.0133
0.0331
0.2362
0.0610
0.0638
Crew Safety
...................................
Cos t 0.1349
Conflict 0.1000
0.6544
11.1690
0.1766
0.1214
0.0135
138
Table 4. Architecture Evaluation Scale
For Cost Attributes
very high
0
1.0
high 3.0
average 5.0
low 7.0
very low 9.0
10.0
0
1.0
3.0 low
For Benefit Attributes
very low
5.0 average
7.0 high
9.0
10.0
very high
139
Table 5. Architecture Evaluation Matrix
r
(Sub) Criterion / Architecture Evaluation
I
--+ A
Econffech/Educ 6
Benefit
Scientific 6
Benefit
......................
Visibility 6
Benefit
Political 6
Benefit
...................................
Technical 7
Feasibility
...........................
SChedule 4
Feasibility
Political 5
Feasibility
Launch/Schedule 5
Flexibility
Mission 7
Flexibility
Design 6
Flexibility
Manageability 6
...... l
Crew Safety 6
Risk
Techn/Per formance 4
Uncertainty
Econ/Schedule 5
Uncertainty
+__
Life Cycle Cost 5
Conflict Cost 3
7 8 7
9
8
7
5
2
5
5
5
6
_
5
8
9
6
6
!
1
3
8 5
6 6
i
.... i ....
4 _ 5
6 4 6
5 5
6 6
7 6
3 9
2 9
5 8
5 7
7
7
8
6
4 3 4
3
6
3 2 7
2 5 7 7
2 1 2 5
140
L
sTable 6. Ranking of the Architectures
/"tl k, 1 i 1 U_I,,, t I I1 I_
Separation Measures
A
B
(From A') S_,
0.08135
C
D 0.11353
E
0.12002
0.14060
0.00724
-z ................. J
(From A) Si_
0.11308
0.05481
0.03552
0.07253
0.15107
Relative
Isloseness
Ci,
0.5816 2
0.3135 4
0.2017 5
0.3898 3
0.9543 1
Rank
141


Application of multiple criteria decision methods in space exploration initiative design and planning

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