1© 2008 The Aerospace Corporation
Perspectives on NASA Mission Cost and Schedule Performance Trends
Presentation for the Future In-Space Operations (FISO) Colloquium
2 July 2008
Bob Bitten
Acknowledgments: Claude Freaner, Dave Bearden, Debra Emmons, Tom Coonce
2© 2008 The Aerospace Corporation
Typical Questions
• What is the magnitude of cost and schedule growth?
• How reliable are projects’ estimates in the conceptual design stage?
• Why does cost growth occur?
• What is the relationship between cost, schedule and “complexity”?
• Are there any improvements that can be made in estimating the costs of future design concepts?
3© 2008 The Aerospace Corporation
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Cost Ratio
Sche
dule
Rat
io
within cost and schedule
within 100% overrun
Forty NASA Robotic Science Missions Experienced 27% Cost and 22% Schedule Growth*
* “Using Historical NASA Cost and Schedule Growth to Set Future Program and Project Reserve Guidelines”, Bitten R., Emmons D., Freaner C.
4© 2008 The Aerospace Corporation
While Significant Variability is Evident, for Every 10% of Schedule Growth, there is a Corresponding 12% Increase in Cost*
%Cost Growth = 1.2348 * %Schedule GrowthR2 = 0.6124
-50%
0%
50%
100%
150%
200%
0% 20% 40% 60% 80% 100%
Schedule Growth for Non-Restricted Launch Window Projects
Cost
Gro
wth
* “Using Historical NASA Cost and Schedule Growth to Set Future Program and Project Reserve Guidelines”, Bitten R., Emmons D., Freaner C.
5© 2008 The Aerospace Corporation
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6.0
0.3 m 0.3 m 0.5 m 0.85 m 0.95 m 2.4 m
Gro
wth
per
Dev
elop
men
t Yea
r
Comparison of Schedule Growth Data with Agency Guidelines: NASA Telescope Missions
7 7 13
21 16
36
0
10
20
30
40
50
60
70
80
90
100
110
120
0.3 m 0.3 m 0.5 m 0.85 m 0.95 m 2.4 m
Syst
em D
evel
opm
ent T
ime
(Mon
ths)
Schedule GrowthInitial Schedule
General Rule of Thumb1 Month per Year
NASA/JPL Guidance1.8 Month per Year
Four of Six Telescope Missions Exceeded Common Schedule
Reserve Guidelines
Four of Six Telescope Missions Exceeded Common Schedule
Reserve Guidelines
Growth shown is above planned schedule reserve
6© 2008 The Aerospace Corporation
Comparison of Schedule Growth and Success for Planetary Missions vs. Earth-orbiting Missions*
0
12
24
36
48
60
72
84
96
0 12 24 36 48 60 72 84 96
Planned development time (mos)
Act
ual d
evel
opm
ent t
ime
(mos
)
Earth Orbiting MissionsPlanetary Missions
Planetary Earth-Orbiting
Sample Size 10 56
Schedule Growth 3.9% 38.3%
• Development times for Planetary missions less than Earth-orbiting missions due to constrained launch windows
• Planetary missions experienced less schedule slip on average than earth-orbiting missions
• However, planetary missions failed or impaired twice as often
0 10 20 30 40 50
Failures
Successes
Average Development Time
Outcome Planetary Earth-orbiting
% Successful 30% 84% % Partial 40% 7% % Catastrophic 30% 9%
* “The Effect of Schedule Constraints on the Success of Planetary Missions”, Bitten R.E., Bearden D.A., Lao N.Y. and Park, T.H.
7© 2008 The Aerospace Corporation
Typical Questions
• What is the magnitude of cost and schedule growth?
• How reliable are projects’ estimates in the conceptual design stage?
• Why does cost growth occur?
• What is the relationship between cost, schedule and “complexity”?
• Are there any improvements that can be made in estimating the costs of future design concepts?
8© 2008 The Aerospace Corporation
How Reliable are the Projects’ Estimates at the Conceptual Design Stage and How Does Confidence Progress?
Ten Missions Demonstrate How Accuracy of Project Estimates Increases Over Time however Cost Growth, Over and Above Reserves, Still Occurs
Deep into the Project Life Cycle
Ten Missions Demonstrate How Accuracy of Project Estimates Increases Over Time however Cost Growth, Over and Above Reserves, Still Occurs
Deep into the Project Life Cycle
39.3%
29.6%
33.7%
0%
10%
20%
30%
40%
50%
60%
70%Pe
rcen
t Cos
t Diff
eren
ce fr
om M
ilest
one
to F
inal
Cos
t (%
)
Avg.
Avg.
Avg.
Start of Phase B @ PDR @ CDR
9© 2008 The Aerospace Corporation
In What Phase Does Cost Growth Occur?
Greatest Growth Occurs During Integration and Test (Phase D) When Trying to Get Hardware & Software to Function as Designed
Greatest Growth Occurs During Integration and Test (Phase D) When Trying to Get Hardware & Software to Function as Designed
13.3%
47.9%
6.4%
-20%
0%
20%
40%
60%
80%
100%
120%
140%Pe
rcen
t Cos
t Gro
wth
from
Pre
viou
s M
ilest
one
(%)
Avg.
Avg.
Avg.
ATP-PDR PDR-CDR CDR-LaunchPhase B Phase C Phase D
10© 2008 The Aerospace Corporation
Typical Questions
• What is the magnitude of cost and schedule growth?
• How reliable are projects’ estimates in the conceptual design stage?
• Why does cost growth occur?
• What is the relationship between cost, schedule and “complexity”?
• Are there any improvements that can be made in estimating the costs of future design concepts?
11© 2008 The Aerospace Corporation
Some of the Reasons
• Inadequate definition of technical and management aspects of a program prior to seeking approval
(NASA’s Project Management Study, 1980)
• Program and funding instability; difficulties in managing programs in an environment where funding must be approved annually and priorities change
(Advisory Committee on the Future of the U.S. Space Program, 1990)
• Lack of emphasis on technological readiness and requirements on the front end of a program
(NASA’s Roles and Missions Report, 1991)
• Program redesign, Technical Complexity, Budget Constraints, Incomplete Estimates
(GAO Report on NASA Program Costs, 1992)
12© 2008 The Aerospace Corporation
The Reasons for Growth - Study of 40 NASA Missions:Internal versus External Factors Driven-Growth*
• Internal Growth (within Project’s control)
– Technical• Spacecraft development difficulties • Instrument development difficulties• Test failures• Optimistic heritage assumptions
– Programmatic• Contractor management issues• Inability to properly staff an activity
• External Growth (outside Project’s control)
– Launch vehicle delay– Project redesign– Requirements growth– Budget constraint– Labor strike– Natural disaster
External Only
20.0%
Both10.0%
No Growth12.5%
Internal Only
57.5%
Distribution of Growth
S/C Only22.2%
Other14.8%
Inst. Only33.3%
Both Inst & S/C29.6%
Launch83.3%
Other16.7%
Distribution of Internal Growth
Distribution of External Growth
* “Using Historical NASA Cost and Schedule Growth to Set Future Program and Project Reserve Guidelines”, Bitten R., Emmons D., Freaner C.
13© 2008 The Aerospace Corporation
Mass Growth Exceeds Typical Guidance*
• Average mass growth for ten missions studied is 43% which exceeds the typical industry guidelines of 30% mass reserves (over CBE) at the start of Phase B
43%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
Mission#1
Mission#2
Mission#3
Mission#4
Mission#5
Mission#6
Mission#7
Mission#8
Mission#9
Mission#10
Average
Sate
llite
Mas
s G
row
th R
elat
ive
to C
BE
(%)
Typical Reserves
* “An Assessment of the Inherent Optimism in Early Conceptual Designs and its Effect on Cost and Schedule Growth”, Freaner C., Bitten R., Bearden D., and Emmons D.
14© 2008 The Aerospace Corporation
Assessing Relationships for Causality:Inherent Optimism in Initial Design & Estimates*
Progression of Average Cost Growth for Discovery Selections May be Indicative of Competitive Pressures Leading to More Aggressive DesignsProgression of Average Cost Growth for Discovery Selections May be
Indicative of Competitive Pressures Leading to More Aggressive Designs
-8.4%
21.4%
40.3%42.7%
0.0%
-20%
-10%
0%
10%
20%
30%
40%
50%
1993 1995 1997 1999 2001
Discovery Selection Year
Aver
age
Perc
ent C
ost G
row
th fo
r Di
scov
ery
Mis
sion
s Se
lect
ed
* “Using Historical NASA Cost and Schedule Growth to Set Future Program and Project Reserve Guidelines”, Bitten R., Emmons D., Freaner C.
15© 2008 The Aerospace Corporation
Typical Questions
• What is the magnitude of cost and schedule growth?
• How reliable are projects’ estimates in the conceptual design stage?
• Why does cost growth occur?
• What is the relationship between cost, schedule and “complexity”?
• Are there any improvements that can be made in estimating the costs of future design concepts?
16© 2008 The Aerospace Corporation
Hypothesis*
• Complexity Index could be derived using a broad set of parameters to arrive at a top-level representation of the system
• Correlation to spacecraft cost and/or development time based on actual program experience might be apparent
• Data assembled for most spacecraft launched during past two decades (1989 to present) including technical specifications, costs, development time, mass properties and operational status
• Complexity Index calculated based on performance, mass, power and technology choices for purposes of comparison
• Relationship between complexity and “failures” investigated compared with adequacy of cost and schedule resources
• Method to assess complexity at the system-level should allow more informed overall decisions to be made for new systems being conceived
Illustrations reprinted courtesy of NASA* “A Complexity-based Risk Assessment of Low-Cost Planetary Missions: When is a Mission Too Fast and Too Cheap?”, Bearden, D.A.
17© 2008 The Aerospace Corporation
Payload Mass (kg) 0 265 6065 90 55%Payload Orbit Average Power (W) 0 166 1600 62 38%Payload Peak Power (W) 0 174 750 85 31%Payload Data Rate (average) (Kbps) 0 11678 304538 175 55%Number of Instruments 1 4 18 3 43%Aperture diameter (cm) 3 67 240 60 58%Foreign Partnership None GS, LV, SC Bus PL, mult PL 0 0%Mission Design Life (mos) 0 39 240 7 5%Launch Mass Margin (%) -4% 23% 60% 24% 43%Spacecraft Launch Mass (Wet) (kg) 12 1076 18189 973 73%Spacecraft Mass (Dry) (kg) 6 806 16329 916 77%Spacecraft Bus Dry Mass (kg) 26 598 10264 589 76%Spacecraft Heritage (%) 0% 42% 100% 57% 37%Radiation Total Dose (krads) 0 74 600 50 61%Level of Redundancy (%) 0% 36% 100% 25% 49%Orbit Regime STS/ISS, GEO LEO/MEO, H-LEO/Dip, NE Interplan (au) 3 90%
Payload Mass (kg) 0 265 6065 90 55%Payload Orbit Average Power (W) 0 166 1600 62 38%Payload Peak Power (W) 0 174 750 85 31%Payload Data Rate (average) (Kbps) 0 11678 304538 175 55%Number of Instruments 1 4 18 3 43%Aperture diameter (cm) 3 67 240 60 58%Foreign Partnership None GS, LV, SC Bus PL, mult PL 0 0%Mission Design Life (mos) 0 39 240 7 5%Launch Mass Margin (%) -4% 23% 60% 24% 43%Spacecraft Launch Mass (Wet) (kg) 12 1076 18189 973 73%Spacecraft Mass (Dry) (kg) 6 806 16329 916 77%Spacecraft Bus Dry Mass (kg) 26 598 10264 589 76%Spacecraft Heritage (%) 0% 42% 100% 57% 37%Radiation Total Dose (krads) 0 74 600 50 61%Level of Redundancy (%) 0% 36% 100% 25% 49%Orbit Regime STS/ISS, GEO LEO/MEO, H-LEO/Dip, NE Interplan (au) 3 90%
Factor Unit Min Mean Max ExampleFactor Unit Min Mean Max Example
Complexity Index Example
BOL Power (W) 12 761 8000 1750 89%EOL Power (W) 3 653 6600 1651 92%Solar Array Area (m^2) 0 5 58 7.5 82%Solar Cell Type/Power Source Si GaAs, GaAs-mult GaAs-conc, RTG/R GaAs-mult 75%Battery Type Lead-acid NiCd, SNiCd NiH2, Li-Ion Li-Ion 100%Battery Capacity (A-hr) 1 36 516 266 98%# Articulated Structures 0 1 6 2 87%# Deployed Structures 0 2 9 3 81%Mech. Degrees of Freedom (max) 0 1 6 2 63%Solar Array Configuration body-fixed deployed, single-axis articulated B 0%Structures Material Aluminum Al w/Comp-face, Exotic Composite Al 0%
Pointing Accuracy (deg) 0 2 35 0.0039 88%Pointing Knowledge (deg) 0 1 20 0.0036 80%Platform Agility (slew rate) (deg/sec) 0 1 5 0.62 80%Pointing Stability (Jitter) (urad/sec) 0 87 524 5.000 64%Number of Thrusters+Tanks (#) 0 6 26 18 86%Propulsion Type None, Cold-Gas Mono, Biprop-(blow,pres) OB+US, Ion mono 40%Total Impulse (delta-V) (m/sec) 0 314 5845 190 61%Downlink Comm Band UHF/VHF/SHF S, L, X K/Ka/Ku X 75%
Max Uplink Data Rate (kbps) 0 38 2000 2.0 27%Transmitter Power (peak) (W) 1 10 60 20 85%Central Processor Power (Mips) 0 58 1600 119 81%Onboard Software Code (KSLOC) 2 78 650 110 79%Flight Software Reuse (%) 0% 36% 90% 47% 44%Data Storage Capacity (Mbytes) 0 4186 136000 512.0 60%Thermal Type passive heaters, semi-active active, cryo heaters 25%Multi-Element System? single-sc CL, mult (aerobr, rend) entry/landed/dock mult 66%
Complexity IndexNormalized Complexity Index
60%79%
18© 2008 The Aerospace Corporation
Schedule as Function of Complexity y = 20.084e1.7203x
R2 = 0.7165
01224364860728496
108120132144
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Complexity Index
Dev
elop
men
t Tim
e (m
onth
s)
Successful
Failed
Impaired
To-be-determined
When is a Mission Too Fast?*
* “A Complexity-based Risk Assessment of Low-Cost Planetary Missions: When is a Mission Too Fast and Too Cheap?”, Bearden, D.A.
19© 2008 The Aerospace Corporation
Development Cost as Function of Complexity y = 5.6931e5.9893x
R2 = 0.8973
10
100
1000
10000
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Complexity Index
Cos
t (FY
05$M
)
Successful
Failed
Impaired
To-be-determined
When is a Mission Too Cheap?*
* “A Complexity-based Risk Assessment of Low-Cost Planetary Missions: When is a Mission Too Fast and Too Cheap?”, Bearden, D. A.
20© 2008 The Aerospace Corporation
3-D Trade Space – Intuitive Result: Missions that have the greatest complexity, are highest cost and longest development*
Higher Cost,Longer ScheduleMore Complex
Missions
* “A Quantitative Assessment of Complexity, Cost, And Schedule: Achieving A Balanced Approach For Program Success”, Bitten R.E., Bearden D.A., Emmons D.L.
21© 2008 The Aerospace Corporation
2.5 Year$50MCap
Complexity Bands vs. Cost and Schedule Help Proposers Define Scope of Mission to Fit Fixed Cost & Schedule*
$50 $150 $250 $350 $450 $550 $65024
36
48
60
72
Complexity
Development Cost (FY04$M)
Sche
dule
(Mon
ths)
0.75-0.80.7-0.750.65-0.70.6-0.650.55-0.60.5-0.550.45-0.5
75% - 80%
70% - 75%
65% - 70%
60% - 65%
55% - 60%
45% - 50%
50% - 55%
4 Year$350M
Cap
* “A Quantitative Assessment of Complexity, Cost, And Schedule: Achieving A Balanced Approach For Program Success”, Bitten R.E., Bearden D.A., Emmons D.L.
22© 2008 The Aerospace Corporation
NASA’s Report Card Following Mars ’98 Failures
• Complexity of Failed Missions High in Both Catagories!
• Planetary Missions are “Fastest”– But fail more often than earth-orbiters
• NASA Earth-Orbiting Missions are “Cheapest”
– But longer to develop than planetary• Overall Success Record is About 3
out of 4 !
NASA Planetary
NASA Earth Orbiting All NASA
Average Complexity of Failed/Impaired Missions 94% 91% 93%Average Complexity of Successful Missions 70% 55% 58%Overall Average Complexity 82% 60% 67%Success Ratio: "Better" 50% 86% 74%Average Development Time: "Faster" (mos) 41 46 44Total Spacecraft Cost: "Cheaper" ($M) 132 75 98
Reprinted with permission of Aviation Weekly and Space Technology
AW&ST 12 June 2000
23© 2008 The Aerospace Corporation
0
18
36
54
72
90
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Complexity Index
Dev
elop
men
t Tim
e (m
onth
s)
For a project that has fixed requirements and schedule, the inevitable outcome is that cost will grow if developmental problems occur
• Case Study: Mars Exploration Rover (MER)– 90-day surface lifetime; ~9-mos cruise– Launch Mass: 1050 kg (Delta II)– Mobile platform: 1000-m range
• Assessment found that:– 33-month development appeared inadequate– “Open Checkbook” and heritage offset shortfall
• Mitigations:– Focused on rapidly deploying staff to front load
schedule (dual/triple shifts)– Developed extra hardware test-beds
• Cost grew from $299M to $420M
10
100
1000
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Complexity Index
Dev
elop
men
t Cos
t (FY
03$M
)
AW&ST, 26 May 2003
Reprinted with permission of Aviation Weekly and Space Technology
24© 2008 The Aerospace Corporation
Typical Questions
• What is the magnitude of cost and schedule growth?
• How reliable are projects’ estimates in the conceptual design stage?
• Why does cost growth occur?
• What is the relationship between cost, schedule and “complexity”?
• Are there any improvements that can be made in estimating the costs of future design concepts?
25© 2008 The Aerospace Corporation
Example: Substantial Differences Exist between STEREO Science Definition Team (SDT) and Final Implemented Configuration*
STEREO STEREOProgrammatics SDT Final
Schedule (months) 40 70Launch Vehicle Taurus Delta II
TechnicalMass (kg)
Satellite (wet) 211 612Spacecraft (dry) 134 414Payload 69 133
Power (W)Satellite (Orbit Average) 152 515Payload (Orbit Average) 58 108
OtherTransponder Power (W) 20 60Downlink Data Rate (kbps) 150 720Data Storage (Gb) 1 8
SDT Configuration
Final Configuration
Illustrations reprinted
courtesy of NASA
* “An Assessment of the Inherent Optimism in Early Conceptual Designs and its Effect on Cost and Schedule Growth”, Freaner C., Bitten R., Bearden D., and Emmons D.
26© 2008 The Aerospace Corporation
Effect of Increased Complexity on Flight System Cost:STEREO Complexity Increased from 40% to 60%*
System Cost as Function of Complexity y = 11.523e5.7802x
R2 = 0.8832
10
100
1000
10000
0% 20% 40% 60% 80% 100%
Complexity Index
Cos
t (FY
08$M
)
Successful
Failed
Impaired
To-be-determined
STEREO @ SDT
STEREO @Launch
* “An Assessment of the Inherent Optimism in Early Conceptual Designs and its Effect on Cost and Schedule Growth”, Freaner C., Bitten R., Bearden D., and Emmons D.
27© 2008 The Aerospace Corporation
Schedule as Function of Complexity y = 24.22e1.6479x
R2 = 0.6889
01224364860728496
108120132
0% 20% 40% 60% 80% 100%
Complexity Index
Dev
elop
men
t Tim
e (m
onth
s)
Successful
Failed
Impaired
To-be-determinedSTEREO @ SDT
STEREO @Launch
Effect of Increased Complexity on Development Time:STEREO Complexity Increased from 40% to 60%*
* “An Assessment of the Inherent Optimism in Early Conceptual Designs and its Effect on Cost and Schedule Growth”, Freaner C., Bitten R., Bearden D., and Emmons D.
28© 2008 The Aerospace Corporation
Typical Cost-risk Analyses Won’t Capture Large Changes During Concept Evolution*
0%10%20%30%40%50%60%70%80%90%
100%
$200 $250 $300 $350 $400 $450 $500 $550 $600 $650 $700 $750 $800Total Mission Cost (FY07$M)
Perc
ent L
ikel
ihoo
d of
Com
plet
ing
at C
ost
SDT DesignFinal Design
$299M Estimate with 20% Reserve
Final Cost$551M
* “An Assessment of the Inherent Optimism in Early Conceptual Designs and its Effect on Cost and Schedule Growth”, Freaner C., Bitten R., Bearden D., and Emmons D.
29© 2008 The Aerospace Corporation
Inadequate Budget Planning for One Project Results in a Domino Effect for Other Projects in the Program Portfolio
$0
$50
$100
$150
$200
1999 2000 2001 2002 2003 2004 2005 2006
MMSSTEREOSolar-BTIMED
$0
$50
$100
$150
$200
1999 2000 2001 2002 2003 2004 2005 2006
MMSSTEREOSolar-BTIMED
STP 2000 Planned Funding STP Actual Funding History
Total Program Funding 1999-2006• Planned = $689M• Actual = $715M
Although the total program funding remained essentially the same over this time period, implementation of successive missions (e.g. MMS) was
substantially affected
Although the total program funding remained essentially the same over this time period, implementation of successive missions (e.g. MMS) was
substantially affected
MMS
STEREO
MMS
STEREO
30© 2008 The Aerospace Corporation
Summary
• Methods exist to estimate cost and schedule at the conceptual phase albeit with some level of uncertainty
• The greatest growth manifests itself late in project during Integration & Test
• Data highlighted that the primary reason for cost and schedule growth is internal project technical and development issues often associated with instruments
• Initial project estimates may be unreliable due to design and technology immaturity and inherent optimism
• Success dependence on system complexity and adequacy of resources observed with identification of a “no-fly zone”
• Better technical and programmatic appraisal early in lifecycle is needed along with independent assessment of design and programmatic assumptions
31© 2008 The Aerospace Corporation
References and Further Reading
1) Bearden, David A., “A Complexity-based Risk Assessment of Low-Cost Planetary Missions: When is a Mission Too Fast and Too Cheap?”, Fourth IAA International Conference on Low-Cost Planetary Missions, JHU/APL, Laurel, MD, 2-5 May, 2000.
2) Dornheim, Michael, "Aerospace Corp. Study Shows Limits of Faster-Better-Cheaper", Aviation Week and Space Technology, 12 June 2000.
3) Bearden, David A., "Small Satellite Costs", Crosslink Magazine, The Aerospace Corporation, Winter 2000-2001.4) Dornheim, Michael, “Can $$$ Buy Time?", Aviation Week and Space Technology, 26 May 2003.
5) Bitten R.E., Bearden D.A., Lao N.Y. and Park, T.H., “The Effect of Schedule Constraints on the Success of Planetary Missions”, Fifth IAA International Conference on Low-Cost Planetary Missions, 24 September 2003.
6) Bearden, D.A., “Perspectives on NASA Robotic Mission Success with a Cost and Schedule-constrained Environment”, Aerospace Risk Symposium, Manhattan Beach, CA, August 2005
7) Bitten R.E., Bearden D.A., Emmons D.L., “A Quantitative Assessment of Complexity, Cost, And Schedule: Achieving A Balanced Approach For Program Success”, 6th IAA International Low Cost Planetary Conference, Japan, 11-13 October 2005.
8) Bitten R.E., “Determining When A Mission Is "Outside The Box": Guidelines For A Cost- Constrained Environment”, 6th IAA International Low Cost Planetary Conference, October 11-13, 2005.
9) Bitten R., Emmons D., Freaner C., “Using Historical NASA Cost and Schedule Growth to Set Future Program and Project Reserve Guidelines”, IEEE Aerospace Conference, Big Sky, Montana, March 3-10, 2007.
10) Emmons D., “A Quantitative Approach to Independent Schedule Estimates of Planetary & Earth-orbiting Missions”, 2008 ISPA-SCEA Joint International Conference, Netherlands, 12-14 May 2008.
11) Freaner C., Bitten R., Bearden D., and Emmons D., “An Assessment of the Inherent Optimism in Early Conceptual Designs and its Effect on Cost and Schedule Growth”, 2008 SSCAG/SCAF/EACE Joint International Conference, Noordwijk, The Netherlands, 15-16 May 2008.