April 2011 

NASA/CR–2011-216847 

Subsonic Ultra Green Aircraft Research: 

Phase I Final Report 

Marty K. Bradley and Christopher K. Droney 

Boeing Research & Technology, Huntington Beach, California 
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April 2011 

NASA/CR–2011-216847 

Subsonic Ultra Green Aircraft Research: 

Phase I Final Report 

Marty K. Bradley and Christopher K. Droney 

Boeing Research & Technology, Huntington Beach, California 
Available from: 

NASA Center for AeroSpace Information 

7115 Standard Drive 

Hanover, MD 21076-1320 

443-757-5802 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Abstract 

This Final Report summarizes the work accomplished by the Boeing Subsonic Ultra Green 

Aircraft Research (SUGAR) team in Phase 1, which includes the time period of October 2008 

through March 2010. 

The team consisted of Boeing Research and Technology, Boeing Commercial Airplanes, General 

Electric, and Georgia Tech. The team completed the development of a comprehensive future 

scenario for world-wide commercial aviation, selected baseline and advanced configurations for 

detailed study, generated technology suites for each configuration, conducted detailed 

performance analysis, calculated noise and emissions, assessed technology risks, and developed 

technology roadmaps. 

Five concepts were evaluated in detail: 1) 2008 baseline, 2) N+3 reference, 3) N+3 high span 

strut braced wing, 4) N+3 gas turbine battery electric concept, and 5) N+3 hybrid wing body. 

A wide portfolio of technologies was identified to address the NASA N+3 goals. Significant 

improvements in air traffic management, aerodynamics, materials and structures, aircraft 

systems, propulsion, and acoustics are needed. 

Recommendations for Phase 2 concept and technology projects have been identified. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Acknowledgements 

This project and report reflect the combined efforts of the SUGAR team. The team members are 

Boeing Research and Technology, Boeing Commercial Airplanes, GE Aviation, and the Georgia 

Institute of Technology. The combined effort of this dedicated team has produced this 

comprehensive final report. 

The team would like to thank Erik Olson of the NASA Langley Research Center for his guidance 

as the NASA Contracting Officer Technical Representative (COTR). 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Table of Contents 

Abstract ............................................................................................................................................ i

Acknowledgements ......................................................................................................................... ii

Table of Contents ........................................................................................................................... iii

Index of Tables and Figures ........................................................................................................... vi

1.0 – Introduction and Background ................................................................................................ 1

1.1 – Defining “N” ...................................................................................................................... 2

1.2 – Vehicle Class Definitions .................................................................................................. 2

2.0 – Future Scenario ...................................................................................................................... 3

2.1 – Forecasting Tools ............................................................................................................... 3

2.2 – Current Market Outlook ..................................................................................................... 7

2.3 – Future Scenario Update: Configuration Economic and Mobility Impact ........................ 10

3.0 – Advanced Concept Selection ............................................................................................... 12

3.1 – Process Overview and Background ................................................................................. 12

3.2 – Pre-Workshop Steps ........................................................................................................ 13

3.3 – Workshop Steps ............................................................................................................... 20

3.4 – IRMA Process Payoff ...................................................................................................... 25

3.5 – Post Workshop Selection of Concepts for Detailed Analysis .......................................... 25

4.0 – Advanced Technologies Selection ....................................................................................... 32

4.1 – Aerodynamics Technologies ............................................................................................ 32

4.1.1 – Laminar Flow Control ............................................................................................... 32

4.1.2 – Riblets ....................................................................................................................... 33

4.1.3 – Excrescence Drag ...................................................................................................... 33

4.1.4 – Empennage ................................................................................................................ 33

4.1.5 – Airfoil Technology .................................................................................................... 33

4.1.6 – Additional Aero Technologies .................................................................................. 34

4.2 – Structural Technologies ................................................................................................... 34

4.2.1 – Materials and Manufacturing .................................................................................... 35

4.2.2 – Structural Health Management (SHM) ..................................................................... 35

4.2.3 – Loads and Environments ........................................................................................... 36

4.2.4 – Design and Criteria – Reliability Based Loads and Design ...................................... 36

4.2.5 – Adaptive Structures and Control Systems ................................................................ 36

4.2.6 – Integrated Energy Management ................................................................................ 37

4.2.7 – Coatings .................................................................................................................... 37

4.2.8 – Interiors ..................................................................................................................... 37

4.2.9 – Multi-functional Structures Technologies ................................................................ 37

4.2.10 – Additional Structures Technologies ........................................................................ 37

4.3 – Subsystem Technologies .................................................................................................. 37

4.3.1 – Power Demand, Generation, and Management ........................................................ 38

4.3.2 – Auxiliary Power Unit ................................................................................................ 39

4.3.3 – Actuators ................................................................................................................... 39

4.3.4 – Control Architecture ................................................................................................. 40

4.3.5 – Thermal Technology ................................................................................................. 40

4.3.6 – Electromagnetic and Lightning Effects .................................................................... 40

4.3.7 – Fuel ........................................................................................................................... 40
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4.3.8 – Flight Avionics .......................................................................................................... 40

4.3.9 – Wiring ....................................................................................................................... 40

4.3.10 – Computing Networks .............................................................................................. 40

4.4 – Propulsion Technologies .................................................................................................. 40

5.0 – Vehicle Development and Analysis ..................................................................................... 42

5.1 – Vehicle Requirements ...................................................................................................... 42

5.1.1 – Configuration Synthesis Ground Rules .................................................................... 42

5.1.2 – Choosing a Cruise Speed .......................................................................................... 45

5.1.3 – Initial Sizing and Points of Departure ....................................................................... 46

5.2 – Vehicle Development and Analysis Tools ....................................................................... 50

5.2.1 – Aerodynamic Buildup Methods ................................................................................ 50

5.2.2 – Mass Properties Methods .......................................................................................... 51

5.2.3 – Propulsion Methods .................................................................................................. 53

5.3 – 765-093 – SUGAR Free (2008 Baseline Configuration) ................................................. 53

5.3.1 – Configuration Layout ................................................................................................ 53

5.3.2 – Aerodynamic Buildup ............................................................................................... 57

5.3.3 – Mass Properties ......................................................................................................... 61

5.3.4 – Engine Data – CFM-56 ............................................................................................. 62

5.4 – 765-094 – Refined SUGAR (2030 Reference Configuration) ......................................... 63

5.4.1 – Configuration Layout ................................................................................................ 63

5.4.2 – Aerodynamic Buildup ............................................................................................... 65

5.4.3 – Mass Properties ......................................................................................................... 69

5.4.4 – Engine Data – “gFan” ............................................................................................... 70

5.5 – 765-095 – SUGAR High (2030 Advanced Strut Braced High Span) .............................. 72

5.5.1 – Configuration Layout ................................................................................................ 72

5.5.2 – Aerodynamic Buildup ............................................................................................... 74

5.5.3 – Mass Properties ......................................................................................................... 78

5.5.4 – Engine Data – “gFan+” ............................................................................................. 81

5.6 – 765-096 - SUGAR Volt (2030 Advanced Electric) ......................................................... 82

5.6.1 – Configuration Layout ................................................................................................ 82

5.6.2 – Aerodynamic Buildup ............................................................................................... 84

5.6.3 – Mass Properties ......................................................................................................... 84

5.6.4 – Engine Data – “e-f-hFan” Engines ........................................................................... 84

5.7 – 765-097 - SUGAR Ray (2030 Advanced Low Noise Hybrid Wing Body) .................... 89

5.7.1 – Configuration Layout ................................................................................................ 89

5.7.2 – Aerodynamic Buildup ............................................................................................... 92

5.7.3 – Mass Properties ......................................................................................................... 96

5.7.4 – Engine Data – “gFan+” ............................................................................................. 97

6.0 – Vehicle Performance and Environmental Impact ................................................................ 98

6.1 – Performance and Noise Analysis Methods and Ground Rules ........................................ 98

6.1.1 – Performance Analysis Tools ..................................................................................... 98

6.1.2 – Mission Profiles ........................................................................................................ 99

6.1.3 – DNL Contour Methods ........................................................................................... 102

6.2 – Vehicle Performance and Sizing .................................................................................... 103

6.3 – Vehicle Opportunities Trades ........................................................................................ 120

6.4 – Evaluation of NASA Metrics ......................................................................................... 124
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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6.4.1 – Fuel Burned and Energy Consumed ....................................................................... 124

6.4.2 – Takeoff Field Length and Metroplex Compatibility ............................................... 126

6.4.3 – LTO NOx Emissions ............................................................................................... 127

6.4.4 – Airport DNL Contours ............................................................................................ 128

6.4.5 – Environmental Impact of Cruise Emissions ........................................................... 130

6.5 – Sized Configuration Summary Table ............................................................................ 131

7.0 – Technology Roadmaps and Risk Assessment ................................................................... 133

7.1 – Technology Ranking ...................................................................................................... 133

7.2 – Technology Risk Assessment ........................................................................................ 142

7.2.1 – Candidate Technologies .......................................................................................... 142

7.2.2 – TRL Assessment ..................................................................................................... 143

7.2.3 – Risk Assessment ..................................................................................................... 144

7.2.4 – Risk Breakdown by Concept .................................................................................. 146

7.2.5 – Risk Breakdown by Technology Impact ................................................................. 148

7.3 – Technology Roadmapping ............................................................................................. 151

7.3.1 – Next Generation Air Traffic Management .............................................................. 151

7.3.2 – Alternative Fuels ..................................................................................................... 155

7.3.3 – Aerodynamic Technologies for Improved Airplane Performance .......................... 158

7.3.4 – Airframe Acoustic Technologies ............................................................................ 161

7.3.5 – Engine Acoustic Technologies ............................................................................... 165

7.3.6 – Advanced Subsystems ............................................................................................ 168

7.3.7 – Structural Materials ................................................................................................. 172

7.3.8 – Structural Concepts Roadmap ................................................................................. 175

7.3.9 – Advanced Engine Technologies.............................................................................. 178

7.3.10 – Hybrid Engine Technologies ................................................................................ 181

7.3.11 – High Span Strut Braced Wing Technology Integration ........................................ 184

8.0 – Summary, Conclusions, and Recommendations ................................................................ 187

8.1 – Summary ........................................................................................................................ 187

8.2 – Conclusions .................................................................................................................... 189

8.3 – Recommendations .......................................................................................................... 190

9.0 – References .......................................................................................................................... 192
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Index of Tables and Figures 

Figures: 

Figure 1.1 – The Rise and Volatility of Fuel Prices is Seriously Impacting Aviation1,2 ................ 1

Figure 1.2 – SUGAR Vehicle Class Definitions ............................................................................ 2

Figure 2.1 – Airline Revenue as Percentage of GDP ...................................................................... 3

Figure 2.2 – Time Trend Travel Share of GDP .............................................................................. 4

Figure 2.3 – Traffic forecasted within and between 12 world regions ........................................... 4

Figure 2.4 – Underlying Dynamics of the Airline Industry ............................................................ 5

Figure 2.5 – CMO Process .............................................................................................................. 6

Figure 2.6 – World Ticketed Origin and Destinations .................................................................... 6

Figure 2.7 – 2010 to 2030 Forecast: Strong Long Term Growth ................................................... 7

Figure 2.8 – Increasing Demand for Replacing Older, Less Efficient Aircraft .............................. 8

Figure 2.9 – Weekly Frequency vs. Airplane Size ......................................................................... 9

Figure 2.10 – Minimum Economic Aircraft Speed ...................................................................... 10

Figure 3.1 – Interactive Matrix of Alternatives for Conceptual Design Formulation .................. 13

Figure 3.2 – Pre-Workshop Activity Sequence ............................................................................ 14

Figure 3.3 – Functional Decomposition of Vehicle Characteristics ............................................. 15

Figure 3.4 – SUGAR’s Morphological Matrix ............................................................................. 16

Figure 3.5 – Part of SUGAR’s Compatibility Matrix ................................................................... 17

Figure 3.6 – Example of IRMA Dashboard with a couple selections. Red cells indicate 

incompatible options. ............................................................................................ 18

Figure 3.7 – Notional IRMA before Workshop ............................................................................ 20

Figure 3.8 – Workshop Workflow Diagram ................................................................................. 20

Figure 3.9 – Step 2: Identification of Relative Benefit ................................................................. 21

Figure 3.10 – Scoring the Alternatives ......................................................................................... 22

Figure 3.11 – Intermediate Results from the IRMA ..................................................................... 22

Figure 3.12 – Team Y’s Configuration Results from IRMA process ........................................... 23

Figure 3.13 – Concept sketches .................................................................................................... 23

Figure 3.14 – Large group configuration down-selection ............................................................ 24

Figure 3.15 – Workshop concept drawings .................................................................................. 25

Figure 3.16 – Candidate Configurations for Detailed Analysis .................................................... 26

Figure 3.17 – Configuration Groupings and Selections (Shaded) ................................................ 27

Figure 3.18 – Final Five airplanes selected for further study ....................................................... 28

Figure 3.19 – Alternatives Selected for Analysis ......................................................................... 28

Figure 3.20 – GE Engine Family for Consideration in SUGAR Vehicles ................................... 29

Figure 4.1 – Structural Weight Reduction Expeccted from SHM ................................................ 36

Figure 5.1 – Payload-Range Requirements .................................................................................. 42

Figure 5.2 – Approximation of Maximum Endurance and Maximum Range, and the Definition 

of Carson's Speed .................................................................................................. 45

Figure 5.3 – Fuel Burn vs. Mach Number for a family of high span airplanes optimized at 

different cruise speeds ........................................................................................... 45

Figure 5.4 – Initial Sizing: 765-093 – SUGAR Free Aspect Ratio Trade .................................... 47

Figure 5.5 – Initial Sizing: 765-094 – Refined SUGAR Aspect Ratio and Mach Number Trade 47

Figure 5.6 – Takeoff Gross Weight vs. Range for Battery Powered SUGAR Volt ..................... 49
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Figure 5.7 – Fuel burn from a Fuel Cell Powered SUGAR Volt .................................................. 49

Figure 5.8 – Hybrid Brayton-Battery Airplane Carries More Batteries as Range is Increased Until 

MTOW is Reached ............................................................................................... 50

Figure 5.9 – Initial Sizing: 765-097 – SUGAR Volt Fuel Burn ................................................... 50

Figure 5.10 – Standard CASES High Speed Buildup ................................................................... 51

Figure 5.11 – Mass Properties Methods Flowchart ...................................................................... 52

Figure 5.12 – 765-093 3-View Drawing ....................................................................................... 55

Figure 5.13 – 765-093 LOPA ....................................................................................................... 56

Figure 5.14 – 765-093 High Speed Buildup ................................................................................. 57

Figure 5.15 – 765-093 - M * L / D Total ...................................................................................... 58

Figure 5.16 – 765-093 - Low Speed Lift Curve; Free Air ............................................................ 59

Figure 5.17 – 765-093 - Low Speed Polar; Free Air .................................................................... 59

Figure 5.18 – 765-093 - Low Speed Lift / Drag; Free Air ............................................................ 60

Figure 5.19 – 765-093 Weight Summary ..................................................................................... 62

Figure 5.20 – CFM56-7B Engine Walk Around .......................................................................... 62

Figure 5.21 – 765-094 3-View Drawing ....................................................................................... 64

Figure 5.22 – 765-094 High Speed Buildup ................................................................................. 65

Figure 5.23 – 765-094 Aerodynamic Technologies Application .................................................. 66

Figure 5.24 – 765-094 - M * L / D Total ...................................................................................... 66

Figure 5.25 – 765-094 - Low Speed Lift Curve; Free Air ............................................................ 67

Figure 5.26 – 765-094 - Low Speed Polar; Free Air .................................................................... 68

Figure 5.27 – 765-094 - Low Speed Lift / Drag; Free Air ............................................................ 68

Figure 5.28 – 765-094 Weight Summary ..................................................................................... 70

Figure 5.29 – “gFan” Engine Walk Around ................................................................................. 71

Figure 5.30 – 765-095 3-View Drawing ....................................................................................... 73

Figure 5.31 – 765-095 High Speed Buildup a) Turbofan b) Open Fan ........................................ 75

Figure 5.32 – 765-095 – Aerodynamic Technologies Application ............................................... 75

Figure 5.33 – 765-095 - M * L / D Total ...................................................................................... 76

Figure 5.34 – 765-095 - Low Speed Lift Curve; Free Air ............................................................ 77

Figure 5.35 – 765-095 - Low Speed Polar; Free Air .................................................................... 77

Figure 5.36 – 765-095 - Low Speed Lift / Drag; Free Air ............................................................ 78

Figure 5.37 – 765-095 Weight Summary ..................................................................................... 80

Figure 5.38 – 765-095 Weight Opportunities ............................................................................... 80

Figure 5.39 – "gFan+" Engine Walk Around ............................................................................... 81

Figure 5.40 – 765-096 3-View Drawing ....................................................................................... 83

Figure 5.41 – "fFan" Propulsion System General Arrangement ................................................... 86

Figure 5.42 – “hFan” Engine Walk Around ................................................................................. 88

Figure 5.43 – 765-097 Configuration Layout ............................................................................... 90

Figure 5.44 – 765-097 LOPA ....................................................................................................... 91

Figure 5.45 – 765-097 High Speed Buildup ................................................................................. 92

Figure 5.46 – 765-097 - Aerodynamic Technologies Application ............................................... 93

Figure 5.47 – 765-097 - M * L / D Total ...................................................................................... 93

Figure 5.48 – 765-097 - Low Speed Lift Curve; Free Air ............................................................ 94

Figure 5.49 – 765-097 - Low Speed Polar; Free Air .................................................................... 94

Figure 5.50 – 765-097 - Low Speed Lift / Drag; Free Air ............................................................ 95

Figure 5.51 – 765-097 Weight Summary ..................................................................................... 97
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Figure 6.1 – Airplane Sizing Using ADNav ................................................................................. 98

Figure 6.2 – 2008 Reference Mission Profile ............................................................................. 101

Figure 6.3 – 2030 Mission Profile with NextGen Air Traffic Management .............................. 101

Figure 6.4 – Noise Methods Calibrated to Airport Data ............................................................. 102

Figure 6.5 – 765-093 Sizing........................................................................................................ 103

Figure 6.6 – 765-094 Sizing........................................................................................................ 106

Figure 6.7 – 765-095 Sizing (assumes 15,000 pound weight reduction) .................................... 110

Figure 6.8 – Restricting Cruise Altitude to 27,000 ft ................................................................. 120

Figure 6.9 – Potential for a Super Refined SUGAR ................................................................... 121

Figure 6.10 – SUGAR High Opportunities ................................................................................. 122

Figure 6.11 – SUGAR Volt Fuel Burn Opportunities ................................................................ 123

Figure 6.12 – Medium Airplane Frequencies vs. Range and SUGAR Volt Fleet Fuel Burn ..... 123

Figure 6.13 – Fuel Burn and Carbon Emissions ......................................................................... 124

Figure 6.14 – Fuel Burn Reduction vs. Range ............................................................................ 125

Figure 6.15 – Energy Utilization ................................................................................................ 126

Figure 6.16 – Vehicle Field Length Capability .......................................................................... 127

Figure 6.17 – Vehicle NOX Emissions ....................................................................................... 128

Figure 6.18 – 100% Replacement with N+3 Technology May Meet Goals ............................... 129

Figure 6.19 – Sensitivity of 55 DNL Distance to N+3 Noise Reduction ................................... 130

Figure 6.20 – Sized Baseline Configuration Payload-Range ...................................................... 132

Figure 7.1 – Generation of Technology Groups ......................................................................... 133

Figure 7.2 – Technology Ranking Dashboard Layout ................................................................ 134

Figure 7.3 – Refined SUGAR Technology Ranking with Equal Goal Weighting ..................... 135

Figure 7.4 – Refined SUGAR Technology Ranking for Fuel Burn Goal ................................... 135

Figure 7.5 – Refined SUGAR Technology Ranking for Cruise Emissions Goal ....................... 135

Figure 7.6 – Refined SUGAR Technology Ranking for NOx Reduction Goal .......................... 136

Figure 7.7 – Refined SUGAR Technology Ranking for Noise Reduction Goal ........................ 136

Figure 7.8 – SUGAR High Technology Ranking with Equal Goal Weighting .......................... 136

Figure 7.9 – SUGAR High Technology Ranking for Fuel Burn Goal ....................................... 137

Figure 7.10 – SUGAR High Technology Ranking for Cruise Emissions Goal .......................... 137

Figure 7.11 – SUGAR High Technology Ranking for NOx Reduction Goal ............................ 137

Figure 7.12 – SUGAR High Technology Ranking for Noise Reduction Goal ........................... 138

Figure 7.13 – SUGAR Volt Technology Ranking with Equal Goal Weighting ......................... 138

Figure 7.14 – SUGAR Volt Technology Ranking for Fuel Burn Goal ...................................... 138

Figure 7.15 – SUGAR Volt Technology Ranking for Cruise Emissions Goal .......................... 139

Figure 7.16 – SUGAR Volt Technology Ranking for NOx Reduction Goal ............................. 139

Figure 7.17 – SUGAR Volt Technology Ranking for Noise Reduction Goal ............................ 139

Figure 7.18 – SUGAR Ray Technology Ranking with Equal Goal Weighting ......................... 140

Figure 7.19 – SUGAR Ray Technology Ranking for Fuel Burn Reduction .............................. 140

Figure 7.20 – SUGAR Ray Technology Ranking for Cruise Emissions .................................... 140

Figure 7.21 – SUGAR Ray Technology Ranking for NOx Reduction Goal .............................. 141

Figure 7.22 – SUGAR Ray Technology Ranking for Noise Reduction Goal ............................ 141

Figure 7.23 – Risk Map .............................................................................................................. 145

Figure 7.24 – Risk Map for Refined SUGAR ............................................................................. 146

Figure 7.25 – Risk Map for SUGAR High ................................................................................. 147

Figure 7.26 – Risk Map for SUGAR Volt .................................................................................. 147
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Figure 7.27 – Risk Map for SUGAR Ray ................................................................................... 148

Figure 7.28 – Risk Map for the Fuel Burn Technologies ........................................................... 148

Figure 7.29 – Risk Map for the Cruise Emissions Technologies ............................................... 149

Figure 7.30 – Risk Map for the LTO NOx Technologies ........................................................... 149

Figure 7.31 – Risk Map for the Noise Technologies .................................................................. 150

Figure 7.32 – Risk Map for the TOFL Technologies ................................................................. 150

Figure 7.33 – Next Generation Air Traffic Management Operational Roadmap ....................... 153

Figure 7.34 – Next Generation Air Traffic Management Technical Roadmap .......................... 154

Figure 7.35 – Alternative Fuels Roadmap .................................................................................. 157

Figure 7.36 – Aerodynamic Technologies Roadmap ................................................................. 160

Figure 7.37 – Airframe Acoustic Technology Roadmap (part 1 of 2) ........................................ 163

Figure 7.38 – Airframe Acoustic Technology Roadmap (part 2 of 2) ........................................ 164

Figure 7.39 – Engine Acoustic Technology Roadmap* ............................................................. 167

Figure 7.40 – Advanced Subsystems Roadmap (part 1 of 2) ..................................................... 170

Figure 7.41 – Advanced Subsystems Roadmap (part 2 of 2) ..................................................... 171

Figure 7.42 – Structural Materials Roadmap .............................................................................. 174

Figure 7.43 – Structural Concepts Roadmap .............................................................................. 177

Figure 7.44 – Advanced Engine Technologies Roadmap* ......................................................... 180

Figure 7.45 – Hybrid Engine Technologies Roadmap* .............................................................. 183

Figure 7.46 – High Span Strut Braced Wing Technology Integration Roadmap ....................... 186

Tables: 

Table 1.1 – NASA's Technology Goals for Future Subsonic Vehicles6 ......................................... 1

Table 2.1 – SUGAR Fleet Mix by Year and Aircraft Class ........................................................... 9

Table 2.2 – CMO 2030 Aircraft Fleet Information ....................................................................... 10

Table 4.1 – Aero Technology Summary ....................................................................................... 32

Table 4.2 – Structural Technologies Summary ............................................................................. 34

Table 4.3 – Advanced Material Applications and Improvements ................................................ 35

Table 4.4 – Subsystems Technology Summary ............................................................................ 38

Table 4.5 – Installed Aircraft Power (Bleed, Hydraulic, Electric) ............................................... 39

Table 4.6 – APU Power and Weight ............................................................................................. 39

Table 4.7 – Control Systems Architecture .................................................................................... 40

Table 4.8 – Propulsion Technologies Applied to Various Engine Concepts ................................ 41

Table 5.1 – Airport Compatibility Group Codes .......................................................................... 44

Table 5.2 – Configuration Ground Rules ...................................................................................... 44

Table 5.3 – Initial Sizing: 765-093 SUGAR Free Results ............................................................ 47

Table 5.4 – Initial Sizing: 765-094 Refined SUGAR Results ...................................................... 48

Table 5.5 – Initial Sizing: 765-095 SUGAR High Results ........................................................... 48

Table 5.6 – Initial Sizing: 765-096 SUGAR Volt Results ............................................................ 50

Table 5.7 – Mass Properties Reduction Factors ............................................................................ 52

Table 5.8 – 765-093 High Speed Buildup .................................................................................... 57

Table 5.9 – 765-093 Group Weight Statement ............................................................................. 61

Table 5.10 – CFM56 Key Weight, Dimensions, and Performance Data ...................................... 63

Table 5.11 – 765-094 High Speed Buildup .................................................................................. 65

Table 5.12 – 765-094 Group Weight Statement ........................................................................... 69

Table 5.13 – gFan Engine Description ......................................................................................... 71
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Table 5.14 – 765-095 High Speed Buildup .................................................................................. 74

Table 5.15 – 765-095 Group Weight Statement ........................................................................... 79

Table 5.16 – gFan+ Key Weight, Geometry, Performance, and Technologies ............................ 82

Table 5.17 – eFan Key Weight, Dimensions, Performance, and Technologies ........................... 85

Table 5.18 – fFan Key Weight Geometry, Performance, and Technologies ................................ 87

Table 5.19 – hFan Key Weight, Geometry, Performance, and Technologies .............................. 89

Table 5.20 – 765-097 High Speed Buildup .................................................................................. 92

Table 5.21 – 765-097 Group Weight Statement ........................................................................... 96

Table 6.1 – Mission Changes due to NextGen ATM .................................................................. 100

Table 6.2 – 765-093 - SUGAR Baseline Sizing ......................................................................... 104

Table 6.3 – 765-093 – SUGAR Free Mission Profile Trade ...................................................... 105

Table 6.4 – 765-094 - Refined SUGAR Baseline Sizing ............................................................ 106

Table 6.5 – 765-094 – Refined SUGAR Time and Distance to Climb Trade ............................ 107

Table 6.6 – 795-094 – Refined SUGAR Advanced Engine Trade ............................................. 108

Table 6.7 – 795-094 – Refined SUGAR Takeoff Field Length Trade ....................................... 109

Table 6.8 – 765-095 Baseline Sizing .......................................................................................... 110

Table 6.9 – 765-095 OEW Trade ................................................................................................ 111

Table 6.10 – 765-095 Open Fan Trade ....................................................................................... 112

Table 6.11 – 765-095 TOFL Trade ............................................................................................. 112

Table 6.12 – 765-096 Baseline Sizing ........................................................................................ 113

Table 6.13 – 765-096 Power Trade ............................................................................................. 114

Table 6.14 – 765-096 Power Trade for Core Sizing ................................................................... 115

Table 6.15 – 765-096 MTOW Trade .......................................................................................... 116

Table 6.16 – 765-096 TOFL Trade ............................................................................................. 116

Table 6.17 – 765-096 Open Fan Trade ....................................................................................... 117

Table 6.18 – 765-096 Open Fan Power Trade ............................................................................ 118

Table 6.19 – 765-097 Baseline Sizing ........................................................................................ 119

Table 6.20 – 765-097 OEW Trade .............................................................................................. 120

Table 6.21 – Vehicle Segment Fuel Burn ................................................................................... 125

Table 6.22 – Parametrics on dB Reduction and Extent of Noise Footprint ................................ 128

Table 6.23 – Vehicle Noise Comparison .................................................................................... 130

Table 6.24 – Vehicle Emissions Summary ................................................................................. 131

Table 6.25 – Sized Baseline Vehicle Summary .......................................................................... 131

Table 7.1 – Candidate Technologies by Concept ....................................................................... 142

Table 7.2 – Candidate Technologies by NASA N+3 goal .......................................................... 143

Table 7.3 – Estimated TRL ......................................................................................................... 144

Table 7.4 – Candidate Technologies Risk Assessment .............................................................. 145

Table 7.5 – Next Generation Air Traffic Management Success Criteria .................................... 152

Table 7.6 – Alternative Fuels Success Criteria ........................................................................... 156

Table 7.7 – Aerodynamic Technologies Success Criteria .......................................................... 159

Table 7.8 – Airframe Acoustic Technologies Success Criteria .................................................. 162

Table 7.9 – Advanced Subsystems Success Criteria .................................................................. 169

Table 7.10 – Structural Materials Success Criteria ..................................................................... 173

Table 7.11 – Structural Concepts Success Criteria ..................................................................... 176

Table 7.12 – High Span Strut Braced Wing Technology Integration Success Criteria .............. 185
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

 1 

1.0 – Introduction and Background 

Air travel had a profoundly positive impact on the world in the 20th century. Airliners provide 

efficient, fast, and safe transport unmatched by any other mode of long distance travel. 

Furthermore, air travel has rapidly expanded to connect all corners of the earth due to its flexible 

capacity and routing, low infrastructure cost and freedom from geographic barriers. However, 

several factors are now combining to threaten air transportation over the coming decades. 

Increased demand for fuel and diminishing 

supply is resulting in increasing and volatile 

fuel prices. As illustrated in Figure 1.1, the 

inflation-corrected jet fuel price started 

climbing rapidly in 2000 and increased nearly 

four-fold compared to prices of previous 

decades. Growth of the world’s economy is 

straining natural resources, increasing the cost 

of fuel while simultaneously growing travel 

demand. Global consumption of carbon-based 

energy for all purposes is changing the 

environment in worrisome and unpredictable 

ways3

. While commercial aviation’s share of 

global CO2 production is only about 2%4, it is 

a conspicuous contributor, subject to 

regulation or taxation that may reduce its ability to sustain growth into the future. 

Anticipated air travel growth may also become restricted due to airport capacities and mounting 

resistance to airport noise and air pollution. These factors present an important opportunity for 

the aerospace community to apply exciting new technologies and design tools for the benefit of 

the United States and the world in the 21st century. 

The most challenging factors point toward the need for reduced energy consumption by airliners 

thus mitigating both the impact of high fuel prices and environmental effects. Exploration of 

alternative fuels and forms of energy along with more energy efficient aircraft will reduce the 

volume of fossil fuel required. These more efficient airplanes tend to be less noisy and combined 

with additional active and passive acoustic suppression measures can address NASA goals 

(Table 1.1). 

The ambitious goals of the study 

force reconsideration of every 

aspect of airplane efficiency. 

Changes in operations can 

provide significant improvements in energy consumption. 

For example, some airlines have 

recently reduced cruise speeds to 

increase efficiency5

 and 

improved flight paths are 

increasingly applied as a means 

$0.50

$1.00

$1.50

$2.00

$2.50

$3.00

$3.50

$4.00

19751980198519901995200020052010

USD/ Gallon

www.bts.gov (1977‐1999)

www.bts.gov (1986‐2007)

www.bts.gov (2000‐2010)

Figure 1.1 – The Rise and Volatility of Fuel Prices is 

Seriously Impacting Aviation1,2

Table 1.1 – NASA's Technology Goals for Future Subsonic Vehicles6

-33% -50% exploit metro-plex concepts Performance:

Field Length

-33% -40% better than -70% Performance:

Aircraft Fuel Burn

-60% -75% better than -75% LTO NOx Emissions

(below CAEP 6)

55 LDN at average airport 

boundary -32 dB -42 dB Noise(cum. below Stage 4)

N+3 (2030-2035 EIS)

Advanced Aircraft Concepts

(relative to user defined 

reference)

N+2 (2020 IOC)

Generation

Unconventional

Hybrid Wing Body

(relative to B777/GE90)

N+1 (2015 EIS)

Generation

Conventional

Tube and Wing

(relative to B737/CFM56)

CORNERS OF THE 

TRADE SPACE

-33% -50% exploit metro-plex concepts Performance:

Field Length

-33% -40% better than -70% Performance:

Aircraft Fuel Burn

-60% -75% better than -75% LTO NOx Emissions

(below CAEP 6)

55 LDN at average airport 

boundary -32 dB -42 dB Noise(cum. below Stage 4)

N+3 (2030-2035 EIS)

Advanced Aircraft Concepts

(relative to user defined 

reference)

N+2 (2020 IOC)

Generation

Unconventional

Hybrid Wing Body

(relative to B777/GE90)

N+1 (2015 EIS)

Generation

Conventional

Tube and Wing

(relative to B737/CFM56)

CORNERS OF THE 

TRADE SPACE
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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to wring the greatest possible efficiency from existing airplanes. While valuable, these changes 

alone cannot provide improvements that meet the goals of this study. A change to improve one 

factor of fuel efficiency can diminish another. However, new technologies promise to improve 

individual factors of airplane energy consumption with reduced adverse effects. For example, 

advances in material and structural technology may mitigate the increase in structural weight that 

usually results from using higher span to increase L/D. The broad time frame of the study 

encourages exploration and extrapolations of current technology trends as well as the invention 

of new technologies. These must be physically realistic and reasonable in the study time frame. 

1.1 – Defining “N” 

The definition of “N” technology is important as it serves as the reference for meeting the four 

NASA goals. At the beginning of the contract, communication with NASA verified that for the 

purpose of this study, 737NG vehicle and CFM56 engine technology are the in-service standards 

and thus the definition of “N”. It should be noted that the 737 will not be used directly for 

comparison to any advanced concepts developed. The “N” Baseline configuration will be 

developed using the same rules, tools, and levels of fidelity as the advanced concepts but with 

technology levels consistent with a 737NG. 

1.2 – Vehicle Class Definitions 

The Boeing Company recognizes Regional Jets (RJ’s), Single Aisles, Twin Aisles, Very Large 

Jets (VLJ’s), and Freighters as five classes of commercially operated airliners. For the SUGAR 

contract (with exception to the future scenario), these classifications will be simplified into 

Regional, Medium, and Large classes. The simplification also serves the purpose of separating 

the vehicle classes from the species discriminating names Twin Aisle and Single Aisle. 

Passenger airplanes dominate the commercial market and tend to push airplane technology 

forward. Freighters are historically fallouts from passenger driven designs and are thus excluded 

from the SUGAR study. These class definition changes are illustrated in Figure 1.2. 

Boeing Classification

– Regional

– Single Aisle

 737

 757

 A320

– Twin Aisle

 767

 777

 A340

– Very Large Jets

 747

 A380

– Freighters

SUGAR “N+3” Contract 

Classification

– Regional

– Medium

– Large

All vehicles sized for this 

contract are considered 

family center points

Figure 1.2 – SUGAR Vehicle Class Definitions 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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2.0 – Future Scenario 

A 20 year forecast of the commercial airline current market outlook (CMO)7 has been published 

for 40 years and shared with airlines, journalists, bankers, investment analysis, governments, 

suppliers and educators. The forecast includes all commercial aircraft 30 seats and over in all 

regions of the world. It is the only complete forecast that combines a top down and bottom up 

analysis. 

Historically the CMO has a good record of predicting aggregate air travel demand, however at 

disaggregated levels it has somewhat under predicted the demand for the future number of new 

airplanes in various size categories. This under-prediction is comprised primarily of an underforecasting of demand for the single-aisle market and the ability of twin-aisle airplanes to open 

up new long-range city pairs with a higher number of frequencies. In addition, the distortion of 

market forces with the introduction of Regional Jets and associated scope clause also impacted 

demand in these size categories. Much of the misestimated demand for large airplanes (e.g.747, 

A380) was predicated on historical behavior and regulatory régimes in force at the time. These 

impacts have been reduced as these phenomena have been incorporated into the knowledge base 

and tools underpinning the CMO. 

The CMO tools, described in Section 2.1, were exercised for the SUGAR contract and provide 

specific forecasts for the 2030 and 2055 timeframes which are discussed in Section 2.2. 

2.1 – Forecasting Tools 

Prior to understanding how Boeing’s market forecasting tools work, one must understand the 

underlying dynamics of the airline industry. The airline operating environment is challenging 

and is driven by pressures that are hard to predict including volatile oil prices, a varying world 

economy, shifting regulatory policies, geopolitical events, slowing traffic growth, congestion, 

and environmental pressures. 

Typically, world airline revenue is approximately one percent of Gross Domestic Product (GDP). 

This relationship varies by country and is shown in Figure 2.1. While airline revenues remain a 

constant percentage of GDP, travel demand grows over time. 

0.00%

0.20%

0.40%

0.60%

0.80%

1.00%

1.20%

1.40%

1.60%

1.80%

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Africa

Asia-Pacific

Europe

Latin America

Middle East

North America

World

Figure 2.1 – Airline Revenue as Percentage of GDP 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Trade, measured as imports and exports, typically grows one and a half to two times faster than 

GDP. The ratio of GDP to Available Seat Miles (ASM), or travel share, grows with increased 

trade. A steady positive trend of travel share with time is illustrated in Figure 2.2. 

0

20

40

60

80

100

120

140

160

180

1990 1995 2000 2005 2010 2015 2020 2025

Travel Share of GDP (GDP/ASK index

Figure 2.2 – Time Trend Travel Share of GDP 

These relationships are used in conjunction with a world model that predicts the GDP growth of 

twelve economic regions (Figure 2.3). These regions were formed to best represent major world 

traffic flows and do not always match political or geographic regions. This defines 64 traffic 

flows both internal to the region and between regions. Recognition of the impact of liberalization 

of air services on airline competition and the subsequent stimulation of traffic as the value of air 

travel increases are also modeled and incorporated into the demand model. 

North 

America 

Central 

America 

South 

America 

Europe

Africa

Mid

East

C.I.S.

Oceania 

China

South East

Asia 

North 

East 

South Asia 

West

Asia 

Figure 2.3 – Traffic forecasted within and between 12 world regions 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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The GDP forecasted demand is met by forecast airline operators. 149 individual airlines 

(including cargo, charter, regional, low cost carriers (LCC), and subsidiary carriers) are modeled 

based on their existing fleet, operational models, and financial situation. Predictions estimate 

how airlines react to forecast demand. Factors that would affect airline decisions are illustrated in 

Figure 2.4 and primarily depend on the duration of the forecasted demand and the financial 

impact on the airline. The airline models also try to predict what additional new markets would 

be served by each airline. 

Demand modeling also includes effects of transportation mode shifts, infrastructure, air traffic 

management (ATM), and operations. Transportation mode shifts (e.g. air-rail in Europe, rail-air 

in India) both positive and negative to air travel in the short-haul markets are estimated and 

incorporated. Infrastructure in general is assumed to lag demand, there is a build-up of pressure 

to improve the infrastructure before it is improved. NextGen ATM is included in the model, but 

is assumed to not be as efficient as planned. Metroplex operations are not explicitly in the 

forecast but they are also not excluded from being a solution to pent-up demand from 

infrastructure lag. Environmental concerns are modeled as a broadening cap and trade 

arrangement lead by Europe, followed by USA and Asian countries. This equates to an 

increasing cost of flying and, by holding %GDP constant, leads to less demand for travel than 

would be otherwise expected. 

Economic growth + 

Liberalization

Traffic growth

Fleet Requirements

Fleet Growth

Airline Decisions

Capital intensity

Utilization

Used Airplanes

New Airplanes

Parked Airplanes

Low High

Short term

Long term

Delayed 

Retirement

Global economic growth drives air 

travel and in turn airline fleet growth

Figure 2.4 – Underlying Dynamics of the Airline Industry 

The CMO is driven by economics. Boeing’s product forecasters create a bottom-up scenario at 

the airline level by adding services (frequency, city pairs, and capacity) to balance the top-down 

traffic forecast (driven by GDP) on a regional flow basis (Figure 2.5). 

The product forecast used for the process is derived by examining data about the current and 

projected fleet. Figure 2.6, an example of this data, shows the number of tickets sold in a day for 

every origin-destination pair (international and domestic). Highlighted areas have low traffic 

density and thus limited product availability. These are created by geography, (few fly to the 

middle of an ocean), and probability, (the odds of needing to fly to exactly the opposite side of 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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the world). This data is an example of what is used to determine which product characteristics 

show consistent and stable demand over time; this stability is utilized to forecast what the market 

will look like in 2030 and beyond. Top-Down Bottom-Up Product Forecast Service Forecast Traffic Forecast 

Fleet Forecast 

By Airline 

-Product Scenario- 

-Airplane Characteristics- 

-Known Plans- 

-Firm Orders- 

-RetirementsService Forecast = Airline ASMs?

Service Forecast

By Airline 

Share Allocation 

by Airline

ASM Forecast – 

Regional Flows

GDP Growth 

& World Trade

-Liberalization-

-Environment- 

-Geopolitics-

-Fuel Price- 

-Travel Spend-

-Growth Rates- 

-OAG- 

-Non Scheduled- 

-Market Share- 

-OAG- 

-Non Scheduled- 

-Known Plans- 

-Airline Strategies-

-Business Models- 

-Utilization-

-Current FleetASMs by Airline 

by Flow 

Traffic Forecast ASMs = Service Forecast ASMs?

Figure 2.5 – CMO Process 

Figure 2.6 – World Ticketed Origin and Destinations 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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2.2 – Current Market Outlook 

Market forecast results are shown in Figure 2.7, and indicate that strong long term growth will 

continue. Short term economic fluctuations are not expected to significantly change the long 

term growth trends. 

Figure 2.7 – 2010 to 2030 Forecast: Strong Long Term Growth 

Over the past 20 years, air travel grew by an average of 4.8 percent each year, despite two major 

world recessions, terrorist acts, the Asian financial crisis of 1997, the severe acute respiratory 

syndrome (SARS) outbreak in 2003, and two Gulf wars. During 40 years of producing the CMO, 

Boeing has learned that the resilience of air transport growth comes from its intrinsic importance 

to the livelihood of people around the world. 

On average over the next 20 years, passenger travel will grow at 5.0 percent and cargo at 5.8 

percent. The fastest growing economies will lead the transformation into a more geographically 

balanced market. The average growth in airline passenger numbers will be around 4.0 percent 

each year. More people will be traveling by air as economies grow. Markets will open up 

through reduced regulation and increased competition. As these markets expand, new travel 

opportunities will mostly be on longer-distance flights. 

The air transport fleet plays a fundamental role in stimulating and sustaining economic activity. 

This tie-in is clear, with the 3.2 percent annual fleet growth in line with expected long-term 

economic growth of 3.2 percent. 

Total fleet size as well as the rate of aircraft replacement have been estimated and are shown in 

Figure 2.8. This shows a large demand for replacing older, less efficient aircraft. 

With the projected passenger and cargo growth, the total in-service fleet will nearly double by 

2030 growing from 18,000 airplanes to over 32,000. It will take 14,000 new airplanes to meet the 

growth requirements. In addition, it will take about 11,900 new airplanes to replace retiring 

airplanes. That’s a total need of about 25,900 new airplanes over the next 20 years. 

Approximately 54 percent of the 25,900 new airplanes being delivered over the next 20 years are 

attributable to growth in the market. The remaining 46 percent of the demand for new aircraft is 

coming from replacing older airplanes, up from 36 percent last year. This strong replacement 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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demand is being driven by high fuel prices and the introduction of new, very efficient, very 

capable aircraft. In a tough, competitive environment, airlines are looking for ways to cut costs 

from their operations. With high fuel prices, it certainly makes more and more sense for airlines 

to replace their old aircraft with new, fuel efficient airplanes, and we have reflected that trend in 

our analysis. 

Approximately 6,100 airplanes, about 34 percent of the fleet operating today, will still be in 

operation 20 years from now. 

0

10,000

20,000

30,000

40,000

Units

32,000

18,000

2008 2030

14,000

Growth

54%

11,900

Replacement

46%

6,100

Retained Fleet

25,900

Figure 2.8 – Increasing Demand for Replacing Older, Less Efficient Aircraft 

The projected fleet compositions for 2008, 2030, and 2055 are listed in Table 2.1. The table 

shows the rate of fleet retirement based on aircraft technology level and also helps illustrate the 

time it takes for a new airplane to comprise a significant percentage of the market. A new 

medium sized aircraft with an entry to service of 2030 will comprise about 50% of the fleet in 25 

years. This trend is consistent with other sized aircraft though the actual percentage varies. 

The CMO also predicts the required airplane size for the estimated entry to service. The size is 

driven by many factors. Technology and the environment, depending on specifics, may pull 

toward either larger or smaller vehicles. Seat mile economics and airport congestion generally 

drive toward larger aircraft. Crew costs, direct markets, turn time, competition, and the overall 

passenger experience drive toward smaller aircraft. 

Figure 2.9 shows the weekly frequencies of airplanes with relation to their size. Future markets, 

fuel prices, infrastructure, and environmental issues are predicted to force an up-gauging in the 

small airplane market driving small and medium regional jets into large regional jets and small 

single-aisle categories. Single aisle and regional jets comprise 90% of airplane frequencies, a 

trend which should continue into 2055. 

Detailed future fleet information is needed for aircraft sizing. The CMO was used to predict the 

number of aircraft in the fleet in 2030 as discussed in the previous paragraphs. It was also used to 

generate more specific data about each airplane class shown in Table 2.2. The data in the table is 

a mixture of design goals and operational characteristics generated with the assumption that 

vehicles will fly the same speed they fly today and in the current air traffic management system. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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The number of seats, average trip distance, and maximum trip distance are used as design 

parameters for the airplane. 

Table 2.1 – SUGAR Fleet Mix by Year and Aircraft Class 

Series Class Generation 2008 2030 2055 

Regional 

N+3 0 0 2,000 

N 0 1,000 1,250 

N-1 1,800 1,575 150 

N-2 1,350 100 0 

N-3 75 0 0 

Total 3,225 2,675 3,400 

Medium 

N+3 0 0 20,000 

N+1&2 0 9,000 18,000 

N 0 1,500 1,000 

N-1 6,050 11,350 1,000 

N-2 4,400 300 0 

N-3 950 0 0 

Total 11,400 22,150 40,000 

Large 

N+3 0 0 5,000 

N+1&2 0 1,000 3,350 

N 0 4,400 5,000 

N-1 1,550 1,700 250 

N-2 1,800 125 0 

Total 3,350 7,225 13,600 

Grand Total 18,000 32,000 57,000 

Regional jets

(below 90 seats)

Single-aisle

(90-240 seats)

Twin-aisle

(180-400 seats)

747 & larger

(over 400 seats)

0

50

100

150

200

250

300

350

400

450

Airplane Size

Weekly Frequency (1,000)

2030

2010

90% of all frequencies 

99% of all frequencies 

Notional 2050

Figure 2.9 – Weekly Frequency vs. Airplane Size 

Since the air traffic management system is unconstrained for SUGAR the airplanes are allowed 

to fly slower than what is listed in the chart. The effects of flying slower are hard to estimate. It 

can be argued that slowing down will reduce demand because flights will get longer or that 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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demand will increase because flights will cost less. It is expected that slowing down one class 

will push demand onto other classes of vehicles. These types of market changes are very hard to 

simulate and are beyond the scope of this study. For SUGAR the assumption is that the fleet 

daily air miles (fleet size times daily miles), or demand, remains fixed independent of speed. 

Slowing a vehicle class down will result in an increased fleet size inversely proportionate to the 

change in speed. Since the total fleet daily air miles remains fixed, each airplane would fly less 

cycles in a day and thus burn less fuel for the day. On a fleet basis, the fuel burn benefit for 

slowing down is proportional to the individual airplane fuel burn benefit. 

Table 2.2 – CMO 2030 Aircraft Fleet Information 

 Regional Medium Large 

Number of Aircraft 2,675 22,150 7,225 

Family Midpoint # of Seats 70 154 300 

Avg Distance 575 900 3,300 

Max Distance 2,000 3,500 8,500 

Avg Trips/day 6.00 5.00 2.00 

Avg MPH 475 500 525 

Fleet Daily Air Miles (K) 8,500 100,000 55,000 

Daily Miles 3,200 4,500 7,600 

Daily Hours 6.92 9.23 13.96 

Aircraft utilization, desired operational city pairs, and airline driven economics drive a minimum 

speed for aircraft. Figure 2.10 shows this minimum speed per aircraft class and was derived from 

the future scenario study. The minimum speed of the medium and large categories is being 

driven primarily by geography and utilization, less than these speeds would have a large impact 

on the airline networks and value of travel (these impacts are beyond the scope of this study). 

– Minimum Speed Drivers:

 Desired City Pairs

 Flight Crew Rules

 Aircraft Utilization

SUGAR will estimate the best speed to fly at or above the 

MINIMUM speed allowed by the future scenario

– Current Class Speeds:

 Regional: ~ 0.70 – 0.75 Mach

 Medium: ~ 0.75 – 0.80 Mach

 Large: ~ 0.80 – 0.85 Mach

 Regional: Optimum

 Medium: 0.70 Mach

 Large: 0.80 Mach

Figure 2.10 – Minimum Economic Aircraft Speed 

2.3 – Future Scenario Update: Configuration Economic and Mobility Impact 

The Future Scenario was generated assuming a technology development path similar to our 

historical long term trend. Since 1970 the air transportation system is about 70% more efficient, 

this improvement has come from airspace management, airline operations, airplane design, and 

material technology. The underlying assumption of progress aligns with this trend. Projecting 

forward to 2030-2035 yields ~35% improvement from the current system. It is important to 

remember that in 1970 the world was a much different place, and one would be hard pressed to 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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imagine all of the advancements that have been delivered over that time. After the configurations 

discussed later in this report were analyzed, it was determined that, when combined with air 

traffic control improvements, the assumptions in the Future Scenario are similar to the results 

achieved by the Refined SUGAR, SUGAR High, and SUGAR Ray. Therefore, the technologies 

and designs studied are in-line with the assumptions made at the beginning of this study, so the 

existing Future Scenario is still valid for the SUGAR advanced concepts. Even though these 

aircraft fly slower than what is suggested by Table 2.2, their gate to gate time is actually a little 

faster due to improvements in direct routing and taxi times (Figure 6.3). The city pairs the 

aircraft can serve are not greatly impacted because the cruise Mach number was held to Mach 

0.70. Overall, the data in the table remains valid. 

The SUGAR Volt concept uses less fuel but assumes significant changes in airport infrastructure 

to handle the charging and transportation of modular batteries. A separate analysis of energy and 

battery cost associated with this concept is recommended. 

Recent changes in the World economy, although significant, are still thought to be captured by 

the long term trends assumed in the Future Scenario. The influence of oil price fluctuations on 

Boeing forecasts have also been studied, and tend to influence all forms of transportation, 

reducing the unique impact on aviation. 

The baseline Future Scenario is driven by many factors, like technology investment, regulation 

of air travel, as well as basics like airport and airspace infrastructure. There is a basic assumption 

that government and industry worldwide will continue to invest to allow air travel to compete 

with other transportation modes and continue to act as a catalyst for trade and business 

development in the future. If this assumption were to be removed, then the Future Scenario 

would change greatly. 

For this alternate Future Scenario, the resulting travel demand can be evaluated and there is a 10-

15% decrease in travel that depends on the rate of technology investment in other modes, i.e. 

would they slow down their investment because they have less competition. The decrease in 

travel is equivalent of not needing ~10,000 airplanes during the 20 years after the change in 

technology assumption, or ~7,000,000 passengers per day. More speculatively, the effect on 

trade and global economic development could slow GDP by 0.3%, but this effect has not been 

accounted for. 

In this alternate Future Scenario, the cost of flying is up, while the level of service is down; this 

is a compounding effect that reduces travel demand further and squeezes profits across the 

industry. The profit squeeze reduces investments and slows development compounding the issue. 

The total effect of this is not captured in the forecast of the reduction in fleet need because it 

quickly spirals out of control until there is no more air travel; we know that something would 

change and equilibrium would be restored. 

In this alternate Future Scenario, seat mile economics and scarce infrastructure drive toward 

larger aircraft, while direct markets, competition, and the overall passenger experience suffer. 

This alternate Future Scenario is not considered likely, but is discussed here only to serve as an 

indication of the value of the technology work that is being conducted at NASA, Boeing, the 

engine companies, and universities. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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3.0 – Advanced Concept Selection 

The Boeing Company solicited input from the Georgia Tech (Ga. Tech) Aerospace Systems 

Design Laboratory (ASDL) to facilitate a workshop for concept selection for the SUGAR 

aircraft. Working closely with Boeing and General Electric, ASDL formalized a custom process 

and created tools specifically created for the concept selection activity based on past experience 

in similar programs. 

The overall goal of the workshop was to downselect a few operational, airframe and engine 

concepts for further analysis and study. The workshop required coordination between the 

partners prior to the actual events of the workshop to create the interactive tools which would aid 

in workshop activities. 

3.1 – Process Overview and Background 

The workshop for SUGAR concept selection was centered on using an Interactive 

Reconfigurable Matrix of Alternatives (IRMA) as a tool to aid in the discovery of configurations. 

IRMA is a systematic qualitative procedure that is unique to the conceptual design process 

developed by ASDL. It was created to provide an “audit-trail” to define reference systems upon 

which quantitative analysis could be performed in a traceable, structured and systematic manner. 

IRMA builds on the concept of a Morphological Analysis created by Fritz Zwicky. Zwicky states 

that “within the final and true world image everything is related to everything, and nothing can 

be discarded a priori as being unimportant.”8

Given the complexity of the new systems, there are millions of possible alternatives in the 

hyperspace of requirements, technologies and responses. Not all these alternatives can be 

quantitatively compared within the practical time limits imposed by the program management. 

To overcome this issue, a qualitative brain-storming exercise has been developed by ASDL to 

prioritize and down-select the important requirements and alternatives with feedback from 

disciplinary experts and program management. This allows the quantitative process of the downselected alternatives to be much more manageable. 

The IRMA is a combination of Systems Engineering techniques such as Matrix of Alternatives, 

Multi-Attributes Decision Making (MADM) and Technique for Ordered Preference by Similarity 

to Ideal Solutions (TOPSIS)9

. Figure 3.1 depicts the Interactive Reconfigurable Matrix of 

Alternatives (IRMA) which was created for the SUGAR workshop. These tools provide a 

process for functionally decomposing the problem, identifying alternatives and technologies to 

meet the functions, and identifying the solutions that meet the top level needs. These tools and 

processes provide a mechanism for encouraging collaborative communication at the early stages 

of conceptual design. 

The general procedure for selecting a system through the Morphological Matrix of Alternatives 

is as follows: 

- Functionally decompose the existing system 

- For each function, list all the possible ways in which it might be satisfied 

- Examine the matrix for the possible new permutations. 
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Fuel Burn and 

Energy 

Consumed

Order of 

Selection Alternative #1 Score Select Alternative #2 Score Select Alternative #3 Score Select Alternative #4 Score Se

Number of Fuselages None 0 Yes 1 2

Wing-Body Blend None None Fairing Moderate Blend Extreme Blend

No. of Passenger Decks None 1 1.5 2

Number High 3 1 2

Location Med 9 Low Mid High Pylon Mount

High Lift System Low Conventional Triple Slotted Flap Yes USB EBF

Bracing Low None Strut Cable Truss

Join Med 7 None Tip Mid Box

Folding Med 8 None In Flight On Ground

Morphing Low None Planform Variable Camber Both

Winglet High 2 None Conventional Raked Feathers

Pitch Effecter High Conv. Horizontal T-Tail V-Tail Canard

Yaw Effecter Med Conv. Vertical V-Tail H-Tail Winglet

Roll Effecter Med Aileron / Spoiler No Wing Warping Yes

Location Low Under Wing Mid Wing Above Wing Aft Fuselage

Propulsor Type None Propeller Open Rotor High BPR Fan Ultra High BPR Fan

Propulsor Arrangement High 1 Discrete Distributed

Energy Conversion Low Brayton Const. Vol. Fuel Cell / Motor Piston

Augmentation None None Batteries Fuel Cell Brayton

Primary Fuel None Liquid Hydrocarbon Gaseous Hydrogen Batteries

Metrics Selection Alternatives (First)

Vehicle Characteristics

Fuselage Wing S&C Propulsor Integration

Figure 3.1 – Interactive Matrix of Alternatives for Conceptual Design Formulation 

The last step offers great ambiguity which the ASDL developed IRMA process is attempting to 

solve. The IRMA process contains a dynamic dashboard for visualizing the effects of each 

decision. When a selection is made, incompatible options are filtered out thereby facilitating 

down-selection. The interactive nature of the IRMA tool allows for decision makers to 

understand the impact of decisions at the initial point of decision making. In a collaborative 

group such as seen at the SUGAR workshop, this tool provides a mechanism for understanding 

the impacts of the order of decisions as well as facilitating discussions among group members. 

3.2 – Pre-Workshop Steps 

In order to create an IRMA and have a successful workshop for selecting advanced vehicle 

concepts, a fair amount of systems engineering activities must occur prior to the workshop. 

Figure 3.2 depicts the necessary general steps to creating the IRMA in preparation for the 

workshop. This section will describe the details and major outcomes of each step. 

These steps are carried through by a subset of workshop participants who have demonstrated 

technical competence in systems engineering techniques as well as the technical aspects for the 

problem at hand. The subgroup for the development of the SUGAR IRMA consisted of 

representatives from The Boeing Company as well as representatives from General Electric. The 

representatives from General Electric provided input and guidance supporting engine 

technologies and integration issues. 
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Identify 

alternatives to 

decomposition 

and compose 

morphological 

matrix 

Create 

conditional 

relationships of 

functional 

decomposition

Identify and 

discuss 

attributes for 

each row of 

decomposition 

Rank order 

decomposition 

based on 

relative 

importance to 

requirements 

Set optimal 

suitable 

reference 

systems 

IRMA 

Set of Customer 

Requirements 

Decompose 

requirements 

in terms of 

functional 

taxonomy

Define 

Problem in 

terms of 

Requirements 

Figure 3.2 – Pre-Workshop Activity Sequence 

Pre-workshop Step 1: Identify a set of customer requirements 

Preparation for the workshop begins first with understanding the needs of the customer. Section 

1.0 and 2.0 discusses the current outlook for the commercial aircraft market and illustrates the 

need for a more efficient, environmentally friendly fleet. In response to this, NASA has issued an 

aggressive set of goals to drive next generation aircraft design. Table 1.1 shows the various goals 

NASA has set for future aircraft design. The SUGAR initiative strives to develop N+3 vehicle 

concepts to meet the most aggressive set of goals: reduction of aircraft noise, NOx emissions, 

takeoff field length, and fuel burn. These requirements, coupled with the current market outlook, 

provide the initial constraints for the SUGAR initiative and direct IRMA construction. 

Pre-workshop Step 2: Define problem in terms of requirements 

Once the customer has issued a set of requirements, and the overall project goal has been 

established, the requirements must be translated such that the problem can later be mapped to 

realizable engineering characteristics. Section 2.0 discusses how the aircraft fleet is changing and 

how aircraft will be used in the future. This information, coupled with NASA’s goals, helps 

formulate the overall problem: to design advanced concept, improved performance aircraft which 

can fit the changing market while also meeting aggressive environmental standards. Therefore, 

the problem can be understood as one primarily involving aircraft architecture; changes to the 

aircraft architecture will either enhance or detract from the vehicle performance relative to one or 

more of NASA’s goals. In order to thoroughly address vehicle performance, the specific vehicle 

systems that most affect performance should be identified and targeted as important areas for the 

conceptual design process. The Boeing team noted that design changes made to the aircraft 

fuselage, wing, stability and control system, and propulsion system would most impact the 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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vehicle’s performance. The problem then becomes one that involves conceptual design tradeoffs 

of the vehicle characteristics. 

Pre-workshop Step 3: Decompose requirements in terms of functional taxonomy 

Once the targeted areas of vehicle architecture have been defined, it is important to break down 

the architecture in terms of its functional components. This is the first step in building the 

morphological matrix essential to IRMA. Using the sub-categories defined by Boeing (i.e. 

fuselage, wing, stability and control, propulsion) as a starting place, the vehicle can be 

functionally broken down into its parts. These functional “parts” will serve as points of decision 

for each concept created. Design decisions are then made at this level of detail, ensuring that the 

concepts can be built from the “bottom up” with much freedom to generate the N+3 concepts 

that will best address NASA’s goals. 

In order to begin vehicle decomposition, it is important to know the vehicle components which 

make up each subsystem as these generate decision making points in the IRMA. For example, a 

few of the design points that make up the wing subsystem are the number of wings, wing 

location, the type of high lift system, and the type of wing bracing. 

The functional decomposition was completed by Boeing and GE in keeping with the fuselage, 

wing, stability and control, and propulsion categories. A complete visualization of the finished 

functional taxonomy can be seen in Figure 3.3. 

Number of Fuselages

Wing-Body Blend

No. of Passenger Decks

Number

Location

High Lift System

Bracing

Join

Folding

Morphing

Winglet

Pitch Effecter

Yaw Effecter

Roll Effecter

Location

Propulsor Type

Propulsor Arrangement

Energy Conversion

Augmentation 

Primary Fuel

Vehicle Characteristics

Fuselage Wing S&C Propulsor Integration

Figure 3.3 – Functional Decomposition of Vehicle Characteristics 

Pre-workshop Step 4: Identify alternatives to decomposition and compose morphological 

matrix 

Once the functional taxonomy is complete, each entry to the decomposition must be given 

possible alternatives that could function in a vehicle design. For example, an airplane may 

realistically have 1 or 2 wings. Therefore these are the two alternatives which would populate the 

“number of wings” category. Similarly, the realistic options for “wing morphing” would be to 

have no wing morphing, variable camber morphing, planform morphing, or simultaneous 

variable camber and planform morphing. It is important to populate the list with as many 

alternatives as one can think of, also allowing for capabilities which may not be developed now 

but are projected to be fully developed by the N+3 timeframe. These alternatives serve as 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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possible “choices” in the IRMA, guiding the users in creating vehicle concepts. The alternatives 

are populated across a row for each entry created in the functional taxonomy. Once the 

alternatives have been entered, the morphological matrix is complete and the backbone for the 

IRMA is set. 

The complete morphological matrix created by Boeing and GE for the SUGAR workshop is 

shown in Figure 3.4. 

Alternative #1 Alternative #2 Alternative #3 Alternative #4 Alternative #5 Alternative #6

Number of Fuselages 0 12

Wing-Body Blend None Fairing Moderate Blend Extreme Blend

No. of Passenger Decks 1 1.5 2

Number 1 2

Location Low Mid High Pylon Mount Low-High Low-Pylon

High Lift System Conventional Triple Slotted Flap USB EBF IBF AFC

Bracing None Strut Cable Truss

Join None Tip Mid Box

Folding None In Flight On Ground

Morphing None Planform Variable Camber Both

Winglet None Conventional Raked Feathers Morphing

Pitch Effecter Conv. Horizontal T-Tail V-Tail Canard Wing TE

Yaw Effecter Conv. Vertical V-Tail H-Tail Winglet Drag Rudder

Roll Effecter Aileron / Spoiler Wing Warping

Location Under Wing Mid Wing Above Wing Aft Fuselage

Propulsor Type Propeller Open Rotor High BPR Fan Ultra High BPR Fan

Propulsor Arrangement Discrete Distributed

Energy Conversion Brayton Const. Vol. Fuel Cell / Motor Piston Electric Motor

Augmentation None Batteries Fuel Cell Brayton

Primary Fuel Liquid Hydrocarbon Gaseous Hydrogen Batteries

Vehicle Characteristics

Alternatives

Fuselage Wing S&C Propulsor Integration

Figure 3.4 – SUGAR’s Morphological Matrix 

Pre-workshop Step 5.1: Create conditional relationships of functional decomposition 

Once the morphological matrix is complete, the dynamic nature of the matrix must be set up. 

This is done through the creation of a compatibility matrix which summarizes the conditional 

relationships within the functional decomposition. The goal of conditional relationships is to 

eliminate alternatives that are physically incompatible with each other. For example, if the user 

initially selected a flying wing configuration with no fuselage, it would be unnecessary and 

physically impossible, to have any type of wing bracing or join. Therefore, the alternatives under 

these categories on other rows of the matrix would be removed as alternatives for the vehicle 

configuration. 

It is important to note that the incompatibilities being dealt with merely reflect those vehicle 

attributes which are impossible by the laws of physics or by engineering standards. These 

incompatibilities do not reflect combinations of attributes which may be uncommon or suggested 

against. This allows for more freedom in generating concepts. It is important that the users also 

apply their engineering judgment when making decisions to ensure the designs are not only 

physically possible, but also logical, as incompatibilities cannot account for engineering logic. 

The compatibility matrix should be filled in by those who helped populate the morphological 

matrix. It is helpful if each individual fills out the compatibility matrix for those attributes which 

fall under their discipline specialty. The compatibility matrix is symmetrical and at minimum, 

consists of the numbers 1 and 0. A 0 indicates that two alternatives are incompatible while a 1 

indicates they are compatible. The compatibility covers alternatives in the same row as the 

attribute in question as well as those alternatives in other rows that affect other aspects of the 

vehicle architecture. A section of the compatibility matrix created for the SUGAR workshop is 

shown in Figure 3.5. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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012NoneFairingModerate BlendExtreme Blend11.5212LowMidHighPylon MountLow-HighLow-PylonConventionalTriple Slotted FlapUSBEBFIBFAFCNoneStrutCableBraced Biplane

2 1111111001 111111111111111221

Number 1 1111111111 101111001111111110

2 0111111111 010000111111111111

Location Low 1111111111 101000001111111100

Mid 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0 0 0 0 1 1 1 1 1 1 1 0 0 0

High 1 1 1 1 1 1 1 1 1 1 1 0 0 0 1 0 0 0 1 1 1 1 1 1 1 1 1 0

Pylon Mount 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 1 0 0 1 1 1 1 1 1 1 2 2 0

Low-High 0 1 1 1 1 1 1 1 1 1 0 1 0 0 0 0 1 0 1 1 1 1 1 1 1 1 1 1

Low-Pylon 0 1 1 1 1 1 1 1 1 1 0 1 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1

High Lift System Conventional 1111111111 111111111000001111

Triple Slotted Flap 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 0 0 0 0 1 1 1 1

USB 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0 0 0 1 1 1 1

EBF 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 1 0 0 1 1 1 1

IBF 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 1 0 1 1 1 1

AFC 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 1 1 1 1 1

Bracing None 1111111111 111111111111111000

Strut 0 1 1 1 1 1 0 1 1 2 1 1 1 0 1 2 1 1 1 1 1 1 1 1 0 1 0 0

Cable 0 1 1 1 1 1 0 1 1 2 1 1 0 0 1 2 1 1 1 1 1 1 1 1 0 0 1 0

Truss 0 1 1 1 1 1 0 1 1 1 0 1 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 1

Join None 1111111111 111111111111111111

Tip 0 1 1 1 1 1 1 1 1 1 0 1 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 0

Mid 0 1 1 1 1 1 1 1 1 1 0 1 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 0

Box 0 1 1 1 1 1 1 1 1 1 0 1 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1

Folding None 1111111111 111111111111111111

In Flight 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0

On Ground 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Morphing None 1111111111 111111111111111111

Planform 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Variable Camber 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Both 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Winglet None 1111111111 111111111111111111

Conventional 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Raked 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Feathers 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Morphing 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Pitch Effecter Conv. Horizontal 0111111111 111111111111111111

T-Tail 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

V-Tail 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Canard 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Wing TE 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 1 1 1 1 1

Compatibility numbering:

0: NOT compatible

1: Compatible

2: Enhances

Do not fill in yellow cells

Number of 

Fuselages Wing-Body Blend Number Passenger Decks Location High Lift System Bracing

Figure 3.5 – Part of SUGAR’s Compatibility Matrix 

Additionally, the matrix can be enhanced by using the number 2 to indicate when two 

alternatives are not only compatible, but also that using those two alternatives together provides 

a benefit to using just one or the other. When an alternative is selected, any alternatives that will 

couple with the previously selected one and thereby improve performance will be highlighted for 

the user to view. However, the SUGAR team elected not to incorporate this option into the 

compatibility matrix. 

Once the compatibility matrix is complete, it is linked to the morphological matrix to enable 

dynamic decision making. The results of the compatibility will automatically be reflected to the 

user with each choice made during the workshop. This can be seen in Figure 3.6. The red cells 

indicate those options which have been ruled out due to the incompatibility matrix. Which cells 

appear red is a result of choices selected previously in the decision making chain (these choices 

are marked with a green “yes”) and helps to drive vehicle concept design. This is a function of 

IRMA and will be discussed in more detail in the workshop section of this report. Note that 

Figure 3.6 does not reflect work done at the workshop, it merely indicates the functionality of the 

built in compatibility matrix. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Alternative #1 Score Select Alternative #2 Score Select Alternative #3 Score Select Alternative #4 Score Select Alternative #5 Score Select Alternative #6

Number of Fuselages 0 12

Wing-Body Blend None Fairing Moderate Blend Extreme Blend

No. of Passenger Decks 1 1.5 2

Number 1 Yes 2

Location Low Mid High Pylon Mount Low-High Low-Pylon

High Lift System Conventional Triple Slotted Flap USB EBF IBF AFC

Bracing None Strut Cable Truss

Join None Tip Mid Box

Folding None In Flight On Ground

Morphing None Planform Variable Camber Both

Winglet None Conventional Raked Feathers Morphing

Pitch Effecter Conv. Horizontal T-Tail V-Tail Canard Wing TE

Yaw Effecter Conv. Vertical V-Tail H-Tail Winglet Drag Rudder

Roll Effecter Aileron / Spoiler Wing Warping

Location Under Wing Mid Wing Above Wing Aft Fuselage

Propulsor Type Propeller Open Rotor High BPR Fan Yes Ultra High BPR Fan

Propulsor Arrangement Discrete Distributed

Energy Conversion Brayton Const. Vol. Fuel Cell / Motor Piston Electric Motor

Augmentation None Batteries Fuel Cell Brayton

Primary Fuel Liquid Hydrocarbon Gaseous Hydrogen Batteries

Vehicle Characteristics

Alternatives

Fuselage Wing S&C Propulsor Integration

Figure 3.6 – Example of IRMA Dashboard with a couple selections. Red cells indicate incompatible options. 

Pre-workshop Step 5.2: Identify and discuss attributes of each row of the decomposition 

Once the backbone of the IRMA has been completed, it is important to go over the results of the 

functional decomposition to ensure it is comprehensive. Additionally, it is important to discuss 

each attribute and alternative to ensure that the function and meaning of each is understood by all 

those involved. It is also especially important to identify the benefit or cost of each attribute and 

alternative, in this case to identify how each affects aircraft performance relative to NASA’s 

goals. Understanding the importance of each attribute is crucial to the next pre-workshop step. 

Additionally, it allows the users to scrutinize the choices they made in the functional 

decomposition to ensure that the problem can be adequately addressed with those attributes listed 

in the matrix. 

Pre-workshop Step 6: Rank order decomposition based on relative importance to requirements 

Using the discussions begun in step 5.2, it is important to set up the basics for IRMA scoring by 

identifying the importance of each functional attribute to the problem. IRMA scoring ensures 

that those decisions which most directly impact the customer requirements get weightings 

reflecting their importance. For example, fuel burn is highly affected by the aircraft propulsor 

type. Therefore, the functional attribute “propulsor type” would be given a high rating such that 

it would count highly towards the overall score of the vehicle concept. Additionally, knowing the 

propulsor type is an attribute highly affecting fuel burn, the user is given a logical place to start 

the decision making process. Because of the incompatibility matrix, the order in which decisions 

are made will affect the vehicle architecture options available towards the end of the decision 

making chain. Therefore, it is important to begin making decisions with those attributes that will 

most highly affect the vehicle’s performance. 

In order to use the rankings effectively in the decision making process, each attribute must be 

evaluated prior to the workshop. For this instance, each attribute was evaluated for its effect on 

each one of NASA’s goals. The attributes are marked as having a high impact, medium impact, 

low impact, or no impact on a specific goal. The impact may be positive or negative; a positive 

or negative influence is accounted for during the workshop when scoring each alternative. The 

“high-none” scale allows for the user to think of the problem qualitatively rather than 

quantitatively while still capturing the importance of a specific attribute. Once the attributes have 

been rated, the stage is set to allow for more logical, effective decision making, allowing those 

decisions which are more critical to vehicle performance relative to a certain goal to occur early 

on in the chain of decisions. 
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This step is performed both pre-workshop and during the workshop. Conducting this exercise 

prior to the workshop helps users ensure that the matrix is complete and its entries are 

understood. Conducting the exercise during the workshop helps check the work done before the 

workshop and brings all participants together. It is important that the rankings are as accurate as 

possible, as they end up driving the decision making process heavily. 

Pre-workshop Step 7: Select optimal suitable reference systems 

Before groups can come together and begin to brainstorm unique vehicle concepts at the 

workshop, it is important that everyone be given a frame of reference in which they must make 

decisions. This frame of reference includes a baseline vehicle as well as the type of mission for 

which the vehicle is being designed. 

The baseline vehicle provides a reference system for users when they are scoring alternatives in 

the workshop. During the workshop, each alternative will be given a score (1-10) reflecting how 

well they contribute to the customer goals. In this case, the score reflects how well an alternative 

will improve performance towards specific NASA goal. Knowing the features of the baseline, 

the user is able to make these decisions relative to existing systems. For example, the baseline 

alternative may be given a score of 5. Each alterative can then be scored against that, being given 

a higher score if it improves performance or a lower score if it hinders performance. 

Additionally, choosing a reference mission is important prior to the workshop. The reference 

mission stipulates such decisions as the class of vehicle being designed and the mission it will be 

expected to perform. Users will make different design choices for a regional jet than for a long 

range aircraft. In order to minimize confusion, it is important to stipulate these parameters ahead 

of time so everyone may understand the context in which they are designing. 

The SUGAR team selected a 2008 technology conventional configuration (similar to 737NG) as 

the baseline aircraft and assumed a medium range aircraft flying at approximately M=0.7 for all 

vehicle concepts created. 

Having these guidelines gives structure to the workshop and ensures the participants are able to 

effectively contribute to the overall workshop process. 

Pre-workshop Step 8: Exercise IRMA 

The group is now ready to exercise the IRMA at the workshop. The IRMA will simply aid the 

group in the decision making process by providing structure and support for the conceptual 

design process. The steps of the workshop and details on how the IRMA is used to aid dynamic 

decision making will be discussed in the next section of this report. A complete IRMA, ready for 

a workshop, is depicted in Figure 3.7. Again, this IRMA is a notional example and does not 

reflect real decisions made prior to the workshop. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Energy 

Consumed

Order of 

Selection Alternative #1 Score Select Alternative #2 Score Select Alternative #3 Score Select Alternative #4 Score Select Alternative #5 Score Select Alternative #6

Number of Fuselages None 0 12

Wing-Body Blend None None Fairing Moderate Blend Extreme Blend

No. of Passenger Decks None 1 1.5 2

Number Med 1 2

Location Med Low Mid High Pylon Mount Low-High Low-Pylon

High Lift System High Conventional Triple Slotted Flap USB EBF IBF AFC

Bracing Low None Strut Cable Truss

Join Low None Tip Mid Box

Folding Med None In Flight On Ground

Morphing Low None Planform Variable Camber Both

Winglet High None Conventional Raked Feathers Morphing

Pitch Effecter Low Conv. Horizontal T-Tail V-Tail Canard Wing TE

Yaw Effecter Low Conv. Vertical V-Tail H-Tail Winglet Drag Rudder

Roll Effecter Low Aileron / Spoiler Wing Warping

Location Med Under Wing Mid Wing Above Wing Aft Fuselage

Propulsor Type High Propeller Open Rotor High BPR Fan Ultra High BPR Fan

Propulsor Arrangement High Discrete Distributed

Energy Conversion High Brayton Const. Vol. Fuel Cell / Motor Piston Electric Motor

Augmentation Med None Batteries Fuel Cell Brayton

Primary Fuel High Liquid Hydrocarbon Gaseous Hydrogen Batteries

Metrics Selection Alternatives (First)

Vehicle Characteristics

Fuselage Wing S&C Propulsor Integration

Figure 3.7 – Notional IRMA before Workshop 

3.3 – Workshop Steps 

The work prepared prior to the workshop created tools and resources to facilitate a more 

streamlined execution of the workshop steps. These workshop steps are composed of small group 

breakout activities and larger group down-selection activities. This workflow is depicted in 

Figure 3.8. This section will describe in more detail the major accomplishments of each of the 

steps involved in the workshop and the outcomes. 

Pre-Workshop 

Tasks 

Score Matrix of 

Alternatives

Down-Select 

Group 

Concepts 

Break Out 

Groups 

Sketch Group 

Concepts 

Down-select 

Workshop 

Concepts

Sketch 

Workshop 

Concepts 

Big Group 

Figure 3.8 – Workshop Workflow Diagram 

Workshop Step 1: Participant Planning and Pre-workshop review 

The information provided in the pre-workshop activities contributed to the creation of the tools 

that will be available to the workshop participants. The Interactive Reconfigurable Matrix of 

Alternatives (IRMA), information on specific technologies, information on the baseline vehicle, 

information on mission requirements and information for the NASA goals will be provided to 

each of the teams. The IRMA integrates the decomposition of requirements, the alternatives in 

the matrix of alternatives and the compatibility matrix in an interactively accessible format. 

The workshop participants consist of a subset of the individuals who participated in the preworkshop activities and other technical experts who may not have been involved in the preworkshop activities. These participants were selected by their past experience in specific 

technology areas, configuration design or possess a broad understanding of engineering trades. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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The purpose of the Workshop Step 1 is to orient the participants to the mission that they are 

designing for and the steps that they will be required to go through during the workshop. 

An orientation for the tools that will be available to them along with reference vehicle and 

mission information. Furthermore, each of the groups will be required to select architectures that 

relate to each of the functional metrics. These metrics were specified by NASA and refined in 

the earlier phases of the program. 

Workshop Step 2: Score Matrix of Alternatives 

The participants were broken up into three groups consisting of an averaged level of experience, 

both on years of experience and technical expertise. These groups worked together to identify the 

initial aircraft configurations for each of the NASA Goals or “Metrics of Interest” (MOI). 

The teams investigated a single MOI and qualitatively ranked the benefit of each characteristic 

relative to the MOI. The groups identified the characteristics with high benefits progressing from 

medium to identifying characteristics with low or no benefit to the MOI. This progressive 

identification of relative benefit supplies the team with a general “order of selection” to be used 

in the future. A snapshot of the exercise is depicted in Figure 3.9. 

TOFL

Order of 

Selection

Number of Fuselages Med

Wing-Body Blend Med

No. of Passenger Decks Med

Number High

Location Low

High Lift System High

Bracing Low

Join High

Folding High

Morphing Low

Winglet Med

Pitch Effecter Med

Yaw Effecter Med

Roll Effecter None

Location High

Fuselage Wing S&C

Order of Selection 

Benefit of High Lift Systems with 

respect to TOFL ranked as High 

Benefit of Roll Effector with 

respect to TOFL ranked as None 

Metric of Interest 

Figure 3.9 – Step 2: Identification of Relative Benefit 

Upon identifying the order of selection, the teams will progress in the specified order and rank 

the alternatives associated with the metrics of interest. This ranking will be used to facilitate 

discussions for assessing the benefit and tradeoffs between configuration options. For a given 

metric, starting with the high impact characteristics, score the elements within each row based on 

their value to the specified metrics where 1 is low and 10 is high. The teams will progress in the 

specified order of selection ranking each of the alternatives. A snapshot of selected results is 

depicted in Figure 3.10 below. 

The teams repeat step 2 until all the MOI have been evaluated. Upon the completion of 

identifying the order of selection and the scoring of alternatives, the teams have the necessary 

information to exercise the IRMA to select concepts. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Fuel Burn and 

Energy Consumed

Order of 

Selection Alternative #1 Score Select Alternative #2 Score Select Alternative #3 Score Select Alternative #4 Score Select

Number of Fuselages High 5 0 6 1 10 2 2

Wing-Body Blend Med 11 None Fairing Moderate Blend Extreme Blend

No. of Passenger Decks Med 12 1 1.5 2

Metric of Interest: Fuel Burned and Energy Consumed 

0 fuselages scores a 6 

with respect to Fuel Burn 

1 fuselage scores a 10 

with respect to Fuel Burn 

2 fuselage scores a 2 with 

respect to Fuel Burn 

Figure 3.10 – Scoring the Alternatives 

Workshop Step 3: Down-Select Group Concepts 

Beginning with the characteristic labeled #1 in the order of selection column for a specific MOI, 

the teams will begin to select alternatives for each of the characteristics. The teams utilize the 

interactive capability of the IRMA tool with the built in compatibility matrix. When the team 

selects an alternative, the incompatible options in other characteristic rows turn red if they are 

incompatible with that selection. Ideally, the team will specify the highest ranked alternative on 

each row for a given MOI, but the incompatibilities may make this impossible. The team will 

progress in the order of selection, discussing the selection of the alternative. Once there is an 

option selected in each of the rows, a configuration is complete. The intermediate results are 

shown in Figure 3.11. This figure shows the filtered out results based on a few selections for a 

characteristic. 

Fuel Burn and 

Energy 

Consumed

Order of 

Selection Alternative #1 Score Select Alternative #2 Score Select Alternative #3 Score Select Alternative #4 Score Select Alternative #5

Number of Fuselages High 1 0 2 1 10 Yes 2 5

Wing-Body Blend Med 7 None 3 Fairing 4 Moderate Blend 10 Extreme Blend 1

No. of Passenger Decks Low 13 1 10 1.5 1 2

Number Med 8 1 3 2 10

Location None 17 Low 4 Mid 7 High Pylon Mount 2 Low-High

High Lift System High 2 Conventional 10 Yes Triple Slotted Flap 3 USB 4 EBF 1 IBF

Metrics Selection Alternatives (First)

No

Yes

Selections are made 

according to the 

order of selection

As selections are 

made, incompatible 

elements turn red

Selections are made 

according to the 

order of selection

Figure 3.11 – Intermediate Results from the IRMA 

The team continues to select alternatives for each of the characteristics in the prescribed order of 

selection for each of the MOI, discussing each selection, ultimately arriving at a couple of 

configurations for further investigation. These various configurations represent the corners of the 

design space and will be used for sensitivity analysis once the workshop process is complete. 

Figure 3.12 shows the results of the configuration selection for one of the groups participating in 

the workshop. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Team Y Fuel Burn #1 Team Y TOFL #1 Team Y Cruise 

Emissions #1 Team Y LTO NOx #1 Team Y DNL #1

Fuselages 1 11 11

Wing-Body Blend Fairing Fairing Fairing Fairing Extreme Blend

Passenger Decks 1 11 11

Number 1 11 11

Location High High High High Mid

High Lift System Conventional AFC Conventional Conventional AFC

Bracing Strut Strut Strut Strut None

Join None None None None None

Variable Span On Ground On Ground On Ground On Ground On Ground

Morphing None None Variable Camber None None

Tip Devices Raked Raked Raked Conventional Raked

Pitch Effecter Conv. Horizontal Conv. Horizontal Conv. Horizontal Conv. Horizontal Wing TE

Yaw Effecter Conv. Vertical Conv. Vertical Conv. Vertical Conv. Vertical H-Tail

Roll Effecter Aileron/Spoiler Aileron/Spoiler Aileron/Spoiler Aileron/Spoiler Aileron/Spoiler

Location Below Wing Mid Wing Below Wing Below Wing Above Wing

Propulsor Type Open Rotor Open Rotor Open Rotor Propeller Fan

Propulsor /core Single Multiple Single Single Single

Energy Conversion Const. Vol. Combustion Brayton Electric Motor Const. Vol Combustion Brayton

Augmentation None None Brayton Fuel Cell None

Primary Fuel Liquid Hydrocarbon Liquid Hydrocarbon Batteries Liquid Hydrocarbon Hydrocarbon

Fuse Wing S&C Propulsor Integration

Figure 3.12 – Team Y’s Configuration Results from IRMA process 

Workshop Step 4: Sketch group concepts 

Identifying specific alternatives for each of the characteristics alone lends itself to a myriad of 

interpretations for integration and sizing effects. In this conceptual phase of the program, 

performing a sizing algorithm on the alternatives is premature. In order to bring the concept to 

life and understand different individual’s interpretations of the integration aspect of the design 

choices, each member of the group will sketch each of the proposed aircraft. 

The result is a collage of interpretations of drawings. The teams then compared individual 

sketches for each of the different aircraft and reach group consensus on what the aircraft should 

look like. Based on the results of the discussions, the team will redraw the concepts 

incorporating any changes. An example of one of the group’s original interpretations and final 

drawing is depicted below in Figure 3.13. 

Figure 3.13 – Concept sketches 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Workshop Step 5: Down-select among group concepts 

At this stage of the workshop, there exist at least three concepts to meet each of the NASA goals. 

In order to arrive at a select few configurations to apply technologies toward, the teams regroup 

and present their concepts. 

Each team presents their concept sketch and provides discussion for the rational for their 

configuration selection. Since different alternatives for each of the vehicle characteristics provide 

advantages and disadvantages alone as well as the integrated, the teams discuss the expected pros 

and cons for their concepts. 

Once all the groups have discussed their concepts, the large group down-selects to one or two 

concepts per metric. To facilitate the down-select, the group compares the concepts to each of 

the metrics of interest based on the perceived pros and cons of each concept. The group discusses 

commonalities among all concepts, configuration selection issues and integration issues which 

may lead to reassessing the configuration selection. Upon reaching consensus, the large group 

will arrive at a concept or two for each metric as and repeats the concept selection process to 

identify a configuration that represents a compromise between all metrics. An example of the 

results of the large group discussion is depicted below in Figure 3.14. 

Team X Fuel Burn #1 Team Y Fuel Burn #1 Team Z Fuel Burn #1 Whole Team 

Fuel Burn #1

Fuselages 111 Fuselages 1

Wing-Body Blend Extreme Blend Fairing Fairing Wing-Body Blend Fairing

Passenger Decks 111 Passenger Decks 1

Number 111 Number 1

Location Mid High High Location High

High Lift System AFC Conventional Conventional High Lift System Conventional

Bracing None Strut Strut Bracing Strut

Join None None None Join None

Variable Span On Ground On Ground On Ground Variable Span On Ground

Morphing None Variable Camber Variable Camber Morphing Variable Camber

Tip Devices Conventional Raked Morphing Tip Devices Raked

Pitch Effecter Wing TE Conv. Horizontal Conv. Horizontal Pitch Effecter Conv. Horizontal

Yaw Effecter Winglet Conv. Vertical Conv. Vertical Yaw Effecter Conv. Vertical

Roll Effecter Aileron/Spoiler Aileron/Spoiler Wing Warping Roll Effecter Aileron / Spoiler

Location Aft Fuselage Below Wing Below Wing Location Below Wing

Propulsor Type Open Rotor Open Rotor Open Rotor Propulsor Type variable RPM, pitch

Propulsor /core Single Single Single Propulsor /core Single

Energy Conversion Fuel Cell/Motor Electric Motor Fuel Cell/Motor Energy Conversion Fuel Cell/Motor

Augmentation Batteries None Brayton Augmentation Brayton

Primary Fuel Hydrogen Batteries Liquid Hydrocarbon Primary Fuel Liquid Hydrocarbon

Fuse Wing S&C Propulsor IntegrationFuse Wing S&C Propulsor Integration

Figure 3.14 – Large group configuration down-selection 

Workshop Step 6: Final workshop configuration and sketch workshop concepts 

Upon reaching consensus among the large group, the concepts are reviewed for completeness 

and sketches are drawn by a selected individual to bring the concepts to life. This final sketching 

provides a mechanism for discussion as well as a product of the workshop. Figure 3.15 depicts 

the results from the SUGAR workshop. These drawings were used as a starting point in future 

steps of the contracted work. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Figure 3.15 – Workshop concept drawings 

3.4 – IRMA Process Payoff 

By utilizing the ASDL created IRMA process, the SUGAR team was able to develop several 

alternatives for evaluation utilizing a systematic approach with documented decisions. By 

exercising the interactive tool, the teams were able to gain an enhanced understanding of the 

systems selections for the vehicle characteristics and the impacts of selecting a particular 

alternative without the need of exercising expensive analysis codes. The tool’s dynamic nature 

and extensible, flexible framework allowed for the down-selection process to be rapidly repeated 

in order to select multiple configuration alternatives. This tool also facilitated discussions related 

to all major components of the aircraft and the integration issues. 

The process used for exercising the tool provided a systematic process to obtain a sufficient set 

of reference systems and a mechanism for documenting the decisions that were made over the 

course of the workshop. The resulting files were given to the participants for use in further 

analysis in the follow on phases of the contract. 

3.5 – Post Workshop Selection of Concepts for Detailed Analysis 

The Concept Workshop resulted in six advanced concepts (Figure 3.15). It was decided that 

because of resource limitations, only one HWB concept would be considered and that it would 

emphasize low noise (Combined DNL #2) rather than performance (Combined Fuel Burn #2). 

There were two possible architectures for the “Combined NOx and Emissions” concept: One 

using fuel cells and the other batteries. Therefore, two reference concepts and six advanced 

concepts were selected for consideration (Figure 3.16). 

Combined DNL #2 Combined TOFL Combined NOx and Emissions 

Combined Fuel Burn #1 Combined Fuel Burn #2 Combined DNL #1 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Figure 3.16 – Candidate Configurations for Detailed Analysis 

Based on available contract resources, we decided to focus our efforts on the corner points of the 

design space that appeared the most challenging and to reduce the number of advanced concepts 

to three. To achieve this, we decided to group the fuel-cell, battery, and hybrid electric aircraft 

into an “Electric Trade Aircraft”. The HWB configuration was judged to be the configuration 

with the best chance of making the aggressive N+3 low noise goal, so it was selected over a strut 

braced wing configuration with tail shielding. The dedicated take-of-field-length (TOFL) 

optimized aircraft was dropped in favor of looking at TOFL sensitivities for one or more of the 

other configurations (Figure 3.17). All of the eliminated configurations have merit, and should be 

considered for inclusion in future studies. The five aircraft selected for detailed analysis are 

shown in Figure 3.18, and are summarized below: 

1. SUGAR Free – Current technology, similar to 737 class aircraft. Used as Baseline for 

performance comparisons. 

2. Refined SUGAR – Reference conventional configuration with estimated 2030-2035 

technologies. This vehicle requires no new additional technology initiatives from NASA. 

It includes a turbofan engine which will be designed by GE. A variation of this 

configuration with N+3 advanced technologies will be provided for direct comparison to 

the advanced concepts. 

3. SUGAR High – High span strut-braced wing configuration with advanced 2030-2035 

N+3 technologies. Assumes significant technology development beyond the technologies 

N+3 Improved L/D 

N Baseline N+3 Reference 

N+3 Reduced Noise HWB 

N+3 Fuel Cell N+3 Emissions 

(Batteries) N+3 TOFL N+3 Reduced Noise 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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in the Refined SUGAR concept. Turbofan and open fan propulsion concepts are supplied 

by GE. 

4. SUGAR Volt – Electric Trade Aircraft that builds off of SUGAR High configuration to 

add electric propulsion technologies. Considers a variety of electric-propulsion 

architectures (Battery electric only, fuel-cell gas turbine hybrid, battery electric gas 

turbine hybrid) which are supplied by GE. 

5. SUGAR Ray – A HWB configuration that uses a similar suite of advanced technologies 

as the SUGAR High. Primary design emphasis is on reducing aircraft noise, while 

maintaining performance similar to the SUGAR High. 

In summary, the matrix of configuration and operations alternatives are repeated here (Figure 

3.19), with configuration and operations alternatives that are being actively evaluated by the 

SUGAR study highlighted in green. 

* Includes hybrids with conventional Brayton cycle engines 

Figure 3.17 – Configuration Groupings and Selections (Shaded) 

N+3 Improved L/D 

N Baseline N+3 Reference 

N+3 Reduced Noise HWB 

N+3 Fuel Cell N+3 Emissions 

(Batteries) N+3 TOFL N+3 Reduced Noise 

Electric Trade Aircraft* 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Figure 3.18 – Final Five airplanes selected for further study 

Alternative #1 Alternative #2 Alternative #3 Alternative #4 Alternative #5 Alternative #6

Number of Fuselages 0 1 2

Wing-Body Blend None Fairing Moderate Blend Extreme Blend

No. of Passenger Decks 1 1.5 2

Number 1 2

Location Low Mid High Pylon Mount Low-High Low-Pylon

High Lift System Conventional Triple Slotted Flap USB EBF IBF AFC

Bracing None Strut Cable Truss

Join None Tip Mid Box

Folding None In Flight On Ground

Morphing None Planform Variable Camber Both

Winglet None Conventional Raked Feathers Morphing

Pitch Effecter Conv. Horizontal T-Tail V-Tail Canard Wing TE

Yaw Effecter Conv. Vertical V-Tail H-Tail Winglet Drag Rudder

Roll Effecter Aileron / Spoiler Wing Warping

Location Under Wing Mid Wing Above Wing Aft Fuselage

Propulsor Type Propeller Open Rotor High BPR Fan Ultra High BPR Fan

Propulsor Arrangement Discrete Distributed

Energy Conversion Brayton Const. Vol. Fuel Cell / Motor Piston Electric Motor

Augmentation None Batteries Fuel Cell Brayton

Primary Fuel Liquid Gaseous Hydrogen Batteries

ATM 2008 NextGen

Aircraft Class Regional Medium Large

Formation Flight FALSE TRUE

In Flight Refueling FALSE TRUE

Ground Refueling FALSE TRUE

Mission

Alternatives Selected for Analysis as Part of SUGAR

Vehicle Characteristics

Alternatives

Fuselag Wing S&C Propulsor Integration

Figure 3.19 – Alternatives Selected for Analysis 

765-093 

N Baseline 

“SUGAR Free” 

765-094 

N+3 Reference 

“Refined SUGAR” 

765-095 

N+3 High L/D “SUGAR High” 

765-096 

N+3 High L/D “SUGAR Volt” 

765-097 

N+3 High L/D “SUGAR Ray” 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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A total of five advanced engine designs were delivered for the SUGAR study and are 

summarized in Figure 3.20. Each of these engines was designed to the thrust requirements for 

their respective point-of-departure vehicle designs (Section 5.1.3) and each is shown 

approximately to scale. The engines were given the informal designations “eFan”, “fFan”, 

“gFan”, “gFan+”, and “hFan”. Starting at the top left of the figure, the baseline engine for this 

study is a conventional gas turbine (GT), the CFM56 with a 61” fan diameter and 27,000 pound 

takeoff thrust rating. The “eFan” is an all-electric propulsor that is basically an electric motor 

connected to a high bypass fan via a gearbox. The electric power required to drive this propulsor 

is derived from a source external to the propulsor itself. 

Figure 3.20 – GE Engine Family for Consideration in SUGAR Vehicles 

The “fFan” is a fuel cell-gas turbine hybrid concept featuring a single spool gas generator 

attached to the same shaft as an electric motor. A portion of the compressor discharge air is 

pulled from the primary flowpath via a scroll system and fed to a fuel cell stack external to the 

propulsion nacelle (not shown). The exhaust effluent from the fuel cell is then fed back into the 

combustor and subsequently expanded in the turbine. The electric power from the fuel cell is 

used to power the electric motor/fan for some portions of the mission, provide electric power to 

airframe systems, and (possibly) power external electric propulsion units. 

The “gFan” and “gFan+” engines are advanced high bypass 2-spool turbofan engines. The 

primary difference between the two is that the “gFan+” represents an aggressive push on gas 

turbine technology whereas the “gFan” is intended to be an extrapolation on were gas turbine 

technology will be in 2035 given a more moderate (but still aggressive) pace of development. 

Finally, the “hFan” is a gas turbine-electric hybrid engine capable of operating in an all gas 

turbine, all-electric, or combined modes depending on mission requirements, where the electric 

power is assumed to come from a source external to the engine (e.g. batteries). 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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The “eFan” engines, when integrated on the point-of-departure version of the SUGAR Volt, 

could not achieve the needed 3,500 nmi mission range without assuming a phenomenal 

improvement in battery technology relative to today’s state-of-the-art. The “fFan” showed some 

promise, but was ultimately not as competitive as the “hFan” engine concept. This, in 

combination with the challenges of realizing a compact, lightweight, high power output, primereliable fuel cell subsystem, deterred further work on the “fFan” concept. As such, only the 

“hFan” was selected for more detailed analysis and sizing on the SUGAR Volt. 

Finally, one area holding considerable promise toward meeting the aggressive fuel burn goals of 

this project is the open fan. Open fan is also desirable from an emissions reduction point of view 

inasmuch as emissions are correlated to fuel burn. Open fan is less desirable from the point of 

view of meeting the very aggressive noise goals of this project, though it is clear that 

considerable progress could be made in this area with concerted effort. 

It was clear at the outset that the number of possible engine concepts worthy of study in this 

project far outstrips the resources available. Furthermore, it was clear that the team would need 

to set a strategy on how to approach the number of engine concepts to be evaluated versus the 

depth of analysis. In general, the philosophy of this study has been to study a fewer number of 

the most promising engine concepts, and to do so at a level of analysis fidelity conducive to 

drawing useful conclusions from the results. 

Thus, the team made a conscious decision early in this study to eschew the detailed evaluation of 

an open fan in favor of spending additional time and resources developing other “out of the box” 

concepts such as fuel cell and electric hybrids. Furthermore, open fan is presently being studied 

by industry and NASA in other venues. It therefore seems logical to focus the bulk of the effort 

in this project on those concepts that have heretofore received little or no attention. 

As a result, the open fan is evaluated in only the most rudimentary way for this project. 

Specifically, the open fan’s impact on vehicle fuel burn is estimated by treating the open fan as a 

simple cruise SFC delta and an engine weight delta applied on top of the “gFan+” engine 

performance and weight estimates. This is sufficient to give some insight as to how the open fan 

performance benefit might be expected to impact the sized vehicle system. No attempt was made 

to evaluate open fan noise, as this would have required considerable effort and would have 

detracted from resources available to develop other concepts. 

To recap, propulsion selections and top level technology assumptions are summarized below: 

o N Baseline (SUGAR Free) 

o CFM56 

o Fuel burn Baseline 

o N+3 Reference (Refined SUGAR) 

o “gFan” 

o High bypass ratio turbofan with 2030 engine technologies 

o SFC reduction goal of 20% 

o N+3 High L/D (SUGAR High) 

o “gFan+” 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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o High bypass ratio turbofan 

o An open fan variant was also evaluated at a very high level using simple weight 

and SFC deltas relative to the “gFan+” concept 

o Advanced technologies to improve engine performance relative to Refined 

SUGAR 

o SFC reduction goal of 25% 

o N+3 Electric Trade Aircraft (SUGAR Volt) 

o “hFan” 

o Ducted fan 

o Hybrid gas turbine-battery electric architecture 

o Fuel cell hybrid (“fFan”) and battery electric (“eFan”) versions were evaluated 

but not selected for further analysis 

o N+3 Low Noise HWB (SUGAR Ray) 

o “gFan+” (same as SUGAR High) 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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4.0 – Advanced Technologies Selection 

This section provides a brief overview of the technologies included in this study. 

4.1 – Aerodynamics Technologies 

A team of aerodynamicists developed a list of technologies that would be applicable to a 2030-

2035 technology aircraft. The technologies to be applied to vehicles are shown in Table 4.1. As 

cost was not considered directly, trade studies were not performed to determine the optimum mix 

of technologies for each vehicle. Subject Matter Experts (SMEs) determined the matching of the 

technologies to the configurations. 

Table 4.1 – Aero Technology Summary 

Configuration 

‘N’ 

SUGAR Free 

‘N+3’ 

Refined 

SUGAR 

‘N+3’ 

SUGAR High 

‘N+3’ 

SUGAR Volt 

‘N+3’ 

SUGAR Ray 

Aero Technology Areas 

Laminar Flow None Natural / 

Passive Natural, Passive and Active Where Appropriate 

Riblets None Fuselage Fuselage, Wing, Tails, 

Nacelles Where Appropriate TBD 

Excrescence 

Drag Conventional 

Multi-Functional Structures, 

Reduced Fasteners, 

Reduced Flap Fairings, Gapless 

Empennage Conventional 

Size 

C.G. Control 

Relaxed Static Stability & Increased CLMax for reduced Size 

Airfoil 

Technology Supercritical 

Advanced Super Critical 

Adaptive Camber w/ 

Spanload Control 

TBD 

Additional 

Technologies None Low Interference Drag Nacelle 

Low Drag Strut Integration 

Airframe 

Noise 

Shielding 

4.1.1 – Laminar Flow Control 

Laminar flow can significantly increase the aerodynamic performance of an air vehicle by 

reducing viscous drag. Drag Reduction is accomplished by delaying the buildup of two primary 

transition mechanisms, Stationary Cross-Flow (SCF) and Tollmien-Schlicting (T-S) waves. For 

the SUGAR study, the following strategies are discussed: 

- Natural Laminar Flow (NLF): is achieved through shaping. Wing airfoil design with 

extended favorable gradients delays the buildup of T-S waves. 

- Passive Laminar Flow: is similar to Hybrid Laminar Flow but does not require power for 

a suction system. The delta pressure needed for suction is designed into the airplane. 

- Hybrid Laminar Flow (HLFC): employs suction in a non-structural region ahead of the 

front spar and design for favorable gradients to sustain laminar flow over the wing box. 

Power is still needed for the suction system. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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- Active Laminar Flow: is achieved through integrating the suction system with the 

structural wing box to ensure laminar flow. This requires power and plumbing for the 

suction system. 

As shown in Table 4.1, different levels of laminar flow designs will be applied to each 

configuration. The trade between the strategies depends on the design features of the 

configuration. No trade studies will be performed to determine which level of laminar flow is to 

be applied and the chosen amount will be determined by SMEs. 

Kruger flaps were chosen for the low speed leading edge device. This provides the high lift 

needed for low speed and is an enabler for laminar flow at cruise. The Kruger also stows below 

the wing behind the attachment line providing a clean uninterrupted upper surface for laminar 

flow in cruise. 

In the Aerodynamic drag buildup, the laminar surface area must be calculated to apply the proper 

drag reduction relative to turbulent values. Transition Reynolds Number of 12 to 17 million 

(variation with span) was used to determine the extent of the laminar run in the streamline 

direction. An eight-degree turbulent wedge created by the intersection of the body and the 

leading edge of the wing establish the inboard wing boundary for laminar flow. It is also 

assumed that NLF can achieve the same transition Reynolds number as HLFC. These 

assumptions were used in the Aerodynamic buildups. 

4.1.2 – Riblets 

Riblets have been studied for fuselage drag reduction in the past. They offer drag reduction but 

traditionally are not damage tolerant. The lower surface of wings may also benefit but these 

surfaces typically encounter more extreme environments resulting in riblet delamination. In these 

studies, aircraft using the technology will assume features are manufactured into the vehicle 

wing skin or take the place of paint resulting in no weight change. A 7% drag benefit on skin 

friction drag will be applied to each component using this technology (based on wind tunnel and 

flight tests). 

4.1.3 – Excrescence Drag 

Application of multi-functional structures, reduction in fasteners, reduced flap fairings, and 

sealed surfaces will result in a 20% reduction of excrescence drag. Structures enables a portion 

of this savings, the rest comes from reduced flap fairings resulting from optimized high lift 

systems. 

4.1.4 – Empennage 

Reducing the tail size for horizontals and verticals attained through active CG management and 

increased design lift coefficient results in drag reduction. This is reflected in the configuration 

geometry and is not explicitly carried as an aerodynamics increment. 

4.1.5 – Airfoil Technology 

Advanced supercritical airfoil technology will be applied to the baseline and reference vehicles. 

The SUGAR High and SUGAR Volt configurations will benefit from higher cruise lift 

coefficients compared to conventional configurations. A 3% reduction in airplane drag is 

assumed from wind tunnel derived database levels for a given lift coefficient based on wing 

design studies. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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4.1.6 – Additional Aero Technologies 

Additional technologies include low drag strut integration, low interference drag nacelle, and 

airframe noise shielding. For the strut-braced wing a 4.8% drag improvement was used over 

empirical methods. Low interference nacelle assumes an interference drag free installation. 

Airframe noise shielding is an Aerodynamic technology which enables future takeoff and 

approach operations. 

4.2 – Structural Technologies 

A team of structural engineers developed a list of technologies that would be applicable to a 

2030-2035 technology aircraft. The technologies, and vehicles they can be applied on, are shown 

in Table 4.2. As cost was not considered directly, trade studies were not performed to determine 

the optimum mix of technologies for each vehicle. The application of the technologies was left to 

the aircraft designers and discipline experts. 

Table 4.2 – Structural Technologies Summary 

Configuration 

‘N’ 

SUGAR Free 

‘N+3’ 

Refined 

SUGAR 

‘N+3’ 

SUGAR 

High 

‘N+3’ 

SUGAR 

Volt 

‘N+3’ 

SUGAR Ray 

Structural Technology Areas 

Materials / 

Manufacturing Aluminum Adv. Composites incl. Hybrid Polymer, Adv. Metals, Adv. 

Joining, Adv. Ceramics

Health 

Management

None OnBoard On-board Structurally Integrated SHM, Advanced NDE/NDI

Loads & 

Environments None Max. Flight 

Control Int.

Maximize Flight Control Integration, 

Active/Passive Aeroelastic Response for 

Load Control

Design & Criteria Deterministic Reliability Based, Robust/Unitized, Multi-Functional 

Structures, Support for NLF

Adaptive 

Structures for 

Control Systems

Conventional

Conformal, 

Gapless, 

Simplified HL

Conformal, Gapless, Adaptive, Spanwise 

Load Control, Simplified HL

Energy 

Management

No Structural 

Integration

Structurally Integrated Thermal and Electrical Energy 

Management

Coatings

Conventional 

Paint and 

Corrosion 

Prev.

Enable 

Lightweight 

Materials

Enable Lightweight Materials, Energy 

Harvesting, Thermal Management, Drag 

Reduction

Interiors Standard More Lightweight

Additional 

Structures 

Technologies

None

Environmentally 

Compliant 

Manufacturing,

Structurally 

Integrated 

Systems 

(Wiring)

Lightweight Wing 

Folds, 

Adv. Lightweight High 

Lift Systems, 

Adaptive Wing 

Camber, 

Adv. Material Forms

Lightweight Wing 

Folds, 

Adaptive Wing 

Camber, 

Adv. Material 

Forms, 

Adv. NonCircular Fuse., 

Adaptive 

Inlets/Nozzles
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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4.2.1 – Materials and Manufacturing 

There are many areas of material development including Advanced Composites, Metals, Joining, 

and Ceramics technologies. The estimated structural weight reductions for advanced materials 

are shown in Table 4.3. These are based on expected improvements in critical material properties 

and the distribution of the dominant material properties. 

Table 4.3 – Advanced Material Applications and Improvements 

Component Weight 

Reduction Material Type 

Strength Dominated Structure 15% Advanced Composites 

Stiffness Dominated Structure 25% Advanced Composites 

Metallic Structure 10% Advanced Metals 

Landing Gear 25% Advanced Materials (MMC / CMC) 

All Structure 15% Advanced Joining 

High Temperature Structure 25% Advanced Ceramics 

4.2.2 – Structural Health Management (SHM) 

This is an enabling technology required for the weight reductions claimed in Sections 4.2.1 and 

4.2.3. The technology works in close conjunction with non-deterministic design criteria by 

permitting reduced conservatism in the structural design criteria. The amount of structural weight 

that can be reduced depends upon the critical structural sizing criteria and the damage 

assumptions built into those criteria. The primary structural weight savings results from the 

enhanced knowledge of the probability of occurrence of damage scenarios coupled with 

quantitative knowledge of actual damage events. This permits damaged structure to be designed 

for Design Limit Load (DLL) or in some cases for 70% of DLL. Full application of this 

technology to save weight will require significant changes to current aircraft design requirements 

and methods. 

The weight penalty for this SHM system itself is estimated to add 0.005 pounds per square foot 

to all wing and fuselage wetted areas. This SHM weight is based on our experience using current 

technology piezoelectric guided wave technology, but assumes in the 2030 time frame we take 

full advantage of advanced structurally integrated wiring technology (Direct Write) to reduce 

SHM system weight allowing for large area coverage at very high sensor density. Structural 

weight reduction is estimated to be dependent upon SHM sensor density as shown in Figure 4.1. 

The weight savings are estimated at 5% - 30% away from fastener holes, 5% - 12% near edges 

and fastener attachment holes. It is expected that bonded/welded structural joining will result in a 

large reduction in the use of fasteners. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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0

5

10

15

20

25

30

35

0.00 0.20 0.40 0.60 0.80 1.00 1.20

Sensor density (#/in)

% Weight Reduction

Large Damage Critical

Small Notch Critical

Barely Visible Damage

Critical

Figure 4.1 – Structural Weight Reduction Expeccted from SHM 

4.2.3 – Loads and Environments 

Load alleviation is currently being used on Boeing’s latest aircraft. Conservatively extrapolating 

this technology to 2030 would yield about a 15% reduction in wing weight due to Gust Load 

Alleviation and Maneuver Load Alleviation. A significant technology push in this area will 

provide the ability to integrate active aeroelastic response control into the flight controls and 

enable the tailoring of spanwise load control into the flight controls. This is likely a larger benefit 

to high aspect ratio configurations and 25% reduction is estimated for the high aspect ratio 

configurations. 

4.2.4 – Design and Criteria – Reliability Based Loads and Design 

Structural Health Management (SHM) technology will work in conjunction with a transition 

from current deterministic structural design methods to probabilistic analyses, also known as 

Reliability Based Design. This will have the dual advantage of quantifying the actual reliability 

of a structure in terms of both probability distributions of load levels and probability distributions 

of load carrying capability. SHM sensors will provide real time data to validate both probability 

distributions (applied load levels) and the current load carrying capabilities of the structures. The 

joint probability of these distributions will define reliability of the structure and dictate 

restrictions as required to assure safe operation of the aircraft. Taking advantage of these 

technologies will require a significant shift in structural design requirements and practices that 

can only be achieved through an extended evolution of these criteria to assure continued 

airworthiness throughout the transition. 

4.2.5 – Adaptive Structures and Control Systems 

Adaptive structures and control systems are assumed to allow a 50% reduction in complex high 

lift systems and a 20% reduction in simple high lift systems. High Lift and control surface 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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systems currently comprise approximately 50% of the weight of typical commercial aircraft 

wings. It is estimated that conformal wing shape change (adaptive structures, sometimes known 

as morphing) will provide benefits that include reduced weight for high lift systems primarily 

through simplification of these structures. Additional benefits include significantly reduced noise 

through elimination of slat and flap gaps and possibly reduced drag due to elimination of gaps 

and joints between flaps and control surfaces and the main wing surface. Elimination of such 

gaps will also support the drag reduction estimates by supporting enhanced laminar flow. 

Because of the reduced need for extensive high lift systems for the high aspect ratio concepts, 

only 20% reduction is estimated for SUGAR High and Volt. 

4.2.6 – Integrated Energy Management 

Integrated energy management provides reduced overall aircraft weight through the use of 

electrical and thermal management approaches that are highly integrated with aircraft structure. 

Electrical power distribution systems in addition to wiring weight include parasitic structural 

weight required to attach wiring to the structure as well as weight penalty due to the required 

structural penetrations. As subsystems thermal loads continually increase, conducting those heat 

loads will require increasingly complex thermal energy management technologies. Using 

structure as thermal conduction paths will reduce overall aircraft weight. 

4.2.7 – Coatings 

A 50% Reduction in paint weight has been estimated base on use of advanced coatings and 

appliqué. Advanced coatings also enable the use of advanced metals. 

4.2.8 – Interiors 

A 5% reduction in insulation weight is estimated using advanced insulation materials and 

through integration of insulation with structure. A 20% reduction in weight of interior walls and 

seats is also estimated. 

4.2.9 – Multi-functional Structures Technologies 

Multi-functional design and integrated systems/structures technology has been estimated to yield 

a 50% reduction in wiring weight. Further reductions are expected through structural integration 

of thermal and electrical energy management systems and components and of lightning 

protection. 

4.2.10 – Additional Structures Technologies 

Additional technologies include environmentally friendly manufacturing processes, and features 

such as lightweight wing folds for large span aircraft and adaptive structural features such as 

variable geometry wing tips, adaptive wing camber and adaptive engine inlets and nozzles. Large 

unitized structures will reduce the weight of joints. Hybrid composite and metallic structures 

with advanced joining technology will permit the usage of the best materials depending upon 

application. 

4.3 – Subsystem Technologies 

Boeing technology engineers compiled a list of anticipated subsystem technologies that could be 

available in the 2030 timeframe (Table 4.4). Industry experts have chosen technologies to 

include based on their engineering judgment and experience. 
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Table 4.4 – Subsystems Technology Summary 

Configuration 

‘N’ 

SUGAR Free 

‘N+3’ 

Refined SUGAR 

‘N+3’ 

SUGAR 

High 

‘N+3’ 

SUGAR 

Volt 

‘N+3’ 

SUGAR 

Ray 

Subsystems Technology Areas 

Power 

Management Conventional Adaptive 

Power 

Generation

Eng. Primary 

APU Gnd. & Bkup. 

APU Conventional Conventional or Diesel 

Actuators Hydraulic Hydraulic & EMA EMA 

Control 

Architecture Cable / Pulley Maximize Use of Fiberoptics 

Thermal 

Technology Conventional Lightweight 

Electro 

Magnetic 

Effects / 

Lightning

Conventional More Tolerant Systems and Dual Use Structure 

Fuel Jet-A Low Sulfur Jet-A / Synthetic / Biofuels 

Flight Avionics Conventional NextGen ATM Capable 

Wiring Copper & Aluminum 

Copper & 

Aluminum with 

Current Return 

Networks 

High Conductivity, Lightweight 

Computing 

Networks None Integrated 

4.3.1 – Power Demand, Generation, and Management 

Power is required for aircraft systems. Power demands are driven by payloads and TOGW. ECS 

loads drive power requirements for steady state and are dependent primarily on the payload and 

cabin altitude constraints while landing gear, and control system power loads are aircraft weight 

and technology driven. Passenger comfort enhancements like lower cabin altitude, in flight 

entertainment systems, and reduced recirculation ECS all increase power demand. However, 

peak power demand may be reduced by intelligent power management systems. 

It should be noted that for all ‘N+3’ airplanes the ECS is expected to be completely electrified 

incorporating more advanced generations of the “787 No-Bleed Electrical Systems 

Architecture”. The primary motivation for the no-bleed architecture is fuel burn reduction, as 

well as improved airplane maintenance and dispatch reliability. The architecture incorporates 

highly efficient electrical cabin pressurization scheme utilizing adjustable speed electrical 

motors, as well as electrical wing ice protection, engine starting, and driving the high capacity 

hydraulic pumps if required. The engine start function is accomplished via starter/generators that 

act as the starter motors for the engines, as well as providing electrical power when the 

respective engine is running. 

Table 4.5 shows the power requirements for each configuration. It also shows the peak power 

reduction attained by the use of advanced energy management. The advanced concepts show 

greater use of electrical power with a reduction in hydraulic power and engine bleed. Additional 
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system requirements for aircraft certification have historically increased total electrical power 

demand. 

Table 4.5 – Installed Aircraft Power (Bleed, Hydraulic, Electric) 

Configuration 

Aircraft Systems 

‘N’ 

SUGAR Free 

‘N+3’ 

Refined 

SUGAR 

‘N+3’ 

SUGAR 

High, 

‘N+3’ 

SUGAR 

Volt 

‘N+3’ 

SUGAR 

Ray 

Bleed 

(lb/s) 

Hyd. 

(Hp) 

Ele. 

(KVA) 

Hyd. 

(Hp) 

Ele. 

(KVA) 

Ele. 

(KVA) 

Ele. 

(KVA) 

Ele. 

(KVA) 

Total (Peak / Avg) 1.05 109 / 

50 

180 / 

140 

60 / 

34 

600 / 

500 670 / 575 780 / 600 670 / 575 

Adaptive Peak Pwr. 

Reduction ~ ~ ~ ~ 10% 10% 10% 10% 

Reduced Total 

(Peak / Avg) 1.05 109 / 50 

180 / 

140 

60 / 

34 

540 / 

500 600 / 575 700 / 600 600 / 575 

Engine CFM-56 Equivalent 2030 Reference 

Turbine 2030 Adv. Electric 

4.3.2 – Auxiliary Power Unit 

The APU for SUGAR Free is a conventional turbine type. The N+3 advanced concepts use either 

an advanced conventional turbine, Diesel Cycle APU, or a Fuel Cell power center. At this time, 

it is not clear which approach will be the best. Table 4.6 shows the expected use and power 

output for each configuration’s APU. 

Table 4.6 – APU Power and Weight 

Configuration 

‘N’ 

SUGAR Free 

‘N+3’ 

Refined SUGAR 

‘N+3’ 

SUGAR 

High 

‘N+3’ 

SUGAR 

Volt 

‘N+3’ 

SUGAR 

Ray 

APU Use APU Gnd. & Bkup. 

APU Type Turbine Turbine or Diesel Cycle 

APU Power (KVA) 90 254 308 

4.3.3 – Actuators 

Actuators are hydraulic for SUGAR Free. Without NASA funding a shift toward a hybrid system 

would occur by 2030. This system would use both electro-hydraulic and electrical mechanical 

actuators. With NASA funding, an all EMA system could be attained and is used on the three 

advanced configurations. Any hydraulic system in the ‘N+3’ configurations would operate at 

5,000 PSI yielding a 20% weight savings over an ‘N’ 3,000 PSI system. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Table 4.7 – Control Systems Architecture 

Configuration 

Aircraft Load ‘N’ 

SUGAR Free 

‘N+3’ 

Refined SUGAR 

‘N+3’ 

SUGAR High, Volt, Ray 

Hydraulic 

Pressure 3,000 PSI 5,000 PSI None 

Hydraulic Systems Two Systems Single System None 

4.3.4 – Control Architecture 

It is anticipated that redundant, multiplexed, fiberoptic networks will provide data to remote 

mounted actuator systems in the N+3 timeframe. 

4.3.5 – Thermal Technology 

N+3 aircraft will utilize lightweight heat exchanger technology, as well as light weight heat 

transfer media to utilize the excess heat generated in some areas of the airplane in areas that 

require heating. 

4.3.6 – Electromagnetic and Lightning Effects 

Flight safety requires lightning protection and advanced composite structures must include 

special provisions. 

4.3.7 – Fuel 

For this study, it is assumed that N+3 aircraft will operate on conventional Jet-A, synthetic, or 

biofuels that are essentially “drop-in” fuels. It is assumed that there is no fuel system penalty or 

aircraft performance change due to the use of alternative fuels. 

4.3.8 – Flight Avionics 

The aircraft will include avionics required to utilize Advanced Air Traffic Management. Due to 

improvements in avionics technology, this is not expected to add significant avionics weight to 

N+3 aircraft. 

4.3.9 – Wiring 

Current return networks will be required to reduce the weight penalty to wiring due to light 

weight composite materials that are generally non-conductive. For ‘N+3’ airplanes, significant 

wire weight reduction may be achieved by utilizing newer generations of the current return 

technology utilized in the 787. 

4.3.10 – Computing Networks 

Integrated computing networks using multiplexed fiber optic transport technology will reduce 

the weight of data and processing subsystems. 

4.4 – Propulsion Technologies 

An overview of the general propulsion technologies applied to the various engines designed for 

the SUGAR aircraft is shown in Table 4.8. The engine designed for the Refined SUGAR vehicle 

contains a suite of technologies that represent a moderately aggressive push forward in gas 
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turbine technology including improved combustion emissions technology, improvements in both 

cold section and hot section materials/processes, and the use of CMC turbine blade/vane 

technology. In addition, a suite of acoustics technologies are included as well as a suite of 

mechanical technologies needed to enable attainment of the aerothermodynamic cycle. 

The SUGAR High technologies represent an aggressive push on gas turbine technology and 

generally include all the technologies of the refined SUGAR in addition to those noted in the 

column. In particular, the SUGAR High features a next-gen CMC material/process, additional 

noise technologies, and a variety of additional mechanical technologies. 

The SUGAR Volt considered three engine concepts, one being an all-electric propulsor, the 

second being a fuel cell-gas turbine hybrid, and the third being a gas turbine-electric hybrid. All 

use a common suite of electric propulsor technologies including advanced lightweight motors, 

motor controllers, and power conditioning equipment. The fuel cell concept includes an 

advanced solid oxide fuel cell. Both the fuel cell hybrid and the gas turbine-electric hybrid 

concepts utilize the same basic suite of gas turbine technologies as the SUGAR High. 

The SUGAR Ray utilizes the propulsion system from SUGAR High. 

Table 4.8 – Propulsion Technologies Applied to Various Engine Concepts 

Configuration 

‘N’ 

SUGAR Free 

‘N+3’ 

Refined 

SUGAR 

‘N+3’ 

SUGAR High 

‘N+3’ 

SUGAR Volt 

‘N+3’ 

SUGAR 

Ray 

Propulsion Technology Areas 

Engine Cycle CFM56 

Very high 

BPR turbofan 

with 2030 

engine 

technologies 

Very high BPR 

turbofan with 

Advanced engine 

technologies 

Battery, Fuel 

Cell/Gas 

Turbine Hybrid 

(SUGAR High 

Tech Level) 

SUGAR 

High 

Combustor Conventional 

Advanced 

low-emissions 

combustor 

Variable Flow 

Splits, Ultracompact low 

emissions 

combustor 

SUGAR High + 

on fuel cell 

reformer 

SUGAR 

High 

Materials Conventional 

Adv. PMCs, 

TiAl, Adv disk 

material/proc

ess, Adv shaft 

mat’l, CMC 

blades/vanes 

Refined SUGAR 

Mat’ls + MMC’s, 

Advanced CMC 

mat’ls & 

processes 

SiC MOSFET, 

motor 

controller, 

lightweight 

magnetics & 

ferrites, CMC’s 

SUGAR 

High 

Acoustic Conventional 

Adv. 

inlet/nozzle 

treatment, 

Adv. liner 

mat’ls, Adv. 

Chevrons, 

Blade & OGV 

optimization 

Refined SUGAR Techs. + Active noise 

control/fluidics, Non-Ax symmetric nozzles, 

Unique/shielded installations, others (as 

needed) 

Mechanical Conventional 

High DN 

Bearings, 

Adv. High 

Temp Seals 

Additional advanced systems (as needed) 
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5.0 – Vehicle Development and Analysis 

5.1 – Vehicle Requirements 

A set of top level requirements for the SUGAR vehicles was generated from the future scenario 

and was previously shown in Table 2.2. These top level requirements were turned into specific 

payload-range requirements which are illustrated in Figure 5.1. The figure has several points of 

interest called out. 

1. The airplane is required to fly the average range at max payload (also maximum zero fuel 

weight). Max payload is required to be 15,200 pounds heavier than the payload from 

point 2 for a Medium sized airplane. 

2. The airplane is required to fly the maximum range at the average number of seats using 

200 pounds per passenger and no revenue payload. This point must be achieved using 

less than 90% of the useable fuel. 

3. This point will be used to calculate vehicle fuel burn performance and TOFL 

performance for the SUGAR program. This represents the point that represents how an 

operator would most commonly operate the vehicle class. Payload

Range

Low Density Payload

Max Zero Fuel Weight

Average Range

Maximum Range

1

3 2

Figure 5.1 – Payload-Range Requirements 

Both point 1 and 2 are required for sizing because airplane characteristics may change which 

point is critical. 

5.1.1 – Configuration Synthesis Ground Rules 

Critical requirements shape conceptual airplane configurations. Several configuration rules have 

been utilized for the SUGAR study. 

Overall Configuration: When an advanced concept is developed, it is often difficult to 

determine which performance advancements are attained because of the configuration layout and 

which are obtained due to technology improvements. In response to NASA’s request, the team 

has developed an N+3 reference airplane to help separate the performance improvements. The N 
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and N+3 reference vehicles are required to topologically be 737 like layouts (also known as tubeand-wing). Both will have turbofans, low wings, conventional tail layouts, etc. All the advanced 

concepts are allowed to take whatever form makes the integration developed during the Georgia 

Tech workshop possible. 

Interior Arrangement: The interior layout of the all configured aircraft will be generated using 

the appropriate rules for the vehicle size. For regional aircraft this is a single class arrangement 

with relatively short seat pitch. For medium aircraft, dual class seating will be used. For Large 

configurations, long range tri-class rules will be used. 

Span: Airport infrastructure is the primary reason for airplane span limitations. The future 

scenario predicts an increase of flight operations in the 2030 timeframe and airports are already 

congested. Increasing the distance between gates, assuming the airport cannot expand, would 

reduce the number available thus reducing throughput. Secondly, a considerable amount of 

infrastructure already exists that would have to be replaced if spans were increased beyond that 

of the current fleet. Span constraints are not just an issue at the gate. They are also an issue on 

runways and taxiways. 

Airport regulations dealing with span limitations are described in an FAA Advisory Circular10. In 

order to accurately assess the impact of increasing airplane span beyond 118’ a survey of which 

airports currently served by 737/A320 class airplanes would be affected is necessary. This would 

determine how much of current and projected service a larger span airplane would be unable to 

perform and how big an impact that would have on its utility and marketability. Table 5.1 shows 

all of Boeings commercial products FAA / ICAO designations. 

The SUGAR team has decided that all Regional airliners should be Group I or II, a typical 

Medium airliner would be Group III, and that a Large airliner would be Groups IV thru VI. 

Greater spans are allowed on advanced concepts provided a folding mechanism is used to meet 

the gate constraints. All folding is done AFTER landing or BEFORE takeoff. The airport 

operations aspect of takeoff and landing with high span has been ignored in this study and its 

impact should be addressed in future studies. 
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Table 5.1 – Airport Compatibility Group Codes 

AIRCRAFT FAA / ICAO DESIGNATION 

CODE I / A II / B III / C IV / D V / E VI / F 

SPAN 

LIMITS 

0 – 49’ 

0 – 15m 

49 – 79’ 

15 – 24m 

79 – 118’

24 – 36m 

118 – 171’

36 – 52m 

171 – 214’ 

52 – 65m 

214 – 262’

65 – 80m 

707 IV / D 

720 IV / D 

717 III / C 

727 III / C 

737 III / C 

747 V / E 

757 IV / D 

767 IV / D 

777 V / E 

DC-8 IV / D 

DC-9 III / C 

DC-10 IV / D 

MD-11* IV E 

MD-80 III / C 

MD-90 III / C 

* NOTE: MD-11 is the only aircraft that doesn’t remain in the same category between FAA 

and ICAO. This is due to wingspan conversion from English to Metric units. 

Tail Strike Angle: Tail strike angle is left unconstrained at this point. This will fall out of the 

vehicle analysis and ultimately be set by takeoff and landing requirements. 

Tip Strike Angle: Since a stability and control analysis will not be performed, an assumed tip 

clearance angle will not be allowed below eight degrees when measured at the maximum tail 

down angle. 

A summary of the configuration ground rules is provided in Table 5.2. 

Table 5.2 – Configuration Ground Rules 

“N” Reference 

Vehicle 

“N+3” Reference 

Vehicle 

“N+3” Advanced 

Concepts 

Max 

Span 

Regional 79 ft Ground folding if 

larger than span 

constraint 

Medium 118 ft 

Large 262 ft 

Configuration Conventional Unconstrained 

Tail Strike Angle Unconstrained 

Tip Strike Angle 8° 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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5.1.2 – Choosing a Cruise Speed 

Changing to an advanced air traffic management 

system allows the cruise speed for future aircraft 

to be optimized without constraints imposed by 

heritage vehicles. There are several ways to 

determine what speed an aircraft should fly and 

which one is chosen depends heavily on the goal 

of the operator. For simplicity, the following 

discussion assumes that the engine thermal 

efficiency does not change with speed. Four of 

the possible speeds (Figure 5.2) that can be 

chosen are discussed below: 

Maximum Endurance is the speed which yields 

the lowest energy used per unit time (lowest 

power). This isn’t a speed of interest for SUGAR 

because it doesn’t account for the need to travel a 

distance. 

Maximum Range is the speed which gives the 

lowest energy per unit distance. It can be shown 

that this is achieved at maximum lift-to-drag 

ratio. This does not take into account the value of 

time. 

Carson’s Speed11 is the “most productive use of 

excess fuel for cruising purposes”11. Carson 

argues that airplanes are operated at speeds well 

in excess of one that would achieve maximum lift-to-drag ratio (or maximum range) because 

they have excess power from the takeoff and climb. Carson also states that flying at this speed is 

equivalent to flying at the airplanes maximum lift-to-drag ratio times speed (M*L/D at fixed 

altitude). This is the heritage speed at which 

airliners fly which Carson states is “the least 

wasteful way of wasting fuel.”11

The Boeing Current Market Outlook

does include the impacts of speed. For a 

vehicle to be economically competitive, our 

future scenario forecasts a minimum cruise 

speed for vehicles based on their size 

classification. This is shown in Figure 2.10 

in the future scenario section. 

The paragraphs about Maximum Endurance, 

Maximum Range, and Carson’s speed are 

from an aerodynamic standpoint and do not 

account for changes that can be imparted by 

engine-airframe matching (the thermal 

efficiency of the fuel energy converted to 

Figure 5.2 – Approximation of Maximum 

Endurance and Maximum Range, and the 

Definition of Carson's Speed 

5,000

5,200

5,400

5,600

5,800

6,000

6,200

6,400

0.55 0.6 0.65 0.7 0.75 0.8 0.85

Cruise Mach

Fuel Burn (900 nm)

Future Scenerio Limit

Figure 5.3 – Fuel Burn vs. Mach Number for a family of 

high span airplanes optimized at different cruise speeds Drag 

Speed 

Speed 

Maximum 

Endurance

Maximum 

Range 

Carson’s 

Speed

Maximum 

Range 

Drag x Speed 
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thrust energy as a function of speed and altitude). At first glance, the speed for maximum range 

appears to be a good choice for SUGAR vehicles, since a wide range of engine possibilities exist. 

Using an initial sizing process (discussed in Section 5.1.3) several vehicles were optimized for 

varying cruise Mach numbers. Initial cruise altitude (ICA) was allowed to vary but was limited 

to 43,000 ft. The fuel burn for these optimized aircraft is shown in Figure 5.3. Each vehicle is 

optimized to minimize fuel burn for the given Mach number. The curve clearly shows an 

advantage for slowing down. 

For this study we will adhere to the lower limit of Mach 0.70 for Medium sized airplanes as 

suggested by the Boeing Current Market Outlook (CMO). 

5.1.3 – Initial Sizing and Points of Departure 

To size the advanced configurations, an initial sizing tool was developed based on a combination 

of textbook aerodynamic methods, Douglas heritage compressibility tables, textbook mass 

properties methods with span and strut corrections, a scaled engine deck, and simplistic stability 

and control for tail sizing. The analysis was calibrated to a known airplane and then used for 

sizing wing area and aspect ratio, while respecting span constraints and vehicle performance 

requirements (Section 6.1.2). The tool accepts factors for technology impacts such as weight 

factors and laminar flow percentage. 

SUGAR Free (765-093) is a 2008 technology conventional configuration sized for the 2008 

reference mission rules (discussed in Figure 6.2). The sizing for SUGAR Free is particularly 

important because it sets the baseline performance for all of the advanced configurations 

analyzed for the contract. Simply analyzing or using the performance of an existing airplane 

would not be acceptable for this study because it would not be sized for the mission defined by 

the future scenario (either in number of passengers or range). Early in the analysis of SUGAR 

Free (765-093) it became clear that any span less than the constraint was a penalty. This leaves 

wing area, thickness to chord ratio, and sweep as the highest level optimization variables of 

interest. Figure 5.4 shows the wing area trade using aspect ratio as a surrogate for wing area 

(span is fixed). Table 5.3 shows the input parameters and information on the selected initial 

sizing point for the configuration. Note that the effective aspect ratio and span include the virtual 

span added from a winglet. The actual span was held to the constraint of 118 feet. 
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Table 5.3 – Initial Sizing: 765-093 SUGAR Free Results 

12,650

12,700

12,750

12,800

12,850

12,900

12,950

13,000

13,050

8 9 10 11 12 13

Wing Aspect Ratio

Fuel Burn (lbs)

Figure 5.4 – Initial Sizing: 765-093 – SUGAR 

Free Aspect Ratio Trade 

Conditions and 

Assumptions: Vehicle Specifications: 

Mach: 0.78 Effective AR: 10.5 

Max Range (nm): 3,500 Area: 1,440 

TOFL: 7,000 Effective Span: 123 

ICA: 37,000 t/c Root: 0.145 

Strut: NO t/c Tip: 0.094 

ROC at ICA (fpm): 300 Taper Ratio: 0.18 

CL Takeoff: 2.4 CL Cruise: 0.625 

Reserves: N Sweep: 20.0° 

SFC Delta: 0% L/D: 18.45 

Laminar: NO ICA: 37,000 

Riblets: NO OEW: 101,642

Indirect Routing: 5% TOGW: 175,635

Tail Size Factor: 1.05 SLS Thrust: 56,315 

 Fuel Burn (900nm): 12,681 

Refined SUGAR (765-094) was sized in a similar way to SUGAR Free. The span constraint left 

the same parameters for optimization. The optimization did allow for Mach number to be traded 

with a lower bound set by the future scenario analysis (Section 2.0) to Mach 0.70. The results are 

shown in Table 5.4 and Figure 5.5. 

5,000

5,500

6,000

6,500

7,000

7,500

0.6 0.65 0.7 0.75 0.8 0.85

Cruise Mach

Fuel Burn (900 nm)

6,300 

6,400 

6,500 

6,600 

6,700 

6,800 

6,900 

9 10 11 12 13 14

Fuel Burn (lbs)

Wing Aspect Ratio

Figure 5.5 – Initial Sizing: 765-094 – Refined SUGAR Aspect Ratio and Mach Number Trade 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Table 5.4 – Initial Sizing: 765-094 Refined SUGAR Results 

Conditions and 

Assumptions: Vehicle Specifications: 

Mach: 0.70 Effective AR: 11.7 

Max Range (nm): 3,500 Area: 1,293 

TOFL: 7,000 Effective Span: 123 

ICA: 38,500 t/c Root: 0.145 

Strut: NO t/c Tip: 0.094 

ROC at ICA (fpm): 300 Taper Ratio: 0.20 

CL Takeoff: 2.4 CL Cruise: 0.718 

Reserves: N+3 Sweep: 15.0° 

SFC Delta: 20% L/D: 20.54 

Laminar: YES ICA: 38,408 

Riblets: YES OEW: 81,612 

Indirect Routing: 0% TOGW: 136,412 

Tail Size Factor: 1.00 SLS Thrust: 37,799 

 Fuel Burn (900nm): 6,388 

All the advanced concepts have more degrees of freedom as the wing span is allowed to grow 

past the constraint. However, they are required to fold any structure extending beyond 118 feet. 

The wing fold weight is scaled from existing proprietary data based on a known commercial 

design. The initial sizing results for SUGAR High (765-095) are shown in Table 5.5. The initial 

sizing points to very high span even with weight penalties for the wing fold. As expected, the 

configuration wants to fly as slow as possible and is more sensitive to speed than Refined 

SUGAR. 

Table 5.5 – Initial Sizing: 765-095 SUGAR High Results 

Conditions and 

Assumptions: Vehicle Specifications: 

Mach: 0.70 Effective AR: 24 

Max Range (nm): 3,500 Area: 1,700 

TOFL: 7,000 Effective Span: 202 

ICA: 44,000 t/c Root: 0.130 

Strut: YES t/c Tip: 0.85 

ROC at ICA (fpm): 300 Taper Ratio: 0.20 

CL Takeoff: 2.4 CL Cruise: 0.733 

Reserves: N+3 Sweep: 8.0° 

SFC Delta: 25% L/D: 27.31 

Laminar: YES ICA: 44,000 

Riblets: YES OEW: 85,100 

Indirect Routing: 0% TOGW: 138,576 

Tail Size Factor: 0.85 SLS Thrust: 35,325 

 Fuel Burn (900nm): 5,342 

SUGAR Volt (765-096) has a very similar layout to the SUGAR High and is used as a trade 

study platform for alternative propulsion systems. An optimization of wing area and aspect ratio 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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was performed for battery, fuel cell, and hybrid battery-Brayton cycle propulsion systems. The 

curves of Figure 5.6 thru Figure 5.9 represent the best solutions after optimizing each case. 

Figure 5.6 illustrates that ranges of up to one 

thousand nautical miles may be possible with 

advanced battery technology but at significant 

penalty to takeoff gross weight (TOGW). 

Recall that SUGAR Free had a TOGW of less 

than 180,000 pounds. Even at 300,000 pounds 

the battery powered airplane cannot make the 

range requirement with very aggressive 

energy densities. The battery powered 

airplane produces no in flight emissions, 

burns no fuel, and could potentially be very 

quiet. However, it was discarded from this 

study based on its inability to meet range 

requirements for a medium sized airliner. It 

could be attractive for Regional airplanes for 

missions less than 1000 nm. 

A fuel cell powered version of the Volt was 

also traded. Once again, aspect ratio and area 

were optimized for varying levels of fuel cell 

performance. It is shown in Figure 5.7 that, 

while able to perform the mission, the vehicle 

performance was not better than the SUGAR 

High fuel burn reduction for the fuel cell 

performance range considered. 

The Hybrid Brayton-Battery propulsion 

system shows the greatest promise in reducing 

vehicle fuel burn. The propulsion system is 

envisioned to have both a Brayton core and an 

electric motor powering a propulsor (fan or 

open fan). The airplane performs takeoff and 

climb using power from both systems, but 

throttles down one of the systems during 

cruise. Jet fuel powers the Brayton core and batteries power the electric motor. Maximizing 

propulsive energy use from batteries is desirable when trying to reduce fuel burn. However, 

batteries have much lower energy density, limiting range under battery power alone. A key 

feature of this concept is the ability to use modular batteries, so that the same vehicle can trade 

battery and fuel depending on the mission. Generally, more fuel and fewer batteries are used for 

long ranges, and less fuel and more batteries are used for short ranges. For all but the shortest 

missions, the aircraft has the same takeoff weight, as illustrated in Figure 5.8. 

By designing the vehicle to carry more battery weight (increase the design TOGW), greater 

distances can be flown using energy from batteries. This results in lower jet fuel burn, but higher 

TOGW. Lower gross weights result in shorter range capability when cruising on electric 

propulsion only. Figure 5.9 shows the anticipated fuel burn verses range for vehicles of 215,000 

100,000

120,000

140,000

160,000

180,000

200,000

220,000

240,000

260,000

280,000

300,000

0 500 1000 1500 2000 2500 3000 3500

Range (NM)

TOGW (lbs)

500

700

1000

1500

Battery

Wh/kg

Figure 5.6 – Takeoff Gross Weight vs. Range for 

Battery Powered SUGAR Volt 

1,500 

750 

 500 

 429 

375 

4,000

4,500

5,000

5,500

6,000

6,500

7,000

180,000 220,000 260,000 300,000 340,000 380,000

TOGW

Fuel Burn (lbs)

Fuel Cell 

Watts/kg

-34%

65% Thermal Efficiency

-55%

(lb)

Figure 5.7 – Fuel burn from a Fuel Cell Powered 

SUGAR Volt 
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pounds of gross weight with varying levels of battery technology. For a 900 nautical mile 

mission (the average mission length and the range fuel burn reduction will be measured) 90% 

fuel burn reductions may be attainable at modest levels of battery technology. Table 5.6 shows 

the initial sizing point from the figure which will be used for the SUGAR Volt initial sizing 

point. 

Mission Range

Fuel and 

Battery Wt.

Jet-A

Batteries

Max. TOGW

Mission Range

Fuel and 

Battery Wt.

Jet-A

Batteries

Max. TOGW

Figure 5.8 – Hybrid Brayton-Battery 

Airplane Carries More Batteries as Range 

is Increased Until MTOW is Reached 0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

0 300 600 900 1200 1500 1800 2100

Range

Fuel Burn

500

750

1000

1500

TOGW: 215,000

Max Range: 8000 NM

Fuel Burn (lbs)

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

0 300 600 900 1200 1500 1800 2100

Range

Fuel Burn

500

750

1000

1500

TOGW: 215,000

Max Range: 8000 NM

Fuel Burn (lbs)

-90%

TOGW: 215,000 lb

(lb)

Wh/kg

Figure 5.9 – Initial Sizing: 765-097 – SUGAR Volt Fuel Burn 

Table 5.6 – Initial Sizing: 765-096 SUGAR Volt Results 

Conditions and 

Assumptions: Vehicle Specifications: 

Mach: 0.65 Effective AR: 24 

Max Range (nm): 3,500 Area: 2,473 

TOFL: 7,000 Effective Span: 244 

ICA: 42,000 t/c Root: 0.130 

Strut: YES t/c Tip: 0.85 

ROC at ICA (fpm): 300 Taper Ratio: 0.18 

CL Takeoff: 2.4 CL Cruise: 0.833 

Reserves: N+3 Sweep: 8.0° 

SFC Delta: 25% L/D: 32.43 

Laminar: YES ICA: 42,000 

Riblets: YES Battery Weight: 26,314 

Indirect Routing: 0% TOGW: 215,000 

Tail Size Factor: 0.85 SLS Thrust: 24,810 

 Fuel Burn (900nm): 1,490 

5.2 – Vehicle Development and Analysis Tools 

5.2.1 – Aerodynamic Buildup Methods 

CASES (Computer Aided Sizing and Evaluation System), a heritage empirical Douglas 

application, was used to develop the low and high speed aerodynamic buildups for SUGAR. The 

CASES standard high speed buildup is comprised of parasite, induced, compressibility, and trim 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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drag. This is illustrated in Figure 5.10. These components are built up using Boeing empirical 

data and vortex lattice methods. When a configuration is outside the empirical database, methods 

are substituted as appropriate. For example, vehicles of high span adjust the use of vortex lattice 

methods to calculate induced drag. Hybrid wing body (HWB) does not use the CASES database. 

HWB reference drag buildup uses wing-body CFL3D RANS. 

Figure 5.10 – Standard CASES High Speed Buildup 

After the initial CASES buildup is attained, additional increments are applied for technology 

enhancements such as laminar flow. These additional increments are based on engineering 

knowledge about technology applicability and are applied via spreadsheet adjustments. Powered 

increments may also be applied for configurations with propellers or open fans. 

CASES is also used for the low speed buildup. The total lift coefficient is calculated as a 

function of the taxi lift coefficient, lift coefficient at ground angle limit, and the maximum free 

air lift coefficient. The total drag coefficient is comprised of empirically defined components 

including, parasite, twist, profile, induced, and trim. The resulting polars may be adjusted for 

vehicles outside the database such as powered lift or vehicles with propellers, open fans, or 

HWB’s. 

It should be noted that CASES databases are based on trapezoidal wing projected reference 

system. Non-Dimensional quantities for all high and low speed buildups use this area as the 

reference. HWB is an exception using the gross wing reference area. 

5.2.2 – Mass Properties Methods 

This section describes the process shown in Figure 5.11 below. SUGAR Mass Properties were 

derived from N+3 technology enhancements incorporated into Boeing proprietary mass 

modeling tools. N+3 technology enhancements were rigorously reviewed with technology and 

weights Subject Matter Experts (SME’s) to understand and obtain design and integration 

philosophies. These data were applied to existing detail weights to derive the reduction factors 

Parasite

CDP

Induced

CDI

Compressibility

∆CDC

Trim

CDt

Lift Coefficient Squared, CL

2

Drag Coefficient, CD

M = 0.50
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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shown in Table 5.7. These factors were used in aircraft level empirical weight prediction tools 

for performance sizing. 

SUGAR 

Structures 

(SME’s)

787 Systems, 

Structures & 

Materials

(Weights SMEs)

SUGAR 

Systems 

(SME’s)

Derived 

Reduction 

Factors Table

Representative 

Calculations

TIP’s*

(eg Advanced 

Fuselage Materials)

CWEP Weights 

Prediction Tool

(Calibrated to comparable 

commercial aircraft)

SUGAR Weights

BWB Weights 

Prediction Tool

(HWB)

* Technology Integration Programs 

Figure 5.11 – Mass Properties Methods Flowchart 

CWEP, a Boeing proprietary weights parametric estimating tool, is based on empirical data of 

current and existing commercial transports. It was calibrated to a SUGAR Free class aircraft 

using extensive in-house data. Refined SUGAR weights were estimated by applying the weight 

reduction factors of Table 5.7 to this model. 

The BWB weights prediction tools are based on in-house generated BWB data derived from 

engineering analysis. 

Table 5.7 – Mass Properties Reduction Factors 

Affected Group Change in Weight 

Wing Bending Material -26 % 

Tails -15% 

Fuselage -12% 

Landing Gear 0.6% of TOGW 

Nacelle Structure -2% 

On Board Structural Health Management +100 lb 

Insulation -5% 

Light Weight Seats -20% 

Paint -44 lb 

Advanced Heat Exchanger -50% 

Signal Wiring Reduction -50% 

 
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5.2.3 – Propulsion Methods 

Performance of the eFan, gFan, gFan+, and hFan engines was estimated using NPSS cycle 

models. The component performance calculations for the typical gas turbine components were 

based on GE standard calculation methods. Simplified PD representations were developed for 

non-standard components, notably the electric motor and motor controller, such that the impact 

of those components on overall engine performance could be estimated for the eFan and hFan 

concepts (the fFan concept was not evaluated to this level of analysis fidelity). The component 

performance levels assumed were based on GE historical data for current engines with 

projections for advances in the N+3 timeframe. Additional component performance corrections 

were included based on specific technology concepts included in the basic engine design, as 

needed. Cycle performance for the fFan concept was estimated via simple spreadsheet-type 

calculations based on available fuel cell component performance data. 

Engine weight and flowpath geometry were estimated using GE internal tools. These tools utilize 

a combination of physics-based analysis and historical correlations. These tools design to the 

level of estimating turbomachinery vector diagrams at the pitch line with corrections for hub and 

tip of each stage. Thus, the aeromechanical design is consistent with the cycle and suitable for 

further refinement if selected. Engine weights were adjusted to reflect materials technology 

assumptions. Electric motor and motor controller weights were scaled from a current state-of-the 

art machine with corrections to account for the assumed N+3 technology timeframe. 

Engine emissions were estimated based on GE internal correlations with adjustments to account 

for the future progression of technology. Noise was estimated by anchoring to a known 

comparable baseline. Estimates on noise deltas for specific noise reduction technologies were 

then applied to this baseline at both the engine and airframe levels to arrive at an overall estimate 

of vehicle noise levels. 

A detailed evaluation of open fan engine concepts was beyond the intended scope of this study 

due to resource constraints. However, this does not mean that the open fan isn’t promising for 

this application and it is desirable to at least give some insight into the potential benefit available 

from open fan concepts. Thus, the open fan was treated as a cruise SFC delta and an engine 

weight delta applied to the gFan+ engine concept. It should be noted that the open fan is 

expected to be somewhat more challenging with respect to meeting the very aggressive N+3 

noise goals. No attempt was made to assess the noise implications of open fan in this project. 

5.3 – 765-093 – SUGAR Free (2008 Baseline Configuration) 

The configuration that serves as a baseline for all metrics in our study is defined as the 765-093 

‘SUGAR Free’. SUGAR Free is used as a name since the vehicle is free of any future technology 

advancements and adheres to the ‘N’ ground rules for vehicle development. 

5.3.1 – Configuration Layout 

The 765-093 configuration is a low wing airplane with turbofan engines mounted on pylons 

below the wing and conventional tail layout. The wing planform is conventional and of moderate 

sweep. It features a substantial inboard trailing edge extension (yehudi) that provides reduced 

wing root thickness/chord ratio at the body and provides the space required to mount the main 

landing gear. The main landing gear trunnion is supported between the wing rear spar and a 

landing gear beam. 
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All major structure is aluminum and the airplane is configured to be consistent with current 

technology medium sized aircraft. 

A three view drawing of the configuration is shown in Figure 5.12. 

The fuselage is nominally circular in cross section and is sized to provide a seating arrangement 

of 6 abreast in economy class. The cabin length is sized to provide an airplane seating capacity in 

a dual class configuration of 154 passengers. The lower lobe accommodates bulk baggage only. 

A Layout of Passenger Accommodations (LOPA) is shown in Figure 5.13. 
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Figure 5.12 – 765-093 3-View Drawing 
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Figure 5.13 – 765-093 LOPA 

12 First 

36-in Pitch 

142 Economy 

32-in Pitch 

Interior Arrangement

SUGAR 

IAC Short / Medium Range – Dual Class 

1038.5” 

Class 

(%) 

7.79 

92.20 

100.00 

Carts 

(qty) 

3.0 7.0 

10.0 

Cart Ratio 

(Carts/Pax) 

0.250 0.049 0.649 

Lavatory Ratio 

(Pax/Lav) 

12 71 

– 

Closet Ratio 

(Rod-in/Pax) 

4.00 0.00 

– 

First Economy Total 
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5.3.2 – Aerodynamic Buildup 

High Speed: 

The CASES high speed aerodynamic buildup for the 765-093 is shown in Table 5.8 and is 

summarized in Figure 5.14. 

Table 5.8 – 765-093 High Speed Buildup 

CDc

5%

CDtrim

2%

CDi

37%

CDo

56%

Figure 5.14 – 765-093 High Speed Buildup 

Configuration 765-093 

SWEEP (DEG) 25° 

T/C-AVE 0.1258 

AIRFOIL TYPE SUPERCRITICAL 

F BUILD-UP (FT2) 

FUSELAGE 8.8533 

WING 8.6164 

WINGLET 0.2105 

HORIZONTAL 1.9395 

VERTICAL 1.6832 

N&P 2.9600 

CANOPY 0.0405 

GEAR PODS 0.0000 

ETC BEFORE SUB 0.0400 

EXCRESCENCE 2.2883 

INTERFERENCE 0.0000 

UPSWEEP 0.5076 

WING TWIST 0.3415 

STRAKES 0.0000 

ETC AFTER SUB -0.6000 

FUSELAGE BUMP 0.5000 

F-TOTAL (FT2) 27.3808 

E-VISC 0.944 

CRUISE CD BUILD-UP 

M-CRUISE 0.78 

CL-CRUISE 0.625 

CRUISE ALTITUDE 35000 

CD0 0.01916 

CDI 0.01265 

CDC 0.00186 

CDTRIM 0.00069 

CDTOT 0.03436 

L/D 18.189 

ML/D 14.187 

 

It should be noted that the categories ETC BEFORE SUB and ETC AFTER SUB in the parasite 

drag buildup are used to calibrate the vehicle drag and/or to compensate for the application of 

advanced technologies. In this case, the appropriate values are used to match the expected 

performance of an airplane of this configuration. For the advanced concepts, advanced 
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technology increments will also be applied as appropriate. The two categories are required as 

each is scaled differently as the airplane is sized. 

The aerodynamic characteristics reflect the design Mach number of 0.78 for current air traffic 

management integration. The resulting high speed data is shown in Figure 5.15. The figure 

illustrates the maximum aerodynamic efficiency (M*L/D) occurring at the design cruise Mach 

(0.78) and CL (0.625). 

Figure 5.15 – 765-093 - M * L / D Total 

Low Speed: 

Figure 5.16 through Figure 5.18 show the low speed aerodynamic characteristics for SUGAR 

Free. Low speed data are trimmed as a function of angle of attack, lift coefficient, and drag 

coefficient at each flap detent. Low speed high lift devices on wing leading and trailing edges are 

deployed. 
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Figure 5.16 – 765-093 - Low Speed Lift Curve; Free Air 

Figure 5.17 – 765-093 - Low Speed Polar; Free Air 
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Figure 5.18 – 765-093 - Low Speed Lift / Drag; Free Air 
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5.3.3 – Mass Properties 

The SUGAR Free configuration was calibrated using extensive in-house data to provide a 

baseline. Table 5.9 below shows the group weight statements and each group’s percentages of 

takeoff gross weight (TOGW). Figure 5.19 shows the SUGAR Free group weights as a 

percentage of TOGW. 

Table 5.9 – 765-093 Group Weight Statement 

GROUP WEIGHT (LB) % TOGW 

WING 18,728 10.7 

BENDING MATERIAL 9,621 5.5 

SPAR WEBS 1,290 0.7 

RIBS AND BULKHEADS 1,226 0.7 

AERODYNAMIC SURFACES 3,351 1.9 

SECONDARY STRUCTURE 3,240 1.8 

TAIL 3,779 2.2 

FUSELAGE 18,392 10.5 

LANDING GEAR 6,712 3.8 

PYLON 1,858 1.1 

PROPULSION 14,874 8.5 

ENGINE 10,404 5.9 

ENGINE SYSTEMS 263 0.1 

EXHAUST SYSTEM 3,688 2.1 

FUEL SYSTEM 520 0.3 

FLIGHT CONTROLS 3,084 1.8 

COCKPIT CONTROLS 252 0.1 

SYSTEM CONTROLS 2,832 1.6 

POWER SYSTEMS 4,483 2.6 

AUXILIARY POWER PLANT 1,032 0.6 

HYDRAULICS 894 0.5 

ELECTRICAL 2,557 1.5 

INSTRUMENTS 686 0.4 

AVIONICS & AUTOPILOT 1,533 0.9 

FURNISHINGS & EQUIPMENT 10,866 6.2 

AIR CONDITIONING 1,678 1.0 

ANTI-ICING 118 0.1 

MANUFACTURER’S EMPTY WEIGHT (MEW) 86,790 49.4 

OPERATIONAL ITEMS 7,342 4.2 

OPERATING EMPTY WEIGHT (OEW) 94,132 53.6 

USEABLE FUEL 45,313 25.8 

PAYLOAD 36,190 20.6 

TAKEOFF GROSS WEIGHT (TOGW) 175,635 100.0 
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WING

11%

TAIL

2%

FUSELAGE

10%

LANDING GEAR

4%

PYLON

PROPULSION 1%

8%

FLIGHT 

CONTROLS

POWER 2%

SYSTEMS

3%

FURNISHINGS & 

EQUIPMENT

6%

OPERATIONAL 

ITEMS

4%

OTHER

2%

USEABLE FUEL

26%

PAYLOAD

21%

Fuel Payload OEW

Figure 5.19 – 765-093 Weight Summary 

5.3.4 – Engine Data – CFM-56 

The engine used for SUGAR Free is a scaled CFM-56-7B shown in Figure 5.20. Basic weight, 

geometry, and performance information for the scale 1.0 engine is shown in Table 5.10. This 

engine represents today’s state-of-the-art turbofan and is the baseline against which the various 

advanced engines are compared. It should be noted that the power extraction levels required 

from this engine are relatively high and would likely require adjustments in the engine to 

accommodate all operability requirements. No attempt was made in this study to account for 

these effects in the baseline engine other than to apply the requested power extraction levels. 

Figure 5.20 – CFM56-7B Engine Walk Around 
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Table 5.10 – CFM56 Key Weight, Dimensions, and Performance Data 

Basic dry weight 5216 lbm

Fan diameter 61 in

Length 98.7 in

Performance Thrust, lbf SFC, lbm/lbf-hr

SLS 27300 - - -

Rolling takeoff - - - - - -

Top-of-climb 5962 - - -

Cruise 5480 - - -

Emissions -30% relative to CAEP/6

Projected Technologies

Current CFM56-7B bill of materials

5.4 – 765-094 – Refined SUGAR (2030 Reference Configuration) 

The Refined SUGAR configuration is the 2030 reference. Improvement over the SUGAR Free 

concept is gained entirely from incremental development of existing technologies. 

The configuration layout is constrained to be conventional and the technology levels relatively 

conservative when compared to the three advanced concepts (described in Sections 5.5 through 

5.7). The configuration targets lower fuel burn through reduced structural weight and Specific 

Fuel Consumption (SFC) which should promote reduced noise and emissions (through the 

scaling down of thrust with weight). 

5.4.1 – Configuration Layout 

The 765-094 configuration is a low wing airplane with turbofan engines mounted on pylons 

below the wing and conventional tail layout. 

The wing planform is conventional and of moderate sweep. It features a substantial inboard 

trailing edge extension (yehudi) that provides reduced wing root thickness/chord ratio at the 

body and provides the space required to mount the main landing gear. The main landing gear 

trunnion is supported between the wing rear spar and a landing gear beam. A three view drawing 

of the configuration is shown in Figure 5.21. 

The fuselage is nominally circular in cross section and is sized to provide a seating arrangement 

of 6 abreast in economy class. The cabin length is sized to provide an airplane seating capacity in 

a dual class configuration of 154 passengers. The lower lobe accommodates bulk baggage only. 

A Layout of Passenger Accommodations (LOPA) is shown in Figure 5.13) and is the same as the 

SUGAR Free (765-093). 
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Figure 5.21 – 765-094 3-View Drawing 
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5.4.2 – Aerodynamic Buildup 

High Speed: 

The high-speed aerodynamic buildup for the Refined SUGAR configuration is summarized in 

Table 5.11. 

Table 5.11 – 765-094 High Speed Buildup 

CDo

53%

CDi

40%

CDtrim

CDc 2%

5%

Figure 5.22 – 765-094 High Speed Buildup 

Configuration 765-094 

SWEEP (DEG) 15.08° 

T/C-AVE 0.1248 

AIRFOIL TYPE SUPERCRITICAL 

F BUILD-UP (FT2) 

FUSELAGE 9.2989 

WING 8.1036 

WINGLET 0.2173 

HORIZONTAL 1.4215 

VERTICAL 1.2158 

N&P 2.8600 

CANOPY 0.0405 

GEAR PODS 0.0000 

ETC BEFORE SUB -3.5400 

EXCRESCENCE 1.5239 

INTERFERENCE 0.0000 

UPSWEEP 0.6012 

WING TWIST 0.3948 

STRAKES 0.0000 

ETC AFTER SUB -0.6500 

FUSELAGE BUMP 0.5430 

F-TOTAL (FT2) 22.0305 

E-VISC 0.966 

CRUISE CD BUILD-UP 

M-CRUISE 0.74 

CL-CRUISE 0.675 

CRUISE ALTITUDE 38408 

CD0 0.01713 

CDI 0.01290 

CDC 0.00159 

CDTRIM 0.00065 

CDTOT 0.03227 

L/D 20.915 

ML/D 15.477 

 

For Refined SUGAR, the ETC BEFORE SUB includes technology projections for natural 

laminar flow over a portion of the wing and riblets on the fuselage, as shown in Figure 5.23. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Red = Surfaces affected by riblets

Blue = Surfaces affected by laminar flow

Figure 5.23 – 765-094 Aerodynamic Technologies Application 

The resulting high speed data is shown in Figure 5.24. The figure illustrates the maximum 

aerodynamic efficiency (M*L/D) occurring at a cruise Mach of 0.74 and a CL of 0.625. This is 

slightly higher than the efficiency at the Mach 0.7 cruise condition. 

Figure 5.24 – 765-094 - M * L / D Total 

Low Speed: 

Figure 5.25 through Figure 5.27 show the low speed aerodynamic characteristics for Refined 

SUGAR. Low speed data are trimmed as a function of angle of attack, lift coefficient, and drag 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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coefficient at each flap detent. Low speed high lift devices on wing leading and trailing edges are 

deployed. 

Figure 5.25 – 765-094 - Low Speed Lift Curve; Free Air 
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Figure 5.26 – 765-094 - Low Speed Polar; Free Air 

Figure 5.27 – 765-094 - Low Speed Lift / Drag; Free Air 
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5.4.3 – Mass Properties 

The Refined SUGAR configuration was estimated by applying the N+3 weight reduction factors 

to SUGAR Free. Table 5.12 shows the resulting group weight statement which includes each 

group’s percentage of TOGW. This information is presented graphically in Figure 5.28. 

Table 5.12 – 765-094 Group Weight Statement 

GROUP WEIGHT 

(LB) % TOGW 

WING 13,695 10.0 

BENDING MATERIAL 5,881 4.3 

SPAR WEBS 1,016 0.7 

RIBS AND BULKHEADS 1,036 0.8 

AERODYNAMIC SURFACES 2,850 2.1 

SECONDARY STRUCTURE 2,911 2.1 

TAIL 2,671 2.0 

FUSELAGE 14,991 11.0 

LANDING GEAR 5,052 3.7 

PYLON 4,412 3.2 

PROPULSION 9,027 6.6 

ENGINE 8,410 6.2 

FUEL SYSTEM 617 0.5 

FLIGHT CONTROLS 2,900 2.1 

COCKPIT CONTROLS 252 0.2 

SYSTEM CONTROLS 2,648 1.9 

POWER SYSTEMS 4,146 3.0 

AUXILIARY POWER PLANT 1,014 0.7 

HYDRAULICS 836 0.6 

ELECTRICAL 2,297 1.7 

INSTRUMENTS 773 0.6 

AVIONICS & AUTOPILOT 1,504 1.1 

FURNISHINGS & EQUIPMENT 9,115 6.7 

AIR CONDITIONING 1,441 1.1 

ANTI-ICING 108 0.1 

MANUFACTURER’S EMPTY WEIGHT (MEW) 69,835 51.2 

OPERATIONAL ITEMS 7,207 5.3 

OPERATING EMPTY WEIGHT (OEW) 77,042 56.5 

USEABLE FUEL 23,180 17.0 

PAYLOAD 36,190 26.5 

TAKEOFF GROSS WEIGHT (TOGW) 136,412 100.0 
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WING

10%

TAIL

2%

FUSELAGE

11%

LANDING GEAR

4%

PYLON

PROPULSION 3%

7%

FLIGHT 

CONTROLS

POWER 2%

SYSTEMS

FURNISHINGS & 3%

EQUIPMENT

OPERATIONAL 7%

ITEMS

5%

OTHER

3%

USEABLE FUEL

17%

PAYLOAD

26%

Fuel Payload OEW

Figure 5.28 – 765-094 Weight Summary 

5.4.4 – Engine Data – “gFan” 

The engine designed for the refined SUGAR vehicle is a boosted 2-spool separate flow turbofan 

configuration informally designated “gFan”. This engine is shown in Figure 5.29 and features a 

66 OPR, 9.2 BPR, and relatively low hot section temperatures. The high OPR in conjunction 

with advanced component aerodynamic and materials technologies gives this engine very good 

thermal efficiency. The modest hot section temperatures in conjunction with advanced TAPS 

combustor technology make this engine very compatible with the aggressive N+3 emissions 

goals. This engine features an advanced shrouded fan/nacelle arrangement that yield good noise 

characteristics. This engine makes extensive use of CMCs in the hot section both for weight 

reduction and performance improvement. Key geometry, performance and weight information 

for this engine is provided in Table 5.13. This table also provides an overview of the various 

component technologies employed in this engine. 

The combustor selected for this engine is a generation beyond the advanced TAPS combustors 

presently being planned for future products. This “GEN++ TAPS” combustor is of generally 

similar design to today’s TAPS system but with improved mixing and improved operability 

features. This, in conjunction with significantly reduced cruise T4 levels relative to today’s 

narrowbody engines, enables drastic reductions in NOx emissions. It is anticipated that this 

combustor design will yield significant reductions in particulate emissions levels. The impact on 

contrail formation is a topic for future research and will be better defined as the combustor 

design progresses in the future. 
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Advanced nacelle

Highly integrated

Minimum OD

Unitized composite

Advanced Composite Fan

1.4 PR, 70” fan

Advanced 3-D aero design

Sculpted features, low noise

Integrated thrust reverser/VFN

Variable fan nozzle

4-Stage Booster

Ultra-high PR core compressor

66 OPR, 9 BPR

9 stages HPT

2-Stage

CMC nozzles + blades

Advanced aero features

LPT

7-Stage

Moderate loading

CMC & TiAl nozzles + blades Advanced

combustor

Figure 5.29 – “gFan” Engine Walk Around 

Table 5.13 – gFan Engine Description 

Propulsion system wt 6411 lbm

Fan diameter 70 in

Length 122 in, spinner to TRF

Performance Thrust, lbf SFC, lbm/lbf-hr

SLS 18,900 0.256

Rolling takeoff 14303 0.344

Top-of-climb 4229 0.534

Cruise 4025 0.528

Emissions -58% relative to CAEP/6

Projected Technologies

Advanced 3-D aero composite fan

Ultra-high PR compressor

Advanced low-emissions combustor

Integrated thrust reverser/variable fan nozzle

CMC turbine blades/vanes

Next-gen component aero technology

Next-gen nacelle technology

Improved shaft material

Acoustics technology suite

High DN bearings, high speed/temperature seals

TiAl materials & process technology
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5.5 – 765-095 – SUGAR High (2030 Advanced Strut Braced High Span) 

The SUGAR High configuration is a high span strut-braced wing concept that is tailored toward 

reducing fuel burn and noise via the aerodynamic benefits of high span. 

5.5.1 – Configuration Layout 

The 765-095 configuration is a high wing airplane with turbofan engines mounted on pylons 

below the wing and a T-tail layout. The very high aspect ratio wing is braced by a strut which 

joins the fuselage at the location of the body-mounted main landing gear in order to maximize 

load sharing. The main landing gear stows compactly in a fairing on the underside of the 

fuselage. The kinematics of the gear are similar to that of the BAe 146. 

A three view drawing of the configuration is shown in Figure 5.30. 

The fuselage is nominally circular in cross section and is sized to provide a seating arrangement 

of 6 abreast in economy class. The cabin length is sized to provide an airplane seating capacity in 

a dual class configuration of 154 passengers. The lower lobe accommodates bulk baggage only. 

A Layout of Passenger Accommodations (LOPA) is shown in Figure 5.13 and is the same as the 

SUGAR Free (765-093). 
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Figure 5.30 – 765-095 3-View Drawing 
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5.5.2 – Aerodynamic Buildup 

High Speed: 

The high-speed drag buildup for Sugar HIGH is shown in Table 5.14, and is summarized in 

Figure 5.31. CASES database is extrapolated for the high span configuration. 

Table 5.14 – 765-095 High Speed Buildup 

Configuration 765-095 Turbofan 765-095 Open Fan 

SWEEP (DEG) 8° 8° 

T/C-AVE 0.1119 0.1119 

AIRFOIL TYPE SUPERCRITICAL SUPERCRITICAL 

F BUILD-UP (FT2) 

FUSELAGE 8.8661 8.8661 

WING 12.1223 12.1223 

WINGLET 2.6111 2.6111 

HORIZONTAL 1.8454 1.8454 

VERTICAL 1.6581 1.6581 

N&P 3.1500 1.7900 

CANOPY 0.0405 0.0405 

GEAR PODS 4.0542 4.0542 

ETC BEFORE SUB -6.6897 -5.8090 

EXCRESCENCE 1.9001 1.8835 

INTERFERENCE 0.0000 0.0000 

UPSWEEP 0.6012 0.6012 

WING TWIST 0.5219 0.5219 

STRAKES 0.0000 0.0000 

ETC AFTER SUB -2.5913 -2.5603 

FUSELAGE BUMP 1.0350 1.0350 

F-TOTAL (FT2) 29.1249 28.6600 

E-VISC 0.824 0.824 

CRUISE CD BUILD-UP 

M-CRUISE 0.74 0.74 

CL-CRUISE 0.75 0.75 

CRUISE ALTITUDE 44000 44000 

CD0 0.01713 0.01686 

CDI 0.00905 0.00905 

CDC 0.00212 0.00212 

CDTRIM 0.00058 0.00057 

CDTOT 0.02888 0.0286 

L/D 25.970 26.224 

ML/D 19.217 19.406 

 

The ETC BEFORE SUB category includes technology projections for natural laminar flow over 

a portion of the wing, strut, and vertical tail as well as riblets applied to the turbulent portion of 

the wing and the fuselage, as illustrated in Figure 5.32. ETC AFTER SUB includes a technology 

projection for advanced supercritical airfoils with divergent trailing edge. In addition, 
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technologies for low interference nacelles and strut/brace were included in the parasite buildup. 

Future work is needed to address airfoils and wings with extreme spans and high lift coefficients. 

CDo

60%

CDi

31%

CDtrim

CDc 2%

7%

CDo

59%

CDi

32%

CDtrim

CDc 2%

7%

a. b.

Figure 5.31 – 765-095 High Speed Buildup a) Turbofan b) Open Fan 

Red = Surfaces affected by riblets

Blue = Surfaces affected by laminar flow

Figure 5.32 – 765-095 – Aerodynamic Technologies Application 

The resulting high speed data is shown in Figure 5.24. The figure illustrates the maximum 

aerodynamic efficiency (M*L/D) occurring at a cruise Mach of 0.74 and a CL of 0.75. This is 

slightly higher than the efficiency at the Mach 0.7 and CL of 0.828 cruise point. 
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Figure 5.33 – 765-095 - M * L / D Total 

Low Speed: 

Figure 5.34 through Figure 5.36 show the turbofan low speed characteristics for SUGAR High. 

Low speed data are trimmed as a function of angle of attack, lift coefficient, and drag coefficient 

at each flap detent. Low speed high lift devices on wing leading and trailing edges are deployed. 
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Figure 5.34 – 765-095 - Low Speed Lift Curve; Free Air 

Figure 5.35 – 765-095 - Low Speed Polar; Free Air 
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Figure 5.36 – 765-095 - Low Speed Lift / Drag; Free Air 

5.5.3 – Mass Properties 

The weight for the SUGAR High configuration was estimated by applying the N+3 weight 

reduction factors to a calibrated model which included factors for the high aspect ratio wing. 

Table 5.15 and Figure 5.37 show the subsystem weights and their percentages of TOGW for the 

as-drawn analyzed weight. 

To derive the factors for the SUGAR High wing, additional analysis was needed to account for 

its high aspect ratio strut-braced wing. The wing was analyzed using station based analyses 

where the bending material was sized using empirical data, assuming that the strut reacted all 

outboard shear. Due to the inherent low bending and torsional resistance properties of this wing, 

an analysis was performed to account for aeroelastic effects. As a surrogate to more rigorous and 

costly analyses, a tip rotation constraint was imposed to assess the torsional penalty incurred by 

the bending material. The high weight of this wing is primarily due to the bending material 

thickness relative to the available box depth, even after including advanced aeroelastic load 

relief. The standard methods used to estimate the wing weight are not considered adequate to 

account for all of the advanced technologies. Therefore, there is high wing weight uncertainty 

and significant, although unproven, potential for weight reduction. 

Further analysis using simple spreadsheet methods was done to explore potential weight 

reductions, as summarized in Figure 5.38. A non-optimized planform and the need for increased 

torsional rigidity were major contributors to the high wing weight of the point design 

configuration. With the goal of reducing this, parametric variations were made to the simple 

analysis model. Provisions were made to preserve the same stiffness while reducing structural 

material. The thickness of the wing was increased slightly; resulting in greater stiffness over the 
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entire wing. The planform was modified to reduce taper inboard of the strut, which increased the 

chord at the strut-to-wing intersection. This allowed the strut to have greater leverage in resisting 

twist at the strut-to-wing intersection. These changes might allow the wing cover panels to be 

sized almost entirely by bending loads alone, with just a small increment added to meet the 

torsion requirement. The reduced stresses, which would result in lower skin thicknesses, would 

allow the N+3 weight reduction factors to be applied. The total benefit of these changes, when 

incorporated, could result in up to 20,000 lbs of weight savings (Figure 5.38). Additional work is 

needed to determine if this reduction is achievable. 

Table 5.15 – 765-095 Group Weight Statement 

GROUP WEIGHT (LB) % TOGW 

WING 36,798 22.5 

BENDING MATERIAL 20,602 12.6 

SPAR WEBS 3,434 2.1 

RIBS AND BULKHEADS 3,434 2.1 

AERODYNAMIC SURFACES 4,925 3.0 

SECONDARY STRUCTURE 4,403 2.7 

STRUT 2,800 1.7 

TAIL 3,157 1.9 

FUSELAGE 16,327 10.0 

LANDING GEAR 5,595 3.4 

PYLON 5,036 3.1 

PROPULSION 9,984 6.1 

ENGINE 9,156 5.6 

FUEL SYSTEM 828 0.5 

FLIGHT CONTROLS 2,873 1.8 

COCKPIT CONTROLS 252 0.2 

SYSTEM CONTROLS 2,621 1.6 

POWER SYSTEMS 4,138 2.5 

AUXILIARY POWER PLANT 1,014 0.6 

HYDRAULICS 827 0.5 

ELECTRICAL 2,297 1.4 

INSTRUMENTS 773 0.5 

AVIONICS & AUTOPILOT 1,504 0.9 

FURNISHINGS & EQUIPMENT 9,115 5.6 

AIR CONDITIONING 1,441 0.9 

ANTI-ICING 141 0.1 

MANUFACTURER’S EMPTY WEIGHT (MEW) 99,682 60.8 

OPERATIONAL ITEMS 7,207 4.4 

OPERATING EMPTY WEIGHT (OEW) 106,889 65.2 

USEABLE FUEL 20,774 12.7 

PAYLOAD 36,190 22.1 

TAKEOFF GROSS WEIGHT (TOGW) 163,853 100.0 
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WING & STRUT

24%

TAIL

2%

FUSELAGE

10%

LANDING GEAR

3% PYLON

3%

PROPULSION

FLIGHT 6%

CONTROLS

2%

POWER 

SYSTEMS

3%

FURNISHINGS 

& EQUIPMENT

6%

OPERATIONAL 

ITEMS

4%

OTHER

2%

USEABLE FUEL

13%

PAYLOAD

22%

Fuel Payload OEW

Figure 5.37 – 765-095 Weight Summary 

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000

As Drawn (no

torsional

rigidity from

strut)

Planform

Change,

Lower

Inboard

Taper, Same

Span and

Area

Constant

Inboard

Thickness

(13%)

Torsion

Credit from

Strut

Composites

Optimization 

Wing Weight (lbs)

Additional Wing Weight

For Torsional Rigidity

Wing Weight if Sized For

Bending Moment Only

Weight of Strut

-15,000 lb*

-20,000 lb

+5,000 lb OEW

Point Design Weight

* Assumes 12,000 lb wing weight reduction 

+ 3,000 lb other system weights reduced 

due to decreased wing weight = 15,000 

OEW reduction

Minimal aero impact is expected from these changes

Wing thickness and planform optimization 

and improved strut integration

Figure 5.38 – 765-095 Weight Opportunities 
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5.5.4 – Engine Data – “gFan+” 

The engine designed for the SUGAR High vehicle was given the informal designation “gFan+” 

and is shown in Figure 5.39. The overall engine design very similar to the gFan reference engine, 

but incorporates a variety of advanced technologies above and beyond those in the gFan design. 

Thus, the architectural concept is again a 2-spool separate flow turbofan but with a 59 OPR and 

13 BPR (at top of climb). The difference in OPR between the gFan and gFan+ is primarily due to 

the lower FPR employed on the gFan+, which in turn leads to a slightly lower OPR for the same 

basic booster and compressor design. The difference in OPR is more than made up for in the 

improved propulsive efficiency and higher bypass ratio that ensue with the lower FPR. This 

engine also features relatively low hot section temperatures and makes extensive use of advanced 

CMCs. 

Like the gFan, this engine design is compatible with the aggressive emissions goals by virtue of 

the relatively low hot section temperatures and an advanced low emissions combustor design. 

The combustor is a “NGEN+ TAPS” design that is similar to the gFan engine but with additional 

mixing effectiveness improvements and other features to improve NOx and particulate emissions 

levels. This engine is also more compatible with the very aggressive noise goals in that it 

features a conventional shrouded fan/nacelle that provides good inherent shielding and also has a 

suite of advanced acoustics technologies for lowest possible noise. Finally, this engine design 

features an advanced nacelle design to minimize nacelle drag associated with low FPRs and 

larger fan diameters. General geometry, weight, and performance information is shown in Table 

5.16. 

Advanced Composite Fan

1.35 PR, 77.3” fan

Advanced 3-D aero design

Sculpted features, low noise

Thin, durable edges

Integrated thrust reverser/VFN

Highly variable fan nozzle

4-Stage Booster Ultra-high PR core compressor

59 OPR, 9 stages

Active clearance control

HPT

2-Stage, uncooled

CMC nozzles + blades

Next-gen CMC

Active purge control

Next-gen disk material

LPT

8-Stage

Moderate-high stage loading

Advanced nacelle CMC blades/vanes (weight)

Highly integrated

Minimum OD

Unitized composite

Advanced

combustor

Figure 5.39 – "gFan+" Engine Walk Around 
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Table 5.16 – gFan+ Key Weight, Geometry, Performance, and Technologies 

Propulsion system wt 7096 lbm

Fan diameter 77 in

Length 122 in, spinner to TRF

Performance Thrust, lbf SFC, lbm/lbf-hr

SLS 18800 0.211

Rolling takeoff 13385 0.301

Top-of-climb 3145 0.475

Cruise 3028 0.470

Emissions -72% relative to CAEP/6

Projected Technologies

Advanced 3-D aero composite fan

Ultra-high PR compressor

Advanced low-emissions combustor

Integrated thrust reverser/variable fan nozzle

Next-gen CMC HPT vanes, blades, and shrouds

Next-gen component aero technology

Next-gen nacelle technology

Improved shaft material

Acoustics technology suite

High DN bearings, high speed/temperature seals

TiAl materials & process technology

Advanced hot section disk material

Active purge control

Advanced CMC blade and vane features

Closed-loop, fast-response turbine ACC

5.6 – 765-096 - SUGAR Volt (2030 Advanced Electric) 

The SUGAR Volt is a derivative of the SUGAR High configuration that has been resized to 

accommodate modular battery packages and a hybrid gas turbine electric propulsion system. 

5.6.1 – Configuration Layout 

The 765-096 configuration is a high wing airplane with hybrid gas turbine-electric engines 

mounted on pylons below the wing and a T-tail layout. 

The configuration is identical in concept to the 765-095 SUGAR High configuration with the 

exception of the propulsion system and accommodating changes. In addition to the engine 

package itself the airplane has modular batteries fitted beneath the fuselage on centerline. The 

configuration also permits batteries to be mounted in wing pods instead of the body. The 

fuselage mount accommodates the battery volume and hard point structure better while the wing 

while pod mounts may benefit from flutter relief, spanload, and ground servicing. The mounting 

arrangements have not been traded. A three view drawing of the configuration is shown in Figure 

5.40. 

The fuselage and LOPA are nominally the same as that of the 765-093 configuration (SUGAR 

Free). The LOPA can be seen in Figure 5.13. 
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Figure 5.40 – 765-096 3-View Drawing 
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5.6.2 – Aerodynamic Buildup 

The 765-096 aerodynamic buildup is the same as SUGAR High (765-095) (Section 1.1.1) with a 

2.5 count parasite drag increase (applied with the performance tools) to account for the battery 

fairing. Only the battery fairing is different from the SUGAR High’s outer mold line (OML). No 

new polars were generated for this configuration. The drag increase reduces the maximum M * 

L/D from 19.22 to 19.05 for the turbofan installation. 

5.6.3 – Mass Properties 

The group weights statements for SUGAR Volt were the same as SUGAR High with a few 

exceptions. The engine weight was increased 9,522 pounds to account for the difference between 

the gFan+ and hFan. Battery weight was added dependent on the sizing outputs. The capability 

to carry batteries was accompanied by an estimated 6,000 pound weight increase for mounting 

and wiring. The data represented for the SUGAR Volt include a lightweight wing consistent with 

a 15,000 pound weight reduction applied as a fixed increment during sizing. This weight 

reduction was applied with the assumption that three quarters of the total opportunity will be 

attainable from SUGAR High (765-095) discussed in Section 5.5.3. 

It should be noted that the SUGAR Volt propulsion system could also be integrated on the 

Refined SUGAR or SUGAR Ray. Most of the benefit obtained by the SUGAR Volt concept 

would be available on the other concepts in the event the wing weight reduction goals are not 

met. It is recommended the installation be studied on other platforms since configurations with 

lower L/D will have larger performance decrements due to the increased propulsion system and 

battery weights. 

5.6.4 – Engine Data – “e-f-hFan” Engines 

Several engine designs were developed for consideration on the SUGAR Volt vehicle platform. 

These were given the informal designations “eFan”, “fFan”, and “hFan”. The eFan is an allelectric propulsor basically consisting of an electric motor coupled to a fan via a gearbox. The 

fFan is a gas turbine-fuel cell hybrid engine concept utilizing the gas turbine core to produce the 

power required for takeoff and climb, but relying mainly on the fuel cell system to provide cruise 

electric power to a motor/gearbox attached to the LP spool. The hFan is a gas turbine-electric 

hybrid that has both a gas turbine and an electric motor attached to the LP spool such that it can 

run on a combination of jet fuel and battery power. This section describes each of these concepts 

in further detail. 

“eFan” Propulsor: 

The “eFan” propulsion system is effectively an advanced fan coupled to a lightweight, high 

power motor via a gearbox. The electric power required to drive the motor is assumed to come 

from an external source (batteries). The propulsion system is contained in a nacelle and lends 

itself to a variety of configurations, including distributed propulsion. The engine as sized for this 

application is intended to be one of two engines mounted on the vehicle but the basic design 

could easily be scaled down to a size appropriate for a plurality of distributed propulsors. 

Key dimensions, weight and performance figures for the eFan propulsor are provided in Table 

5.17. This propulsion system is surprisingly lightweight for its size, and this is aided by the fact 

that large portions of the nacelle and structure can be fabricated from composites. It should be 

noted, however, that the eFan geometry is not designed to the same level of fidelity as the gas 
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turbine-based counterparts, simply because the database and tool set is much more limited for 

this type of engine. The weight estimate must therefore be recognized as having significantly 

wider error bands than the comparable gas turbine concept. Also, note that the engine is designed 

for a much higher thrust than the competing gas turbine concepts due to the mass of the battery 

required for an all-electric airplane to make the required mission range. This in turn makes the 

absolute weight of the eFan propulsor higher than the competing gas turbine concept. 

Table 5.17 – eFan Key Weight, Dimensions, Performance, and Technologies 

Propulsion system wt ~7000 lbm

Fan diameter 90 in

Length ~105 in, spinner to TRF

Performance Thrust, lbf Elec. Power In, HP

SLS 25500 15417

Rolling takeoff 18258 15926

Top-of-climb 4732 8667

Cruise 3333 5645

Emissions -100% relative to CAEP/6

Projected Technologies

Advanced 3-D aero composite fan

Integrated thrust reverser/variable fan nozzle

Next-gen nacelle technology

Acoustics technology suite

Advanced high efficiency gearbox

High-efficiency lightweight motor controller

Advanced lightweight high efficiency motor

Advanced battery technology (booked w/ airframe techs)

Lightweight, low loss radiators and surface coolers

“fFan” Propulsor: 

The “fFan” engine concept is a hybrid fuel cell-gas turbine engine wherein the power required to 

drive the fan comes primarily from the gas turbine at takeoff and climb conditions, and primarily 

from the fuel cell system during cruise. This is intended to take advantage of the strengths of 

each subsystem while mitigating the weaknesses. Specifically, use of the gas turbine to produce 

the high horsepower requirements at takeoff and climb takes advantage of the inherently high 

power/weight of gas turbines while use of the fuel cell-electric subsystem for cruise takes 

advantage of the high theoretical thermal efficiency of the fuel cell system while minimizing the 

physical size and weight of the fuel cell. 

The general arrangement of the fFan propulsion system is shown in Figure 5.41. The nacelle 

contains the gas turbine propulsor, an electric motor, gearbox, and the fan. The gas turbine 

portion of the propulsor consists of a single spool unit connected to the main fan via a gearbox. 

This gas turbine core is designed to be compatible with the RPM requirement needed for an 

efficient, lightweight electric motor. The single spool arrangement provides relative simplicity 

and the modest pressure ratio and temperatures employed in the gas turbine portion of the unit 

are conducive to low cost and very good emissions characteristics. The principal disadvantage of 

this arrangement is the need for a high power gearbox to connect the fan and core shafts. 

Alternate 2-spool arrangements are possible, but the electric motor will still require a gearbox in 

order to minimize motor size and weight. 

The fuel cell itself consists of a solid oxide fuel cell (SOFC) stack fed by pressurized air bled 

from the gas turbine subsystem when in cruising flight. The solid oxide fuel cell was chosen 
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primarily because it offers the possibility of on-cell fuel reform of Jet-A type fuels (a 

fundamental assumption of this study was that the propulsion system had to use Jet-A fuel). 

Further, the SOFC offers the possibility of a self-cooled system and its inlet/discharge 

temperatures are quite compatible with the gas turbine. 

The relatively low power/weight of projected fuel cell systems as well as their physical bulk 

(volume/power) makes them too large to fit inside the propulsion nacelle for the configuration 

studied. Thus, the fuel cell itself is presumed to be located outside the propulsion nacelle 

(presumably in the fuselage). The air supplied to the fuel cell is taken from compressor discharge 

and is collected in a volute as shown in the figure. The effluent discharged from the fuel cell is 

passed back into the gas turbine through the combustor and subsequently through the turbine. 

Note that the provision of a variable bleed system to supply the necessary cruise flow to the fuel 

cells while maintaining acceptable gas turbine performance is non-trivial and requires the use of 

innovative features in the gas turbine portion of the engine. Also, the reintroduction of the fuel 

cell effluent back into the combustor is a challenge, as the available pressure drop across the fuel 

cell system will be limited to something on the order of 5%. It is unclear at this point what 

impact the reintroduction of fuel cell effluent into the combustor would have on the emissions 

levels of the gas turbine portion of the system and this is an area that would require further study. 

It became evident relatively early in the course of developing the fFan propulsion concept design 

that a fuel cell-based propulsion system would face numerous challenges relative to the 

incumbent gas turbine-based system. Further, the experience base and tools available to aid in 

the design are in a relatively primitive state in comparison to the gas turbine knowledge base. 

Thus, this design was not developed to the level of detail that the other engines were. Engine 

performance was only roughly estimated for cruise and takeoff, and no detailed performance 

model is yet available. Table 5.18 provides a general overview of fFan engine geometry, 

performance, weight and technologies as they were defined at the conclusion of the fuel cell 

portion of this study. 

Fuel Cell Stack

Geometry TBD

Volume comparable to or 

greater than main engine

1.4 PR Fan

3.6:1 reduction 

gearbox

Electric motor 

(sized for cruise)

10-stage low RR, 

moderate PR compressor

Fuel cell air supply

Fuel cell return

3-stage drive/ 

power turbine

Figure 5.41 – "fFan" Propulsion System General Arrangement 
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Table 5.18 – fFan Key Weight Geometry, Performance, and Technologies 

Propulsion system wt ~15K-20K lbm

Fan diameter 89 in

Length >120 in, spinner to TRF

Performance Thrust, lbf SFC, lbm/lbf-hr

SLS TBD TBD

Rolling takeoff TBD TBD

Top-of-climb TBD TBD

Cruise TBD TBD

Emissions TBD relative to CAEP/6

Projected Technologies

Advanced lightweight prime-reliable Solid Oxide FC

On-cell fuel reform technology

Advanced 3-D aero composite fan

Next-gen nacelle technology

Acoustics technology suite

Advanced high efficiency gearbox

High-efficiency lightweight motor controller

Advanced lightweight high efficiency motor

Lightweight, low loss radiators and surface coolers

Advanced low-emissions combustor

Next-gen component aero technology

“hFan” Propulsor: 

The overall engine design of the “hFan” engine is very similar to “gFan+” propulsion system in 

that the architectural concept is a boosted 2-spool separate flow turbofan having a 59 OPR at top 

of climb, but with an 18 BPR. The hFan also features a conventional fan and nacelle arrangement 

for lowest possible noise, as shown in Figure 5.42. The hFan and gFan+ engines share a common 

core design with only minor differences between the two cores. However, the LP spools are 

considerably different. Specifically, the hFan engine is designed to the same FPR as the gFan+ 

but with a higher thrust level (required to cope with the added weight of the batteries needed to 

power the electric subsystem). The additional power required to drive the larger hFan fan is 

derived from the electric subsystem, which consists of an electric motor mounted inside the core 

exhaust nozzle and attached to the LP spool via a gearbox. 

The hybrid electric system offers considerable flexibility to utilize gas turbine versus battery for 

various missions. In general, the gas turbine is used for long range cruise while the electric motor 

is used for short range cruise. This enables dramatic reductions in mission fuel burn for short 

range missions. The electric motor and gearbox are sized to 5500 HP output. This is sufficient to 

make adequate top-of-climb thrust in electric mode but is not adequate to make full thrust at 

takeoff and climb (the fan power input requirement at takeoff is on the order of 20,000 HP). 

Thus, the gas turbine is always needed for the low altitude portions of the mission. 

A further consideration in the design of this engine is the attainment of top-of-climb thrust. The 

original requirements for this engine design specified that the engine should be able to make full 

top-of-climb thrust in either electric or gas turbine modes. However, when in electric mode, the 

loss of the thrust from the core nozzle implies that some other means would be required to make 

up the difference (such as increased electric power to the fan or oversizing the fan to regain the 

additional thrust). However, this may be a heavier solution because it increases the electric 

horsepower requirement and may compromise the design of the fan. Therefore, the thrust 

requirements were modified such that the top-of-climb thrust available in electric mode is 
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somewhat less than that available in combined mode. As a result, the full top-of-climb thrust can 

only be made in combined mode using both the gas turbine and the electric subsystems. 

Specifically, if the gas turbine core is operating at full power output at the top-of-climb 

condition, an additional 1275 HP motor power input to the LP spool is required to reach full 

thrust. This translates into an electrical power input of 1363 HP (1.01 MW). 

This arrangement yields a good compromise between providing maximum capability to provide 

mission thrust via the electric subsystem while minimizing the required motor size and power 

output. General weight, dimension and performance characteristics for the hFan engine are 

shown in Table 5.19. This table also shows the suite of technologies envisioned for this engine. 

These technologies include all those applicable to the gFan+ propulsion system as well as many 

of the eFan electric power technologies. A final technology unique to this engine is the use of a 

variable core nozzle that is independent from the variable fan nozzle. This is needed to 

compensate to the speed-speed shift and accompanying booster operating line migration induced 

by modulation of the electric motor power input to the LP spool during the operating mode shifts 

between gas turbine, hybrid, and electric modes. 

Advanced nacelle

Highly integrated

Minimum OD

Unitized composite

Advanced acoustic features

Advanced Composite Fan

1.35 PR, 89.4” fan

Advanced 3-D aero design

Sculpted features, low noise

Thin, durable edges

Integrated thrust reverser/VFN

Highly variable fan nozzle

4-Stage Booster

Ultra-high PR core compressor

59 OPR, 9 stages

Active clearance control

HPT

2-Stage

CMC nozzles + blades

Next-gen ceramic

Active purge control

Next-gen disk material

Advanced Motor & Gearbox

5500 HP power output

Advanced gear box

Advanced

combustor LPT

8-Stage

Highly loaded stages

CMC blades/vanes (weight)

Variable core nozzle

Figure 5.42 – “hFan” Engine Walk Around 
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Table 5.19 – hFan Key Weight, Geometry, Performance, and Technologies 

Propulsion system wt 10475 lbm

Fan diameter 89 in

Length 156 in, spinner to motor

Performance Thrust, lbf SFC, lbm/lbf-hr

SLS (GT mode) 18800 0.211

Rolling tkoff (GT mode) 13385 0.301

Top-of-clmb (hybrid md) 4364 0.372 + 1363 HP in

Cruise (typ. hybrid mode) 3344 0.341 + 1363 HP in

Emissions -72% to -100% relative to CAEP/6

Projected Technologies

Advanced 3-D aero composite fan

Ultra-high PR compressor

Advanced low-emissions combustor

Integrated thrust reverser/variable fan nozzle

Next-gen CMC HPT vanes, blades, and shrouds

Next-gen component aero technology

Next-gen nacelle technology

Improved shaft material

Acoustics technology suite

High DN bearings, high speed/temperature seals

TiAl materials & process technology

Advanced hot section disk material

Active purge control

Advanced CMC blade and vane features

Closed-loop, fast-response turbine ACC

Advanced high efficiency gearbox

High-efficiency lightweight motor controller

Advanced lightweight high efficiency motor

Advanced battery technology (booked w/ airframe techs)

Lightweight, low loss radiators and surface coolers

5.7– 765-097 - SUGAR Ray (2030 Advanced Low Noise Hybrid Wing Body) 

The SUGAR Ray configuration is an advanced HWB concept with a technology suite similar to 

the SUGAR High. 

5.7.1 – Configuration Layout 

The 765-097 configuration is a semi-high wing blended body consisting of a center body, a 

transition region and an outboard wing. The transition region between the center body and 

outboard wing provides for main landing gear (forward) retraction and the bulk of the fuel. The 

advanced turbofan engines are mounted on pylons above the center body which provides noise 

shielding downward for both the inlet (fan) and the exhaust nozzle. The vertical tail surfaces are 

mounted at the outboard boundary of the center body and provide lateral stability and control, 

and sideline noise shielding for the engine core and fan nozzles. A three view drawing of the 

configuration is shown in Figure 5.43. The outboard wing provides additional fuel, control 

surfaces, and accommodates folding at BL = 702 as no fuel is carried outboard of this location. 

The center body provides accommodations for 155 passengers in two classes together with bulk 

cargo provisions, crew accommodations, flight deck and control surfaces. The LOPA is shown in 

Figure 5.44 
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Figure 5.43 – 765-097 Configuration Layout 

WING V-TAIL H-TAIL

Area (gross) 4,136.0 90.8 N/AAspect Ratio (gross) 6.865 1.705Taper Ratio (trap) 0.228 0.366MAC Inches (gross) 489.7 101.3Dihedral (Deg.) 3.0 62.01/4 Chord Sweep (Deg.) 27.7 39.2Root Chord (Inches) (trap) 322.6 129.23Tip Chord (Inches) (trap) 73.6 44.90Span (W/O Winglet) 1,936.8

18.00

Wing Fold Line BL = 

21.0’

2022.2 (168.5’)

1936.8

946.3 (78.9’)

888.5 40% MAC Nominal CG

(gross wing)

429.4 139.9

459.4

230.4

(available)
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Figure 5.44 – 765-097 LOPA 

16 

36-i

55 E

32-i

Interior Arrangement

IAC Short / Medium Range – Dual Class 

Class 

(%) 

10.32 89.68 

100.00 

Carts 

(qty) 

4.0 7.0 

11.0 

Cart Ratio 

(Carts/Pax) 

0.250 0.050 0.071 

Lavatory Ratio 

(Pax/Lav) 

16 70 

–

Closet R

(Rod-in/P

3.75 0.27 

–

First Economy 

Total

60 E

32-i

24 E

32-i
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5.7.2 – Aerodynamic Buildup 

High Speed: 

The high-speed buildup for SUGAR Ray is shown in Table 5.20, and is summarized in Figure 

5.45. This configuration uses gross wing reference wing area. Trim drag is zero since the wing, 

at the cruise design point, has zero pitching moment. 

Table 5.20 – 765-097 High Speed Buildup 

CDo

52%

CDi

42%

CDtrim

CDc 0%

6%

Figure 5.45 – 765-097 High Speed Buildup 

Configuration 765-097 

SWEEP (DEG) 27.7 

T/C-AVE 0.1312 

AIRFOIL TYPE CONVENTIONAL 

F BUILD-UP (FT2) 

FUSELAGE 0.0000 

WING 29.2743 

WINGLET 0.2365 

HORIZONTAL 0.4800 

VERTICAL 0.9025 

N&P 2.9900 

CANOPY 0.0000 

GEAR PODS 0.0000 

ETC BEFORE SUB -5.7256 

EXCRESCENCE 2.2808 

INTERFERENCE 0.0000 

UPSWEEP 0.0000 

WING TWIST 0.0000 

STRAKES 0.0000 

ETC AFTER SUB 0.0000 

FUSELAGE BUMP 0.0000 

F-TOTAL (FT2) 30.4384 

E-VISC 0.965 

CRUISE CD BUILD-UP 

M-CRUISE 0.74 

CL-CRUISE 0.3 

CRUISE ALTITUDE 35000 

CD0 0.00596 

CDI 0.00468 

CDC 0.00063 

CDTRIM 0.00000 

CDTOT 0.01127 

L/D 26.611 

ML/D 19.692 

 

The ETC BEFORE SUB category includes technology projections of natural laminar flow over a 

portion of the wing and verticals as well as riblets applied to the turbulent portion of the wing 

and body, as illustrated in Figure 5.46. ETC AFTER SUB is not used in this case because the 
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configuration does not need advanced supercritical airfoils like the other advanced concepts. The 

M * L / D for the configuration is shown in Figure 5.47. 

Red = Surfaces affected by riblets 

Blue = Surfaces affected by laminar flow 

Figure 5.46 – 765-097 - Aerodynamic Technologies Application 

The resulting high speed data is shown in Figure 5.47. The figure illustrates the maximum 

aerodynamic efficiency (M*L/D) occurring at a cruise Mach of 0.74 and a CL of 0.30 which is 

very close to the Mach 0.7 cruise point. 

Figure 5.47 – 765-097 - M * L / D Total 

Low Speed: 

Figure 5.48 through Figure 5.50 show the low speed characteristics for SUGAR Ray. Low speed 

data are trimmed as a function of angle of attack, lift coefficient, and drag coefficient at near zero 

elevon deflections. Low speed high lift devices on wing leading and trailing edges are deployed. 
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Figure 5.48 – 765-097 - Low Speed Lift Curve; Free Air 

Figure 5.49 – 765-097 - Low Speed Polar; Free Air 
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Figure 5.50 – 765-097 - Low Speed Lift / Drag; Free Air 
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5.7.3 – Mass Properties 

The SUGAR Ray configuration was estimated by applying the N+3 weight reduction factors to a 

calibrated BWB model. Table 5.21 and Figure 5.51 show the group weights and their 

percentages of TOGW. 

Table 5.21 – 765-097 Group Weight Statement 

GROUP WEIGHT (LB) % TOGW 

WING 12,500 6.8 

TAIL 904 0.5 

BODY 41,137 22.5 

LANDING GEAR 7,198 3.9 

PROPULSION 15,918 8.7 

ENGINE, NACELLE, PYLON 14,192 7.8 

ENGINE SYSTEM 400 0.2 

FUEL SYSTEM 1,326 0.7 

FLIGHT CONTROLS 6,015 3.3 

ELECTRICAL 3,346 1.8 

INSTRUMENTS 1,079 0.6 

AVIONICS & AUTOPILOT 3,225 1.8 

FURNISHINGS & EQUIPMENT 9,080 5.0 

PNEUMATICS, AIR CONDITIONING, APU 3,553 1.9 

ANTI-ICING 186 0.1 

MANUFACTURER’S EMPTY WEIGHT (MEW) 104,142 57.1 

OPERATIONAL ITEMS 6,350 3.5 

OPERATING EMPTY WEIGHT (OEW) 110,493 60.5 

USEABLE FUEL 35,582 19.5 

PAYLOAD 36,425 20.0 

TAKEOFF GROSS WEIGHT (TOGW) 182,500 100.0 

 
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WING

7%

BODY

23%

LANDING GEAR

PROPULSION 4%

9%

FLIGHT 

CONTROLS

3%

ELECTRICAL

AVIONICS & 2%

AUTOPILOT

2%

FURNISHINGS & 

EQUIPMENT

5%

PNEUMATICS, AIR 

CONDITIONING, 

APU

2%

OPERATIONAL 

ITEMS

3%

OTHER

1%

USEABLE FUEL

19%

PAYLOAD

20%

Fuel Payload OEW

Figure 5.51 – 765-097 Weight Summary 

5.7.4 – Engine Data – “gFan+” 

The HWB configuration uses the same “gFan+” engine as SUGAR High which is discussed in 

Section 5.5.4. 
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6.0 – Vehicle Performance and Environmental Impact 

6.1 – Performance and Noise Analysis Methods and Ground Rules 

The performance analysis methods and ground rules are discussed in the subsections below. For 

a definition of the payload-range requirements please reference Table 2.2 and Figure 5.1. 

6.1.1 – Performance Analysis Tools 

The Boeing Mission Analysis Program (BMAP) is the principal tool used by Boeing 

Commercial Airplanes (BCA) to calculate mission performance such as payload, range, or fuel 

burn. It can analyze missions of varying complexity and has been validated to actual airplane 

performance. It has the capability to model complex tracks with enroute and alternate waypoints 

and complex profiles with multiple cruise segments including step and cruise climbs. It will 

calculate airplane performance including redispatch, through-stop, radius, and extended-range 

twin-engine operations (ETOPS) capability. 

Use of the Low Speed Performance System (LSPS) provides field length analysis. LSPS can 

calculate takeoff performance at any specified atmospheric condition (altitude and temperature 

within its atmospheric model) and includes One Engine Inoperative (OEI) in its calculations. 

Like BMAP, it is calibrated to existing commercial airplanes. 

Vehicle performance and sizing is performed with Boeing’s Aircraft Design Navigator (ADNav) 

which encapsulates both mission performance (BMAP) and airfield performance calculations 

(LSPS). It provides the capability to scale engine thrust and wing area and provides the ability to 

size airplanes to their optimum sizes given a set of constraints (such as TOFL, ICAC, time and 

distance to climb, etc). It also provides some data visualization tools. 

The sizing process is illustrated in Figure 6.1 

Airplane Weight Data

- Basic OEW

- Sizing Data

- f (Sw, TOGW, Fn) 

Airplane Drag Data

- Basic Polar

- CDPmin Buildup

- Takeoff Polars

- Stall Lift Coefficients

Airplane Propulsion Data

- Takeoff Thrust / Fuel Flow

- Cruise Thrust / Fuel Flow

- Idle thrust / Fuel Flow

Basic Airplane Performance

- Mission Performance

- Takeoff Field Length

Size Airplane (Wing and Engine) to 

Meet Performance Requirements

- Design Range

- Climb Performance

- Takeoff Field Length

Required Inputs

Figure 6.1 – Airplane Sizing Using ADNav 
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It should be noted that BCA uses reference Wimpress area as the reference area for nondimensional quantities. 

6.1.2 – Mission Profiles 

The future scenario (discussed in Section 2.0) was used to generate the desired vehicle 

characteristics (Table 2.2). These characteristics, along with the payload range requirements 

(discussed in Section 5.1) and the mission profiles outlined in this section, are used for vehicle 

sizing. 

Future Ground and Air Traffic Management systems will allow for reduced mission fuel burn, 

emissions, and noise. The current environment introduces delays and mission inefficiencies into 

the system, which in the future can be eliminated. In addition, future predictive technologies and 

real-time mission optimization will allow for a higher confidence level in completing the mission 

as planned. 

Mission Profiles have been developed to approximate the difference between an airplane 

operating in the current environment, versus an airplane operating in the future environment. 

Differences between the two profiles are shown in Table 6.1. 

A schematic of the 2008 Reference Mission Profile is shown in Figure 6.2, and a schematic of 

the 2030 Mission Profile is shown in Figure 6.3. The sizing payload is the low density seats (dual 

class) at 200 pounds per passenger at the maximum range specified in Table 2.2 and Figure 5.1. 

The still air range of Figure 6.2 is five percent longer than the maximum range shown in Table 

2.2 while in Figure 6.3 they are the same. 
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Table 6.1 – Mission Changes due to NextGen ATM 

2008 Mission Profile 

Figure 6.2 

2030 Mission Profile 

Figure 6.3 

Mission 

Taxi Out Airport congestion and queues at 

runways increase airplane idle time 

while waiting to takeoff 

Better Ground Traffic 

Management allows airplane to 

taxi directly from gate to runway 

Climb Air Traffic Management requires airplane 

to climb at or below 250 kts below 

10,000 ft altitude. Traditional time and 

distance to climb requirements. 

Airplane is allowed to climb at 

optimum fuel burn speed below 

10,000 ft altitude. No time and 

distance to climb requirements. 

Cruise Air Traffic Management requires an 

airplane to fly specific altitudes and 

tracks which may not be optimum, this 

increases fuel burn and flight distance to 

destination. 5% increase in range is 

assumed. 

Free Flight allows airplane to realtime optimize airplane altitude and 

speed in 4D to minimize track 

distance and fuel burn while 

maintaining safe separation 

distances 

Descent Air Traffic Management may require an 

airplane to descend in a non-optimum 

flight path, potentially leveling off at 

different altitudes and having to increase 

thrust. This is modeled with an additional 

12 minute loiter. 

Air Traffic Management requires airplane 

to descend at or below 250 kts below 

10,000 ft altitude 

Tailored Arrivals allow for 

continuous idle descent 

approaches optimized for fuel 

burn in a 4D environment 

Taxi In Airport congestion and waiting for gates 

to clear increase time airplane idles 

while waiting to unload 

Better Ground Traffic 

Management allows airplane to 

taxi directly from runway to gate 

Reserves 

Flight Fuel Allowance Assumed 5% flight fuel allowance for 

contingencies 

Better enroute weather and track 

predictions, along with 4D flight 

optimization, allow airline to 

decrease contingency fuel to 3% 

Climb Air Traffic Management requires airplane 

to climb at or below 250 kts below 

10,000 ft altitude 

Airplane is allowed to climb at 

optimum fuel burn speed below 

10,000 ft altitude 

Descent Air Traffic Management requires airplane 

to descend at or below 250 kts below 

10,000 ft altitude 

Airplane is allowed to descend at 

optimum fuel burn speed below 

10,000 ft altitude 

Hold Assumed 30 minute hold time allowance 

at alternate for contingencies 

Better weather and track 

predictions allow airline to 

decrease hold time allowance at 

alternate to 10 minutes 

Note: Segments not listed indicate no change between profiles. 
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Figure 6.2 – 2008 Reference Mission Profile 

Figure 6.3 – 2030 Mission Profile with NextGen Air Traffic Management 

200 nm 

Climbing Cruise 

Economy Climb 

Cruise at LRC Mach 

Approach & Land (4 Minutes) 

10 Minute Hold @ 1,500 ft 

Mission Reserves 

Still Air Range 

Flight Time & Fuel

Block Time & Fuel 

Climbout and Accelerate to 1,500 ft at Optimum Speed 

Taxi Out (4 Minutes) 

Takeoff to 35 ft 

Optimized Climb to Cruse 

Approach and Land (4 Minutes) 

Taxi In (4 Minutes - From Reserves) 

3% Flight Fuel Allowance 

Missed Approach 

Descend to 1,500 ft 

Descend to 1,500 ft at Optimum 

200 nm 

o Nominal Performance 

o Standard Day 

o Fuel Density: 6.7 lb/US Gallon 

Step Climb, Cruise 

Economy Climb 

Cruise at LRC Mach 

Approach & Land (4 Minutes) 

30 Minute Hold @ 1,500 ft 

Mission Reserves 

Increased Still Air Range

Flight Time & Fuel

Block Time & Fuel 

Accelerate to Climb Speed 

Climb to 10,000 ft at 250 kts 

Climbout and Accelerate to 1,500 ft & 250 kts 

Taxi Out (16 Minutes) 

Takeoff to 35 ft 

Climb & Accelerate to  LRC Cruise Mach 

Approach and Land (4 Minutes) 

Taxi In (10 Minutes - From Reserves) 

5% Flight Fuel Allowance 

Missed Approach 

Descend to 1,500 ft 

Descend to 1,500 ft at 250 kts 

5% Range NonOptimum Track

Additional Loiter (12 Minutes) 
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6.1.3 – DNL Contour Methods 

The process for developing DNL contours for the concept aircraft has been established. A 

generic airport, similar to Cleveland Hopkins International Airport, was selected. This enables 

model calibration to actual Cleveland airport noise data, but allows additional flexibility in 

establishing the airport boundaries and defining the airport scenarios. Cleveland is an airport that 

has a recent Noise Exposure Map (NEM) approved by FAA and this airport has an appropriate 

fleet mix that contains a significant number of medium sized aircraft that are being evaluated in 

the SUGAR study. The future scenario supplies the fleet mix and generation mix for today, 2030, 

and in the future when N+3 aircraft will be present in large numbers. 

Noise Power Distance (NPD) information for the current aircraft in the fleet mix, the expected 

fleet mix in 2030, 2055, and an all N+3 technology aircraft fleet was generated. An Integrated 

Noise Model (INM) was then used to generate 55, 60, and 65 DNL contours and compare the 

contours for the different fleet scenarios. Sensitivities to fleet size and N+3 fleet replacement 

percentage were also generated. 

Initial calculations were made using 2008 Cleveland noise data, and the model has been 

calibrated to match these results (Figure 6.4). The noise performance of all five concept aircraft 

was estimated to allow a comparison between the concepts. The noise signature for the SUGAR 

Ray low noise configuration, and how it performs relative to the NASA noise goals was studied 

in detail. 

Figure 6.4 – Noise Methods Calibrated to Airport Data 
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6.2 – Vehicle Performance and Sizing 

765-093 – SUGAR Free: 

The reference 2008 performance level airplane is known as “SUGAR Free”. SUGAR Free was 

sized to provide a 3,500 nmi range with 154 passengers @ 200 lb / passenger dual-class payload 

(design range). SUGAR Free performance is quoted using the 2008 Reference Mission Profile. 

The SUGAR Free sizing chart is shown in Figure 6.5. The chart represents a matrix of airplane 

performance variation as airplane wing area and engine scale vary, while design range is held 

constant. The x-axis is wing area variation, and the y-axis is engine scale variation. Plotted on 

the chart are contour lines of constant takeoff field length, distance to altitude, approach speed, 

Operational Empty Weight (OEW), and block fuel / seat on a 500 nmi mission. Constraint lines 

of takeoff field length ~ 8,200 ft at Maximum Takeoff Weight (MTOW), at Sea Level, on an 86° 

day, and a distance to climb to 35,000 ft after a takeoff at Maximum Takeoff Weight (MTOW) 

on a Standard Day are also plotted in red. These two constraints were chosen as representative of 

the performance level of airplanes in service today, and the intersection of those two constraints 

was used as the wing and thrust sizing point for SUGAR Free. All other performance levels, as 

shown in Table 6.2, were a fallout from these two constraints. 

Figure 6.5 – 765-093 Sizing 
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Table 6.2 – 765-093 - SUGAR Baseline Sizing 

MODEL

Sizing Level SUGAR Free

PASSENGERS / CLASS 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

184,800

151,000

142,000

96,000

9,710

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled CFM56-7B27

62

28,200

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1429 / 122

10.41

0.583

18.068

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN / NMI

FT

FT

FT

KT

3,500

0.785

0.785

37,200

23 / 148

35,000

36,200

8,190

126

BLOCK FUEL / SEAT (900 NMI) LB 92.35

A trade was done to quantify the block fuel benefit of changing from the 2008 Reference 

Mission Profile to the 2030 Mission profile using SUGAR Free as the base airplane. The trade 

was done by changing the mission profile in BMAP, rerunning the performance, and resizing the 

airplane. The airplane wing and engine were sized using the same procedure and constraints as 

were used in sizing the base SUGAR Free. A comparison of the airplane using the 2008 

Reference Mission Profile versus an airplane using the 2030 Mission Profile is shown in Table 

6.3. Comparing the two airplane performance levels, one can see design range, distance to climb, 

and takeoff field length are constant between the two airplanes, while block fuel / seat is 

improved 17.5% using the 2030 Mission Rules, and the airplane is altogether smaller and lighter. 
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Table 6.3 – 765-093 – SUGAR Free Mission Profile Trade 

MODEL

Sizing Level

N Reference 

Mission

N+3 Reference 

Mission

PASSENGERS / CLASS 154 / Dual 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

184,800

151,000

142,000

96,000

9,710

173,300

147,500

138,500

92,500

8,414

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled CFM56-7B27

62

28,200

Scaled CFM56-7B27

61

26,800

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1429 / 122

10.41

0.583

18.068

1314 / 117

10.41

0.589

17.695

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN / NMI

FT

FT

FT

KT

3,500

0.785

0.785

37,200

23 / 148

35,000

36,200

8,190

126

3,500

0.785

0.785

37,100

22 / 148

34,700

35,700

8,190

130

BLOCK FUEL / SEAT (900 NMI) LB 92.35 (Base) 76.14 (-17.5%)

765-094 – Refined SUGAR: 

“Refined SUGAR” is a high technology version of the SUGAR Free configuration. A list of 

technologies included in Refined SUGAR is contained in Section 4.0. Refined SUGAR was 

sized using the same procedure as was used for SUGAR Free, the one change being the distance 

to climb constraint was relaxed to 182 nmi from 148 nmi, as will be the case for all the 

remaining airplanes. This change results in an airplane sized with a relatively larger wing area, 

but smaller engine, and an overall block fuel / seat benefit compared to an airplane that climbs 

faster. Figure 6.6 shows the sizing chart, and the resultant sizing point for the Refined SUGAR 

configuration. Table 6.4 details the performance characteristics of Refined SUGAR. The 

airplane, with increased airframe and engine technology, and using the 2030 mission profile 

shows a 44.2% block fuel / seat benefit relative to SUGAR free. 
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Figure 6.6 – 765-094 Sizing 

Table 6.4 – 765-094 - Refined SUGAR Baseline Sizing 

MODEL

Sizing Level Refined SUGAR

PASSENGERS / CLASS 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

139,700

131,800

123,800

77,800

5,512

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled gFan

66

15,700

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1440 / 129

11.63

0.654

21.981

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN / NMI

FT

FT

FT

KT

3,500

0.70

0.70

38,800

29 / 182

38,400

45,200

8,190

115

BLOCK FUEL / SEAT (900 NMI) LB 51.53

Engine size is primarily due to takeoff field length and time and distance to climb constraints. 

Takeoff thrust required can be reduced with larger wing area, resulting in lower fuel burn, 

however using wing area to reduce thrust required will result in an airplane with increased time 

and distance to climb. This trend can be seen in the Table 6.5 sizing chart for Refined SUGAR. 
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One of the considerations which drives up thrust requirements for time and distance to climb, are 

Air Traffic Control (ATC) constraints which may restrict an airplane to lower than optimum 

altitude if the airplane does not climb to optimum altitude quickly enough. The future ATC 

environment should alleviate this consideration and allow engines to size down accordingly. This 

change in time and distance to climb requirements results in a 1.1% block fuel / seat benefit as 

shown in Table 6.5. 

Table 6.5 – 765-094 – Refined SUGAR Time and Distance to Climb Trade 

MODEL

Sizing Level

Meet SUGAR Free 

Climb Performance

Relax Climb 

Requirement

PASSENGERS / CLASS 154 / Dual 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

139,800

131,500

123,500

77,500

5,582

139,700

131,800

123,800

77,800

5,512

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled gFan

68

16,200

Scaled gFan

66

15,700

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1367 / 126

11.63

0.659

21.639

1440 / 129

11.63

0.654

21.981

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN / NMI

FT

FT

FT

KT

3,500

0.70

0.70

39,100

24 / 152

37,400

44,100

8,190

118

3,500

0.70

0.70

38,800

29 / 182

38,400

45,200

8,190

115

BLOCK FUEL / SEAT (900 NMI) LB 52.08 (Base) 51.53 (-1.1%)

General Electric (GE) provided data for several engines, the engine used on the Refined SUGAR 

was a high technology advanced turbofan labeled the gFan. Another version of the engine, the 

gFan+, was a higher technology advanced turbofan. Table 6.6 compares the Refined SUGAR 

airplane to an airplane sized using the higher technology gFan+. While the gFan+ has a larger 

diameter, i.e. higher drag, and a higher bare engine weight, the improved Specific Fuel 

Consumption (SFC) of the engine more than offsets these penalties, and the airplane sized with 

the gFan+ has a 6.2% block fuel / seat benefit compared to the airplane sized with the basic 

gFan. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Table 6.6 – 795-094 – Refined SUGAR Advanced Engine Trade 

MODEL

Sizing Level Refined SUGAR Refined SUGARgFan+ Engine

PASSENGERS / CLASS 154 / Dual 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

139,700

131,800

123,800

77,800

5,512

139,500

133,600

125,600

79,600

5,208

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled gFan

66

15,700

Scaled gFan+

76

15,300

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1440 / 129

11.63

0.654

21.981

1407 / 128

11.63

0.708

21.428

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN/ NMI

FT

FT

FT

KT

3,500

0.70

0.70

38,800

29 / 182

38,400

45,200

8,190

115

3,500

0.70

0.70

40,100

29 / 186

39,600

44,800

8,190

117

BLOCK FUEL / SEAT (900 NMI) LB 51.53 (Base) 48.31 (-6.2%)

As stated previously, the airplane requirement for TOFL was ~ 8,200 ft at MTOW. Designing an 

airplane to be able to utilize smaller metroplex airports, i.e. ones with shorter field lengths, 

would result in an airplane which required more thrust and wing area, and hence pay a penalty in 

block fuel / seat. This penalty is quantified in Table 6.7. Operationally, an airplane can takeoff 

from smaller fields, as noted by quoting the 900 nmi takeoff weight mission takeoff field length 

without paying this penalty, but would need to reduce payload, or range, or both. Alternately, the 

high lift system can be made more powerful to reduce field lengths, with potentially less fuel 

burn penalty, but this option has not been explored in this study. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Table 6.7 – 795-094 – Refined SUGAR Takeoff Field Length Trade 

MODEL

Sizing Level +500 ft Base TOFL -500 ft -1,000 ft

PASSENGERS / CLASS 154 / Dual 154 / Dual 154 / Dual 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

138,400

130,800

122,800

76,800

5,457

139,700

131,800

123,800

77,800

5,512

141,200

132,900

124,900

78,900

5,571

142,900

134,300

126,300

80,300

5,615

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled gFan

65

15,100

Scaled gFan

66

15,700

Scaled gFan

68

16,300

Scaled gFan

69

16,700

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1400 / 128

11.63

0.660

21.874

1440 / 129

11.63

0.654

21.981

1490 / 132

11.63

0.652

22.109

1580 / 136

11.63

0.653

22.374

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

TOFL (900 NMI MISS, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN/ NMI

FT

FT

FT

FT

KT

3,500

0.70

0.70

38,400

30 / 189

38,400

45,100

8,680

5,790

116

3,500

0.70

0.70

38,800

29 / 182

38,400

45,200

8,190

5,510

115

3,500

0.70

0.70

39,500

28 / 177

38,800

45,700

7,690

5,240

113

3,500

0.70

0.70

40,100

29 / 168

39,900

46,800

7,190

4,940

111

BLOCK FUEL / SEAT (900 NMI) LB 50.84 (-1.3%) 51.53 (Base) 52.29 (+1.5%) 52.97 (+2.8%)

765-095 – SUGAR High: 

“SUGAR High”, is a strut-braced, large span, high wing airplane configuration utilizing the 

gFan+ engine, and increased technology beyond the Refined SUGAR as defined in Section 4.0. 

SUGAR High was sized using the same process, mission profile, and performance requirements, 

as Refined SUGAR. The SUGAR High sizing chart is shown in Figure 6.7 uses these 

assumptions, but this particular sizing chart includes an additional 15,000 lb OEW benefit which 

is not included in the base SUGAR high shown in Table 6.8. This OEW benefit is further 

explained in the SUGAR High OEW Trade in Section 5.5.3. While the base SUGAR High 

utilizes higher technology levels and engines than Refined SUGAR, the block fuel / seat benefit 

relative to the SUGAR Free airplane is only 38.9%, which is less than the Refined SUGAR value 

of 44.2%. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Figure 6.7 – 765-095 Sizing (assumes 15,000 pound weight reduction) 

Table 6.8 – 765-095 Baseline Sizing 

MODEL

Sizing Level SUGAR High

PASSENGERS / CLASS 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

176,800

167,300

159,300

113,300

5,754

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled gFan+

86

19,600

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1722 / 215

26.94

0.828

25.934

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN/ NMI

FT

FT

FT

KT

3,500

0.70

0.70

43,300

29 / 182

42,100

44,000

8,190

115

BLOCK FUEL / SEAT (900 NMI) LB 56.43

Much of the block fuel / seat penalty of SUGAR High relative to Refined SUGAR is due to the 

high wing weight of SUGAR High’s large span wing. Currently, there is a lot of uncertainty as to 

the structural characteristics of this wing, which in turn results in a large uncertainty in the OEW 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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of the airplane. Because of this large uncertainty in wing weight, a trade was done to quantify the 

spread in potential fuel burn uncertainty for this airplane. The results of this trade are shown in 

Table 6.9. For the remainder of the performance section, the airplane assumed to have a 15,000 

lb weight reduction, as sized in Figure 6.7, will be used as the basis for trades. 

Table 6.9 – 765-095 OEW Trade 

MODEL

Sizing Level +5,000 lb Base -5,000 lb -10,000 lb -15,000 lb -20,000 lb

PASSENGERS / CLASS 154 / Dual 154 / Dual 154 / Dual 154 / Dual 154 / Dual 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

189,200

177,900

169,900

123,900

6,038

176,800

167,300

159,300

113,300

5,754

164,400

156,700

148,700

102,700

5,470

152,100

146,200

138,200

92,200

5,184

140,100

136,000

128,000

82,000

4,928

128,200

125,800

117,800

71,800

4,658

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled gFan+

89

20,800

Scaled gFan+

86

19,600

Scaled gFan+

83

18,400

Scaled gFan+

80

17,200

Scaled gFan+

78

16,200

Scaled gFan+

75

15,000

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1866 / 224

26.94

0.825

26.426

1722 / 215

26.94

0.828

25.934

1578 / 206

26.94

0.831

25.442

1441 / 197

26.94

0.836

24.909

1292 / 187

26.94

0.865

24.161

1153 / 176

26.94

0.877

23.45

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN / NMI

FT

FT

FT

KT

3,500

0.70

0.70

43,500

29 / 184

42,300

44,300

8,190

114

3,500

0.70

0.70

43,300

29 / 182

42,100

44,000

8,190

115

3,500

0.70

0.70

43,100

28 / 180

41,900

43,700

8,180

116

3,500

0.70

0.70

43,000

28 / 180

41,700

43,500

8,180

118

3,500

0.70

0.70

42,900

28 / 181

41,900

42,900

8,150

120

3,500

0.70

0.70

42,600

28 / 180

41,600

42,400

8,230

122

BLOCK FUEL / SEAT (900 NMI) LB 59.72 (+5.8%) 56.43 (Base) 53.14 (-5.8%) 49.84 (-11.7%) 46.78 (-17.1%) 43.55 (-22.8%)

The high wing configuration of SUGAR High lends itself to having an open fan puller engine 

installed on the wing. The Open Fan engine, while heavier because of bare engine weight and 

increased cabin noise insulation, has less wetted area, i.e. lower drag, and much improved SFC 

relative to the base gFan+ engine on the airplane. The SUGAR High airplane with an Open Fan 

engine, sized to the same performance requirements as the SUGAR High airplane with the 

gFan+ engines, has a 7.2% block fuel / seat benefit as shown in Table 6.10. This sizing was done 

without regard to community noise considerations. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Table 6.10 – 765-095 Open Fan Trade 

MODEL

Sizing Level Ducted Fan With Open Fan

PASSENGERS / CLASS 154 / Dual 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

140,100

136,000

128,000

82,000

4,928

144,900

143,100

135,100

89,100

4,566

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled gFan+

78

16,200

Scaled gFan+

Open Fan

~139

16,500

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1292 / 187

26.94

0.865

24.161

1365 / 192

26.94

0.838

24.794

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN / NMI

FT

FT

FT

KT

3,500

0.70

0.70

42,900

28 / 181

41,900

42,900

8,150

120

3,500

0.70

0.70

43,000

28 / 177

41,600

43,300

8,190

120

BLOCK FUEL / SEAT (900 NMI) LB 46.78 (Base) 43.39 (-7.2%)

A takeoff field length trade was done on the SUGAR High airplane using the same approach as 

on the Refined SUGAR airplane. The trade numbers are similar between the airplanes as shown 

in Table 6.11. 

Table 6.11 – 765-095 TOFL Trade 

MODEL

Sizing Level +500 ft Base -500 ft -1000 ft

PASSENGERS / CLASS 154 / Dual 154 / Dual 154 / Dual 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

138,900

134,800

126,800

80,800

4,907

140,100

136,000

128,000

82,000

4,928

142,100

137,700

129,700

83,700

4,968

144,200

139,400

131,400

85,400

5,032

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled gFan+

77

15,700

Scaled gFan+

78

16,200

Scaled gFan+

79

16,600

Scaled gFan+

80

17,300

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1231 / 182

26.94

0.873

23.892

1292 / 187

26.94

0.865

24.161

1365 / 192

26.94

0.843

24.508

1431 / 196

26.94

0.839

24.742

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

TOFL (900 NMI MISS, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN / NMI

FT

FT

FT

FT

KT

3,500

0.70

0.70

42,300

28 / 178

41,200

42,100

8,690

6,290

122

3,500

0.70

0.70

42,900

28 / 181

41,900

42,900

8,150

5,940

120

3,500

0.70

0.70

43,400

28 / 179

42,200

43,700

7,680

5,630

117

3,500

0.70

0.70

44,000

28 / 178

42,700

44,400

7,190

5,310

115

BLOCK FUEL / SEAT (900 NMI) LB 46.27 (-1.1%) 46.78 (Base) 47.45 (+1.4%) 48.32 (+3.3%)
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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765-096 – SUGAR Volt: 

“SUGAR Volt” is a hybrid fuel / electric powered airplane based on the SUGAR High platform. 

SUGAR Volt was sized to the same performance requirements as the other airplanes, but some 

of the energy normally provided by fuel is now being provided by battery power. The General 

Electric hybrid engine is designated hFan. The airplane was sized such that on the design 

mission, while provisioning for batteries is included, no batteries are actually used in the 

mission. The lack of batteries for the design mission results in an airplane with a lower MTOW 

than if batteries were used on that mission. As mission range is decreased, more and more 

potential weight is available for adding batteries and still remaining below MTOW for the 

mission. Table 6.12 shows the performance level of the SUGAR Volt airplane. This airplane 

uses 63.4% less fuel than the SUGAR Free airplane on a 900 nmi mission, while carrying 20,900 

lb of batteries on that mission. 

Table 6.12 – 765-096 Baseline Sizing 

MODEL

Sizing Level SUGAR Volt

PASSENGERS / CLASS 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

154,900

148,600

140,600

94,600

5,250

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled hFan

80

17,300

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1498 / 201

26.94

0.831

24.992

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN / NMI

FT

FT

FT

KT

3,500

0.70

0.70

42,800

29 / 178

42,000

43,900

8,180

116

BLOCK FUEL / SEAT (900 NMI) LB 33.83

Table 6.13 is a table that compares the SUGAR Volt to an airplane with the same design 

requirements, but no electric system (SUGAR High), and the trade in block fuel for using 

varying amounts of horsepower for the 900 nmi mission. The trade shows that as you use more 

horsepower during the mission, the fuel required for the mission decreases, however the amount 

of battery weight required also increases. Eventually the TOW required for the 900 nmi mission 

equals MTOW and no additional battery power can be added. The point at which TOW for the 

900 nmi mission equals MTOW is the maximum benefit available, and is the block fuel value 

used in Table 6.12. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Table 6.13 – 765-096 Power Trade 

MODEL

Sizing Level

No Electric 

Systems

SUGAR Volt

0 lb Battery

1,250 hp

9,150 lb Battery

2,500 hp

16,700 lb Battery

3750 hp

24,250 lb Battery

PASSENGERS / CLASS 154 / Dual 154 / Dual 154 / Dual 154 / Dual 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

140,100

136,000

128,000

82,000

4,928

154,900

148,600

140,600

94,600

5,250

154,900

148,600

140,600

94,600

5,250

154,900

148,600

140,600

94,600

5,250

154,900

148,600

140,600

94,600

5,250

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled gFan+

78

16,200

Scaled hFan

80

17,300

Scaled hFan

80

17,300

Scaled hFan

80

17,300

Scaled hFan

80

17,300

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1292 / 187

26.94

0.865

24.161

1498 / 201

26.94

0.831

24.992

1498 / 201

26.94

0.831

24.992

1498 / 201

26.94

0.831

24.992

1498 / 201

26.94

0.831

24.992

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN / NMI

FT

FT

FT

KT

3,500

0.70

0.70

42,900

28 / 181

41,900

42,900

8,150

120

3,500

0.70

0.70

42,800

29 / 178

42,000

43,900

8,180

116

3,500

0.70

0.70

42,800

29 / 178

42,000

43,900

8,180

116

3,500

0.70

0.70

42,800

29 / 178

42,000

43,900

8,180

116

3,500

0.70

0.70

42,800

29 / 178

42,000

43,900

8,180

116

TAKEOFF WEIGHT REQUIRED (900 NMI)

OPERATING EMPTY WEIGHT (900 NMI)

BLOCK FUEL / SEAT (900 NMI)

LB

LB

LB

123,000

82,000

46.78 (Base)

136,500

94,600

50.64 (+8.25%)

144,300

103,750

42.05 (-10.1%)

151,100

111,300

36.64 (-21.7%)

158,000

118,850

31.67 (-32.3%)

The hybrid fuel / electric engine has maximum thrust characteristics unlike those of a fuel only 

engine. As horsepower applied to the engine is increased, maximum thrust is increased. There is 

then the potential to use increased levels of horsepower during periods of high thrust utilization, 

e.g. takeoff and climb, and less during periods of low thrust required, e.g. cruise and descent. 

Table 6.14 shows the results of one attempt at doing that. The airplane and engine were resized 

using 1,250 horsepower for just the takeoff and climb portion of the design mission. Since the 

engine has more thrust capability during takeoff and climb when horsepower is applied, and the 

engines are sized for climb and cruise thrust, engine scale for the airplane was reduced, as shown 

in the 1,250 hp column airplane. While the airplane sizes to be smaller and lighter, when the 

airplane reaches its cruise altitude, and battery power is exhausted, the airplane is no longer 

capable of remaining at the altitude achievable during climb, if that altitude is at or above the 

optimum altitude. Cruise thrust available without the added horsepower boost from the electric 

motor is not enough to sustain the airplane at its optimum altitude as shown by the cruise thrust 

Initial Cruise Altitude Capability (ICAC) being over 1,000 ft below the airplane optimum 

altitude. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Table 6.14 – 765-096 Power Trade for Core Sizing 

MODEL

Sizing Level

No Electric 

Systems

SUGAR Volt

0 lb Battery

1,250 hp

1,800 lb Battery

PASSENGERS / CLASS 154 / Dual 154 / Dual 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

140,100

136,000

128,000

82,000

4,928

154,900

148,600

140,600

94,600

5,250

152,500

148,300

140,300

94,300

4,930

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled gFan+

78

16,200

Scaled hFan

80

17,300

Scaled hFan

73

14,300

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1292 / 187

26.94

0.865

24.161

1498 / 201

26.94

0.831

24.992

1592 / 207

26.94

0.837

25.751

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

CLIMB THRUST ICAC (MTOW, ISA)

CRUISE THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

FT

MIN / NMI

FT

FT

FT

KT

3,500

0.70

0.70

42,900

44,800

28 / 181

41,900

42,900

8,150

120

3,500

0.70

0.70

42,800

44,900

29 / 178

42,000

43,900

8,180

116

3,500

0.70

0.70

45,200

42,600

29 / 182

43,700

45,400

8,190

113

BLOCK FUEL / SEAT (900 NMI) LB 46.78 (Base) 50.64 (+8.25%) 45.67 (-2.4%)

Because the amount of batteries the airplane can carry on shorter range missions is directly 

proportional to the difference between the airplane’s MTOW and Zero Fuel Weight (ZFW = 

Operational Empty Weight + Payload Weight), the airplane can carry more batteries, i.e. 

decrease fuel burn, by increasing MTOW. This is exactly the opposite effect of fuel only 

airplanes. Increasing the difference between MTOW and ZFW is effectively increasing the 

design range of the airplane. This trend is illustrated in Table 6.15. As design range is increased, 

the airplane becomes bigger and heavier, but because the airplane can carry more batteries on a 

900 nmi mission and utilize that extra power instead of burning fuel, the actual fuel burn on that 

mission decreases. If the airplane is sized large enough to carry enough batteries, the fuel burn 

can reach the NASA goal of a 70% block fuel reduction. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Table 6.15 – 765-096 MTOW Trade 

MODEL

Sizing Level SUGAR Free SUGAR Volt SUGAR VOLTIncrease MTOW

SUGAR VOLT

Increase MTOW

PASSENGERS / CLASS 154 / Dual 154 / Dual 154 / Dual 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

184,800

151,000

142,000

96,000

9,710

154,900

148,600

140,600

94,600

5,250

163,100

152,300

144,300

98,300

5,948

179,700

159,600

151,600

105,600

7,373

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled CFM56-7B27

62

28,200

Scaled hFan

80

17,300

Scaled hFan

82

18,000

Scaled hFan

86

23,600

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1429 / 122

10.41

0.583

18.068

1498 / 201

26.94

0.831

24.992

1597 / 207

26.94

0.827

25.365

1769 / 218

26.94

0.826

25.894

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

CLIMB THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN / NMI

FT

FT

FT

KT

3,500

0.785

0.785

37,200

23 / 148

35,000

36,200

8,190

126

3,500

0.70

0.70

42,800

29 / 178

42,000

43,900

8,180

116

4,000

0.70

0.70

42,900

29 / 181

42,200

44,200

8,190

114

4,900

0.70

0.70

43,100

29 / 177

42,300

44,300

8,200

111

BATTERIES CARRIED (900 NMI)

OPERATING EMPTY WEIGHT (900 NMI)

BLOCK FUEL / SEAT (900 NMI)

LB

LB

LB

0

96,000

92.35 (Base)

20,900

116,500

33.83 (-63.4%)

25,200

123,500

31.54 (-65.8%)

35,500

141,100

26.23 (-71.6%)

Another possibility for exploiting the increased thrust capability of the hybrid engine is to use it 

to reduce TOFL. If the engine is sized using fuel only thrust capability to the TOFL requirement, 

applying horsepower to the engine will have the effect of reducing that TOFL. This effect is 

illustrated in Table 6.16. As more horsepower is applied, the TOFL of the airplane at MTOW, 

and on a 900 nmi mission, is significantly reduced. It was assumed takeoff thrust capability 

would need to be available for 5 minutes, and the weight of the batteries carried is reflected in 

the slight penalty in both design range and block fuel. 

Table 6.16 – 765-096 TOFL Trade 

MODEL

Sizing Level

SUGAR Volt

Base 1,250 hp 2,500 hp 3,750 hp

MAX TAKEOFF WEIGHT

BATTERY WEIGHT

OPERATING EMPTY WEIGHT

LB

LB

LB

154,900

0

94,600

154,900

320

94,600

154,900

530

94,600

154,900

740

94,600

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled hFan

80

17,300

Scaled hFan

80

19,400

Scaled hFan

80

21,300

Scaled hFan

80

23,000

DESIGN MISSION RANGE

TOFL (MTOW, SEA LEVEL, 86 DEG F)

NMI

FT

3,500

8,180

3,450

6,800

3,420

6,040

3,385

5,600

TAKEOFF WEIGHT REQUIRED (900 NMI)

TOFL (900 NMI, SEA LEVEL, 86 DEG F)

BLOCK FUEL / SEAT (900 NMI)

LB

FT

LB

136,500

5,980

50.64 (Base)

136,800

5,140

50.71 (+0.1%)

137,000

4,740

50.76 (+0.2%)

137,200

4,425

50.81 (+0.3%)

Similar to the SUGAR High airplane, a trade was done to examine the effect of applying an 

Open Fan engine to SUGAR Volt. While the SUGAR Volt with Open Fan sizes similar to the 

SUGAR High with Open Fan airplane, the block fuel benefit is not nearly as great. This is 

because, as discussed earlier, the increased efficiency of the Open fan engine decreases the 

difference between MTOW and ZFW, i.e. the amount of batteries the airplane can carry on the 

900 nmi mission, and this difference decreases the ability of the airplane to offset the installation 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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weight penalties of both the Open Fan engines and batteries, plus because the airplane is burning 

far less fuel, the overall effectiveness of the Open Fan’s SFC benefit on block fuel is reduced. 

The results of this trade are shown in Table 6.17. 

Table 6.17 – 765-096 Open Fan Trade 

MODEL

Sizing Level SUGAR Volt SUGAR VoltOpen Fan

PASSENGERS / CLASS 154 / Dual 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

154,900

148,600

140,600

94,600

5,250

159,200

155,500

147,500

101,500

4,854

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled hFan

80

17,300

Scaled hFan

Open Fan

~144

17,600

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1498 / 201

26.94

0.831

24.992

1558 / 205

26.94

0.827

25.457

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN / NMI

FT

FT

FT

KT

3,500

0.70

0.70

42,800

29 / 178

42,000

43,900

8,180

116

3,500

0.70

0.70

42,900

29 / 179

42,200

44,100

8,190

117

BLOCK FUEL / SEAT (900 NMI) LB 33.83 (Base) 32.97 (-2.5%)

A battery power trade was done for the hybrid Open Fan engine similar to the hybrid turbofan 

engine. The results of that trade are shown in Table 6.18. While SUGAR Volt with the hybrid 

turbofan engine was capable of carrying 20,900 lb of batteries on the 900 nmi mission, the 

reduced difference between MTOW and ZFW on the hybrid Open Fan engine only allows it to 

carry 18,700 lb of batteries before reaching MTOW. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Table 6.18 – 765-096 Open Fan Power Trade 

MODEL

Sizing Level

No Electric 

Systems

SUGAR Volt

0 lb Battery

1,250 hp

9,150 lb Battery

2,500 hp

16,700 lb Battery

3750 hp

24,250 lb Battery

PASSENGERS / CLASS 154 / Dual 154 / Dual 154 / Dual 154 / Dual 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

140,100

136,000

128,000

82,000

4,928

159,200

155,500

147,500

101,500

4,854

159,200

155,500

147,500

101,500

4,854

159,200

155,500

147,500

101,500

4,854

159,200

155,500

147,500

101,500

4,854

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled gFan+

78

16,200

Scaled hFan

Open Fan

~144

17,600

Scaled hFan

Open Fan

~144

17,600

Scaled hFan

Open Fan

~144

17,600

Scaled hFan

Open Fan

~144

17,600

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1292 / 187

26.94

0.865

24.161

1558 / 205

26.94

0.827

25.457

1558 / 205

26.94

0.827

25.457

1558 / 205

26.94

0.827

25.457

1558 / 205

26.94

0.827

25.457

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN / NMI

FT

FT

FT

KT

3,500

0.70

0.70

42,900

28 / 181

41,900

42,900

8,150

120

3,500

0.70

0.70

42,900

29 / 179

42,200

44,100

8,190

117

3,500

0.70

0.70

42,900

29 / 179

42,200

44,100

8,190

117

3,500

0.70

0.70

42,900

29 / 179

42,200

44,100

8,190

117

3,500

0.70

0.70

42,900

29 / 179

42,200

44,100

8,190

117

TAKEOFF WEIGHT REQUIRED (900 NMI)

OPERATING EMPTY WEIGHT (900 NMI)

BLOCK FUEL / SEAT (900 NMI)

LB

LB

LB

123,000

82,000

46.78 (Base)

142,500

101,500

46.82 (+0.09%)

150,600

110,700

39.12 (-16.4%)

157,400

118,200

34.19 (-26.9%)

164,300

125,800

29.72 (-36.5%)

765-097 – SUGAR Ray: 

Another alternative airplane configuration looked at was a Hybrid Wing Body (HWB), dubbed 

SUGAR Ray. SUGAR Ray was primarily looked at as an airplane which leveraged maximum 

airframe shielding in order to reduce airplane community noise. The performance of SUGAR 

Ray is shown in Table 6.19. The airplane has a block fuel / seat benefit of 43.3% relative to the 

baseline SUGAR Free configuration. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Table 6.19 – 765-097 Baseline Sizing 

MODEL

Sizing Level SUGAR Ray

PASSENGERS / CLASS 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

172,600

165,300

157,300

111,300

5,392

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled gFan+

81

17,500

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 4139 / 180

26.94

0.316

27.471

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN / NMI

FT

FT

FT

KT

3,500

0.70

0.70

42,400

28 / 180

40,800

7,900

103

BLOCK FUEL / SEAT (900 NMI) LB 52.37

Because of the relative uncertainty of an HWB’s OEW, a trade was done to look at the 

sensitivity of the airplane’s performance to weight. The results of that trade are shown in Table 

6.20. Because of the highly integrated nature of the wing area and cabin area, which is not 

present on “tube-and-wing” airplanes, the trade did not include variation in wing area. This 

results in a trade which is not very sensitive to OEW, but also results in airplanes which are not 

consistent in performance level. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Table 6.20 – 765-097 OEW Trade 

MODEL

Sizing Level -10,000 lb Cycled for Thrust +10,000 lb

PASSENGERS / CLASS 154 / Dual 154 / Dual 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

161,500

155,200

147,200

101,200

5,232

172,600

165,300

157,300

111,300

5,392

184,400

175,900

167,900

121,900

5,576

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled gFan+

82

18,100

Scaled gFan+

81

17,500

Scaled gFan+

81

17,400

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 4139 / 180

26.94

0.323

26.91

4139 / 180

26.94

0.316

27.471

4139 / 180

26.94

0.313

27.96

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN / NMI

FT

FT

FT

KT

3,500

0.70

0.70

44,000

28 / 178

42,700

6,700

100

3,500

0.70

0.70

42,400

28 / 180

40,800

7,900

103

3,500

0.70

0.70

41,200

28 / 178

39,200

9,100

106

BLOCK FUEL / SEAT (900 NMI) LB 50.89 (-2.6%) 52.37 (Base) 54.18 (+3.7%)

6.3 – Vehicle Opportunities Trades 

After the completion of the higher order analysis for each vehicle (covered in Section 5.3 thru 

Section 5.7) the initial sizing methods (used for Section 5.1.3) were calibrated and re-run to 

determine how close to optimum each configuration came. It also allowed for low level trade 

studies to be performed that were calibrated to the higher level analyses. The data in this section 

is a result of these calibrated lower fidelity methods. 

Contrails may contribute to global climate change and can be avoided by flying at altitudes that 

prevent their formation. An extreme solution is to restrict all air traffic to 27,000 feet which 

would adversely affect vehicle performance. To quantify this, a Refined SUGAR configuration 

was sized with both unrestricted and restricted initial cruise altitude allowing thrust, wing area, 

and aspect ratio to change. Maximum span was constrained to 118 feet. The results of this sizing 

is shown in Figure 6.8 

Figure 6.8 – Restricting Cruise Altitude to 27,000 ft 

Refined SUGAR 

gfan+ Engine

Refined SUGAR 

gFan+ Engine

Cruise Altitude (MTOW, ISA) 39,600 27,000

Max Takeoff Weight (lbs) 139,500 141,000

Wing Area (ft^2) 1407 1240

Aspect Ratio (Effective) 11.63 13.5

Wing Span (effective) 128 128

Performance Cruise Mach 0.70 0.672

Performance Cruise Knots 402 402

Block Fuel / Seat (900 NMI) 48.31 51.4 (+6.4%)
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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The Refined SUGAR configuration was also developed to a different technology level than the 

other three advanced configurations. The application of those advanced technologies was 

investigated as an opportunities trade. Figure 6.9 shows the potential for Refined SUGAR with 

the same advanced technologies applied (primarily to propulsion and aerodynamics) both with 

and without a span constraint. The advanced technologies do not reduce fuel burn as much as 

increased span. The non-span constrained version of the Refined SUGAR with the gFan+ engine 

is referred to as the “Super Refined SUGAR”. 

118’

118’

Fold line

Fold line

MODEL

Sizing Level

Refined

SUGAR

gFan

Refined

SUGAR

gFan+

Refined SUGAR

gFan+

Span 118 ft

Refined SUGAR

gFan+

Span 118 ft

SUGAR High Aero

Refined SUGAR

gFan+

No Span Constraint

SUGAR High Aero

Fold Wt

Refined SUGAR

gFan+

No Span Constraint

SUGAR High Aero

2 x Fold Wt

Refined SUGAR

gFan+

No Span Constraint

SUGAR High Aero

No Fold

CRUISE ALTITUDE (MTOW, ISA) ft 38,400 39,600 39,600 39,600 41,500 41,500 41,500

MAX TAKE OFF WEIGHT

WING AREA

ASPECT RATIO (EFFECTIVE)

WING SPAN (TRUE)

CRUISE L/D

CRUISE MACH NUMBER

Lb

ft2

ft

139,700

1,440

11.63

129

21.98

0.70

139,500

1,407

11.63

128

21.4

0.70

139,400

1,407

11.63

118

20.4

0.70

139,500

1,407

11.63

118

21.6

0.70

141,905

1,600

16.0

160

24.8

0.70

143,336

1,600

16.0

160

24.8

0.70

140,100

1,600

16.0

160

25.33

0.70

FUEL BURN / SEAT (900 NMI) lb 51.3 48.31 50.19 47.0 42.50 42.92 41.57

“Super Refined SUGAR”

-45.6% 

fuel 

burn

-54% 

fuel 

burn

-55% 

fuel 

burn

Figure 6.9 – Potential for a Super Refined SUGAR 

SUGAR High, as well as Super Refined SUGAR will benefit from further optimization. This is 

due to the unknowns surrounding the OEW associated with a wing aspect ratio much higher than 

other Boeing transports. Figure 6.10 shows the potential for the SUGAR High configuration. 

This includes the lower wing weight discussed in Section 5.5.3, a more favorable lift distribution, 

as well as some configuration changes that may reduce parasite and compressibility drag. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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34

36

38

40

42

44

46

48

19 20 21 22 23 24 25 26 27 28 29 30

L/D

Block Fuel / Seat (900 NM)

SUGAR High

Optimized lift distribution

Reduced Parasite and Compressibility Drag

SUGAR High 

Optimized lift distribution

SUGAR High (Reduced wing weight) 

-49% 

fuel burn

-51% 

fuel burn

-58% 

fuel burn

Figure 6.10 – SUGAR High Opportunities 

SUGAR Volt, with the same improvements discussed for SUGAR High, can be designed to a 

selectable Maximum Takeoff Gross Weight (TOGW). The vehicle fuel burn will depend on what 

TOGW is selected and what level of battery technology is available. Figure 6.11 shows the 

vehicle’s fuel burn and energy utilization sensitivity to TOGW and battery energy density. As 

TOGW is increased, more batteries are carried, which decreases fuel burn. What is not obvious is 

that, above a critical battery energy density, the energy used starts to decrease also. If fuel burn 

minimization is the only metric and one does not care about wing span or vehicle TOGW, 

maximizing TOGW results in the minimum fuel burn. There is a limit on how little fuel is 

burned that is caused by the operational restrictions placed on the engine. 

As previously stated, the fuel burn is being measured for the average 900 nautical mile mission 

that was an output from the future scenario. In order to verify that increasing TOGW and 

minimizing fuel burn for the 900 nautical mile mission was not increasing fleet fuel burn a 

weighted average was calculated based on projected Medium sized airplane frequencies verses 

range. Figure 6.12 shows that after 220,000 pounds there is diminishing return from a fleet 

standpoint. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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240,000 

220,000 

200,000 

180,000 

163,000 

1000

750

500

0

2

5

7

9

12

14

16

18

21

23

25

28

30

32

35

37

39

42

44

46

90 100 110 120 130 140 150 160 170

Millions of BTU's (900 NMI)

Block Fuel Per Seat (900 NMI)

50%

55%

60%

65%

70%

75%

80%

85%

90%

95%

100%

Percent Fuen Burn Reduction

NASA Goal

Battery 

Wh/kg

TOGW

Scaled hFan,

TOGW 163,100

Scaled hFan,

TOGW 179,700

Percent Fuel Burn Reduction

Fuel burn reduction reaches a limit 

due to taxi and gas turbine operation 

assumptions

Figure 6.11 – SUGAR Volt Fuel Burn Opportunities 

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

0 500 1000 1500 2000 2500 3000 3500

Range (NM)

Mission Frequency

240,000

160,000

180,000

200,000

220,000 0

5

9

14

18

23

28

32

37

42

46

64% 65% 66% 67% 68% 69% 70% 71% 72% 73% 74%

Mission Frequency Weighted Fuel Burn Reduction

Block Fuel Per Seat (900 NMI)

50%

55%

60%

65%

70%

75%

80%

85%

90%

95%

100%

Percent FuelBurn Reduction

(900 NM)

TOGW

750 Wh/kg

Figure 6.12 – Medium Airplane Frequencies vs. Range and SUGAR Volt Fleet Fuel Burn 
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6.4 – Evaluation of NASA Metrics 

The following section contains charts that illustrate the range of the charted variable for each 

configuration that was generated with the low and high fidelity methods. These charts should 

NOT be interpreted as the minimum and maximum attainable values for the configuration. A 

note on the right of each of the bars indicates which trade dominated the variation of the plotted 

variable. For example for take-off field length (TOFL) one would expect to see TOFL on the 

right for all vehicles that have TOFL trades performed as that trade should dominate the range 

for that variable. Also included on the chart is a grey dot that represents the baseline 

configuration shown in the summary tables from the sizing analysis. 

6.4.1 – Fuel Burned and Energy Consumed 

The fuel burn for the five concepts at the average mission range of 900 nm was computed for a 

base vehicle and trade studies were performed using high fidelity methods. The results of these 

trades are illustrated in Figure 6.13. The only trade performed on SUGAR Free was for advanced 

air traffic management (ATM) and the size of the bar illustrates how powerful the ATM is at 

reducing fuel burn. Also of interest is the range of the metric for SUGAR High. Surprisingly 

20,000 pounds of OEW doesn’t affect the fuel burn as much as one would expect. It does show 

that the high span technology must be light in order to beat the Refined or SUPER Refined 

SUGAR. It does show that potential for the airplane to be better for this metric than the 

conventional arrangement. 

SUGAR Volt is the only configuration that is capable of meeting or exceeding the NASA 70% 

fuel burn reduction goal. This hinges on advanced energy densities for batteries. 

The chart also shows carbon emissions since it is directly proportional to the fuel burned. The 

carbon emissions shown are for JP based fuels and take no credit for biofuels. 

0

10

20

30

40

50

60

70

80

90

100

SUGAR Free

Base

Refined SUGAR Super Refined

SUGAR

SUGAR High SUGAR Volt SUGAR Ray

Fuel Burn (900 NMI) (lb / Seat)

Carbon Emissions (900 NMI) (klb) 315

0

OEW Trade

OEW Trade

TOFL Trade

ATM

Trade

FOM Trades

NASA Goal

Nominal Point Design Point Design Trade Range Opportunities Trade Range

Figure 6.13 – Fuel Burn and Carbon Emissions 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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The 900 nautical mile mission was used for the fuel burn metric for SUGAR because it is 

average mission projected for 2030. The fuel burn reduction obviously varies with range. This 

variation is plotted in Figure 6.14. The mission fuel burn for each segment is shown in Table 

6.21. For this figure and table, the reduced wing weight is used on the SUGAR High and 

SUGAR Volt. 

Refined SUGAR

SUGAR Ray

SUGAR High*

SUGAR Volt*

R

e

f

e

r

e

n

c

e

M

i

s

s

i

o

n

L

e

n

g

t

h

Figure 6.14 – Fuel Burn Reduction vs. Range 

Table 6.21 – Vehicle Segment Fuel Burn 

 SUGAR 

Free 

Refined 

SUGAR 

SUGAR 

High 

SUGAR 

Volt 

Taxi-Out (lb) 400 67 62 62 

Takeoff / Climbout (lb) 498 382 394 493 

Climb (lb) 3,762 2,212 2,127 1,521 

Cruise (lb) 7,523 4,130 3,497 1,812 

Descent (lb) 473 889 867 1,025 

Loiter (lb) 1,091 - - - 

Approach / Landing (lb) 225 190 195 232 

Taxi-In (lb) 250 67 62 62 

Total (lb) 14,222 7,937 7,204 5,207 

The NRA stated that any form of energy, and its distribution prior to its use on the airplane is 

free. The purpose was to constrain the efforts of the study to air vehicle design. Using these 

rules, an electric airplane would burn no fuel. However, this may not be the intent of the rules 

outlined by the NRA as electric commercial airliners may have been viewed as an impractical 

solution. The total energy used by each configuration is shown in Figure 6.15. No configuration 

studied would meet the equivalent NASA goal of 70% energy utilization reduction, but a 60% 

energy reduction may be possible. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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0

50

100

150

200

250

300

SUGAR Free

Base

Refined SUGAR Super Refined

SUGAR

SUGAR High SUGAR Volt SUGAR Ray

Mega BTU (900 NMI)

Equivalent NASA Goal

OEW Trade

OEW Trade

TOFL Trade

ATM

Trade

FOM Trades

Nominal Point Design Point Design Trade Range Opportunities Trade Range

Figure 6.15 – Energy Utilization 

6.4.2 – Takeoff Field Length and Metroplex Compatibility 

A Takeoff Field Length (TOFL) of 8,200 feet at Maximum Takeoff Weight (MTOW) was a 

sizing parameter for all configurations. For Metroplex capability, it was assumed that a TOFL of 

5,000 feet or better at the 900 nmi mission weight would be sufficient. Hence, TOFL was used as 

a surrogate to Metroplex compatibility. However, with unfolded spans reaching into 200 feet it is 

obvious that more work needs to be completed prior to declaring these configurations 

“Metroplex Compatible”. 

Overall, achieving field lengths as low as 5,000 feet at the 900 nautical mile mission weight is 

not difficult though only three vehicles were analyzed at that condition. SUGAR Volt is of 

particular interest as it was found that the operator could choose the field length desired at the 

cost of efficiency. For a 900 nautical mile mission, the operator could choose to use JP fuel for 

the entire cruise and climb, thus reducing takeoff weight, and batteries for a thrust augmentation 

on takeoff. The engine has significantly more thrust when operated in the dual mode than with JP 

or batteries alone. That combined with wing areas sized for the long missions with heavy 

batteries yields very high thrust-to-weight and low wing loadings. 
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4,000

4,500

5,000

5,500

6,000

6,500

7,000

7,500

8,000

8,500

9,000

9,500

10,000

SUGAR Free

Base

Refined SUGAR Super Refined

SUGAR

SUGAR High SUGAR Volt SUGAR Ray

TOFL (3,500 NMI Mission unless noted)

No Trades

TOFL Trade

No Trades

OEW Trade

TOFL Trade

900nmi

900 nmi

Point Design Trade Range Opportunities Trade Range TOFL TradeNominal Point Design

900nmi

Figure 6.16 – Vehicle Field Length Capability 

6.4.3 – LTO NOx Emissions 

Figure 6.17 shows the results of the LTO NOx emissions. These trades were only a function of 

engine selection. The Refined SUGAR had the largest spread because it was run with both the 

gFan and gFan+. The SUGAR Volt concept, with its hybrid electric propulsion system could 

beat the NASA goal. If engines are not required to warm up prior to takeoff then the Volt 

concept could have virtually no LTO NOx emissions. It should also be noted that the CAEP/6 

rating doesn’t take into account the amount of time the engine is running. Just switching to the 

advanced air traffic management system reduces emissions due to the significantly reduced 

ground delays assumed. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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0.0

25.0

50.0

75.0

100.0

SUGAR Free

Base

Refined SUGAR Super Refined

SUGAR

SUGAR High SUGAR Volt SUGAR Ray

NOX (% of CAEP/6)

NASA Goal

Nominal Point Design Point Design Trade Range Opportunities Trade Range

Figure 6.17 – Vehicle NOX Emissions 

6.4.4 – Airport DNL Contours 

Prior to the calculation of specific configuration noise performance, we conducted a parametric 

analysis to investigate the impact of projected fleet size and N+3 fleet percentage. These results 

are summarized in Table 6.22. 55 DNL contours were calculated for the actual 2008 fleet mix 

(2008 Calibration), and again with a reduced set of aircraft to approximate the 2008 fleet mix 

(2008 Generic) and serve as a reference to the future fleet mix calculations (2030 Generic & 

2055 Generic). In the various scenarios, N+3 aircraft were assumed to be 30 db or 45 db lower 

than current generation aircraft. 

Table 6.22 – Parametrics on dB Reduction and Extent of Noise Footprint 

MODEL

Sizing Level

55 DNL

(MI2)

55 DNL

SW Extent

(NMI)

55 DNL

NE Extent

(NMI)

2008 CALIBRATION (7 A/C) 8.6 4.8 5.1

2008 GENERIC (FORECAST FLEET MIX) (No N+3)

2030 GENERIC (FORECAST FLEET MIX) (N+3 =N -30 dB)

2055 GENERIC (FORECAST FLEET MIX) (N+3 =N -30 dB)

9.3

14.2

10.2

5.8

7.2

5.4

5.8

7.1

5.3

2008 GENERIC (N+3 ONLY) (N+3 = N -30 dB)

2030 GENERIC (N+3 ONLY) (N+3 = N -30 dB)

2055 GENERIC (N+3 ONLY) (N+3 = N -30 dB)

1.8

2.5

3.6

2.0

2.4

3.1

1.8

2.2

2.9

2008 GENERIC (N+3 ONLY) (N+3 = N -45 dB)

2030 GENERIC (N+3 ONLY) (N+3 = N -45 dB)

2055 GENERIC (N+3 ONLY) (N+3 = N -45 dB)

0.8

1.0

1.4

1.2

1.4

1.8

0.9

1.2

1.6

AIRPORT BOUNDARY ~3.5 1.7 1.0

Increasing

Operations

For the assumed airport layout, the airport boundaries are at 1.7 and 1.0 miles. With projected 

fleet growth in 2055, the only scenario that resulted in the 55 DNL contour being at the 1.7 mile 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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airport boundary (approximately, calculated at 1.8 miles) was a 100% N+3 fleet with a -45 db 

relative noise level (Figure 6.18). To meet the 1.0 mile boundary, only the scenario holding the 

fleet size at 2008 levels with 100% N+3 aircraft with -45 db relative noise was successful (0.9 

miles). All forecast fleet mix scenarios predict a rise in aircraft noise for 2008, 2030, and 2055, 

as the fleet is expected to grow before N+3 aircraft with significant noise reduction become 

available in sufficient numbers to start reducing airport noise. The N+3 only scenarios that 

assume the current fleet is completely phased out, all show a reduction in the 55 DNL contour 

but are not contained within the airport boundary. 

0

1

2

3

4

5

6

7

8

2000 2010 2020 2030 2040 2050 2060

Year

Distance to 55 DNL Contour (NMI)

Projected Fleet Mix*

All N+3 (-30 dB)

All N+3 (-45 dB)

Airport Boundary

* Fleet Growth and Mixed Technology Fleet

100% 

Replacement 

with N+3 

Technology 

Aircraft

0

1

2

3

4

5

6

7

8

2000 2010 2020 2030 2040 2050 2060

Year

Distance to 55 DNL Contour (NMI)

Projected Fleet Mix*

All N+3 (-30 dB)

All N+3 (-45 dB)

Airport Boundary

* Fleet Growth and Mixed Technology Fleet

100% 

Replacement 

with N+3 

Technology 

Aircraft

Figure 6.18 – 100% Replacement with N+3 Technology May Meet Goals 

Using a list of technologies supplied by GE and Boeing noise engineers, a noise assessment was 

made for each aircraft concept. The GE noise reduction technologies are shown in Section 7.3.5. 

The following is a list of assumed airframe noise technologies: 

 Airframe weight reduction from improved structures/materials, propulsion, and systems – 

reduces aircraft size, TOFL, and engine size 

 Lightweight low speed high lift devices to reduce thrust required for cutback flyover and 

approach conditions 

 Airframe noise reduction methods including wing planform (airfoil design), main gear 

fairings, lift & control surface treatments (sealing, etc.) 

 Rear fan duct noise treatment methods 

 Inlet noise shielding from top of wing mounted engines (SUGAR Ray) 

 Rear jet and exhaust fan duct noise shielding from rear deck/platform for flyover and 

approach noise reduction and twin verticals for lateral noise reduction (need to assess 

noise shielding increments) and exhaust nozzle designs for distributed jet noise source 

reduction from shielding (SUGAR Ray) 

The configuration noise results are shown in Table 6.23. The Refined SUGAR with the gFan 

engine acoustic technologies is calculated to have a noise reduction of 16 dB relative to the 

SUGAR Free CFM-56 Baseline. Adding advanced gFan+ engine acoustics technologies yields 

an additional 6 dB reduction for the SUGAR High configuration. The additional shielding 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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provided by the HWB configuration, gives the SUGAR Ray an additional benefit of 15 dB. All 

of the quoted reductions are approximate. The noise build-ups are not necessarily as “linear” as 

we have assumed, as some technologies may not work together in a simple additive manner. The 

SUGAR Volt, which essentially uses a gFan+ engine with an added electric motor, was not 

specifically evaluated, because use of the electric system as part of the noise calculation 

procedure was not investigated. However, since the electric system is inherently quieter than 

conventional propulsion, any electric system use would tend to reduce the overall noise. If the 

best performing configuration, the SUGAR Ray (at -37 dB), is used, then the 55 DNL contour is 

at approximately 2.5 miles, which is 0.8 miles outside the 1.7 mile airport boundary with a 100% 

N+3 fleet (Figure 6.19). Additional noise reduction to achieve -45 dB, or a reduction in fleet size, 

is required to meet the 1.7 mile airport boundary. Both are required to meet the 1.0 mile airport 

boundary. Alternatively, significant aircraft and engine noise reduction (beyond -45 dB), would 

be required to bring the 55 DNL boundary inside the 1.0 mile airport boundary for the projected 

2055 fleet size. 

Table 6.23 – Vehicle Noise Comparison 

MODEL SUGAR Free Refined

SUGAR SUGAR High SUGAR Volt SUGAR Ray

ENGINE MODEL Scaled

CFM56-7B27

Scaled gFan Scaled gFan+ Scaled hFan Scaled gFan+

NOISE dB 0 -16 -22 Better than -22 -37

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

-45 -40 -35 -30 -25 -20 -15

N+3 Noise Reduction

Distance to 55 DNL Contour (NMI)

Assumes 100% N+3 Aircraft in 2055

Assumed Airport 

Boundary

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

-45 -40 -35 -30 -25 -20 -15

N+3 Noise Reduction

Distance to 55 DNL Contour (NMI)

Assumes 100% N+3 Aircraft in 2055

Assumed Airport 

Boundary

Figure 6.19 – Sensitivity of 55 DNL Distance to N+3 Noise Reduction 

Looking at the impact of other N+3 propulsion options is recommended. This includes 

operational optimization of flight path and throttle cutbacks as well as technologies such as the 

hybrid electric engine and open fan. 

6.4.5 – Environmental Impact of Cruise Emissions 

The carbon emissions for each vehicle are calculated from the quantity of fuel burned. The 

emissions are summarized in Table 6.24. For biofuels, a 50% credit is used. Total life cycle 

emissions are assumed. Therefore, the CO2 absorbed by growing biomass can offset the CO2 

emitted during processing and use in aircraft. A 50% credit assumes either a 50% blend of a 

carbon neutral biofuel, a pure biofuel which has a 50% reduction of life cycle CO2 emissions, or 

somewhere in between. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Table 6.24 – Vehicle Emissions Summary 

MODEL

Sizing Level SUGAR Free

Refined

SUGAR

gFan

SUGAR High SUGAR Volt

hFan SUGAR Ray

EMISSIONS (NOX)

EMISSIONS (CO2) (900 NMI, JET A)

EMISSIONS (CO2) (900 NMI, BIOFUEL)

CAEP/6

kLB

kLB

79.2%

291 (Base)

146 (Base)

41.7% 

162 (-44.2%)

81 (-44.5%)

28.0% 

178 (-38.9%)

89 (-39.0%)

21.0%

107 (-63.4%)

54 (-63.0%)

28.0%

148 (-49.1%)

74 (-49.3%)

6.5 – Sized Configuration Summary Table 

The following table (Table 6.25) summarizes the sized aircraft characteristics and performance. 

Note that this is the summary of all the baseline configurations. Many trade studies had 

significantly better and worse performance depending on the trade and metric of interest. 

Table 6.25 – Sized Baseline Vehicle Summary 

MODEL

Sizing Level SUGAR Free Refined

SUGAR SUGAR High SUGAR Volt SUGAR Ray

PASSENGERS / CLASS 154 / Dual 154 / Dual 154 / Dual 154 / Dual 154 / Dual

MAX TAKEOFF WEIGHT

MAX LANDING WEIGHT

MAX ZERO FUEL WEIGHT

OPERATING EMPTY WEIGHT

FUEL CAPACITY REQ

LB

LB

LB

LB

USG

184,800

151,000

142,000

96,000

9,710

139,700

131,800

123,800

77,800

5,512

176,800

167,300

159,300

113,300

5,754

154,900

148,600

140,600

94,600

5,250

172,600

165,300

157,300

111,300

5,392

ENGINE MODEL

FAN DIAMETER

BOEING EQUIVLENT THRUST (BET)

IN

LB

Scaled

CFM56-7B27

62

28,200

Scaled gFan

66

15,700

Scaled gFan+

86

19,600

Scaled hFan

80

17,300

Scaled gFan+

81

17,500

WING AREA / SPAN

ASPECT RATIO (EFFECTIVE)

OPTIMUM CL

CRUISE L/D @ OPT CL

FT2 / FT 1429 / 122

10.41

0.583

18.068

1440 / 129

11.63

0.654

21.981

1722 / 215

26.94

0.828

25.934

1498 / 201

26.94

0.831

24.992

4139 / 180

26.94

0.316

27.471

DESIGN MISSION RANGE

PERFORMANCE CRUISE MACH

LONG RANGE CRUISE MACH (LRC)

THRUST ICAC (MTOW, ISA)

TIME / DIST (MTOW, 35k FT, ISA)

OPTIMUM ALTITUDE (MTOW, ISA)

BUFFET ICAC (MTOW, ISA)

TOFL (MTOW, SEA LEVEL, 86 DEG F)

APPROACH SPEED (MLW)

NMI

FT

MIN / NMI

FT

FT

FT

KT

3,500

0.785

0.785

37,200

23 / 148

35,000

36,200

8,190

126

3,500

0.70

0.70

38,800

29 / 182

38,400

45,200

8,190

115

3,500

0.70

0.70

43,300

29 / 182

42,100

44,000

8,190

115

3,500

0.70

0.70

42,800

29 / 178

42,000

43,900

8,180

116

3,500

0.70

0.70

42,400

28 / 180

40,800

7,900

103

BLOCK FUEL / SEAT (900 NMI) LB 92.35 (Base) 51.53 (-44.2%) 56.43 (-38.9%) 33.83 (-63.4%) 52.37 (-43.3%)

NOISE

EMISSIONS (NOX)

EMISSIONS (CO2) (900 NMI, JET A)

dB

CAEP/6

LB

0 (Base)

79.2%

291 (Base)

-16

41.7% 

162 (-44.2%)

-22

28.0% 

178 (-38.9%)

<=-22

21.0%

107 (-63.4%)

-37

28.0%

148 (-43.3%)

Figure 6.20 shows the baseline configuration payload-range curves. Notice the TOGW curves of 

the advanced concepts have significantly lower slope than SUGAR Free. This is a direct result of 

the advanced technologies and stems from the improvements made in lift-to-drag ratio, specific 

fuel consumption, and empty weight fraction. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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0 

10,000 

20,000 

30,000 

40,000 

50,000 

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 

Payload (lb)

Range (nmi)

SUGAR Free Refined SUGAR SUGAR High SUGAR Volt SUGAR Ray

Figure 6.20 – Sized Baseline Configuration Payload-Range 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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7.0 – Technology Roadmaps and Risk Assessment 

The technology suites generated previously for each configuration were used as the starting point 

for this assessment. These technology tables are in Section 4.0. A comprehensive list containing 

approximately 75 technologies was generated from these technology tables (Figure 7.1). These 

technologies were then grouped into 26 technology groups for sensitivity analysis, ranking, and 

roadmapping. 

Propulsion 

Technology 

Summary

See SUGAR High

SUGAR High Mat’ls

+ lightweight 

magnetics & ferrites, 

SiC MOSFET

Next-gen TAPS See SUGAR High

Refined SUGAR Techs. + additional advanced passive treatments, 

active noise control/fluidics, non-axisymmetric nozzles, others (as 

needed)

High DN Bearings, hot 

section rim seals

Refined SUGAR Mat’ls

+ Advanced CMC

materials & processes

See SUGAR High

Battery Gas Turbine 

Hybrid (SUGAR 

High tech level)

Active purge control, additional advanced systems (as needed)

Next-gen TAPS

Advanced liner mat’ls, 

Blade & OGV 

optimization

Acoustic Conventional

Mechanical Conventional

Advanced PMCs, TiAl, 

High-temp turbine disk 

material and process,

Advanced shaft mat’l,

CMC blades & vanes

Materials Conventional

Combustor Conventional TAPS

Very high bypass ratio 

turbofan with 

advanced engine 

technologies

Very high bypass ratio 

turbofan with 2030 

engine technologies

Engine Cycle CFM56-7B27

‘N+3’

SUGAR Ray

‘N+3’

SUGAR Volt

‘N+3’

SUGAR High

‘N+3’

Refined SUGAR

‘N’

SUGAR 

Free

Configuration

See SUGAR High

SUGAR High Mat’ls

+ lightweight 

magnetics & ferrites, 

SiC MOSFET

Next-gen TAPS See SUGAR High

Refined SUGAR Techs. + additional advanced passive treatments, 

active noise control/fluidics, non-axisymmetric nozzles, others (as 

needed)

High DN Bearings, hot 

section rim seals

Refined SUGAR Mat’ls

+ Advanced CMC

materials & processes

See SUGAR High

Battery Gas Turbine 

Hybrid (SUGAR 

High tech level)

Active purge control, additional advanced systems (as needed)

Next-gen TAPS

Advanced liner mat’ls, 

Blade & OGV 

optimization

Acoustic Conventional

Mechanical Conventional

Advanced PMCs, TiAl, 

High-temp turbine disk 

material and process,

Advanced shaft mat’l,

CMC blades & vanes

Materials Conventional

Combustor Conventional TAPS

Very high bypass ratio 

turbofan with 

advanced engine 

technologies

Very high bypass ratio 

turbofan with 2030 

engine technologies

Engine Cycle CFM56-7B27

‘N+3’

SUGAR Ray

‘N+3’

SUGAR Volt

‘N+3’

SUGAR High

‘N+3’

Refined SUGAR

‘N’

SUGAR 

Free

Configuration

Propulsion Technology Areas

Lightweight Wing Folds,

Adv. Material Forms,

Adv. Non-Circular Fuse.

Enable Lightweight Materials, Energy Harvesting, Thermal Management, Drag 

Reduction

Conformal, Gapless, Adaptive, Spanwise Load Control

Maximize Flight Control Integration,

Active/Passive Aeroelastic Response for Load Control

Design & Criteria Deterministic Reliability Based, Robust/Unitized, Multi-Functional Structures, Support for NLF

Lightweight Wing Folds,

Adv. Lightweight High Lift 

Systems,

Adv. Material Forms

Environmentally 

Compliant 

Manufacturing,

Struct. Integrated 

Systems (Wiring)

None

Additional 

Structures 

Technologies

Interiors Standard More Lightweight

Conventional 

Paint and 

Corrosion Prev.

Coatings

Structurally Integrated Thermal and Electrical Energy Management No Structural 

Integration Energy Management

Conventional Adaptive Structures 

for Control Systems

None Loads & 

Environments

Health Management None On-Board On-board Structurally Integrated SHM, Advanced NDE/NDI

Aluminum Adv. Composites incl. Hybrid Polymer, Adv. Metals, Adv. Joining, Adv. Ceramics Materials / 

Manufacturing

‘N+3’

SUGAR Ray

‘N+3’

SUGAR Volt

‘N+3’

SUGAR High

‘N+3’

Refined SUGAR

‘N’

SUGAR Free

Configuration

Lightweight Wing Folds,

Adv. Material Forms,

Adv. Non-Circular Fuse.

Enable Lightweight Materials, Energy Harvesting, Thermal Management, Drag 

Reduction

Conformal, Gapless, Adaptive, Spanwise Load Control

Maximize Flight Control Integration,

Active/Passive Aeroelastic Response for Load Control

Design & Criteria Deterministic Reliability Based, Robust/Unitized, Multi-Functional Structures, Support for NLF

Lightweight Wing Folds,

Adv. Lightweight High Lift 

Systems,

Adv. Material Forms

Environmentally 

Compliant 

Manufacturing,

Struct. Integrated 

Systems (Wiring)

None

Additional 

Structures 

Technologies

Interiors Standard More Lightweight

Conventional 

Paint and 

Corrosion Prev.

Coatings

Structurally Integrated Thermal and Electrical Energy Management No Structural 

Integration Energy Management

Conventional Adaptive Structures 

for Control Systems

None Loads & 

Environments

Health Management None On-Board On-board Structurally Integrated SHM, Advanced NDE/NDI

Aluminum Adv. Composites incl. Hybrid Polymer, Adv. Metals, Adv. Joining, Adv. Ceramics Materials / 

Manufacturing

‘N+3’

SUGAR Ray

‘N+3’

SUGAR Volt

‘N+3’

SUGAR High

‘N+3’

Refined SUGAR

‘N’

SUGAR Free

Configuration

Structures Technology Areas Structures 

Technologies 

Summary

Subsystems 

Technologies 

Summary

Copper w/ Current 

Return Networks High Conductivity, Lightweight

Power Generation Eng. Primary; APU Gnd. & Bkup.

Flight Avionics Conventional NextGen ATM Capable

Conventional More Tolerant Systems & Dual Use Structure Electro Magnetic 

Effects / Lightning

Computing Networks None Integrated

Wiring Copper

Fuel Jet-A Low Sulfur Jet-A & Drop in Synthetic or Biofuels

Thermal Technology Conventional Lightweight

Control Architecture Cable / Pulley Maximize Use of Fiberoptics

Actuators Hydraulic Hydraulic & EMA EMA

APU Conventional Conventional or Diesel

Power Management Conventional Adaptive

‘N+3’

SUGAR Ray

‘N+3’

SUGAR Volt

‘N+3’

SUGAR High

‘N+3’

Refined SUGAR

‘N’

SUGAR Free

Configuration

Copper w/ Current 

Return Networks High Conductivity, Lightweight

Power Generation Eng. Primary; APU Gnd. & Bkup.

Flight Avionics Conventional NextGen ATM Capable

Conventional More Tolerant Systems & Dual Use Structure Electro Magnetic 

Effects / Lightning

Computing Networks None Integrated

Wiring Copper

Fuel Jet-A Low Sulfur Jet-A & Drop in Synthetic or Biofuels

Thermal Technology Conventional Lightweight

Control Architecture Cable / Pulley Maximize Use of Fiberoptics

Actuators Hydraulic Hydraulic & EMA EMA

APU Conventional Conventional or Diesel

Power Management Conventional Adaptive

‘N+3’

SUGAR Ray

‘N+3’

SUGAR Volt

‘N+3’

SUGAR High

‘N+3’

Refined SUGAR

‘N’

SUGAR Free

Configuration

Subsystem Technology Areas

Aero 

Technologies 

Summary

Low Interference 

Nacelles 

Airframe Noise 

Shielding

Low Interference Nacelles

Low Drag Strut Integration

Advanced Supercritical

Fuselage and Wing Where Appropriate

Relaxed Static Stability & Increased CLMax for reduced Size Conventional 

Size Empennage

None Additional 

Technologies

Airfoil Technology Supercritical Supercritical

Multi-Functional Structures,

Reduced Fasteners,

Reduced Flap Fairings

Excrescence Drag Conventional

Riblets None Fuselage

Laminar Flow None Passive/Natural and Active Where Appropriate

‘N+3’

SUGAR Ray

‘N+3’

SUGAR Volt

‘N+3’

SUGAR High

‘N+3’

Refined SUGAR

‘N’

SUGAR Free

Configuration

Low Interference 

Nacelles 

Airframe Noise 

Shielding

Low Interference Nacelles

Low Drag Strut Integration

Advanced Supercritical

Fuselage and Wing Where Appropriate

Relaxed Static Stability & Increased CLMax for reduced Size Conventional 

Size Empennage

None Additional 

Technologies

Airfoil Technology Supercritical Supercritical

Multi-Functional Structures,

Reduced Fasteners,

Reduced Flap Fairings

Excrescence Drag Conventional

Riblets None Fuselage

Laminar Flow None Passive/Natural and Active Where Appropriate

‘N+3’

SUGAR Ray

‘N+3’

SUGAR Volt

‘N+3’

SUGAR High

‘N+3’

Refined SUGAR

‘N’

SUGAR Free

Configuration

Aero Technology Areas

Technology

Low sulfur Jet-A, Synthetic or Biofuels 

NextGen ATM Capable 

High Performance Batteries 

 Modular Batteries (Combine with High Performance Batteries)

Natural Laminar Flow 

 Active Laminar Flow

 Support for NLF (combine with aero Natural Laminar Flow)

Fuselage Riblets 

 Wing Riblets (Combine with Fuselage Riblets)

Relaxed Static Stability & Increased CLMax Empennage 

Advanced Supercritical Airfoil 

Low Interference Nacelles 

Low Drag Strut 

Airframe Noise Shielding 

Active/Passive Aeroelastic Response for Load Control 

 Spanwise Load Control

 

Lightweight Wing Folds 

Adv. Lightweight High Lift Systems 

Very high bypass ratio turbofan with 2030 engine technologies 

Very high bypass ratio turbofan with advanced engine tech. 

Battery Gas Turbine Hybrid (SUGAR High tech level) 

TAPS 

 Next Gen TAPS (Combine with TAPS)

Additional advanced passive engine treatments 

Active engine noise control/fluidics 

Bundle together advanced material technologies 

 Enable Lightweight Materials Coatings

 Energy Harvesting Coatings

 Thermal Management Coatings

 More Lightweight Interiors

 Environmentally Compliant Manufacturing

 Adv. Composites incl. Hybrid Polymer

 Adv. Metals

 Adv. Ceramics

 Drag Reduction Coatings

Bundle together advanced structures technologies 

 Reduced Fasteners

 Reduced Flap Fairings

 Reliability Based Design

 Robust/Unitized

 Conformal, Gapless, Adaptive Structures

 Adv. Joining

 On-board Structurally Integrated SHM, Advanced NDE/NDI

 Maximize Flight Control Integration

 Adv. Material Forms 

 Adv. Noncircular Fuselage 

Bundle together advanced engine materials 

Bundle together advanced subsystem technologies 

 Adaptive Power Management

 Diesel APU

 EMA Actuators

 Fiberoptic Control Architecture

 Lightweight Thermal Techngology

 High Conductivity, Lightweight Wiring

 Integrated Computing Networks

Open Fan 

Bundle Together Multifunction Structures Technologies 

 Multi-Functional Structures with subsystems

 Multi-Functional Subsystems with structures

 Structurally Integrated Thermal and Electrical Energy Management

 More Tolerant Systems & Dual Use Structure

 Struct. Integrated Systems (Wiring)

 Copper Wiring w/ Current return networks 

Airframe Acoustic Technologies 

Technology Risk ID

Low sulfur Jet-A, Synthetic or Biofuels 1

NextGen ATM Capable 2

High Performance Modular Batteries 3

Natural Laminar Flow 4

Fuselage & Wing Riblets 5

Relaxed Static Stability & Increased CLMax Empennage 6

Advanced Supercritical Airfoil 7

Low Interference Nacelles 8

Low Drag Strut (no interference, laminar flow in NLF) 9

Airframe Noise Shielding 10

Active/Passive Aeroelastic Response for Load Control 11

Lightweight Wing Folds 12

Adv. Lightweight High Lift Systems 13

Very high bypass ratio turbofan with 2030 engine technologies 14

Very high bypass ratio turbofan with advanced engine tech. 15

Battery Gas Turbine Hybrid (SUGAR High tech level) 16

TAPS & Next Generation TAPS 17

Additional advanced passive treatments 18

Active noise control/fluidics 19

Bundle together advanced material technologies 20

Bundle together advanced structures technologies 21

Bundle together advanced engine materials 22

Bundle together advanced subsystem technologies 23

Open Fan 24

Bundle together multi-functional structures technologies 25

Airframe acoustic technologies 26

Comprehensive list 

developed from 

technology tables

26 

Technology 

groups 

created for 

roadmapping

Figure 7.1 – Generation of Technology Groups 

After preparation of these technology lists and groups, and an initial assessment, a virtual 

Technology Workshop was held with all members of the SUGAR team. At this workshop, the 

team accelerated the generation of inputs and validated results to support the technology risk 

assessment and roadmapping process. The risk assessment results are documented here. This 

information was used as a starting point for the generation of the technology roadmaps. 

7.1 – Technology Ranking 

Technology impacts were obtained through either the direct modeling of the technologies on the 

vehicles or sensitivity analysis of certain parameters which they affect. At the top level each 

technology is scored against how much improvement of each NASA goal it produces and then 

these impacts are rolled up to a total value based on weightings for each of the goals. It should be 

noted that these rankings do not capture the compounded effect of synergistic technologies, as 

the sensitivity of each goal to each technology was evaluated independently. All the information 

was compiled into a front end dashboard tool which allowed for dynamic tradeoffs to occur and 

be visualized. 

The dashboard allows for goal weighting tradeoffs to be made and the impacts on the technology 

ranking to be assessed in real time. The layout shows several pieces of information which are 

highlighted in Figure 7.2. The top left corner contains the concept selection and goal weightings 

where the user can determine which technologies to assess and how much priority to assign to 

each of the goals in the calculation of the overall score. The majority of the screen is dominated 

by the technology ranking itself where each tech is listed in order based on its impact to the 
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goals. If a Technology is not applicable to the concept selected or has no impact on the goals 

then it is hidden from view. Next to the rankings the graphs depict the overall score of the 

technologies based on the goal weightings as well as the individual goal contribution that each 

provides. The plot in the lower left hand corner shows the risk of the technologies which appear 

in the ranking with the size of the bubble indicating how many technologies have the associated 

likelihood and consequence value. 

Figure 7.2 – Technology Ranking Dashboard Layout 

This dashboard was utilized to create the following technology ranking figures. For the purpose 

of the final report the technologies were ranked for each aircraft using a variety of weightings: 

equal weighting, fuel burn only, cruise emissions only, NOx only, and noise only (Figure 7.3 – 

Figure 7.22). 

A wide range of technologies contribute to the fuel burn reduction goal. The highest ranking fuel 

burn technologies are the Next Generation Air Traffic Management System, laminar flow, and 

engine technologies. However, 10-15 technologies make significant contributions. For cruise 

greenhouse gas emissions, biofuels and the Next Generation Air Traffic Management System 

have the highest rankings. TAPS & next generation TAPS combustor technologies are key to 

reducing LTO NOx. Finally, engine and airframe noise technologies, as well as airframe 

shielding, are critical to the NASA noise goal. 
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Figure 7.3 – Refined SUGAR Technology Ranking with Equal Goal Weighting 

Figure 7.4 – Refined SUGAR Technology Ranking for Fuel Burn Goal 

Figure 7.5 – Refined SUGAR Technology Ranking for Cruise Emissions Goal 
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Figure 7.6 – Refined SUGAR Technology Ranking for NOx Reduction Goal 

Figure 7.7 – Refined SUGAR Technology Ranking for Noise Reduction Goal 

Figure 7.8 – SUGAR High Technology Ranking with Equal Goal Weighting 
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Figure 7.9 – SUGAR High Technology Ranking for Fuel Burn Goal 

Figure 7.10 – SUGAR High Technology Ranking for Cruise Emissions Goal 

Figure 7.11 – SUGAR High Technology Ranking for NOx Reduction Goal 
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Figure 7.12 – SUGAR High Technology Ranking for Noise Reduction Goal 

Figure 7.13 – SUGAR Volt Technology Ranking with Equal Goal Weighting 

1 0000

1 0000

0 0000

0 0010

0 0000

0 0000

% 0 0000

% 0 0000

% 0 0000

db 0 0000

0 0000

0 0000

0 0000

0 0000

0 0000

0 0000

0 0000

0 0010

0 0100

‐0 ‐0 ‐000

‐0 ‐0 ‐000

‐0 ‐0 ‐000

‐0 ‐0 ‐000

‐0 ‐0 ‐000

0 0000

0 0000

Concept

Cruise Emm. Nox Noise

‐3 NextGen ATM Capable

Natural Laminar Flow

Technology Score

Contribution to NASA Goal

Fuel Burn

Goal

0

Rank 

Importance Value

NASA Goals

‐4

‐4

‐70

‐70

‐75

‐40

2

1

9

10

6

5

4

SUGAR Volt 3

Noise

NoX

Cruise Emissions

Fuel Burn 1

0

0

8

7

11

12

13

14

25

26

3

‐3

‐3

‐3

‐3

‐3

17

18

‐4

‐4

23

24

19

20

21

22

15

16

‐4

‐4

‐4

‐4

‐3

16

0

10

‐4

‐4

16

16

0

Lightweight Wing Folds

Open Fan

0 Airframe Noise Shielding

0

Very high bypass ratio turbofan with advanced engine tech.

Fuselage & Wing Riblets

Bundle together advanced subsystem technologies

Active/Passive Aeroelastic Response for Load Control

Bundle together multi‐functional structures technologies

Low Interference Nacelles

Active noise control/fluidics

Low sulfur Jet‐A, Synthetic or Biofuels

Bundle together advanced structures technologies

Additional advanced passive treatments

Airframe acoustic technologies

Very high bypass ratio turbofan with 2030 engine technologies

Battery Gas Turbine Hybrid (SUGAR High tech level)

High Performance Modular Batteries

TAPS & Next Generation TAPS

Relaxed Static Stability & Increased CLMax Empennage

Low Drag Strut (no interference,  laminar flow in NLF)

Bundle together advanced engine materials

Bundle together advanced material technologies

Advanced Supercritical Airfoil

Adv. Lightweight High Lift Systems

2

1

2

2 5

3

3

1

2

1

1

1

0

1

2

3

4

5

6

0123456

Likelihood

Consequence

Figure 7.14 – SUGAR Volt Technology Ranking for Fuel Burn Goal 
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Figure 7.15 – SUGAR Volt Technology Ranking for Cruise Emissions Goal 

Figure 7.16 – SUGAR Volt Technology Ranking for NOx Reduction Goal 

Figure 7.17 – SUGAR Volt Technology Ranking for Noise Reduction Goal 
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Figure 7.18 – SUGAR Ray Technology Ranking with Equal Goal Weighting 

Figure 7.19 – SUGAR Ray Technology Ranking for Fuel Burn Reduction 

Figure 7.20 – SUGAR Ray Technology Ranking for Cruise Emissions 
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Figure 7.21 – SUGAR Ray Technology Ranking for NOx Reduction Goal 

Figure 7.22 – SUGAR Ray Technology Ranking for Noise Reduction Goal 
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7.2 – Technology Risk Assessment 

7.2.1 – Candidate Technologies 

Table 7.1 shows a list of the candidate technologies and their application to each of the candidate 

concept airplanes. The 26 items listed are consolidated from the original list of 75, combined by 

logical grouping, and organized to allow a quantitative ranking of impact on each configuration. 

Table 7.1 – Candidate Technologies by Concept 

Technology Risk ID SUGAR 

Free

Refined 

SUGAR

SUGAR 

High

SUGAR 

Volt

SUGAR 

Ray

Low sulfur Jet-A, Synthetic or Biofuels 1 - X X X X

NextGen ATM Capable 2 - X X X X

High Performance Modular Batteries 3 - X

Natural Laminar Flow 4 - X X X X

Fuselage & Wing Riblets 5 - X X X X

Relaxed Static Stability & Increased CLMax Empennage 6 - X X X X

Advanced Supercritical Airfoil 7 - X X

Low Interference Nacelles 8 - X X X

Low Drag Strut (no interference, laminar flow in NLF) 9 - X X

Airframe Noise Shielding 10 - X

Active/Passive Aeroelastic Response for Load Control 11 - X X X X

Lightweight Wing Folds 12 - X X X

Adv. Lightweight High Lift Systems 13 - X X

Very high bypass ratio turbofan with 2030 engine technologies 14 - X X X X

Very high bypass ratio turbofan with advanced engine tech. 15 - X X X

Battery Gas Turbine Hybrid (SUGAR High tech level) 16 - X

TAPS & Next Generation TAPS 17 - X X X X

Additional advanced passive treatments 18 - X X X

Active noise control/fluidics 19 - X X X

Bundle together advanced material technologies 20 - X X X X

Bundle together advanced structures technologies 21 - X X X X

Bundle together advanced engine materials 22 - X X X X

Bundle together advanced subsystem technologies 23 - X X X X

Open Fan 24 - X X

Bundle together multi-functional structures technologies 25 - X X X X

Airframe acoustic technologies 26 X X X X

SUGAR Concepts

Table 7.2 shows the applicability of the candidate technologies by NASA N+3 goal. Note that 

there are few areas in which a range is quoted because the technology has a stronger influence on 

some concepts than others. In general, cruise emission impact is directly related to fuel burn, but 

in the case of biofuels, the effective impact on cruise CO2 is substantial, although fuel burn per 

seat is unchanged. It is apparent that most technologies are aimed at fuel burn reduction, several 

at noise and relatively few are targeted at landing and takeoff NOx and takeoff field length. 
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Table 7.2 – Candidate Technologies by NASA N+3 goal 

Technology Risk ID Fuel Burn LTO Nox Noise TOFL Cruise 

Emissions

Low sulfur Jet-A, Synthetic or Biofuels 1 Low-Med

High (biofuels 

only)

NextGen ATM Capable 2 High High

High Performance Modular Batteries 3 High Med Med Low High

Natural Laminar Flow 4 High High

Fuselage & Wing Riblets 5 Med Med

Relaxed Static Stability & Increased CLMax Empennage 6 Med Med

Advanced Supercritical Airfoil 7 Med Med

Low Interference Nacelles 8 Med Med

Low Drag Strut (no interference, laminar flow in NLF) 9 Med Med

Airframe Noise Shielding 10 High

Active/Passive Aeroelastic Response for Load Control 11 High-Med

Lightweight Wing Folds 12 Low Low

Adv. Lightweight High Lift Systems 13 Low Med High Low

Very high bypass ratio turbofan with 2030 engine technologies 14 High High High High

Very high bypass ratio turbofan with advanced engine tech. 15 High High High High

Battery Gas Turbine Hybrid (SUGAR High tech level) 16 High High

TAPS & Next Generation TAPS 17 Med High Med

Additional advanced passive treatments 18 High

Active noise control/fluidics 19 High

Bundle together advanced material technologies 20 High High

Bundle together advanced structures technologies 21 High High

Bundle together advanced engine materials 22 High High

Bundle together advanced subsystem technologies 23 High High

Open Fan 24 High -Med HIgh

Bundle together multi-functional structures technologies 25 High High

Airframe acoustic technologies 26 Med

NASA N+3 Goals

7.2.2 – TRL Assessment 

An initial assessment of Technology Readiness Level (TRL) is shown in Table 7.3. A range of 

values is shown in some cases, especially for the bundled technologies. These TRLs will be 

refined and developed further in the roadmapping exercise. 
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Table 7.3 – Estimated TRL 

Technology Risk ID Current TRL 

Level

Low sulfur Jet-A, Synthetic or Biofuels 1 8=syn 6=bio

NextGen ATM Capable 2 6+

High Performance Modular Batteries 3 2

Natural Laminar Flow 4 5

Fuselage & Wing Riblets 5 5

Relaxed Static Stability & Increased CLMax Empennage 6 4

Advanced Supercritical Airfoil 7 4

Low Interference Nacelles 8 3

Low Drag Strut (no interference, laminar flow in NLF) 9 2 to 3

Airframe Noise Shielding 10 4

Active/Passive Aeroelastic Response for Load Control 11 4

Lightweight Wing Folds 12 3

Adv. Lightweight High Lift Systems 13 3

Very high bypass ratio turbofan with 2030 engine technologies 14 3

Very high bypass ratio turbofan with advanced engine tech. 15 2

Battery Gas Turbine Hybrid (SUGAR High tech level) 16 1

TAPS & Next Generation TAPS 17 3

Additional advanced passive treatments 18 3

Active noise control/fluidics 19 2

Bundle together advanced material technologies 20 4

Bundle together advanced structures technologies 21 3 to 5

Bundle together advanced engine materials 22 2

Bundle together advanced subsystem technologies 23 2 to 5

Open Fan 24 2 to 3

Bundle together multi-functional structures technologies 25 2 to 5

Airframe acoustic technologies 26 4

7.2.3 – Risk Assessment 

These risks were then assigned a number from 1 to 5 on a scale of consequence of failure and a 

scale of 1 to 5 on a scale of likelihood of failure. This helps to differentiate the risks, especially 

the medium ones, as some are more “hard fail” (high consequence), but can be low likelihood of 

failure. Others are “soft fail”, in that the consequence of failure is lower, but the likelihood of not 

reaching the full potential is higher. 

Table 7.4 shows the assessment of risk for each of the candidate technology groups. First, the 

technologies were assessed by subject matter experts on a simple High/Medium/Low scale. 

Imbalances between disciplines were addressed and the risk level assessed on a universal scale. 

Risks were assessed primarily for technical impact. For instance, Risk ID 1, Low sulfur Jet A, 

synthetic fuel and biofuels, the technical risk of integrating the fuels into the airplanes is low – 

noted as “X int” in the table, alternative fuels have been demonstrated at a fairly high TRL. The 

risk for synthetics and especially biofuels are being able to produce them in a large enough 

quantity to make an impact. This is more of an economic and political issue than a technical one, 

and is thus beyond the scope of consideration here. 

For most technologies, the risk across the spectrum of airplane concepts is broadly equal. One 

item where this is not the case is risk item 11, Active/Passive Aeroelastic Response for Load 
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Control. In this case, the technology is much more critical to the high aspect ratio, high wing 

concepts, Sugar High and Sugar Volt, so they have been designated with a consequence of 5, 

versus 3 for the other concepts. However, as the technology is reasonably well understood, the 

risk of failure is designated fairly low, at 2. 

Table 7.4 – Candidate Technologies Risk Assessment 

Technology Risk ID High Med Low Consequence 

(1-5) 

Likelihood 

of Failure 

(1-5)

Low sulfur Jet-A, Synthetic or Biofuels 1 X Prod X Int 4 1

NextGen ATM Capable 2 X 4 1

High Performance Modular Batteries 3 X 5 5

Natural Laminar Flow 4 X 5 3

Fuselage & Wing Riblets 5 X 4 3

Relaxed Static Stability & Increased CLMax Empennage 6 X 3 2

Advanced Supercritical Airfoil 7 X 4 2

Low Interference Nacelles 8 X 3 3

Low Drag Strut (no interference, laminar flow in NLF) 9 X 4 3

Airframe Noise Shielding 10 X 3 3

Active/Passive Aeroelastic Response for Load Control 11 X 5 (HV) 3(oth) 2

Lightweight Wing Folds 12 X 3 1

Adv. Lightweight High Lift Systems 13 X 2 3

Very high bypass ratio turbofan with 2030 engine technologies 14 X 3 1

Very high bypass ratio turbofan with advanced engine tech. 15 X 3 3

Battery Gas Turbine Hybrid (SUGAR High tech level) 16 X 5 4

TAPS & Next Generation TAPS 17 X 3 3

Additional advanced passive treatments 18 X 2 3

Active noise control/fluidics 19 X 4 4

Bundle together advanced material technologies 20 X 4 2

Bundle together advanced structures technologies 21 X 4 2

Bundle together advanced engine materials 22 X 4 4

Bundle together advanced subsystem technologies 23 X 4 3

Open Fan 24 X 3 3

Bundle together multi-functional structures technologies 25 X 3 3

Airframe acoustic technologies 26 X 3 3

Technical Risk

Figure 7.23 shows the basic 5x5 risk map that shows how the grid maps to high, moderate and 

low risk. 

1

2

3

4

5

12345

Low

Moderate

High

Consequence

Likelihood

Figure 7.23 – Risk Map 
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7.2.4 – Risk Breakdown by Concept 

Table 7.1 showed how the risks map to the four different concept airplanes and Table 7.4 shows 

the risk levels for the technologies. The following four figures show how the risks map onto the 

risk grid for each concept. Figure 7.24 shows the map for the Refined SUGAR concept. 

1

2

3

4

5

12345

Consequence

Likelihood

•22-Advanced engine materials

•4-Natural Laminar Flow

•5-Fuselage & Wing Riblets

•20-Advanced material technologies

•23-Advanced subsystem technologies

•17-Next Generation TAPS

•25-Multi-function structures technology

•26-Airframe Acoustic Technologies

•21-Advanced structures technologies

•6-Relaxed Static Stability

•1-Alternative Fuels

•2-NextGen ATM Capable

•14-Very high bypass ratio 2030 

turbofan

Figure 7.24 – Risk Map for Refined SUGAR 

Only about half of the technologies apply to this relatively low risk refinement of the basic 

concept. None of the risks rate in the top three categories (5,5; 5,4; 4,5). The only high risk 

technologies are advanced engine materials – a combination of several technologies, and natural 

laminar flow. While the latter has been around for a very long time, the real challenge is making 

it work reliably in an operational environment. 

Figure 7.25 shows the risk map for the SUGAR High concept. It is very similar to that of the 

Refined SUGAR with a few additional risks added. The only additional high risk technology is 

active engine noise control with fluidics. 
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1

2

3

4

5

12345

Consequence

Likelihood

•19-Active engine noise control/fluidics

•22-Advanced engine materials

•4-Natural Laminar Flow

•5-Fuselage & Wing Riblets

•9-Low Drag Strut

•20-Advanced material technologies

•23-Advanced subsystem technologies

•8-Low Interference Nacelles

•15-Very high HBR turbofan with adv 

tech

•17-Next Generation TAPS

•24-Open Fan

•25-Multi-function structures technology

•26-Airframe Acoustic Technologies

•13-Lightweight High Lift Systems

•18-Additional advanced passive 

treatments

•11-Active/Passive Load Control

•7-Advanced Supercritical Airfoil

•21-Advanced structures technologies

•6-Relaxed Static Stability

•1-Alternative Fuels

•2-NextGen ATM Capable

•12-Lightweight Wing Folds

•14-Very high bypass ratio 2030 

turbofan

Figure 7.25 – Risk Map for SUGAR High 

Figure 7.26 shows the risk map for the SUGAR Volt concept. This includes nearly all of the 

risks, including the highest rated: high performance batteries, and the slightly less risky gas 

turbine/electric hybrid motor. Obtaining batteries with the energy density required to make the 

concept viable is probably the most difficult technology challenge in the portfolio. The concept 

is able to benefit from most of the other technologies too, particularly those found on its “parent” 

aircraft, SUGAR High. 

1

2

3

4

5

12345

Low

Moderate

High

Consequence

Likelihood

•3-High Performance Batteries

•16-Battery Gas Turbine Hybrid

•19-Active engine noise control/fluidics

•22-Advanced engine materials

•4-Natural Laminar Flow

•5-Fuselage & Wing Riblets

•9-Low Drag Strut

•20-Advanced material technologies

•23-Advanced subsystem technologies

•8-Low Interference Nacelles

•15-Very high HBR turbofan with adv 

tech

•17-Next Generation TAPS

•24-Open Fan

•25-Multi-function structures technology

•26-Airframe Acoustic Technologies

•13-Lightweight High Lift Systems

•18-Additional advanced passive 

treatments

•11-Active/Passive Load Control

•7-Advanced Supercritical Airfoil

•21-Advanced structures technologies

•6-Relaxed Static Stability

•1-Alternative Fuels

•2-NextGen ATM Capable

•12-Lightweight Wing Folds

•14-Very high bypass ratio 2030 

turbofan

Figure 7.26 – Risk Map for SUGAR Volt 

Figure 7.27 shows the risk map for the SUGAR Ray concept. The technology list is very similar 

to the SUGAR High concept, with the addition of a medium risk technology of noise shielding. 
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1

2

3

4

5

12345

Consequence

Likelihood

•19-Active engine noise control/fluidics

•22-Advanced engine materials

•4-Natural Laminar Flow

•5-Fuselage & Wing Riblets

•20-Advanced material technologies

•23-Advanced subsystem technologies

•8-Low Interference Nacelles

•10-Airframe Noise Shielding

•15-Very high HBR turbofan with adv 

tech

•17-Next Generation TAPS

•25-Multi-function structures technology

•26-Airframe Acoustic Technologies

•18-Additional advanced passive 

treatments

•21-Advanced structures technologies

•6-Relaxed Static Stability

•1-Alternative Fuels

•12-Lightweight Wing Folds •2-NextGen ATM Capable

•14-Very high bypass ratio 2030 

turbofan

Figure 7.27 – Risk Map for SUGAR Ray 

7.2.5 – Risk Breakdown by Technology Impact 

In this section we show how the risks map by Technology Impact area that map to the N+3 goals 

of Fuel burn (hence also Cruise emissions), Landing and takeoff NOx, Noise and Takeoff field 

length. 

Figure 7.28, the risk map for fuel burn, shows clearly that most of the technologies have an 

impact on fuel burn. Given that, all other things being equal, reduced fuel burn leads to smaller, 

lighter vehicles overall. This impact ripples through to secondary impacts on the other goals. 

The biggest impacts and the biggest risks are propulsion related: advanced engine materials and 

the battery/gas turbine hybrid engine system (including the batteries). Natural laminar flow 

rounds out the high payoff/high risk items. There are ten moderate risk technologies with 

moderate dividends. 

1

2

3

4

5

12345

Consequence

Likelihood

•3-High Performance Batteries

•16-Battery Gas Turbine Hybrid

•22-Advanced engine materials

•4-Natural Laminar Flow

•5-Fuselage & Wing Riblets

•9-Low Drag Strut

•20-Advanced material technologies

•23-Advanced subsystem technologies

•8-Low Interference Nacelles

•15-Very high HBR turbofan with adv 

tech

•17-Next Generation TAPS

•24-Open Fan

•25-Multi-function structures technology

•13-Lightweight High Lift Systems

•11-Active/Passive Load Control

•7-Advanced Supercritical Airfoil

•21-Advanced structures technologies

•6-Relaxed Static Stability

•2-NextGen ATM Capable

•12-Lightweight Wing Folds

•14-Very high bypass ratio 2030 

turbofan

Figure 7.28 – Risk Map for the Fuel Burn Technologies 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Figure 7.29 shows the risk map for Cruise Emissions technologies which adds Alternative Fuels 

in the low technical risk category to the fuel burn map. 

1

2

3

4

5

12345

Low

Moderate

High

Consequence

Likelihood

•3-High Performance Batteries

•16-Battery Gas Turbine Hybrid

•22-Advanced engine materials

•4-Natural Laminar Flow

•5-Fuselage & Wing Riblets

•9-Low Drag Strut

•20-Advanced material technologies

•23-Advanced subsystem technologies

•8-Low Interference Nacelles

•15-Very high HBR turbofan with adv 

tech

•17-Next Generation TAPS

•24-Open Fan

•25-Multi-function structures technology

•13-Lightweight High Lift Systems

•11-Active/Passive Load Control

•7-Advanced Supercritical Airfoil

•21-Advanced structures technologies

•6-Relaxed Static Stability

•1-Alternative Fuels

•2-NextGen ATM Capable

•12-Lightweight Wing Folds

•14-Very high bypass ratio 2030 

turbofan

Figure 7.29 – Risk Map for the Cruise Emissions Technologies 

Figure 7.30 shows the risk map for LTO NOx with a few impacting technologies, all in the 

propulsion field. 

1

2

3

4

5

12345

Consequence

Likelihood

•15-Very high HBR turbofan with adv 

tech

•17-Next Generation TAPS

•1-Alternative Fuels

•14-Very high bypass ratio 2030 

turbofan

Figure 7.30 – Risk Map for the LTO NOx Technologies 

Figure 7.31 shows the risk map for Noise with a few impacting technologies, mostly in the 

propulsion field. Airframe acoustic technologies, airframe noise shielding and lightweight highlift systems are the airframe related technologies that will contribute to noise reduction. 

Note that the Open Fan is included here not because it provides an inherent reduction in noise, 

but because the Open Fan technology package must include design techniques and treatments to 

mitigate the noise characteristics of the counter-rotating fan blade sets. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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1

2

3

4

5

12345

Consequence

Likelihood

•10-Airframe Noise Shielding •19-Active engine noise control/fluidics

•15-Very high HBR turbofan with adv 

tech

•24-Open Fan

•26-Airframe Acoustic Technologies

•13-Lightweight High Lift Systems

•18-Additional advanced passive 

treatments

•14-Very high bypass ratio 2030 

turbofan

Figure 7.31 – Risk Map for the Noise Technologies 

Figure 7.32 shows the risk map for takeoff field length reduction. While some technologies may 

contribute some small effects to improved field performance, only the lightweight high lift 

system technology will contribute directly and primarily to improved field length. 

1

2

3

4

5

12345

Consequence

Likelihood

•13-Lightweight High Lift Systems

Figure 7.32 – Risk Map for the TOFL Technologies 
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7.3 – Technology Roadmapping 

7.3.1 – Next Generation Air Traffic Management 

Goals and Objectives: 

The goal of this project is to integrate avionics components into the aircraft in order to make it 

compatible with the Next generation Air Transportation System (NextGen). This research and 

development plan seeks to increase capacity, reduce delays, and improve safety throughout the 

ATS through technological improvements both on the ground and in the air. 

Performance Area and Impact: 

LTO NOx Substantial Reduction (reduced taxi time) 

Fuel Burn Substantial Reduction (17% for current technology vehicles) 

Cruise Emissions Substantial Reduction (17% for current technology vehicles) 

System Capacity Substantial Increase (increased capacity at airport and increase airports) 

 

Technical Description: 

NextGEN as a program encompasses all the aircraft and ground related improvements that must be 

accomplished in order to realize the benefits to fuel efficiency, capacity and safety. For the purposes of 

this roadmap the technology is limited to the on-aircraft components only. Overall these new concepts 

will impact every phase of flight in some way. Increased situational awareness of other aircraft will 

allow for reduced taxi times. Better aircraft positioning data and route planning will allow for a more fuel 

optimized climb and reduced separation requirements. Better weather detection means that pilots can 

optimize their route in flight to find the compromise in avoiding the weather while still retaining a fuel 

efficient trajectory. Increased communications and optimized planning will allow for better descent 

profiles to save fuel, increase safety, and reduce noise. 

Risk Assessment: 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Current TRL: 

Wake Vortex Detection 6 

Synthetic Vision 4 

Weather Capability 6 

Communications 3 

Collision Avoidance 9 

Navigation 5 

 

Major Milestones: 

Integrate Ground/Air Voice/Data Network 2025 

Wake Detection and Avoidance Protocols 2016 

Aircraft-Aircraft Weather Information Sharing 2019 

Enhanced Vision Systems – Level 3 2017 

Dependency: 

Ground Communications Architecture 

Integrated Route Planning and Optimization 

Airport Operations Improvements 

Success Criteria: 

Table 7.5 – Next Generation Air Traffic Management Success Criteria 

Task 

Number Task Name Success Criteria 

Alternate Steps if 

Unsuccessful 

1 Communications 

Aircraft and ground 

controllers can share 

information and voice 

communications 

simultaneously Current SoA 

2 Navigation 

Ability of the controller to 

accurately predict and control 

the location of aircraft at any 

point in the flight profile Current SoA 

3 Collision Avoidance 

4 Weather Capability 

Aircraft-Aircraft weather 

detection and information 

sharing Current SoA 

5 Wake Vortex Detection 

Aircraft wake prediction 

based off type of aircraft and 

atmospheric conditions allows 

for decreased separation 

distance Current SoA 

6 Synthetic Vision 

 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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IRL Task 2010

3 1 Communications

Avionics - Delegated Separation Digital CommunicationsIntegrated Ground and Air Network for Voice/Data

5 2 Navigation

Trajectory Negotiation - Level 1 CTATrajectory Negotiation - Level 2 En-Route Time-Based MeteringTrajectory Negotiation - Level 3 Automation-Assisted 4DTsTrajectory Negotiation - Level 4 Automated 4DTs

6 3 Collision Avoidance

Airborne Collision Avoidance - Level 2Airborne Collision Avoidance - Level 3Airborne Collision Avoidance - Level 4

5 4 Weather Capability

Aircraft-Aircraft Hazardous Weather Information Sharing

6 5 Wake Vortex Detection

Parameter Driven Aircraft Separation Standards and ProceduresWake Detection/Prediction w/Dynamic Wake Spacing - Level 1 Wake DriftWake Detection/Prediction w/Dynamic Wake Spacing - Level 1 Wake Drift

5 6 Synthetic Vision

Synthetic Vision Systems - Level 2Enhanced Vision Systems - Level 3

2011 2012 2013 2014 2020 202

2015 2016 2017 2018 2019 

TRL=9 I

TRL=9 Initial Availability

TRL=9 Initial Availability TRL=9 Initial Availability

Initial Availability

TRL=9

Initial Availability

TRL=9 Initial Availability

TRL=9 Initial Availability

TRL=9 Initial Availability

TRL=9 Initial Availability

TRL=9 Initial Availability

TRL=9 Initial Availability

TRL=9 Initial Availability

TRL=9 Initial Availability

Figure 7.33 – Next Generation Air Traffic Management Operational Roadmap 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

 1

TRL Task 2010

1 Communications

Applied Research on Integrated Voice/Data and Air/Ground Network Communications

2 Navigation

6 Applied Research on 3D RNAV/RNP Procedures5 Applied Research on a Low Cost INS4 Applied Research on Required Aircraft 4D Intent Data

4 Weather Capability

6 Enhanced Airborne Based Weather Sensors

5 Wake Vortex Detection

6 Dynamic Wake Management for Single Runway Operation6 Advanced Wake Sensing Capabilities

2011 2012 2013 2014 2015 2016 

2017 2018 2019 2020 2

TR

TRL=9

TRL=6 TRL=9

TRL=9

TRL=6

TRL=9

TRL=9

TRL=9

Figure 7.34 – Next Generation Air Traffic Management Technical Roadmap 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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7.3.2 – Alternative Fuels 

Goals and Objectives: 

Develop drop-in replacement alternative fuels with comparable performance to conventional fuel 

and lower life cycle GHG and airport emissions 

Performance Area and Impact: 

LTO NOx Small to Medium Reduction 

Cruise Emissions Substantial Reduction (for biofuels) 

 

Technical Description: 

Fuel Testing (Engine & fuel system components) 

Life Cycle Assessment 

Emissions Testing 

Fuel Testing (Engine System) 

Certification Documentation 

System Changes for Near Drop-In fuels (Alternate) 

Certification of Engine and Aircraft Systems for Near Drop-In fuels (Alternate) 

Low Sulfur Jet-A Implementation (Alternate) 

Risk Assessment: 

1

2

3

4

5

12345

Consequence

Likelihood

X

Current TRL: 

Synthetic Fuel 8 

Biofuel 6 

 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Major Milestones: 

Approval of 50% FT fuel in commercial aircraft 2009 

Approval of 50% HRJ biofuel in commercial aircraft 2010 

Approval of near 100% FT fuel in commercial aircraft 2011 

Approval of near 100% HRJ biofuel in commercial aircraft 2013 

Approval of 50% SPK (generic processes and feedstocks) in commercial aircraft 2014 

Approval of near 100% SPK (generic processes and feedstocks) in commercial aircraft 2015 

USAF 50% Alternative Fuel Use 2015 

Significant Airline Use of Alternative Fuel 2015 

Widespread Airline Use of Renewable Fuels to reduce GHG 2020 

Dependency: 

None 

Success Criteria: 

Table 7.6 – Alternative Fuels Success Criteria 

Task 

Number Task Name Success Criteria 

Alternate Steps if 

Unsuccessful 

1 

Fuel Testing (Engine & 

fuel system 

components) 

Comparable performance and 

compatibility with existing fuel 

and engine systems 

Reduce blend % or initiate 

modification of systems (Task 

6 & 7) 

2 Life Cycle Assessment 

Verifiable reduction in 

lifecycle GHG at competitive 

cost 

Choose sustainable 

feedstock and processes. 

Ultimate fall back is to 

continue to use fossil fuels 

from oil, natural gas, or coal. 

3 Emissions Testing 

Emissions better than existing 

fuels. 

Fall back to conventional 

fuels (Task 8) 

4 

Fuel Testing (Engine 

System) 

Comparable performance and 

compatibility with existing and 

future engines 

Reduce blend % or initiate 

modification of systems (Task 

6 & 7) 

5 

Certification 

Documentation Research report and ballot 

Additional testing or analysis 

to resolve issues 

6 

System Changes for 

Near Drop-In fuels 

(Alternate) 

Compatible system design for 

near drop-in fuels 

Fall back to conventional 

fuels (Task 8) 

7 

Certification of Engine 

and Aircraft Systems for 

Near Drop-In fuels 

(Alternate) 

Verification of compatibility 

and performance 

assumptions 

Fall back to conventional 

fuels (Task 8) 

8 

Low Sulfur Jet-A 

Implementation 

(Alternate) 

Verification of compatibility 

and emissions performance 

9 Feedstock Technologies 

10 

Production 

Technologies 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

 1

TRL Task

Fuel Certification Milestones (Kinder to update)Fuel Usage Milestones

6 1

Fuel Testing (Engine & fuel system components)

HRJ (complete)SPK (generic process)Near 100% blends

2 Life Cycle Assessment

LCA BaselineHRJ LCAHRJ LCA Various FeedstocksSPK LCA Various Processes and Feedstocks

3 Emissions Testing

HRJ (complete)SPK (generic process)Near 100% blends

7 4 Fuel Testing (Engine System)

HRJ (complete)SPK (generic process)Near 100% blends

8 5 Certification Documentation

HRJSPK (generic process)Near 100% blends

7 6

System Changes for Near DropIn fuels (Alternate)

8 7

Certification of Engine and Aircraft Systems for Near DropIn fuels (Alternate)

8 8

Low Sulfur Jet-A Implementation (Alternate)

8 9 Feedstock Technologies8 Tallow3 Halophytes3 Algae6 Non food crops8 10 Production Technologies7 F-T Improvements (CTL/GTL/BTL/CBTL)2 Bacteria / Microbe Hydrocarbon Production3 Alcohol Conversion

2010 2011 2012 2013 2014 2015 

2016 2017 2018 2019 2020 2021

TRL 7

TRL 7

TRL 8

TRL 8

TRL TRL 

TRL 2-8

TRL 2-7

TRL 6

Wide

Use o

by A

50% HRJ ~100% FT ~100% HRJ ~50% SPK ~100% SPK

USAF 50% Alt. Fuel Significant Airline Use of Alt. Fuel

Figure 7.35 – Alternative Fuels Roadmap 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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7.3.3 – Aerodynamic Technologies for Improved Airplane Performance 

Goals and Objectives: 

Develop and Implement Aerodynamic Technologies enabling the design of Airplanes in 2030 

timeframe. These technologies will contribute to the 30% improvement in fuel efficiency relative 

to current fleet. 

Performance Area and Impact: 

Improved Airplane Performance through drag reduction 

Technical Description: 

Aerodynamic technologies have been identified to provide significant improvement toward an Airplane 

in 2030 (N+3) timeframe. 

Laminar flow on any component reduces skin friction drag and pressure drag on the laminarized area. 

Riblets reduces skin friction drag by modifying turbulent structure in the turbulent boundary layer. 

Improve design integration of Nacelles in the presence of wings to reduce interference drag. 

Improve design integration of Strut braced configuration in the presence of wings and body to reduce 

interference drag. 

Reduced static stability reduces trim drag and increased CLmax tail designs reduces tail area and 

weight. 

Wing design to accommodate active/passive aeroelastic response for load control allows tailoring of 

wing spanloads to improve overall mission performance. This technology is shared with Structures. 

Risk Assessment: 

1

2

3

4

5

12345

Consequence

Likelihood

•4-Natural Laminar Flow

•5-Fuselage & Wing Riblets

•8-Low Interference Nacelles

•9-Low Drag Strut

•11-Active/Passive Load Control

•6-Relaxed Static Stability

•7-Advanced Supercritical Airfoil

Current TRL: 

3 to 4 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Major Milestones: 

Natural laminar flow wing design without HLFC systems to achieve a viable configuration. 

Roadmap will address passive/active systems to achieve Aerodynamic goals. Identity system 

benefits for go-no-go. 2020 

Integration of low interference drag struts on high span wing configurations. Improvement in 

interference drag is significant. Identity system benefits for go-no-go. 2020 

Advanced Super-critical wings with improved efficiency. Identify system benefits for go-no-go. 2020 

Design, implement and demonstrate achievable drag improvements of Riblets on fuselage 

and wings. Identity system benefits for go-no-go. 2020 

Integration of low interference drag nacelles on high span wing configurations. Improvement in 

interference drag is significant. Identity system benefits for go-no-go. 2020 

Incorporate aggressive relaxed static stability and improve empennage performance. Identity 

system benefits for go-no-go. 2020 

Collaborate integration of active/passive aeroelastic response for load control. Identity system 

benefits for go-no-go. 2020 

Dependency: 

Configuration Development 

Technologies impact on each other (one technology could prevent another technology from maturing) 

Success Criteria: 

Table 7.7 – Aerodynamic Technologies Success Criteria 

Task 

Number Task Success Criteria 

Alternative steps if 

unsuccessful 

1 Laminar Flow 

Passive LFC 

NLF laminar design matches 

Active LFC 

Achieve 50% of an Active 

LFC laminar Run 

Active LFC 

Achieve Laminar to shocks with 

low power consumption 

Establish break even points 

between 

NLF/Passive/Active 

2 Low Interference Drag 

Struts 

Integrate strut into wing-body for 

only strut parasite drag 

Establish low interference 

levels 

3 

Advanced SuperCritical Wing 

Target 3% airplane drag 

improvement while attaining high 

design lift coefficient 

Achieve 50% of target drag 

improvement 

4 

Riblet Integration 

Target 2% - 3% airplane drag 

improvement 

5 

Low Interference Drag 

Nacelles 

Integrate nacelle/pylon to wing 

body for only nacelle/pylon 

parasite drag 

Establish low interference 

levels 

6 

Relaxed static stability 

Increased CLmax 

Empennage 

Achieve neutral static stability to 

reduce tail size. Improve 

empennage CLmax to reduce tail 

size 

Demonstrate some 

reduction in tail size 

7 

Aeroelastic Load 

Control 

Span load traded for 

Aerodynamics and structural 

efficiencies to improve overall 

mission performance 

Achieve improvement for 

one discipline 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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TRL Task

1 NLF - Maximize Laminarization

 Passive LFC Active LFC

2 Significantly low Interference drag struts on high span wing3 Advanced Super-critical wing design for 20304 Riblets on fuselage and wings

5 Low interference drag nacelles for a highly integrated configuration

6 Relaxed static stablility & increased CLmax Empenage7 Active/Passive aeroelastic response for load control

2011 2012 2013 2014 2020 

2015 2016 2017 2018 2019 

Status Passive HLFC / NLF wing design V

W

Status Interference free strut design V

W

Status Advanced Super-critical wing design V

W

Status Design and applique of Riblets V

W

Status Design low interference drag nacelles V

W

Status Relaxed static stability & Increased CLmax empenage design V

W

Status Active/Passive aeroelatic response for load control design V

W

Design iteration with technologies integrated Designs val

Figure 7.36 – Aerodynamic Technologies Roadmap 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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7.3.4 – Airframe Acoustic Technologies 

Goals and Objectives: 

Develop airplane designs and technologies that reduce airframe noise and increase shielding of 

engine noise, in order to meet future strict noise regulations in airport environments 

Performance Area and Impact: 

Engine noise dominance at take-off (cutback and sideline), and airframe noise dominance at approach 

Impact on Aerodynamics, Propulsion, and Airframe Design 

Technical Description: 

Develop inherently quiet landing gear designs (includes main and nose gear) 

Develop inherently quiet high-lift system designs with good aerodynamic characteristics (includes 

leading and trailing edge devices, and wing trailing edge) 

Develop integrated engine-airframe designs with inherent shielding (includes jet, inlet and aft-fan) 

Develop technologies to reduce landing gear noise, high-lift system noise, jet noise, and aft-fan noise 

Develop technologies to maximize engine noise shielding (includes shielding of jet, inlet, and aft-fan) 

Evaluate and down-select design ideas and technology concepts using the following: (a) acoustics 

integrated into multidisciplinary design, (b) airframe noise and engine noise shielding testing including 

model-scale and full-scale flight tests, and (c) development of tools for acoustic design, analysis, and 

prediction of airframe noise and engine noise shielding 

Risk Assessment: 

1

2

3

4

5

12345

Consequence

Likelihood

X

X

Current TRL: 

Landing Gear 3 

High-Lift System 2 

Source Noise 5 

Noise Shielding 2 

 
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Major Milestones: 

Acoustic design, analysis, and prediction tools (Landing Gear, Shielding, and High-Lift System 

Tools) 2018 

Selection of promising airframe designs and technology concepts for model-scale noise 

testing 2015 

Model-scale acoustic (airframe noise and engine noise shielding) testing for initial 

assessments and candidate down-selection 2015 

Model-scale acoustic (airframe noise and engine noise shielding) testing for optimization and 

final candidate selection 2018 

Selection of best airframe designs and technology concepts for full-scale flight testing 2017 

Full-scale flight testing for final validation and TRL8 assessment of best airframe designs and 

technology concepts 2022 

Dependency: 

Airplane design and development (cross-effect and reaction to engine design, high-lift design and 

airplane performance) 

Facilities for model-scale testing 

Platform (testbed) for full-scale flight testing 

CFD resources 

Success Criteria: 

Table 7.8 – Airframe Acoustic Technologies Success Criteria 

Task Name Success Criteria Alternate Steps if Unsuccessful 

Quiet Landing Gear 

Design 

5 dB reduction in gear noise More testing with alternate concepts or use 

of lowest attained reduction level 

Landing Gear design tool Alternate approach/methodology or use of 

existing gear noise prediction tools 

Advanced Airframe 

and Engine Design 

and Integration for 

Shielding 

Optimization 

5 dB reduction in jet and aftfan noise More testing with alternate concepts or use 

of lowest attained reduction level 

15-20 dB cumulative 

shielding benefit (sum of jet, 

inlet, and aft-fan shielding) 

More testing with alternate concepts or use 

of highest attained shielding benefit 

Shielding design tool Alternate approach/methodology or use of 

existing shielding prediction tools 

Advanced Acoustic 

Design for High-Lift 

Systems 

8-10 dB combined reduction Use of lowest existing high-lift noise levels 

High-Lift System design tool Use of existing noise prediction tools 

Full-Scale Flight 

Testing for Validation 

and Assessment of 

TRL8 

Agreement between modelscale and full-scale results; 

realizing most of the 

expected benefits 

Adjustment/extrapolation of existing data 

Conservative use of model-scale benefits 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

 1

TRL Task 2010

Quiet Landing Gear Design1b) Selection of promising airframe designs and technology concepts for model-scale testing1e) Guidelines for inherently quiet landing gear design1d) Database of results from model-scale gear noise testing2d) Model-scale integrated shielding and inlet and aft-fan noise testing2g) Shielding tool development1g) Landing Gear Tool for acoustic design, analysis, and prediction 

1

Includes: main gear and nose gear1a) Steady State CFD1c) Model-scale gear noise testing1f) Development of Landing Gear tool3a) Integrated aero/acoustic optimization3c) Model-scale high-lift system noise testing3f) High-Lift system design tool development3e) Guidelines for inherently quiet high-lift system designIncludes: jet, inlet, and aft-fan3b) Selection of promising airframe designs and technology concepts for model-scale testing2b) Selection of promising airframe designs and technology concepts for model-scale testing2c) Model-scale integrated shielding and jet noise testingAdvanced Acoustic Design for High-Lift Systems2h) Shielding Tool for acoustic design, analysis, and prediction Includes: leading and trailing edge devices, and wing trailing edge3g) High-Lift System Tool for acoustic design, analysis, and prediction 

2 3

2e) Database of results from model-scale integrated shielding and jet noise testing, and model-scale integrated shielding and inlet and aft-fan noise testing2f) Guidelines for integrated engine-airframe designs with inherent shielding3d) Database of results from model-scale high-lift system noise testing

2

2015 2016 2017 2018 2019

 2 - 5 

3

Advanced Airframe and Engine Design and 

Integration for Shielding Optimization

2a) Integrated aero/acoustic parametric evaluation

2011 2012 2013 2014 2020 

TRL 6

TRL 6

TRL 6

TRL 6

Figure 7.37 – Airframe Acoustic Technology Roadmap (part 1 of 2) 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

 1

TRL Task 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 

4

4n) Flight testing for combined total noise reduction and shielding4g) TRL 8 high jet noise shielding (quiet design and noise reduction technology integration)4a) Selection of best airframe designs and technology concepts for full-scale flight testing (for landing gear, jet, inlet, aft-fan, and high-lift)4e) Flight testing for jet noise reduction and shielding4i) Database of results from full-scale integrated shielding and inlet and aft-fan noise testing4l) Database of results from full-scale high-lift system noise testing4m) TRL8 low noise high-lift system (quiet design and noise reduction technology integration)4f) Database of results from full-scale integrated shielding and jet noise testingFull-Scale Flight Testing for Validation and Assessment of TRL84h) Flight testing for inlet noise and aft-fan noise reduction and shielding4k) Flight testing for high-lift system noise reduction4b) Flight testing for landing gear noise reduction4d) TRL8 low noise landing gear (quiet design and noise reduction technology integration)4c) Database of results from full-scale gear noise testing4j) TRL 8 high inlet and aft-fan noise shielding (quiet design and noise reduction technology integration)

TRL 8TRL 8

TRL 8

Figure 7.38 – Airframe Acoustic Technology Roadmap (part 2 of 2) 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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7.3.5 – Engine Acoustic Technologies 

Goals and Objectives: 

Develop new and innovative designs and methods to reduce propulsion system noise 

Performance Area and Impact: 

Engine Acoustic Properties 

Technical Description: 

Two pronged approach to develop a suite of near-term, mostly passive technologies and far-term 

aggressive suppression technologies 

Risk Assessment: 

1

2

3

4

5

12345

Low

Moderate

High

Consequence

Likelihood

X

X

X

X

Advanced passive sub-bundle of technologies

Aggressive/active noise technology sub-bundle

Passive Technologies: 4 x 4 

Active Technologies: 4 x 5 

Current TRL: 

Engine Acoustic Tech. 3 

 

Major Milestones: 

Overall program: program provides an "onramp" for demo engine test of technology concepts 

every 2 years 

Ongoing design studies / data reduction / methods improvement throughout program 

Phase I - advanced/passive noise treatments full scale tests (typically 2 design/build/test 

iterations), best funding fit with N+2 

Phase II - advanced/active noise treatments subscale/rig design/build/test cycles (3), plus full 

scale design/build/test cycles (2), best funding fir with N+3 

Early thrusts of N+3 acoustic work: 1) sustained work on high-performance bulk absorbers, 2) 

open rotor noise reduction, Basic physics of fluidics and flow control 

Mid-phase thrusts expanded to include Unconventional UHB, soft/active elements, and nonaxisymmetric exhausts 

Far term focus on low noise combustor, shape memory alloy 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Dependency: 

Need dedicated engine asset(s) to use as testbed 

Variable fan nozzle is not shown (appears on advanced engine tech roadmap) 

Notes: 

10-yr sustained development of bulk and tailored absorbers 

Development program utilizes multiple builds of an engine test asset 

Hold pace of 1 engine build and test every 2 years 

Early program focused on full scale demos of incremental/moderate risk concepts 

Early program focused on subscale/rig demos of aggressive and high risk concepts 

Later program focused on full scale demo of aggressive/high risk projects 

Each technology gets 2 build/test cycles (can adjust as needed based on results: most promising 

concepts-->More builds, less promising-->fewer builds) 

Continuous effort to incorporate results into methods and design practices 

Variable fan nozzle is not shown (appears on advanced engine tech roadmap) 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

 1

TRL 2010

Passive noise absorbers--enabling materials

3 Bulk absorber materials program3 2DOF and tailored absorbers

Advanced passive noise supression investigations

3 Advanced inlet/cold section treatments3 Advanced core and fan nozzle treatments3 Inlet lip treatments3 Improved design methods, tailored cutoff3 Advanced blade and OGV optimization3

Aggressive/active noise supressiontechnology investigations

2 Open rotor noise reduction (design for noise)2 Unconventional UHB installations2 Nonaxisymmetric shapes/inserts2 Soft/active primary flowpath elements2 Fluidics & Flow Control2 Low noise combustor2 Shape memory alloy components

Data reduction/design studies/Methods ImprovementsFull scale integrated engine demo

Demo design & integrationDemo component fab & assembly

6+ Demo test

2011 2013 2014 2015 2016 2012 2017 2018 2019 2020 2021 2022 2023 

Full scale 1 Full scale 2 N+1 / N+2 

programfocus

N+2 / N+3 programfocus

Full scale 1 Full scale 2

Full scale 1 Full scale 2

Full scale 1 Full scale 2

Full scale 1 Full scale 2

Full scale 1 Full scale 2

Full scale 1 Full scale 2

Full scale 1 Full 

Full scale 3 Subscale/rig 1 Subscale/rig 2 Subscale/rig 3 Subscale/rig 4

Subscale/rig 1 Subscale/rig 2 Subscale/rig 3

Subscale/rig 1 Subscale/rig 2 Subscale/rig 3

Subscale/rig 1 Subscale/rig 2 Subscale/rig 3

Proof-of-concept Subscale/rig 1 Subscale/rig 2 Subscale/rig 3

Ph 0 Ph Ia Ph Ib Ph Ic Ph Id

Ph IIa Ph IIb 

Figure 7.39 – Engine Acoustic Technology Roadmap* 

* The roadmap schedule shown is notional, suitable for overall program planning purposes only, with no implied guarantee 

part of GE Aviation 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

 168 

7.3.6 – Advanced Subsystems 

Goals and Objectives: 

Significantly improve weight and reliability of aircraft subsystems 

Performance Area and Impact: 

Reduced airplane weight, improved system reliability 

Technical Description: 

Adaptive Power Management 

Diesel APU 

EMA Actuators 

Fiberoptic Control Architecture 

Lightweight Thermal Technology 

Integrated Computing Networks 

Risk Assessment: 

1

2

3

4

5

12345

Consequence

Likelihood

X

X

Current TRL: 

2 to 4 

Major Milestones: 

Diesel APU certification 2017 

Fiberoptic control system certification 2017 

Integrated computing network 3.0 certification 2018 

Adaptive power management system certification 2019 

Lightweight thermal technology certification 2020 

EMA Actuators Flight Demo 2021 

Integrated computing network 4.0 certification 2026 

Dependency: 

Integrated Airplane Systems Architecture 
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Success Criteria: 

Table 7.9 – Advanced Subsystems Success Criteria 

Task 

Number Task Name Success 

Criteria 

Alternate Steps if 

Unsuccessful 

1 Adaptive Power Management Certification Revert to current SOA 

2 Diesel APU Certification Revert to advanced turboshaft 

APU 

3 EMA Actuators Certification Revert to current SOA 

4 Fiberoptic Control Architecture Certification Revert to current SOA 

5 Lightweight Thermal Technology Certification Revert to current SOA 

6 Integrated Computing Networks -

Generation 3.0 Certification Revert to current SOA 

7 Integrated Computing Networks -

Generation 4.0 Certification Revert to generation 3.0 

architecture 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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TRL Task 2010

1 Adaptive Power Management 

3 1.1 Intelligent Energy Management Architecture4 1.2 Adaptive Load Management Models and Simulators5 1.3 Intelligent components 5 1.4 Self-powered passenger control units 5 1.5 Self-powered wireless sensors 6 1.6 High Power Energy Harvesting7 1.7 Prototype Testing and Demonstration8 1.8 Qualification and Certification tests9 1.9 Flight Ready

2 Diesel APU 

4 2.1 Breadboard demo in sub-atmospheric test chamber5 2.2 Ground test of prototype scaled unit6 2.3 Prototype test on the ETD at altitude7 2.4 Beta unit demonstration8 2.5 Qualified through certification tests9 2.6 Flight proven 

3 EMA Actuators 

8 Hybrid Control (Conventional EMA)

9 Integrated Flight Demo (Conventional EMA)

6 High Temp Superconducting (HTS) Motor EMA

7 Integrated HTS Based EMA Ground Demo

9 Integrated HTS Based EMA Flight Demo

4 Fiberoptic Control Architecture 

2 4.2 Technology Concept and/or Application formulated

3 4.3 Analytical and Experimental Critical Function and/or Characteristic Proof‐of‐Concept

4 4.4 Component and/or Breadboard Validation in Laboratory Environment 5 4.5 Component and/or Breadboard Validation in Relevant Environment6 4.6 System/Subsystem Model or Prototype Demonstration in a Relevant Environment7 4.7 System Prototype Demonstration in Target Environment 8 4.8 System Completed & Flight Qualified through Test and Demonstration9 4.9 System Flight Proven through Successful Operation 

2011 2012 2013 2014 2020 2021 

2015 2016 2017 2018 2019 2

TRL 9

TRL 9

T

TRL 4 TRL 5 TRL 6

TRL 7 TRL 8

TRL 4

TRL 5

TRL 6

TRL 7

TRL 8 Diesel 

APU

TRL 3

TRL 4

TRL 6

TRL 7

TRL 8

Figure 7.40 – Advanced Subsystems Roadmap (part 1 of 2) 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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TRL Task 2010

5 Lightweight Thermal Technology 

3 5.1 Integrated Dynamic Models4 5.2 Total Energy Management Models5 5.3 Integrated Power /Thermal/EMI Dynamic Models6 5.4 Total Energy Management Lab Integration7 5.5 Prototype Testing and Demonstration8 5.6 Certification9 5.7 Flight Ready

6 Integrated Computing Networks -Generation 3.0

4 6.1 Component and/or Breadboard Validation in Laboratory Environment 5 6.2 Component and/or Breadboard Validation in Relevant Environment6 6.3 System/Subsystem Model or Prototype Demonstration in a Relevant Environment7 6.4 System Prototype Demonstration in Target Environment 8 6.5 System Completed & Flight Qualified through Test and Demonstration9 6.6 System Flight Proven through Successful Operation 

7 Integrated Computing Networks -Generation 4.0

2 7.1 Technology Concept and/or Application formulated

3 7.2 Analytical and Experimental Critical Function and/or Characteristic Proof‐of‐Concept

4 7.3 Component and/or Breadboard Validation in Laboratory Environment 5 7.4 Component and/or Breadboard Validation in Relevant Environment6 7.5 System/Subsystem Model or Prototype Demonstration in a Relevant Environment7 7.6 System Prototype Demonstration in Target Environment 8 7.7 System Completed & Flight Qualified through Test and Demonstration9 7.8 System Flight Proven through Successful Operation 

2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2

TRL 8

TRL 7

TRL 6

TRL 5

TRL 4

TRL 3

Figure 7.41 – Advanced Subsystems Roadmap (part 2 of 2) 
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7.3.7 – Structural Materials 

Goals and Objectives: 

Implement advanced materials with greatly improved properties are needed to support the N+3 

SUGAR configurations. Improved specific strength and specific stiffness are needed to enable 

very thin, very high aspect ratio wings. 

Performance Area and Impact: 

Primary, structural weight (OWE). Secondary, systems components weights (OEW) 

Secondary, support operations of advanced aerodynamics and control technologies to reduce drag and 

reduce noise 

Technical Description: 

Ultra-High-Modulus, Ultra-High-Strength Fibers - Carbon or other fibers that provide significant 

increase in specific strength or specific stiffness for improvement in both strength driven structure such 

as fuselage and lower wing surfaces, and stiffness driven structures such as wing upper surface. Thin 

wing loads, including dynamic loads such as gust and maneuver loads, and aeroelastic considerations 

will dictate to what extent improved strength is needed vs. improved stiffness 

Metal-Matrix Composites - titanium matrix composites to provide lower weight for very high strength 

applications such as landing gear 

Very Tough Composites - Resin systems with greatly reduced susceptibility to impact damage and 

reduced curing temperatures to support lower cost 

Thermoplastic Composites - thermoplastic resin systems support low cost manufacturing 

High-Temperature Polymer Composites - Composite matrix systems capable of sustained operation at 

temperatures above 350F for use near engine and exhaust 

Layer-by-Layer/Multifunctional nanocomposites for structures with integrated sensors and electronics 

to support structural health management and loads monitoring/active control 

Ceramics/CMC Durable ceramic and ceramic matrix composites for elevated temperature load bearing 

structure 

Risk Assessment: 

High-temperature composites

5

4

3

2

1

12345

Consequence

Likelihood

High

Moderate

Low

X

Thermoplastic 

composites

X Advanced Metals

X

Ultra-high-modulus/strength fibers

X

Metal-Matrix Composites

X

X

Ceramic-Matrix Composites

High-temperature composites

5

4

3

2

1

12345

Consequence

Likelihood

5

4

3

2

1

12345

Consequence

Likelihood

High

Moderate

Low

X

Thermoplastic 

composites

X Advanced Metals

X

Ultra-high-modulus/strength fibers

X

Metal-Matrix Composites

X

X

Ceramic-Matrix Composites
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Current TRL: 

2 to 5 

Major Milestones: 

Identify target applications/requirements for enhanced materials 

Identify new material chemistries for development 

Develop and refine processing methods 

Scale-up for manufacturing 

Dependency: 

None 

Success Criteria: 

Table 7.10 – Structural Materials Success Criteria 

Task 

Number Task Name Success Criteria Alternate Steps if Unsuccessful 

1 Ultra High Modulus Ultra 

High Strength Fibers 

Very high aspect ratio wing 

designs not driven by sizing 

for aeroelasticity and 

gust/maneuver loads 

Active control of aeroelastic 

response and loads 

alleviation 

2 Metal Matrix Composites Lightweight landing gear 

structures 

Conventional materials, e.g., 

stainless steel 

3 Very Tough Composites 

Composite structure weight 

not driven by fracture 

toughness 

Structural health 

management/prognosis to 

reduce fracture critical 

structural weight 

4 Thermoplastic Composites Sufficient strength for use in 

loaded secondary structures 

Continued use of thermoset 

composites 

5 High Temperature Polymer 

Composites Use in engine nacelles 

Titanium or high temperature 

aluminum depending on 

application 

6

Layer-by LayerMultifunctional 

Nanocomposites 

Lightweight broad area 

sensing and distributed 

processing 

Higher weight sensors and 

electronics 

7 Ceramics/Ceramic Matrix 

Composites Use in engines and nacelles High temperature metals 

 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Ultra-High-Modulus, Ultra-High-Strength Fibers

Material and process SelectionProcess RefinementScale-up

Metal-Matrix Composites

Identify new, cost effective and robust processing methodsProcess RefinementScale-up

Very Tough Composites

Identify new chemistries and toughening methodsDownselection and validation of new tougheneing approachesProcess RefinementScale-up

Thermoplastic Composites

Identify target applications/requirementsDevelop new material forms and chemistriesProcess RefinementScale-upHigh-Temperature Polymer CompositesIdentify new chemistriesDownselection and validation of new approachesProcess RefinementScale-upLayer-by-Layer/Multifunctional nanocompositesIdentify target applications/requirementsDependent on selected applications

Ceramics/Ceramic-Matrix Composites

Identify new, cost effective and robust processing methodsProcess RefinementScale-up

2010 2011 2012 2013 2014 

2015 2016 2017 2018 2019 2020 

Figure 7.42 – Structural Materials Roadmap 
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7.3.8 – Structural Concepts Roadmap 

Goals and Objectives: 

Implement advanced structural technologies currently under development enabling design, 

fabrication and operation of advanced high performance structural systems without the 

conservatism inherent in current structures. 

Structural designs will include integrated systems functionality which will benefit both airplane 

systems operations as well lighter weight structures. 

Performance Area and Impact: 

Primary, structural weight (OWE). Secondary, systems components weights (OEW) 

Secondary, support operations of advanced aerodynamics and control technologies to reduce drag and 

reduce noise 

Technical Description: 

Reliability based design (RBD) and certification – quantify and actively manage structural design 

conservatism minimize excess weight while increasing airplane structural reliability 

Structural Health Management (SHM) – know and manage the current state of the structures health 

throughout its life cycle 

Advanced design concepts – design optimized structures using new design tools, advanced materials, 

fabrication and maintenance concepts 

Multifunctional structures (MFS) – integrate system functionality into structures to reduce overall 

airplane weight and increase operational reliability through distributed redundancy 

Adaptive structures – highly distributed actuation and sensing will enable airplanes to conformally 

change shape during flight to optimize L/D across a broad 

Risk Assessment: 

5 Reliability Based Design

4

3

2

1

12345

Consequence

Likelihood

High

Moderate

Low

X

Structural Health Management

X

Advanced Structural 

Design Concepts

X

Adaptive Structures

X

Multifunctional Structures

5 Reliability Based Design

4

3

2

1

12345

Consequence

Likelihood

5

4

3

2

1

12345

Consequence

Likelihood

High

Moderate

Low

X

Structural Health Management

X

Advanced Structural 

Design Concepts

X

Adaptive Structures

X

Multifunctional Structures

Current TRL: 

2 to 5 
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Major Milestones: 

Define objective function forms for each of the selected technologies 

Develop a complete objective function form integrating all the selected technologies 

Perform multidisciplinary optimization that maximizes airplane level performance for one or 

more N+3 configurations 

Dependency: 

None 

Success Criteria: 

Table 7.11 – Structural Concepts Success Criteria 

Task 

Number Task Name Success Criteria Alternate Steps if Unsuccessful 

1 RBD Analysis and 

Certification 

Use of probabilistic design 

methods for balanced design 

conservatism 

Use of probabilistic design 

methods for secondary 

structure 

2 Structural Health 

Management 

Broad area monitoring of 

structure 

Loads monitoring and 

structural hot spot detection 

(minimal weight improvement) 

3 Advanced Structural 

Design Concepts 

New structural concepts 

enable reduced weight Conventional design 

4 Multifunctional 

Structures 

Structure with highly 

integrated systems 

functionality 

Limited integration of wiring 

and thermal paths 

5 Adaptive Structures 

Reduced weight and 

complexity of conformal 

control surfaces and high lift 

systems 

Reduce weight and complexity 

of rigid control and high lift 

surfaces 

 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Development of RBD analysis and

certification methods

Define methods and cert. approach

Design study vs. conventional design

Test program for RBD structureRBD certification

Structural Health Management

Develop and demonstrate hot spot monitoring

Demonstrate broad area coverage

Demonstrate probability of detect (PoD)

Demonstrate condition based maintenance

Advanced Structural Design Concepts

MDO analyses examples for N+3 configs.

Multifunctional Structures

Demonstrate structurally integrated apertures (antennas)Demonstrate structurally integrated

power return and EME sheildingDemonstrate direct write technology for signal wiring

Demonstrate structurally integrated thermal management

Demonstrate direct write technology for integrated electronics

Adaptive Structures

Demonstrate low rate, low deformation conformal

shape change for reduced , g noise

shape change for reduced noise and improvedperformanceDemonstrate high rate, low deformation conformalshape change for flow management

Demonstrate high rate, high deformation conformal

shape change for primary flight controlDemonstrate high rate, high deformation conformalshape change for flight performance (aka morphing)

2010 2011 2012 2013 2014 2020 

2015 2016 2017 2018 2019 

Figure 7.43 – Structural Concepts Roadmap 
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7.3.9 – Advanced Engine Technologies 

Goals and Objectives: 

Develop enabling materials and methods for improved component performance 

Performance Area and Impact: 

Noise, Fuel burn, Emissions 

Technical Description: 

Develop propulsion enabling materials, cooling technology and component technology to support 

continued advancements in gas turbine efficiency, weight, and power 

Risk Assessment: 

1

2

3

4

5

12345

Consequence

Likelihood

X

X

Current TRL: 

2 to 5 

Major Milestones: 

Subscale alloy process development 

Full scale alloy development 

Final alloy ready for engine use 

Man tech milestones--TBD 

Test of gen 1, 2, 3 CMC components 

Tests of seals and bearings components 

Tests of variable fan nozzle concepts 

Tests of modulated cooling concepts 

Tests of advanced Active Clearance Control concepts 

Low emissions combustor cup, sector, full annular rig, and demo engine tests 

Overall program: program provides an "onramp" for demo engine test of technology concepts 

every 2 years 

Dependency: 

Need suitable mule engine(s) to use as dedicated engine test asset 

Need a contingency plan for acquiring a backup asset should a catastrophic test failure occur 
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Notes: 

Program centered around multiple fast-paced builds of dedicated engine test vehicle 

3 parallel materials development programs - 10 yr sustained 

2 parallel man. Tech programs - 10 year sustained 

Base engine is off-the-shelf 

Yields TRL6 by 2025 

Program for continuous improvement of low-emissions combustion technology 

PMC = polymer matrix composites 

CMC = ceramic matrix composites 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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TRL 2010

Propulsion enabling materials

3 Next-gen shaft material3 Next-gen hi-temp disk materials3 Next-gen CMC material

Manufacturing Technology

3 PMC manufacturing technology3 CMC manufacturing technology

Ultra-low emisisons combustor

3 Concept design/refinement

Rig tests (cup, sector, FAR)

CMC Hot section Components

4 Uncooled rotating parts des & fab4 Cooled rotating parts des & fab4 Cooled static parts des & fab

Advanced bearings and seals

4 High speed hot section seals des & fab4 High DN bearings design & fab

Variable fan nozzle

Concept 1 design & fabConcept 2 design & fab

Modulated cooling/purge and ACC

4 Modulated blade cooling des & fab4 Modulated purge des & fab4 Rapid response ACC design & fab

Full scale integrated engine demo

Demo design & integrationDemo component fab & assembly

6+ Demo test

2011 2013 2014 2015 2016 2012 2017 2018 2019 2020 2021 2022 20

GEN1 Design

Gen 1

GEN2

GEN1 Design GEN2

GEN1 Design GEN2 GEN3

Ph II

GEN1 Design

Subscale Alloy/ process dev.

GEN3 GEN5

GEN1 Design GEN2 GEN3

GEN1 Design GEN2 

Ph II

Subscale Dev.

Subscale Dev.

Full scale dev

Full scale dev.

Full scale dev.

Final alloy implementation/refinement

Final alloy implementation/refinement

Final material implementation/refinement

TTG3 feasibility TTG6 feasibility

GEN4 GEN6 G

Downselect & Gen 2 design

GEN1 Design GEN2 GEN3

GEN1 Design GEN2 GEN3

GEN2

GEN2

GEN2

TTG9-ready for engine test

Figure 7.44 – Advanced Engine Technologies Roadmap* 

* The roadmap schedule shown is notional, suitable for overall program planning purposes only, with no 

commitment on the part of GE Aviation 
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7.3.10 – Hybrid Engine Technologies 

Goals and Objectives: 

Develop high performance, flight weight, and prime-reliable electric power components suitable 

for flight propulsion applications. 

Performance Area and Impact: 

Noise, Fuel burn, Emissions 

Technical Description: 

Develop high power, light weight motors, controllers, radiators and surface coolers, variable core 

nozzle 

Risk Assessment: 

Current TRL: 

3 

Major Milestones: 

3 motor design, build, test, report-out cycles 

3 surface cooler/radiator design, build, test, report out cycles 

3 motor controller/power electronics design, build, test, report out cycles 

Sustained program for lightweight high voltage conductors and insulators, with off ramps every 

~18 months 

Lightweight variable core exhaust nozzle design, build, test 

Integration into full scale demo engine 

Demo engine test 

Dependency: 

Need suitable off-the-shelf engine asset to support test 
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Notes: 

Sustained base technology program for flight-worthy conductors and insulators 

2 builds for demo engine 

Base engine is off-the-shelf 

Yields TRL6 by 2025 

3.5 design/build/test cycles for motor, motor controller, and associated cooling system hardware 

yields TRL3+ by 2018 

Base engine is off-the-shelf 

Yields TRL6 by 2025 

Assumes battery technology development program separate from this plan 

Ongoing engine design refinement studies 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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TRL Task 2010

1 Lightweight flightworthy high voltage enabling materials

3 1.1 Insulor Materials Program3 1.2 Conductors and Connectors Program3 1.3 Lightweight Magnetics & Support Structure

2-3-4 2 Flight weight, prime-reliabel motor

2.1 Design Modeling & Analysis2.2 Controller Fabrication & Bench Test

2-3-4 3 Motor Controller/Power Electronics

3.1 Design Modeling & Analysis3.2 Controller Fabrication & Bench Test

2-3-4 4 Light weight, low loss cooler/radiator

4.2 Design Modeling & Analysis4.3 Design Fabrication & Bench Test

2-3-4 5 Variable Core Nozzle

5.1 Design Modeling & Analysis5.2 Nozzle Fabrication & Component Tests

6 Engine Design Studies7 Full Scale Demo

7.1 Demo Engine Design & Integration7.2 Demo Build 1 Component Fabrication & Assembly

5 7.3 Demo Build 1 Test

7.4 Demo Build 2 Design & Integration7.5 Demo Build 2 Component Fabrication & Assembly

6 7.6 Demo Build 2 Test

2011 2012 2013 2014 2015 

2016 2017 2018 2019 2020 2021

GEN1 Design

Gen 1 Gen 2 Gen 3

GEN2 GEN3 GEN3.5

GEN1 Test GEN2 Test GEN3 Test

GEN1 Design GEN2 GEN3 GEN3.5

GEN1 Test GEN2 Test GEN3 Test

GEN1 Design GEN2 GEN3 GEN3.5

GEN1 Test GEN3 Test

Ph I Ph II Ph III Ph IV

GEN1 Design

Gen 1 Gen 2 Gen 3

GEN2 GEN3 GEN3.5

GEN1 Test GEN2 Test GEN3 Test

GEN1 Design GEN2 GEN3 GEN3.5

GEN1 Test GEN2 Test GEN3 Test

GEN1 Design GEN2 GEN3 GEN3.5

GEN1 Test GEN3 Test

Ph I Ph II Ph III Ph IV

Figure 7.45 – Hybrid Engine Technologies Roadmap* 

* The roadmap schedule shown is notional, suitable for overall program planning purposes only, with no 

commitment on the part of GE Aviation 
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7.3.11 – High Span Strut Braced Wing Technology Integration 

Goals and Objectives: 

Develop and integrate technologies required to enable a high speed strut-braced wing. 

Performance Area and Impact: 

Enable integration of high span strut braced wing allowing very high aspect ratio wings for low induced 

drag and natural laminar flow 

Technical Description: 

Ultra-High-Modulus, Ultra-High-Strength Fibers 

Low interference drag struts 

Low interference drag nacelles for a highly integrated configuration 

Active/Passive aeroelastic response for load control 

Advanced high cruise CL supercritical wing design 

Layer-by-Layer/Multifunctional nanocomposites 

Natural laminar flow wing design 

Risk Assessment: 

Current IRL: 

2 to 4 

Major Milestones: 

Ultra High Modulus fibers production ready 2020 

Integration of low interference drag struts on high span wing configurations. Improvement in 

interference drag is significant. Identity system benefits for go-no-go. 2020 

Integration of low interference drag nacelles on high span wing configurations. Improvement in 

interference drag is significant. Identity system benefits for go-no-go. 2020 

Collaborate integration of active/passive aeroelastic response for load control. Identity system 

benefits for go-no-go. 2020 

Layer-by-Layer/Multifunctional nanocomposites production ready 2025 

Natural laminar flow wing design without HLFC systems to achieve a viable configuration. 

Roadmap will address passive/active systems to achieve Aerodynamic goals. Identity system 

benefits for go-no-go. 2020 
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Dependency: 

Items are interdependent to achieve viable high aspect ratio strut-braced wing design. 

Success Criteria: 

Table 7.12 – High Span Strut Braced Wing Technology Integration Success Criteria 

Task 

Number Task Name Success Criteria Alternate Steps if Unsuccessful 

1 Natural Laminar Flow NLF laminar design matches 

Active LFC 

Achieve 50% of an Active LFC 

laminar Run 

2 Low Interference Drag 

Struts 

Integrate strut into wing-body 

for only strut parasite drag 

Establish low interference 

levels 

3 Advanced Supercritical 

Wing Design 

Target 3% airplane drag 

improvement while attaining 

high design lift coefficient 

Achieve 50% of target drag 

improvement 

4 Low Interference Drag 

Nacelles 

Integrate nacelle/pylon to 

wing body for only 

nacelle/pylon parasite drag 

Establish low interference 

levels 

5 Active/Passive 

Aeroelastic Load Control 

Span load traded for 

Aerodynamics and structural 

efficiencies to improve overall 

mission performance 

Achieve improvement for one 

discipline 

6 Multifunctional 

Nanocomposites 

Lightweight broad area 

sensing and distributed 

processing 

Higher weight sensors and 

electronics 

7 Ultra High Modulus and 

Strength Fibers 

Very high aspect ratio wing 

designs not driven by sizing 

for aeroelasticity and 

gust/maneuver loads 

Active control of aeroelastic 

response and loads alleviation 

8 Vehicle Technology 

Integration 

Integrated vehicle design with 

advanced technology suite 

Integrated vehicle design with 

all achieved technology 

advancements 

 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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Task

1 NLF - Maximize Laminarization

 Passive LFC

23 Advanced Super-critical wing design for 2030

4

5 Active/Passive aeroelastic response for load control6 Layer-by-Layer/Multifunctional Nanocomposites7 Ultra-High_Modulus, Ultra-High-Strength Fibers

8 Technology Integration and Full Scale Vehicle Design

Low interference drag nacelles for a highly integrated configurationSignificantly low Interference drag struts on high span wing

2011 2012 2013 2014 2020 2021 2015 2016 2017 2018 2019 

2022 

Status Passive HLFC / NLF wing design Viable Design Wind Tunnel ValidatedStatus Interference free strut design Viable Design Wind Tunnel ValidatedStatus Advanced Super-critical wing design Viable Design Wind Tunnel ValidatedStatus Design and applique of Riblets Viable Design

Wind Tunnel Validated

Status Design low interference drag nacelles Viable Design Wind Tunnel ValidatedStatus Relaxed static stability & Increased CLmax empenage design Viable Design

Wind Tunnel Validated

Status Active/Passive aeroelatic response for load control design Viable Design Wind Tunnel Validated Status Relaxed static stability & Increased CLmax empenage design Viable Design Wind Tunnel Validated

Initial Concepts

Establish Goals 

Update Designs For 

Technology Levels Attained

Update Designs For 

Technology Levels Attained

Figure 7.46 – High Span Strut Braced Wing Technology Integration Roadmap 
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8.0 – Summary, Conclusions, and Recommendations 

8.1 – Summary 

This Final Report summarizes the work accomplished by the Boeing Subsonic Ultra Green 

Aircraft Research (SUGAR) team in Phase 1, which includes the time period of October 2008 

through March 2010. Work completed includes the development of a comprehensive future 

scenario for world-wide commercial aviation, the consideration and selection of baseline and 

advanced configurations for study, the generation of technology suites for each configuration, 

detailed performance analysis of the baseline, reference, and advanced configurations, noise and 

emissions of all concepts, and the development of technology risks and roadmaps. 

The future scenario is based on a 20-year current market outlook process that Boeing has used 

for the last 40 years. The future scenario was used to establish baseline, reference, and advanced 

aircraft in three size classes (regional, medium, and large) for the 2008-2055 timeframe. Also 

derived from the future scenario were the payload, speed, design range, and average range for 

each of the size classes. For this study, it was decided to concentrate design and analysis 

resources on a medium size aircraft carrying 154 passengers to a maximum range of 3500 nm. 

A concept selection workshop was held at Georgia Tech to discuss and select advanced concept 

configurations and enabling propulsion technologies. From the workshop and post-workshop 

discussions, the following five configurations were selected for detailed analysis: 

1. SUGAR Free – Current technology, similar to 737 class aircraft. Used as Baseline for 

performance comparisons. 

2. Refined SUGAR – Basic conventional configuration with estimated 2030-2035 N+3 

technologies, including improved NEXTGEN air traffic control mission efficiency. 

Includes “gFan” turbofan engine from GE. 

3. SUGAR High – High span strut-braced wing configuration with advanced 2030-2035 

N+3 technologies. Assumes significant technology development beyond the technologies 

in the Refined SUGAR concept. “gFan+” turbofan and open fan propulsion options 

supplied by GE. 

4. SUGAR Volt – Builds off of SUGAR High configuration to add electric propulsion 

technologies. Initially considered a variety of electric-propulsion architectures (Battery 

electric only, fuel-cell gas turbine hybrid, battery electric gas turbine hybrid), but Boeing 

point-of-departure sizing analysis and GE analysis led to selection of battery gas turbine 

hybrid propulsion architecture. “hFan” turbofan-electric hybrid engine data developed by 

GE. 

5. SUGAR Ray – A HWB configuration that uses a similar suite of advanced technologies 

as the SUGAR High. Primary design emphasis is on reducing aircraft noise, while 

maintaining performance similar to the SUGAR High. 

Technology and system experts were engaged to establish technology suites for each of the five 

configurations. Technologies were selected in four categories: Aero, Structural, Subsystem, and 

Propulsion. Refined SUGAR technologies assume a “business as usual” technology development 

between now and 2030-2035. SUGAR High, SUGAR Volt, and SUGAR Ray assume significant 

additional focused development of technologies for these aircraft. 
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To begin the analysis and sizing process, a point-of-departure sizing analysis was conducted. 

This conceptual analysis provided initial sizing information to start the more detailed design and 

analysis process. These results established “goal” performance levels for the configurations and 

their technologies. For the SUGAR Volt, the point-of-departure analysis included a trade study 

to establish required battery technology levels and to compare various electric propulsion 

architectures. Ultimately a battery electric, gas turbine hybrid propulsion architecture was 

selected. These results were presented at the 6-month review, and for the average 900 nm 

mission, showed approximately a 50% reduction in fuel burn for the Refined SUGAR, a 58% 

reduction for the SUGAR High, and up to a 90% reduction in fuel used for the SUGAR Volt. 

Detailed analysis and sizing began when the point-of-departure results were used to draw each 

configuration. From this geometry model, aerodynamics and mass properties analyses were 

conducted on the as-drawn configuration. The point-of-departure results were also used to 

develop an initial size for the engines. Then a mission performance analysis was used to resize 

the as-drawn aircraft to meet all constraints. In some cases, constraints were adjusted as part of a 

requirements analysis trade study. Detailed analysis and sizing was completed for all 

configurations. 

The Refined SUGAR results indicate a 44% reduction in fuel burn compared to the 

SUGAR Free baseline on a 900nm mission. Opportunities have been identified for up to 

a 54% fuel burn reduction by using the gFan+ engine and a higher span wing. NOx 

emissions were reduced to 42% of CAEP 6 levels by using an advanced combustor. CO2

emissions can be reduced by 72% by adding biofuels to the other technologies. Noise is 

reduced by 16 db. Design takeoff distances of 8200 ft can be achieved at full weight or 

reduced to 5500 ft or less for the average mission fuel load. 

The SUGAR High results indicate a 39% reduction in fuel burn compared to the SUGAR 

Free baseline on a 900nm mission. Opportunities for wing weight reduction and 

aerodynamic improvements have been identified for up to a 58% fuel burn reduction. 

NOx emissions were reduced to 28% of CAEP 6 levels by using an advanced combustor. 

CO2 emissions can be reduced by 69% by adding biofuels to the other technologies. 

Noise is reduced by 22 db. Design takeoff distances of 8200 ft can be achieved at full 

weight or reduced to 6000 ft or less for the average mission fuel load. 

The SUGAR Volt results indicate a 63% reduction in fuel burn compared to the SUGAR 

Free baseline on a 900nm mission. Opportunities have been identified for up to a 90% 

fuel burn reduction through greater electric usage. If total energy usage (fuel plus 

electricity) is considered, a 56% reduction is achieved. NOx emissions were reduced to 

21% of CAEP 6 levels by using an advanced combustor with a potential for even greater 

reductions (to 11%) by optimizing electric motor usage. CO2 emissions can be reduced 

by 81% by adding biofuels to the other technologies. Noise is reduced by at least 22 db, 

with more reduction available by optimizing the electric motor usage and trajectory 

during takeoff and climb-out. Design takeoff distances of 8200 ft can be achieved at full 

weight or reduced to 4000-5200 ft for the average mission takeoff weight. 

The SUGAR Ray results indicate a 43% reduction in fuel burn compared to the SUGAR 

Free baseline on a 900nm mission. NOx emissions were reduced to 28% of CAEP 6 

levels. CO2 emissions can be reduced by 75% by adding biofuels to the other 

technologies. Due to additional airframe shielding benefits, noise is reduced by 37 db. 
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The team conducted a Technology Workshop in November 2009. At this workshop, the team 

accelerated the final technology roadmap prioritization and risk assessment. The risk associated 

with the technology suites for each configuration has been assessed and the relationship between 

each technology (or technology group) and each NASA goal has been quantified. Development 

roadmaps for each technology (or technology group) have been established. 

A wide range of technologies contribute to substantial fuel burn reduction. Biofuels are a large 

contributor to reducing greenhouse gas emissions. Advanced combustor technology is key to 

reducing NOx emissions. Reducing aircraft noise requires an array of engine and airframe noise 

technologies. 

Finally, the results of the configuration assessment and technology analysis processes were used 

to develop recommendations for Phase 2 work. 

8.2 – Conclusions 

1. Fuel Burn – The NASA fuel burn goal of a 70% reduction is very aggressive. A 

combination of air traffic management, airframe, and propulsion improvements were 

shown to achieve a 44-58% reduction in fuel burn for conventional propulsion. The 

addition of hybrid electric propulsion to the technology suite has the potential for fuel 

burn reductions of 70-90%. If electric energy is considered in a modified goal of “energy 

usage”, then a 56% or greater reduction in energy use is possible. 

2. Greenhouse Gases – Although NASA did not establish a goal for greenhouse gas 

emissions, Boeing considered the goal of reducing life cycle CO2 emissions. The fuel 

burn reductions identified above directly reduce CO2 emissions as well. Sustainable 

biofuels can be used to reduce CO2 emissions by 72% for conventional propulsion and 

even more with hybrid electric propulsion using “green” electrical power to charge the 

battery system. 

3. NOx Emissions – Landing and takeoff NOx emissions can be at or near the NASA goal 

of a 75% reduction from CAEP 6 using advanced combustor technology. The use of 

electric power in the hybrid electric propulsion concept offers the opportunity for even 

lower emissions. 

4. Noise – The original Phase I noise reduction goal to provide a 55 DNL contour at the 

airport boundary is difficult to achieve. An investigation of airport characteristics shows 

that a 1.8 nm boundary distance is representative. At this distance a 45 dB reduction 

relative to the SUGAR Free is needed to provide the 55 DNL contour. However, the best 

performing configuration, SUGAR Ray, achieved only a 37 dB noise reduction and needs 

a larger 2.5 nm boundary to contain the 55 DNL contour. To further reduce the airport 

boundary distance, or meet the updated 71 dB reduction NASA goal, requires significant 

additional reduction in aircraft noise. 

5. Field Length – Takeoff distances are designed to be approximately 8,200 ft at Maximum 

Takeoff Weight (MTOW). For the average 900 nm range with reduced takeoff weight, 

distances of approximately 5,000 ft are achieved. The use of hybrid electric propulsion 

allows additional application of power for takeoff, possibly lowering the takeoff distance 

even more. This was achieved without adding aggressive high lift technologies. For the 

study, it was assumed that a takeoff distance of approximately 5,000 ft for the average 

range mission is sufficient for operation at an adequate number of airports to support 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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necessary operations. We chose not to expend limited study resources to further 

investigate configurations and technologies needed to achieve shorter takeoff distances. 

6. Advanced Configurations – The SUGAR High configuration has potential to beat the 

conventional configuration (Refined SUGAR) with regard to fuel burn, but the present 

uncertainty in the wing weight and high cruise lift coefficient prevents a definitive 

conclusion at this time. The SUGAR Ray HWB configuration is clearly the quietest. 

7. Technologies – A wide portfolio of technologies is needed to achieve the NASA N+3 

goals. Significant improvements in air traffic management, and aerodynamic, structural, 

system, and propulsion technologies are needed to address fuel burn goals. Biofuels are 

needed to further reduce greenhouse gas emissions. Advanced combustor technology is 

necessary to meet NOx goals. Even more aggressive engine and airframe noise reduction 

technologies than applied in this study are needed. The hybrid electric engine technology 

is a clear winner, as it has the potential to improve performance relative to all of the 

NASA goals. 

8.3 – Recommendations 

Based on the Phase 1 configuration assessment and technology analysis results, we recommend 

the following for Phase 2 activities (in approximate order of priority): 

1. Additional design and analysis of hybrid electric gas turbine propulsion architectures and 

the integration of the concept into other configurations (like the Refined SUGAR or 

SUGAR Ray). A noise analysis for the hybrid electric propulsion system needs to be 

conducted to determine potential noise benefits for operating on partial or full electric 

power. 

2. A comprehensive study of high aspect ratio strut/truss braced wings, accounting for 

coupled aerodynamics, structures, materials, propulsion, and control. Making this wing 

aerodynamically effective while controlling weight is key to enabling this high L/D 

configuration. A detailed finite element model is needed, and an aeroelastic test is 

necessary to validate the structural analysis and to determine the weight of the wing. The 

high cruise lift coefficient required at Mach 0.70 for high aspect ratio wings requires 

additional analysis, optimization, and experimental validation. 

3. Additional noise technologies need to be identified and validated to achieve the updated 

NASA -71 db noise goal. This could include use of trajectory optimization, greater use of 

electric propulsion, turboprops, and low noise propellers. Airframe and tail shielding 

should continue to be investigated in HWB and conventional configurations. 

4. A follow-on to this study to consider the synergistic benefits of methane and/or hydrogen 

fuel (high heating value, thermal management, fuel cells, and superconducting electric 

propulsion). 

5. A follow-on to this study to include the large aircraft size class. It is anticipated that some 

technologies will become more important as the length of the cruise segment is increased. 

6. An aircraft power system study to determine the best architecture for aircraft power, 

including diesel and conventional APUs, fuel-cells, batteries, and both engine power 

take-off and bleed air. This study should include traditional, more-electric and all-electric 

aircraft system architectures, per aircraft size class. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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7. A follow-on to this study to include the regional jet size class. Special emphasis should 

be placed on low noise propulsion, field length, and possible use of electric or hybrid 

electric propulsion. 

Additionally, work should continue to investigate and validate the performance for the HWB 

configuration. It is anticipated that the HWB configuration will be emphasized in the N+2 

Environmentally Responsible Aviation (ERA) program, as well as other ongoing NASA, Air 

Force, and Boeing funded projects. This other work can be effectively leveraged, and the HWB 

concept should continue to be carried in the N+3 program, as most N+3 technologies can be 

applied to improve the HWB concept as well. 
NASA Contract NNL08AA16B – NNL08AD01T – Subsonic Ultra Green Aircraft Research – Phase I – Final Report

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9.0 – References 

[1] – US Department of Transportation; Research and Innovative Technology Administration; 

Bureau of Transportation Statistics, Airline Data and Statistics. Retrieved May 14, 2008 

from http://www.bts.gov/programs/airline_information/ 

[2] – US Department of Transportation; Research and Innovative Technology Administration; 

Bureau of Transportation Statistics, Airline Data and Statistics. Retrieved March 09, 2010 

from http://www.transtats.bts.gov/fuel.asp 

[3] – Intergovernmental Panel on Climate Change, Climate Change 2007: Synthesis Report – 

Summary for policy makers., November 2007 

[4] – Intergovernmental Panel on Climate Change (IPCC) Special Report on Aviation and the 

Global Atmosphere, [J. E. Penner, D. H. Lister, D. J. Griggs, D. J. Dokken, and M. 

McFarland (eds.)] Cambridge University Press, 1999. 

[5] – MSNBC (May 1, 2008); Airlines slow down flights to save on fuel, Retrieved May 20, 

2008 from http://www.msnbc.msn.com/id/24410809/ 

[6] – F. Collier, E Zavala, D. Huff, Subsonic Fixed Wing Project: Reference Document

[7] – The Boeing Company; Current Market Outlook. 

http://www.boeing.com/commercial/cmo/index.html 

[8] – Zwicky, F., Discovery, Invention, Research - Through the Morphological Approach, 

Toronto: The Macmillian Company (1969). 

[9] – Engler T., Biltgen P.T., Mavris D.N., Concept Selection Using an Interactive 

Reconfigurable Matrix of Alternatives (IRMA), 45th AIAA Aerospace Sciences 

Meeting and Exhibit 8 - 11 January 2007, Reno, Nevada 

[10] – Federal Aviation Administration, Airport Design: Advisory Circular; September 1989, 

AC150/5300-13 

[11] – Carson, B. H., Fuel Efficiency of Small Aircraft; American Institute of Aeronautics and 

Astronautics, August 1980, AIAA-80-1847 
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Subsonic Ultra Green Aircraft Research: Phase I Final Report 

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This Final Report summarizes the work accomplished by the Boeing Subsonic Ultra Green Aircraft Research (SUGAR) team in Phase 1, 

which includes the time period of October 2008 through March 2010. The team consisted of Boeing Research and Technology, Boeing

Commercial Airplanes, General Electric, and Georgia Tech. The team completed the development of a comprehensive future scenario for 

world-wide commercial aviation, selected baseline and advanced configurations for detailed study, generated technology suites for each 

configuration, conducted detailed performance analysis, calculated noise and emissions, assessed technology risks, and developed 

technology roadmaps. Five concepts were evaluated in detail: 2008 baseline, N+3 reference, N+3 high span strut braced wing, N+3 gas 

turbine battery electric concept, and N+3 hybrid wing body. A wide portfolio of technologies was identified to address the NASA N+3 

goals. Significant improvements in air traffic management, aerodynamics, materials and structures, aircraft systems, propulsion, and 

acoustics are needed. Recommendations for Phase 2 concept and technology projects have been identified.

15. SUBJECT TERMS

Green aircraft; Commercial aircraft; Emissions; Noise; Electric propulsion; Technology roadmaps

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