28th AlAA Applied Aerodynamics Conference AIAA2010-5114 28 June-1 July 2010,Chicago,lllinois Advanced Concept Studies for Supersonic Commercial Transports Entering Service in 2030-35 (N+3) John M.Morgenstern Nicole NorstrudT Dr.Marc Stelmack Lockheed Martin Aeronautics Company,Palmdale,CA93599 Dr.Pratik D Jha Lockheed Martin Information Systems and Global Solutions,Rockville,MD.20850 NASA has chartered teams to study commercial transports that can overcome significant performance and environmental challenges for the benefit of the general public.The key technical objective of this effort was to generate promising supersonic concepts for the 2030-2035 timeframe and to develop plans for maturing the technologies required to make those concepts a reality.The N+3 program is aligned with NASA's Supersonic Project and is focused on providing alternative system-level solutions capable of overcoming the efficiency,environmental,and performance barriers to practical supersonic flight. 1.0 Summary Lockheed Martin Aeronautics Company(LM Aero),working in conjunction with seven industry and academia sub-contracting teammates,executed an 18 month program responsive to the NASA sponsored N+3 NRA:"Advanced Concept Studies for Supersonic Commercial Transports Entering Service in the 2030-2035 Period."N+3'denotes three generations beyond the current commercial transport fleet.The N+3 program is aligned with NASA's Supersonic Project and is focused on providing alternative system-level solutions capable of overcoming the environmental,efficiency and performance barriers to practical supersonic flight.The environmental goals focus on low sonic boom,airport noise and cruise emissions.The program considered promising concepts and enabling technologies in an extensively integrated analysis process required particularly to achieve low sonic boom with efficiency. The reason for investigating alternative system-level solutions has to do with the projected status of our air transportation system.In addition to FAA regulations,the Next Generation (NextGen)Air Traffic System (ATS)congestion levels are a concern as they are expected to increase by a factor of 2 to 3 in the 2030 timeframe.Understanding how supersonic aircraft affect future congestion levels requires a system of systems analysis that integrates vehicle design,operating environment,and economic interaction into a single process.LM Aero worked with a sister company,Transportation Security Solutions (TSS),and Purdue University to assess the value that a supersonic transport concept vehicle brings to the NextGen ATS.A fast time modeling and simulation study done by TSS revealed that commercial supersonic vehicles will not impact future airport capacity.However,supersonic air vehicles in the 2030 timeframe will exert additional demand for airport operations.Purdue University simulated numerous future Civil Air Transport System scenarios,allocating N+3 vehicles to maximize system-wide productivity while also computing fleet-wide emissions and direct operating costs.These results showed that the total value of time saved by passengers on N+3 supersonic transports exceed the added operating costs incurred by the aircraft.These system-level scenarios showed that supersonic transport is a viable solution for increased productivity and promotes the renewed viability of supersonic travel. Our extended team contributed to a preferred supersonic configuration and developed plans for maturing the identified, enabling technologies required to meet the N+3 performance and environmental goals.Working in conjunction with GE Global Research Center(GRC),John Hansman from MIT,Helen Reed Bill Saric from Texas A&M,Wyle Laboratories, Purdue,and Penn State-an initial low-boom,supersonic configuration was used to assess potential airframe and propulsion technologies that were projected to meet or exceed the future supersonic boom,noise,emissions,cruise speed,range,payload, and fuel efficiency goals.Multi-Disciplinary Analysis and Optimization(MDAO)showed it was possible to achieve the N+3 boom goal with an "inverted-V",engine-under wing configuration.Further sizing and quantified analysis proved that using revolutionary technologies enabled this configuration to achieve the range,payload,and cruise speed goals. Program Manager,Advanced Development Programs,1011 Lockheed Way B611 MC1142,AIAA Associate Fellow T Program Manager,Advanced Development Programs,1011 Lockheed Way B611 MC1142 +Conceptual Designer,Advanced Development Programs,1011 Lockheed Way B611 MC1142 s Systems Engineering Staff,IS&GS-Aviation Solutions,9231 Corporate Blvd. Copyright2T920h%9 ahgecorporabonupuoneneaybyahe Reecieannastbeeor是snde8nHc,kcwM钟，sion
Copyright 2010 by Lockheed Martin, Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. 1 Advanced Concept Studies for Supersonic Commercial Transports Entering Service in 2030-35 (N+3) John M. Morgenstern* Nicole Norstrud † Dr. Marc Stelmack ‡ Lockheed Martin Aeronautics Company, Palmdale, CA 93599 Dr. Pratik D Jha§ Lockheed Martin Information Systems and Global Solutions, Rockville, MD, 20850 NASA has chartered teams to study commercial transports that can overcome significant performance and environmental challenges for the benefit of the general public. The key technical objective of this effort was to generate promising supersonic concepts for the 2030-2035 timeframe and to develop plans for maturing the technologies required to make those concepts a reality. The N+3 program is aligned with NASA’s Supersonic Project and is focused on providing alternative system-level solutions capable of overcoming the efficiency, environmental, and performance barriers to practical supersonic flight. 1.0 Summary Lockheed Martin Aeronautics Company (LM Aero), working in conjunction with seven industry and academia sub-contracting teammates, executed an 18 month program responsive to the NASA sponsored N+3 NRA: ―Advanced Concept Studies for Supersonic Commercial Transports Entering Service in the 2030-2035 Period.‖ ‗N+3‘ denotes three generations beyond the current commercial transport fleet. The N+3 program is aligned with NASA‘s Supersonic Project and is focused on providing alternative system-level solutions capable of overcoming the environmental, efficiency and performance barriers to practical supersonic flight. The environmental goals focus on low sonic boom, airport noise and cruise emissions. The program considered promising concepts and enabling technologies in an extensively integrated analysis process required particularly to achieve low sonic boom with efficiency. The reason for investigating alternative system-level solutions has to do with the projected status of our air transportation system. In addition to FAA regulations, the Next Generation (NextGen) Air Traffic System (ATS) congestion levels are a concern as they are expected to increase by a factor of 2 to 3 in the 2030 timeframe. Understanding how supersonic aircraft affect future congestion levels requires a system of systems analysis that integrates vehicle design, operating environment, and economic interaction into a single process. LM Aero worked with a sister company, Transportation Security & Solutions (TSS), and Purdue University to assess the value that a supersonic transport concept vehicle brings to the NextGen ATS. A fast time modeling and simulation study done by TSS revealed that commercial supersonic vehicles will not impact future airport capacity. However, supersonic air vehicles in the 2030 timeframe will exert additional demand for airport operations. Purdue University simulated numerous future Civil Air Transport System scenarios, allocating N+3 vehicles to maximize system-wide productivity while also computing fleet-wide emissions and direct operating costs. These results showed that the total value of time saved by passengers on N+3 supersonic transports exceed the added operating costs incurred by the aircraft. These system-level scenarios showed that supersonic transport is a viable solution for increased productivity and promotes the renewed viability of supersonic travel. Our extended team contributed to a preferred supersonic configuration and developed plans for maturing the identified, enabling technologies required to meet the N+3 performance and environmental goals. Working in conjunction with GE Global Research Center (GRC), John Hansman from MIT, Helen Reed & Bill Saric from Texas A&M, Wyle Laboratories, Purdue, and Penn State – an initial low-boom, supersonic configuration was used to assess potential airframe and propulsion technologies that were projected to meet or exceed the future supersonic boom, noise, emissions, cruise speed, range, payload, and fuel efficiency goals. Multi-Disciplinary Analysis and Optimization (MDAO) showed it was possible to achieve the N+3 boom goal with an ―inverted-V‖, engine-under wing configuration. Further sizing and quantified analysis proved that using revolutionary technologies enabled this configuration to achieve the range, payload, and cruise speed goals. * Program Manager, Advanced Development Programs, 1011 Lockheed Way B611 MC1142, AIAA Associate Fellow † Program Manager, Advanced Development Programs, 1011 Lockheed Way B611 MC1142 ‡ Conceptual Designer, Advanced Development Programs, 1011 Lockheed Way B611 MC1142 § Systems Engineering Staff, IS&GS - Aviation Solutions, 9231 Corporate Blvd. 28th AIAA Applied Aerodynamics Conference 28 June - 1 July 2010, Chicago, Illinois AIAA 2010-5114 Copyright © 2010 by Lockheed Martin Corporation. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission
Based on Lockheed Martin provided requirements and targets,GE developed a Variable Cycle Engine (VCE)propulsion system and a conventional Mixed Flow Turbo Fan(MFTF)propulsion system expected to meet or exceed the environmental goals set by NASA,as well as an MFTF optimized solely for cruise efficiency.These propulsion systems take advantage of an Advanced Thermal Management System (ATMS)to extend the overall pressure ratio(OPR)of the engine and increase thermal efficiency.A low noise,high performance exhaust system takes advantage of the innovative jet noise reduction features that work synergistically with the variable cycle engine features to reduce the exhaust jet noise.Augmented transonic thrust allows the propulsion system to be favorably sized with potential take-off noise abatement.Analysis shows that this propulsion system,along with integrated technology sets,meets the N+3 airport noise,emissions,and fuel efficiency goals. Our integrated airframe and propulsion system,along with identified/enabling technologies,is projected to meet or exceed all N+3 targets.Results of the environmental and performance characteristics of our advanced vehicle concept are summarized in Table 1. Table 1.LM's preferred concept with technology is projected to meet or surpass all N+3 goals NASA N+3 Efficient Multi-Mach N+3 Goal Status Aircraft(Beyond 2030) Environmental Goals Sonic Boom 65-70 PLdB low boom flight 70-76 PLdB 75-80 PLdB unrestricted flight KEY GOAL Airport Noise -20 to-30 EPNdB -32.2 from jet only (cumulative below stage 3) (Fan Airframe add 13.8 without technology improvement) KEY GOAL Cruise Emissions(g/kg fuel) <5 EINOx 5 EINOx Plus particular and water vapor mitigation Performance Goals Cruise Speed Mach 1.3-2.0 low boom flight Mach 1.6 Mach 1.3-2.0 unrestricted Range 4000-5500nm 4850nm Payload 100-200pax 100 pax Fuel Efficiency 3.5-4.5 3.64 (pax-nm/Ib-fuel) (pax-nm/lb-fuel) KEY GOAL Through a collaboration effort,LM Aero and GE GRC identified N+1,N+2,and N+3 technologies critical to meet or surpass the N+3 goals.N+1 and N+2 shaping technologies were considered to be "endemic"or inherent to the baseline design.These configuration technologies were not included in the final technology roadmap,but other N+2 technologies were included to provide a comprehensive technology list.As a result,technology roadmaps were created for all prioritized,airframe tech- nologies to demonstrate the maturation efforts required to raise each technology to a Technology Readiness Level 6(TRL 6). Recommended future work includes Phase 2 testing and Phase 3 maturation efforts to provide a technology set necessary to realize a vision vehicle serviceable in the 2030-2035 timeframe. Current N+2 efforts allow us to reasonably assume that N+2 technologies will be developed during those N+2 program efforts, and the developed technologies will be available for application on the N+3 vehicle.Concentration on N+3 technologies provides a clear roadmap to achieving and surpassing the stated N+3 goals while providing an exciting solution to supersonic travel.Figure I highlights the comprehensive technology set for both airframe and propulsion systems. Future work recommendations for airframe technologies include: Low cost,high impact tools and methodologies such as Low Boom Shaping Fidelity and CFD-based MDAO to address boom mitigation Distributed roughness with plasma augmentation to ensure laminar flow at supersonic conditions Copyright 2010 by Lockheed Martin,Published by the American Institute of Aeronautics and Astronautics,Inc.,with permission. 2
Copyright 2010 by Lockheed Martin, Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. 2 Based on Lockheed Martin provided requirements and targets, GE developed a Variable Cycle Engine (VCE) propulsion system and a conventional Mixed Flow Turbo Fan (MFTF) propulsion system expected to meet or exceed the environmental goals set by NASA, as well as an MFTF optimized solely for cruise efficiency. These propulsion systems take advantage of an Advanced Thermal Management System (ATMS) to extend the overall pressure ratio (OPR) of the engine and increase thermal efficiency. A low noise, high performance exhaust system takes advantage of the innovative jet noise reduction features that work synergistically with the variable cycle engine features to reduce the exhaust jet noise. Augmented transonic thrust allows the propulsion system to be favorably sized with potential take-off noise abatement. Analysis shows that this propulsion system, along with integrated technology sets, meets the N+3 airport noise, emissions, and fuel efficiency goals. Our integrated airframe and propulsion system, along with identified/enabling technologies, is projected to meet or exceed all N+3 targets. Results of the environmental and performance characteristics of our advanced vehicle concept are summarized in Table 1. Table 1. LM’s preferred concept with technology is projected to meet or surpass all N+3 goals NASA N+3 Efficient Multi-Mach Aircraft (Beyond 2030) N+3 Goal Status Environmental Goals Sonic Boom 65-70 PLdB low boom flight 75-80 PLdB unrestricted flight 70-76 PLdB KEY GOAL Airport Noise -20 to -30 EPNdB (cumulative below stage 3) -32.2 from jet only (Fan + Airframe add 13.8 without technology improvement) KEY GOAL Cruise Emissions (g/kg fuel) <5 EINOx Plus particular and water vapor mitigation 5 EINOx Performance Goals Cruise Speed Mach 1.3-2.0 low boom flight Mach 1.3 – 2.0 unrestricted Mach 1.6 Range 4000-5500 nm 4850 nm Payload 100-200 pax 100 pax Fuel Efficiency 3.5 – 4.5 (pax-nm/lb-fuel) 3.64 (pax-nm/lb-fuel) KEY GOAL Through a collaboration effort, LM Aero and GE GRC identified N+1, N+2, and N+3 technologies critical to meet or surpass the N+3 goals. N+1 and N+2 shaping technologies were considered to be ―endemic‖ or inherent to the baseline design. These configuration technologies were not included in the final technology roadmap, but other N+2 technologies were included to provide a comprehensive technology list. As a result, technology roadmaps were created for all prioritized, airframe technologies to demonstrate the maturation efforts required to raise each technology to a Technology Readiness Level 6 (TRL 6). Recommended future work includes Phase 2 testing and Phase 3 maturation efforts to provide a technology set necessary to realize a vision vehicle serviceable in the 2030-2035 timeframe. Current N+2 efforts allow us to reasonably assume that N+2 technologies will be developed during those N+2 program efforts, and the developed technologies will be available for application on the N+3 vehicle. Concentration on N+3 technologies provides a clear roadmap to achieving and surpassing the stated N+3 goals while providing an exciting solution to supersonic travel. Figure 1 highlights the comprehensive technology set for both airframe and propulsion systems. Future work recommendations for airframe technologies include: Low cost, high impact tools and methodologies such as Low Boom Shaping Fidelity and CFD-based MDAO to address boom mitigation Distributed roughness with plasma augmentation to ensure laminar flow at supersonic conditions
Adaptive geometry technologies including lift distribution control and inlet flow control technologies to address the N+3 fuel efficiency goals Future work recommendations for propulsion technologies include: Continued development of VCE technologies Development of the Transonic Thrust Augmentation device-critical technology to meeting N+3 goals ● Alternate combustor/combustion concepts need to be explored,as these propulsion systems are developed to take advantage of the full thermal capability of the system.The currently funded NASA Supersonics Low Emissions combustor program will provide key validation data for high temperature NOx levels,and the maturation of some enabling technologies Predictive and design tool development in many areas need to be continued to be developed including: o Aero-acoustics for both fan and jet noise 0 Combustion and emissions Table 2.N+3 environmental and performance goals N+1 N+2 N+3 Supersonic Small Efficient Multi-Mach Business Class Supersonic Aircraft Aircraft(2015) Airliner(2020) (Beyond 2030) Environmental Goals 65-70 PLdB Sonic Boom 65-70 PLdB 65-70P1dB low boom flight 75-80 PLdB unrestricted flight Airport Noise (cum below stage 3) 10 EPNdB 10-20 EPNdB 20-30 EPNdB Cruise Emissions Equivalent to <5&particulate (Cruise NOx current <10 and water vapor g/kg of fuel) Subsonic mitigation Performance Goals Mach1.3-2.0 Mach1.6-1.8 Mach1.6-1.8 low boom flight Cruise Speed Mach1.3-2.0 unrestricted fight Range (n.mi.) 4000 4000 4000-5500 Payload (passengers) 6-20 35-70 100-200 Fuel Efficiency (passenger-miles 1.0 3.0 3.5-4.5 per Ib of fuel) Copyright 2010 by Lockheed Martin,Published by the American Institute of Aeronautics and Astronautics,Inc.,with permission. 3
Copyright 2010 by Lockheed Martin, Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. 3 Adaptive geometry technologies including lift distribution control and inlet flow control technologies to address the N+3 fuel efficiency goals Future work recommendations for propulsion technologies include: Continued development of VCE technologies Development of the Transonic Thrust Augmentation device – critical technology to meeting N+3 goals Alternate combustor/combustion concepts need to be explored, as these propulsion systems are developed to take advantage of the full thermal capability of the system. The currently funded NASA Supersonics Low Emissions combustor program will provide key validation data for high temperature NOx levels, and the maturation of some enabling technologies Predictive and design tool development in many areas need to be continued to be developed including: o Aero-acoustics for both fan and jet noise o Combustion and emissions Table 2. N+3 environmental and performance goals
2.0 Introduction 2.1 Subject of the Report Research in the area of Advanced Supersonic Transport(AST)has been a focus area for NASA since 1960s,driven by maintaining US leadership in the area of commercial transport.According to a 1980 Open Travel Alliance (OTA)report26 on the impact of advanced air transport technology,the business case in favour of ASTs results from improved aircraft productivity(measured in seat miles generated per unit time)and its capability to transport twice the number of passengers on long distance flight.Higher cost of operations,concerns over environmental impact due to noise and emissions,and restrictions to fly supersonic on land due to sonic boom are some of the technological issues that need to be addressed for production and deployment of ASTs.NASA's research efforts for the advancement of AST are dedicated to address these technical challenges and the AST technology is being matured under N+1,N+2 and N+3 projects.The goal of the N+3 project is to explore a conceptual design for multi-Mach aircraft in 2030 timeframe that has low sonic boom,is environmentally acceptable,fuel efficient,and able to fly at supersonic speed above land.Other,integrated design concerns include: Sonic Boom Reduction Cruise Efficiency Aero-Propulsive-Servo-Elasticity Airport Noise Light Weight Structure for Airframe/Propulsion Systems High Altitude Emissions A complimentary area for NASA research is the Next Generation Air Transportation System (NextGen)(Joint Planning and Development Office,2009).The U.S.Air Traffic Management(ATM)system is today operating at the edge of its capabilities, handling the real-time planning and coordination of over 50,000 flights per day.Although air traffic has seen a decline in the recent year due to severe economic downturn,the recent numbers suggest that traffic is currently stabilizing(Official Airline Guide,2009)however,per market forecasts by MITRE23 and Boeing16(2009)a strong growth in air traffic is expected in both short and long term.Additionally,Boeing's long term market forecast cites that the air transportation industry is resilient and has survived many economic downturns in the past.It has grown at 5%annually and by year 2029 the number of airplanes flying in the National Air Space will be more than double.To address this concern,the Federal Aviation Administration (FAA) along with NASA and other government and industry partners are charting the NextGen. One of the strategic objectives outlined in the NextGen plan is to have a system scalable enough to respond quickly and efficiently to increase in demand and is flexible enough to incorporate new types of airframe for example,Unmanned Aircraft System(UAS),Very Light Jets(VLJs),Large Civil Tiltrotor(LCTR),ASTs,and others.Since supersonic transports provide a step increase in passenger mobility by speed of travel,their incorporation within the NextGen ATS could potentially provide alternative methods of operation,subsonic to supersonic transition regulations,and unforeseen hazards.NASA is focused on providing vehicle designs and identifying enabling technologies that can meet the nation's need for effective,efficient and safe air travel. Overall,the supersonics project is designed to develop knowledge,capabilities,and identify innovative solutions for supersonic air vehicles.Sonic boom,environmental concerns,and NextGen ATS integration are major concerns for commercial supersonic travel.Revolutionary solutions are required to generate viable,supersonic solutions. 2.2 Purpose The purpose of this paper is to preview and highlight the final report to the NASA sponsored program"N+3 NRA Advanced Concept Studies for Supersonic Commercial Transports Entering Service in the 2030-2035 Period."The N+3 program is focused on generating promising supersonic concepts for the 2030-2035 timeframe and to develop plans for maturing the technologies required to make those concepts a reality.An additional system-level focus includes understanding how a supersonic civil transport would integrate and operate within the 2035 NextGen ATS. This program is committed to overcoming significant environmental (sonic boom,airport noise,and cruise emission)and performance (cruise speed,range,payload and fuel efficiency)challenges.The NASA stated N+3 goals are illustrated in Table 2.Meeting or surpassing these goals stimulates innovation and advances the pursuit of revolutionary conceptual designs. System-level multi-disciplinary analysis and optimization (MDAO)and out-of-the-box thinking allows for revolutionary technology identification.This fosters an environment of innovation and generates excitement for future supersonic travel. Overall,the N+3 effort is driven by the need for alternative solutions capable of overcoming the efficiency,environmental,and performance barriers to practical supersonic flight.Results from these studies aid in upcoming research efforts and provides a roadmap for future supersonic funding. Copyright 2010 by Lockheed Martin,Published by the American Institute of Aeronautics and Astronautics,Inc.,with permission
Copyright 2010 by Lockheed Martin, Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. 4 2.0 Introduction 2.1 Subject of the Report Research in the area of Advanced Supersonic Transport (AST) has been a focus area for NASA since 1960s, driven by maintaining US leadership in the area of commercial transport. According to a 1980 Open Travel Alliance (OTA) report26 on the impact of advanced air transport technology, the business case in favour of ASTs results from improved aircraft productivity (measured in seat miles generated per unit time) and its capability to transport twice the number of passengers on long distance flight. Higher cost of operations, concerns over environmental impact due to noise and emissions, and restrictions to fly supersonic on land due to sonic boom are some of the technological issues that need to be addressed for production and deployment of ASTs. NASA‘s research efforts for the advancement of AST are dedicated to address these technical challenges and the AST technology is being matured under N+1, N+2 and N+3 projects. The goal of the N+3 project is to explore a conceptual design for multi-Mach aircraft in 2030 timeframe that has low sonic boom, is environmentally acceptable, fuel efficient, and able to fly at supersonic speed above land. Other, integrated design concerns include: • Sonic Boom Reduction • Cruise Efficiency • Aero-Propulsive-Servo-Elasticity • Airport Noise • Light Weight Structure for Airframe/Propulsion Systems • High Altitude Emissions A complimentary area for NASA research is the Next Generation Air Transportation System (NextGen) (Joint Planning and Development Office, 2009). The U.S. Air Traffic Management (ATM) system is today operating at the edge of its capabilities, handling the real-time planning and coordination of over 50,000 flights per day. Although air traffic has seen a decline in the recent year due to severe economic downturn, the recent numbers suggest that traffic is currently stabilizing (Official Airline Guide, 2009) however, per market forecasts by MITRE23 and Boeing16 (2009) a strong growth in air traffic is expected in both short and long term. Additionally, Boeing‘s long term market forecast cites that the air transportation industry is resilient and has survived many economic downturns in the past. It has grown at 5% annually and by year 2029 the number of airplanes flying in the National Air Space will be more than double. To address this concern, the Federal Aviation Administration (FAA) along with NASA and other government and industry partners are charting the NextGen. One of the strategic objectives outlined in the NextGen plan is to have a system scalable enough to respond quickly and efficiently to increase in demand and is flexible enough to incorporate new types of airframe for example, Unmanned Aircraft System (UAS), Very Light Jets (VLJs), Large Civil Tiltrotor (LCTR), ASTs, and others. Since supersonic transports provide a step increase in passenger mobility by speed of travel, their incorporation within the NextGen ATS could potentially provide alternative methods of operation, subsonic to supersonic transition regulations, and unforeseen hazards. NASA is focused on providing vehicle designs and identifying enabling technologies that can meet the nation‘s need for effective, efficient and safe air travel. Overall, the supersonics project is designed to develop knowledge, capabilities, and identify innovative solutions for supersonic air vehicles. Sonic boom, environmental concerns, and NextGen ATS integration are major concerns for commercial supersonic travel. Revolutionary solutions are required to generate viable, supersonic solutions. 2.2 Purpose The purpose of this paper is to preview and highlight the final report to the NASA sponsored program ―N+3 NRA Advanced Concept Studies for Supersonic Commercial Transports Entering Service in the 2030-2035 Period.‖ The N+3 program is focused on generating promising supersonic concepts for the 2030-2035 timeframe and to develop plans for maturing the technologies required to make those concepts a reality. An additional system-level focus includes understanding how a supersonic civil transport would integrate and operate within the 2035 NextGen ATS. This program is committed to overcoming significant environmental (sonic boom, airport noise, and cruise emission) and performance (cruise speed, range, payload and fuel efficiency) challenges. The NASA stated N+3 goals are illustrated in Table 2. Meeting or surpassing these goals stimulates innovation and advances the pursuit of revolutionary conceptual designs. System-level multi-disciplinary analysis and optimization (MDAO) and out-of-the-box thinking allows for revolutionary technology identification. This fosters an environment of innovation and generates excitement for future supersonic travel. Overall, the N+3 effort is driven by the need for alternative solutions capable of overcoming the efficiency, environmental, and performance barriers to practical supersonic flight. Results from these studies aid in upcoming research efforts and provides a roadmap for future supersonic funding
2.3 Scope Lockheed Martin Aeronautics conducted research,testing,trade studies and sensitivity analysis in support of the NASA's N+3 Supersonic Vehicle effort.A combination of advanced design and an integrated system analysis was taken to define a conceptual vehicle capable of meeting the environmental and performance goals.Viable technology development paths were produced by the design,engineering,and test capabilities of our team.In addition,core technology trades were performed to provide estimates of the advanced vehicle concept's noise,emissions and performance characteristics.LM was also responsible for the coordination and management of all subcontractors and resulting work.Lockheed Martin is committed to helping NASA successfully achieve their goals of first understanding what is necessary in 2030-2035,generating a suite of enabling concepts and technologies to meet those needs,and socializing that vision with the broadest possible audience. 3.0 Work Breakdown Structure LM Aeronautics was responsible for the overall design,development,and technology identification necessary to realize a visionary vehicle capable of achieving the supersonic N+3 environmental and performance goals.A combination of advanced design and an integrated system approach was required to define an advanced concept vehicle serviceable in the 2030-2035 timeframe (Task 3.1).Design of the vehicle included configuration layout,design,analysis,and definition to produce a concept tightly integrated with airframe and propulsion technologies.Using a system-level design space,LM Aeronautics was also tasked to perform various trade and sensitivity studies to understand how a future Next Generation (NextGen)scenario with supersonic transports drove design requirements(range,noise,emissions,boom,fuel,and mobility).The interplay of design constraints was modeled and analyzed in physics based multi-disciplinary analysis and optimization(MDAO)process using Rapid Conceptual Design(RCD).Task 3.2 included RCD model development,integration with technology inputs, quantified analysis,and technology benefit/impact assessments.After multiple design iterations and system-level analysis of the preferred configuration,LM Aeronautics was responsible for developing a technology roadmap of enabling technologies for the N+3 vehicle.This roadmap includes a list of key technologies,definition of roles and quantification of impacts on the concept vehicle,traceability to N+3 goals,baseline Technology Readiness Levels(TRLs),proposed TRL maturations schemes for future N+3 phases,and prioritization.Overall,LM Aeronautics was ultimately responsible to optimize complex multi- variable combinations of airframe and propulsion technologies while iterating,maturing,identifying,and ultimately down- selecting critical technologies required to realize an N+3 vehicle.Figure 1 illustrates the overall work breakdown structure (WBS)of the tasks and duties required for the program. 3.1 Advanced Concept 3.1.1 Concept 3.1.2 3.1.3 Final Layout and Configuration Configuration Vehicle Design Analysis-RCD Definition Defin ition 3.2 Design 3.2.2RCD 3.2.3 3.2.1RCD Model Quantified 3.2.4 Space Trade Model Integration with Analysis Technology Studies Development Technology (Noise, Benefit/Impact Inouts emissions, Assessment pertormancel 3.3 Technology 3.3.1 3.3.2 3.3.3 Risk 3.3.4 Roadmap Roadmap Technology Technology Analysis Identification Down Selection Development Development 3.6 LM Transportation and Security Solutions(TSS)- ATS System-of-Systems Analyses Figure 1.LM work breakdown structure for N+3 phase 1 program Our efforts focused on four major tasks:Advanced Concept Vehicle Definition(Task 3.1),Design Space Trade Studies(Task 3.2),Technology Roadmap Development (Task 3.3),and ATS System-of-Systems Analysis (Task 3.6).LM was also responsible for the management and coordination of seven subcontractors to provide subject-matter data and expertise to the program.Collaboration included teaming with GE Global Research Center(GRC)with GE Aviation for advanced propulsion Copyright 2010 by Lockheed Martin,Published by the American Institute of Aeronautics and Astronautics,Inc.,with permission. J
Copyright 2010 by Lockheed Martin, Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. 5 2.3 Scope Lockheed Martin Aeronautics conducted research, testing, trade studies and sensitivity analysis in support of the NASA‘s N+3 Supersonic Vehicle effort. A combination of advanced design and an integrated system analysis was taken to define a conceptual vehicle capable of meeting the environmental and performance goals. Viable technology development paths were produced by the design, engineering, and test capabilities of our team. In addition, core technology trades were performed to provide estimates of the advanced vehicle concept‘s noise, emissions and performance characteristics. LM was also responsible for the coordination and management of all subcontractors and resulting work. Lockheed Martin is committed to helping NASA successfully achieve their goals of first understanding what is necessary in 2030-2035, generating a suite of enabling concepts and technologies to meet those needs, and socializing that vision with the broadest possible audience. 3.0 Work Breakdown Structure LM Aeronautics was responsible for the overall design, development, and technology identification necessary to realize a visionary vehicle capable of achieving the supersonic N+3 environmental and performance goals. A combination of advanced design and an integrated system approach was required to define an advanced concept vehicle serviceable in the 2030-2035 timeframe (Task 3.1). Design of the vehicle included configuration layout, design, analysis, and definition to produce a concept tightly integrated with airframe and propulsion technologies. Using a system-level design space, LM Aeronautics was also tasked to perform various trade and sensitivity studies to understand how a future Next Generation (NextGen) scenario with supersonic transports drove design requirements (range, noise, emissions, boom, fuel, and mobility). The interplay of design constraints was modeled and analyzed in physics based multi-disciplinary analysis and optimization (MDAO) process using Rapid Conceptual Design (RCD). Task 3.2 included RCD model development, integration with technology inputs, quantified analysis, and technology benefit/impact assessments. After multiple design iterations and system-level analysis of the preferred configuration, LM Aeronautics was responsible for developing a technology roadmap of enabling technologies for the N+3 vehicle. This roadmap includes a list of key technologies, definition of roles and quantification of impacts on the concept vehicle, traceability to N+3 goals, baseline Technology Readiness Levels (TRLs), proposed TRL maturations schemes for future N+3 phases, and prioritization. Overall, LM Aeronautics was ultimately responsible to optimize complex multivariable combinations of airframe and propulsion technologies while iterating, maturing, identifying, and ultimately downselecting critical technologies required to realize an N+3 vehicle. Figure 1 illustrates the overall work breakdown structure (WBS) of the tasks and duties required for the program. 3.1 Advanced Concept Vehicle Definition 3.2 Design Space Trade Studies 3.3 Technology Roadmap Development 3.6 LM Transportation and Security Solutions (TSS) – ATS System-o f-Systems Analyses 3.2.1 RCD Model Development 3.2.2 RCD Model Integration with Technology Inputs 3.2.3 Quantified Analysis (Noise, emissions, performance) 3.2.4 Technology Benefit/Impact Assessment 3.1.1 Concept Layout and Design 3.1.2 Configuration Analysis – RCD 3.1.3 Final Configuration Definition 3.3.1 Technology Identification 3.3.2 Technology Down Selection 3.3.3 Risk Analysis 3.3.4 Roadmap Development RCD Model Technologies Final Model Technologies SoS Considerations SoS Considerations Value Assessment 3.1 Advanced Concept Vehicle Definition 3.2 Design Space Trade Studies 3.3 Technology Roadmap Development 3.6 LM Transportation and Security Solutions (TSS) – ATS System-o f-Systems Analyses 3.2.1 RCD Model Development 3.2.2 RCD Model Integration with Technology Inputs 3.2.3 Quantified Analysis (Noise, emissions, performance) 3.2.4 Technology Benefit/Impact Assessment 3.1.1 Concept Layout and Design 3.1.2 Configuration Analysis – RCD 3.1.3 Final Configuration Definition 3.3.1 Technology Identification 3.3.2 Technology Down Selection 3.3.3 Risk Analysis 3.3.4 Roadmap Development RCD Model Technologies Final Model Technologies SoS Considerations SoS Considerations Value Assessment Figure 1. LM work breakdown structure for N+3 phase 1 program Our efforts focused on four major tasks: Advanced Concept Vehicle Definition (Task 3.1), Design Space Trade Studies (Task 3.2), Technology Roadmap Development (Task 3.3), and ATS System-of-Systems Analysis (Task 3.6). LM was also responsible for the management and coordination of seven subcontractors to provide subject-matter data and expertise to the program. Collaboration included teaming with GE Global Research Center (GRC) with GE Aviation for advanced propulsion
concepts as well as fuel efficiency and emissions,Penn State for jet noise reduction,Purdue for system of system analysis,MIT for green initiatives,Wyle labs for real-world loudness effects and boom guidance,LM Transportation Security Solutions for air traffic analysis,and Helen Reed and Bill Saric for laminar flow analysis.All required tasks include subsequent subtasks that align with the main task.The WBS encompasses all work necessary to oversee and direct the execution of the N+3 Phase 1 Program. 4.0 Tasks and Trade Studies-Airframe Systems 4.1 Advanced Vehicle Concept(WBS 3.1) 4.1.1 Concept Layout and Design (WBS 3.1.1) 4.1.1.1 Description Before laying out a configuration,we looked at the N+3 goals and addressed design methods and strategies necessary to meet those challenges.Based on our past history designing and analyzing supersonic configurations,we first focused our energy on the sonic boom requirement.The N+3 sonic boom goal of 65-70 PLdB is significantly lower than the state of the art 107 PLdB of the (408,000 Ib,100 passenger)Concorde with a shock strength of 2 psf,or the 102 PLdB of the (12,000 Ib-33 times lighter than Concorde)F-5 with a shock strength of 1.3 psf.Meeting the sonic boom goal requires a minimum shock(ramp signature)shock strength of 0.12 to 0.17 psf.One way of meeting this goal is increasing the fuselage length used by SEEB to calculate the minimum shock signature,as shown in Figure 2.In order to reduce the length required,it is anticipated that the perceived level of noise on the ground can be reduced through shock blending,as shown from 2 methods of varying shock separation in Figure 3,and through taking into account real world absorption and turbulence.Results from Wyle's analysis on Effects of Atmospheric Propagation on Low-Boom Shaped Signatures can be seen in Section 4.2.5. 500 MTOW 450,000 Ib 450 400 350 300 Typical Non- 250 Low Boom 200 450,000Ib 150 100 SST Optimum 50 Length 0 60 65 70 75 80 85 90 PLdB Figure 2. Relation between vehicle length and perceived level of noise (PLdB) The other noise challenge was meeting the airport noise goal of 20-30 EPNdB cumulative below FAR36 Stage 3 limits. Current subsonic airplanes,like the Boeing 777-200 with GE 90-85B and the Airbus A380 with RR Trent 970,already meet this goal at 23 EPNdB and 26 EPNdB cum below stage 3 respectively.However,it is more of a challenge for supersonic aircraft.Using the Concorde as a state of the art(SOA)comparison,its supersonic transport status is 45 EPNdB cumulative above Stage 3.Our strategy for meeting the noise goal was to first require GE to meet sideline-3 EPNdB at 90%power also known as PLR(programmed lapse rate),use the GE Variable Cycle Engine,and optimize takeoff procedures.Second,reduce approach noise with a low-noise fan design,inlet liners and inlet flow choking.Third,investigate other promising advanced technologies. Copyright 2010 by Lockheed Martin,Published by the American Institute of Aeronautics and Astronautics,Inc.,with permission. 6
Copyright 2010 by Lockheed Martin, Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. 6 concepts as well as fuel efficiency and emissions, Penn State for jet noise reduction, Purdue for system of system analysis, MIT for green initiatives, Wyle labs for real-world loudness effects and boom guidance, LM Transportation & Security Solutions for air traffic analysis, and Helen Reed and Bill Saric for laminar flow analysis. All required tasks include subsequent subtasks that align with the main task. The WBS encompasses all work necessary to oversee and direct the execution of the N+3 Phase 1 Program. 4.0 Tasks and Trade Studies – Airframe Systems 4.1 Advanced Vehicle Concept (WBS 3.1) 4.1.1 Concept Layout and Design (WBS 3.1.1) 4.1.1.1 Description Before laying out a configuration, we looked at the N+3 goals and addressed design methods and strategies necessary to meet those challenges. Based on our past history designing and analyzing supersonic configurations, we first focused our energy on the sonic boom requirement. The N+3 sonic boom goal of 65-70 PLdB is significantly lower than the state of the art 107 PLdB of the (408,000 lb, 100 passenger) Concorde with a shock strength of 2 psf, or the 102 PLdB of the (12,000 lb—33 times lighter than Concorde) F-5 with a shock strength of 1.3 psf. Meeting the sonic boom goal requires a minimum shock (ramp signature) shock strength of 0.12 to 0.17 psf. One way of meeting this goal is increasing the fuselage length used by SEEB to calculate the minimum shock signature, as shown in Figure 2. In order to reduce the length required, it is anticipated that the perceived level of noise on the ground can be reduced through shock blending, as shown from 2 methods of varying shock separation in Figure 3, and through taking into account real world absorption and turbulence. Results from Wyle‘s analysis on Effects of Atmospheric Propagation on Low-Boom Shaped Signatures can be seen in Section 4.2.5. Figure 2. Relation between vehicle length and perceived level of noise (PLdB) The other noise challenge was meeting the airport noise goal of 20-30 EPNdB cumulative below FAR36 Stage 3 limits. Current subsonic airplanes, like the Boeing 777-200 with GE 90-85B and the Airbus A380 with RR Trent 970, already meet this goal at 23 EPNdB and 26 EPNdB cum below stage 3 respectively. However, it is more of a challenge for supersonic aircraft. Using the Concorde as a state of the art (SOA) comparison, its supersonic transport status is 45 EPNdB cumulative above Stage 3. Our strategy for meeting the noise goal was to first require GE to meet sideline -3 EPNdB at 90% power also known as PLR (programmed lapse rate), use the GE Variable Cycle Engine, and optimize takeoff procedures. Second, reduce approach noise with a low-noise fan design, inlet liners and inlet flow choking. Third, investigate other promising advanced technologies
Signature Variations for Loudness vs.Shock Separation 0.8 -15 msec Separation 0.6 -6 msec Separation same Duration 0.4 -6 msec Separation same Expansion 02 30 120 140 160 200 -0.2 -0.4 0.6 -0.8 Time,msec Loudriess vs.Shock:Separation Rise Time =1/AP +14 ■Same Duration Same Expansion 8 Poly.(Same Duration) -Poly.(Same Expansion) 8p7d 'ssaupno] 20364208 10 20 25 Shock Separation,msec Figure 3. Effect of shock separation on loudness As part of the iterative design process,we looked at a number of different vehicle concepts that would integrate features necessary to achieve the N+3 mission requirements and performance goals.Desirable configuration features included items that would provide low boom,low drag,low weight,and good aeroelasticity performance for cruise and off-cruise conditions. Drawing on previous Quiet Supersonic Transport (QSST)experience,our process started with applying the desirable configuration features to a modified inverted-V,"QSST-like"concept.The four-engine inverted V-tail concept was proposed to better capture advantages of the inverted tail concept-particularly greater wing bending moment relief. Preliminary vehicle sizing with QSST and historical data established the weight breakdown necessary to determine engine thrust,wing sizing,and fuselage length for boom.A slight improvement was assumed,giving an L/D of 10 and an SFC of 0.95 Ib fuel/lb thrust/hr.These assumptions were applied to the reference mission of 100 passengers,4000 nm range,and Mach 1.6 cruise.This resulted in a Max Take-off Gross Weight(MTOW)of just over 300,000 Ib,with an efficiency of 3.07 pax-nm/Ib fuel,as shown in Figure 5.However,this did not meet the requirement of efficiency between 3.5 to 4.5 pax-nm/lb fuel.It was calculated that the efficiency could be raised to 3.97 pax-nm/lb fuel if the L/D increased to 11,the SFC improved to 0.90 Ib fuel/lb thrust/hr,and empty weight reduced by 5%.This quantified the N+3 vehicle improvement values to achieve NASA's desired performance goals.These values were status indicators as opposed to targets.N+3 technologies were sought to maximize performance as much as possible and potentially go beyond these goals. Copyright 2010 by Lockheed Martin,Published by the American Institute of Aeronautics and Astronautics,Inc.,with permission. 7
Copyright 2010 by Lockheed Martin, Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. 7 Signature Variations for Loudness vs. Shock Separation -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 0 20 40 60 80 100 120 140 160 180 200 Time, msec Ground Overpressure, psf 15 msec Separation 6 msec Separation same Duration 6 msec Separation same Expansion Signature Variations for Loudness vs. Shock Separation -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 0 20 40 60 80 100 120 140 160 180 200 Time, msec Ground Overpressure, psf 15 msec Separation 6 msec Separation same Duration 6 msec Separation same Expansion Figure 3. Effect of shock separation on loudness As part of the iterative design process, we looked at a number of different vehicle concepts that would integrate features necessary to achieve the N+3 mission requirements and performance goals. Desirable configuration features included items that would provide low boom, low drag, low weight, and good aeroelasticity performance for cruise and off-cruise conditions. Drawing on previous Quiet Supersonic Transport (QSST) experience, our process started with applying the desirable configuration features to a modified inverted-V, ―QSST-like‖ concept. The four-engine inverted V-tail concept was proposed to better capture advantages of the inverted tail concept – particularly greater wing bending moment relief. Preliminary vehicle sizing with QSST and historical data established the weight breakdown necessary to determine engine thrust, wing sizing, and fuselage length for boom. A slight improvement was assumed, giving an L/D of 10 and an SFC of 0.95 lb fuel/lb thrust/hr. These assumptions were applied to the reference mission of 100 passengers, 4000 nm range, and Mach 1.6 cruise. This resulted in a Max Take-off Gross Weight (MTOW) of just over 300,000 lb, with an efficiency of 3.07 pax-nm/lb fuel, as shown in Figure 5. However, this did not meet the requirement of efficiency between 3.5 to 4.5 pax-nm/lb fuel. It was calculated that the efficiency could be raised to 3.97 pax-nm/lb fuel if the L/D increased to 11, the SFC improved to 0.90 lb fuel/lb thrust/hr, and empty weight reduced by 5%. This quantified the N+3 vehicle improvement values to achieve NASA‘s desired performance goals. These values were status indicators as opposed to targets. N+3 technologies were sought to maximize performance as much as possible and potentially go beyond these goals
b fraction Empty Weight 148,000 0.492 Reference Mission Payload Weight 22,440 0.075 100pax Fuel Weight 130,200 0.433 4.000 Nmi range Mach 1.6.50.000 ft altitude Max Take-Off Weight 300,600 pax-Nmi/Ibfuel Efficiency 3.07 Figure 4. Initial sizing for reference mission 4.1.1.2 Results The initial configuration was sized with an assumed MTOW approximately equal to 300,000 Ibs,resulting in a wing area approximately equal to 3,000 ft,and a take-off thrust approximately equal to 100,000 Ibs.The benefits of this low-boom configuration include stretched boom signature due the inverted V-tail and nose droop,favorable aerodynamic interference and compression lift for aft-under-wing mounted engines,efficient propulsion integration due to the planform trailing edge sweep and airfoil reflex,aerodynamic efficiency for wing planform design,reduced wing gull roll penalties due to wing tip and inverted V-tail anhedral,and structural flexibility suppression due to inverted V-tail wing bracing.Once designed,these specific elements were considered endemic to the configuration and always a part of the initial configuration technology set. The design was used as the "yardstick"to compare other potential configurations.Figure 5 highlights the overall initial configuration definition and design features that were modelled within CATIA V5. Forebody volume buildup and signature requirements Inverted Vfor structural stability per shaped signature requirements Planform TE for 200ft Wing dihedral elevates lift for stretched boom Tip anhedral reducing signature roll in side-slip,allowing greater inboard dihedral Wing Area--3,000 sqft Aft-under-wing mounted T/O Thrust--100.000 lb engines for favorable Nose droop for stretched boom siqnature aerodynamic MToW--300.000b interference and compression lift 80ft Figure 5.Initial Configuration Definition Once the initial concept was defined,an initial inner mold-line(IML)cabin volume constraint was determined to insert passengers within the loft.The initial configuration held 101 passengers including future projected economy seat sizing comfort improvements relative to the Concorde and other regional jets plus the provision for 10%first class seats.The cabin layout included one galley,two lavatories,one supplemental space,and three emergency constraints.The boom constraints on the fuselage outer mold line(OML)forced cabin camber and cross section pinching on each end.This limitation required one 1s class seat to be removed from the forward section of the cabin,and a unification of the next set of seats.Nine rows in the aft section of the cabin changed from 4 across to 3 across while the cabin was lengthened.Cambered cabin slopes less than 5% have to be reconciled in a future design phase.Figure 6 demonstrates a realistic cabin layout that establishes fuselage IML constraints for the initial configuration. Copyright 2010 by Lockheed Martin,Published by the American Institute of Aeronautics and Astronautics,Inc.,with permission
Copyright 2010 by Lockheed Martin, Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. 8 Figure 4. Initial sizing for reference mission 4.1.1.2 Results The initial configuration was sized with an assumed MTOW approximately equal to 300,000 lbs, resulting in a wing area approximately equal to 3,000 ft2 , and a take-off thrust approximately equal to 100,000 lbs. The benefits of this low-boom configuration include stretched boom signature due the inverted V-tail and nose droop, favorable aerodynamic interference and compression lift for aft-under-wing mounted engines, efficient propulsion integration due to the planform trailing edge sweep and airfoil reflex, aerodynamic efficiency for wing planform design, reduced wing gull roll penalties due to wing tip and inverted V-tail anhedral, and structural flexibility suppression due to inverted V-tail wing bracing. Once designed, these specific elements were considered endemic to the configuration and always a part of the initial configuration technology set. The design was used as the ―yardstick‖ to compare other potential configurations. Figure 5 highlights the overall initial configuration definition and design features that were modelled within CATIA V5. Figure 5. Initial Configuration Definition Once the initial concept was defined, an initial inner mold-line (IML) cabin volume constraint was determined to insert passengers within the loft. The initial configuration held 101 passengers including future projected economy seat sizing comfort improvements relative to the Concorde and other regional jets plus the provision for 10% first class seats. The cabin layout included one galley, two lavatories, one supplemental space, and three emergency constraints. The boom constraints on the fuselage outer mold line (OML) forced cabin camber and cross section pinching on each end. This limitation required one 1 st class seat to be removed from the forward section of the cabin, and a unification of the next set of seats. Nine rows in the aft section of the cabin changed from 4 across to 3 across while the cabin was lengthened. Cambered cabin slopes less than 5% have to be reconciled in a future design phase. Figure 6 demonstrates a realistic cabin layout that establishes fuselage IML constraints for the initial configuration
1.Boom constraints on fuselage OML force cabin camber and X-sec plnching on ends 2. One 1 Class seat removed from front,next row 参ats moved to9ther 3.9rows in aft coach changed to 3 across,cabin lengthened 4.Camber slopes below 5 deg,can design workable noor angle垂 Wall encroachment Forward Aft Economy 4X Economy5X (50"pltch) (32"pltch] (32"pitch) Prem.Economy (36"pltch) Galley 165* 70° 58” 月oor camher Ba99(466c not picture 933量 Cabin implications of Low-Boom Area Distribution: 1.Non-uniform seat rows (2+2,3+2) Lowest standing helght 2.Low clearance at forward end Figure 6.Area-ruled cabin layout 4.1.2 Alternative Configurations (WBS 3.1.1) 4.1.2.1 Description The N+3 concept vehicle definition also included exploration of alternative concepts,both conventional and unconventional,to investigate all potential configuration solutions.Figure 7 highlights the various configurations that were studied starting with the family of inverted-v tail configurations and branching off to an oblique wing,a twin-fuselage concept,and a variety of brainstorming concepts. Copyright 2010 by Lockheed Martin,Published by the American Institute of Aeronautics and Astronautics,Inc.,with permission. 9
Copyright 2010 by Lockheed Martin, Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. 9 Figure 6. Area-ruled cabin layout 4.1.2 Alternative Configurations (WBS 3.1.1) 4.1.2.1 Description The N+3 concept vehicle definition also included exploration of alternative concepts, both conventional and unconventional, to investigate all potential configuration solutions. Figure 7 highlights the various configurations that were studied starting with the family of inverted-v tail configurations and branching off to an oblique wing, a twin-fuselage concept, and a variety of brainstorming concepts
Family of Configurations Initial Configuration Definition-Inverted-V Oblique Flying Wing Configuration Engine Over Wing Configuration Twin Fuselage Configuration Mother/ Blue Sky Daughter Session T-Tail Configuration Mother/Daughter,Blue Sky Alternatives Figure 7.Alternative configuration concepts chosen for further analysis "Blue Sky"Configurations After the initial ideas listed above were considered,further brainstorming sessions,called "blue sky,"were conducted with leading experts from outside the program,to identify more revolutionary concepts.However,no further configurations were discovered that could reasonably outperform those concepts already being considered. Engines-Over-Wing Configuration The engine-over-wing configuration was considered to address potential structural benefits (shorter landing gear)and noise level reductions possible with engine placements above the wing.When the engines are placed over the wing,engine spillage shocks are blocked from the ground by the wing.However,this results in higher pressure on the upper surface of the wing predicted to reduce L/D by 2 points. In order to assess the need for noise reduction with the engines over wing configuration,it needed to be determined how low the noise could be for the engine under wing configuration. This was done through a wing configuration study to address propulsion/airframe integration (PAI)issues of a low-boom design.Figure 8 exhibits the trailing edge design study used for favorable interference drag.The wing trailing edge was swept to capture maximum nacelle shock compression lift and airfoil reflex for shock (and drag)cancellation.The nacelle shock was substantially countered;it met a 65-70 PLdB equivalent area target as easily as above the wing engine placements. The high pressure caused by the nacelle shock on the lower surface of the wing resulted in higher efficiency (lower angle-of- attack)through an increased L/D.Since it was possible to meet the sonic boom requirement with the higher efficiency of the engines-under-wing concept,further development of the engines-over-wing configuration was discontinued. Copyright 2010 by Lockheed Martin,Published by the American Institute of Aeronautics and Astronautics,Inc.,with permission. 10
Copyright 2010 by Lockheed Martin, Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. 10 Figure 7. Alternative configuration concepts chosen for further analysis ―Blue Sky‖ Configurations After the initial ideas listed above were considered, further brainstorming sessions, called ―blue sky,‖ were conducted with leading experts from outside the program, to identify more revolutionary concepts. However, no further configurations were discovered that could reasonably outperform those concepts already being considered. Engines-Over-Wing Configuration The engine-over-wing configuration was considered to address potential structural benefits (shorter landing gear) and noise level reductions possible with engine placements above the wing. When the engines are placed over the wing, engine spillage shocks are blocked from the ground by the wing. However, this results in higher pressure on the upper surface of the wing predicted to reduce L/D by 2 points. In order to assess the need for noise reduction with the engines over wing configuration, it needed to be determined how low the noise could be for the engine under wing configuration. This was done through a wing configuration study to address propulsion/airframe integration (PAI) issues of a low-boom design. Figure 8 exhibits the trailing edge design study used for favorable interference drag. The wing trailing edge was swept to capture maximum nacelle shock compression lift and airfoil reflex for shock (and drag) cancellation. The nacelle shock was substantially countered; it met a 65-70 PLdB equivalent area target as easily as above the wing engine placements. The high pressure caused by the nacelle shock on the lower surface of the wing resulted in higher efficiency (lower angle-ofattack) through an increased L/D. Since it was possible to meet the sonic boom requirement with the higher efficiency of the engines-under-wing concept, further development of the engines-over-wing configuration was discontinued