Cruise Efficient Short Take-Off and Landing (CESTOL) Subsonic Transport System (Revolutionary System Concepts for Aeronautics ’05) Hyun Dae Kim NASA Glenn Research Center Jan. 26, 2006

Cruise Efficient Short Take-Off & Landing (CESTOL) Background Brief Concept Vehicle Description Study Plan Graphical Animation Presentation by Boeing Technology / Phantom Works on Vehicle Configuration Q & A

Description of the Problem Cruise Efficient Short Take-Off & Landing (CESTOL) Description of the Problem Saturation of airports and the impact to the surrounding airspace and terrestrial communities are a rapidly increasing limit to world aviation travel. Subsonic commercial concepts appearing on the 25 year horizon must facilitate a more than 4X increase in air traffic, while complying with more stringent respect for the surrounding communities across the expanding world market. Under-utilization of small regional airports (e.g., Cleveland’s Burke Lakefront Airport) OBJECTIVE Need fuel efficient low noise aircrafts that utilize small regional airports to address air traffic growth. -> Low Noise Cruise Efficient STOL (CESTOL) Vehicle

Historical High Subsonic Transport Aircraft Configurations Boeing 707 De Havilland Comet Historically, there have been two distinctive commercial transport configurations. One is a podded engine configuration like the original Boeing 707 and its derivatives. The other is an embedded engine configuration like the British De Havilland Comet aircraft which later became current British Nimrod military aircraft. Northrop YB-49

Cruise Efficient Short Take-Off & Landing (CESTOL) New Vehicle Concept Embedded Distributed Propulsion Vehicle will have: High lift capability via spanwide vectored thrust providing powered and/or circulation control lift to enable STOL operation. Efficient cruise performance through drag reduction by wing wake fill-in with engine thrust stream. Reduction in aircraft noise through airframe shielding and acoustic treatment of the large available surface area of propulsion system. Improvement in safety through a redundant multiple propulsion system. Reduction or elimination of a number of aircraft control surfaces through differential and vectoring thrust for pitch, roll, and yaw moments. Synergistic vehicle-propulsion integration is the key! Now, here are the proposed concept description. The Key to the concept is Synergistic …… Thick wing/box structure weight savings Weight savings thru common structure in inlets, wings, nozzles, etc. No tail. Significant drag reduction possilble Increased internal drag Engine maintenance diffuculty -> Not so. Engines can be installed between wing ribs and lowered thru lower wing surface. Adverse flow interation between wing and propulsion aerodynamcs -> this can be overcome thru prudent CFD design.

Study Plan Task Organization Deliverables Date Define mission design requirements GRC/Boeing Mission Req’s 7/30/05 Define vehicle configuration Boeing Vehicle Definition 10/30/05 1st order engine cycle analysis GRC Engine Deck Explore noise benefits of distributed propulsion system Diversitech Detailed Final Report 1/31/06 Assess system benefits and perform comparison study Assess noise benefits of the defined vehicle Summarize results and recommend research approaches All Final Report

Graphical Animation of CESTOL Aircraft At Cleveland’s Burke Lakefront Regional Airport

Cruise Efficient Short Take-Off and Landing (CESTOL) Subsonic Transport System (Revolutionary System Concepts for Aeronautics ’05) Ronald Kawai Boeing Technology/Phantom Works Huntington Beach

Study Scope Boeing Technology/Phantom Works Huntington Beach Creates Revolutionary Concept and Develops Characteristics, Performance, and Identifies Technology Needs for an Airplane Configuration Embodying Very Low Noise Features Capable of Operations from Regional Airports NASA GRC Separate Contractor Quantifies Low Noise Potential

LITERATURE REVIEW Powered lift can provide high CL for STOL Past STOL transport studies for regional/short range at cruise speeds less than Mach 0.8 DSS turboprops have lowest GW & Cost but speed limited to below Mach 0.7 Efficient Mach 0.8 possible with turbofans or UHB unducted fans Mach 0.8 requires supersonic tip speed fans or counter-rotating fans but the later have high take off and enroute noise A shrouded fan, i.e. turbofan is needed for high speed with low noise IBF/USB/Augmentor Wing have highest high lift efficiency

Other Studies Show Internally Blow Flap Has Better High Lift Performance But Judged Complex

Extensive studies and analyses resulted in AF AMST program fly-off between YC-14 and YC-15 IBF and Augmentor Wing ruled out by hot ducting complexity YC-14 and YC-15 where straight wing airplanes With efficient cruise below Mach 0.7

YC-14 Interior Noise Peak at 70 - 100 hz AFFDL-TR-77-128

BOEING C-17A AF SELECTED THE C-17 WITH EBF TO BECOME THE ONLY SUCCESSFUL LARGE TURBOFAN POWERED STOL TRANSPORT (Swept Wing for Mach 0.74 – 0.77 Cruise, 2750 nmi range w/164,900 lb payload, First flight Sept 15, 1991) FUTURE STOL TRANSPORT CONCEPT IMROVEMENT OPPORTUNIES: - IMPROVE CRUISE EFFICIENCY (INCREASE SPEED AND RANGE) - LOWER NOISE

remain near constant with increased flight frequencies and city pairs 2005 Boeing Current Market Outlook Extrapolation of growth forecast would predict average airplane size to remain near constant with increased flight frequencies and city pairs Future Demand continues for 90 to 175 passenger size Operating from regional airports would relieve long pre-departure times

Noise Restrictions can be expected to escalate with increasing number of flights Very low noise will be required to enable growth for expanded operations at existing and new commercial airports while minimizing noise penalties

Including a minimum 100 ft runway width for larger aircraft showed that 84% or 813 of 973 civil airports have 5,000 ft + AIAA 2003-2891, Regional Jet Operational Improvements resulting from Short Field Performance and Design

Noise Footprint Would Be Very Important at Many Other Airports: Expanded use of regional airports Allow relaxation of curfews/operating at night Allow increased operations per day Allow conversion of military closing to commercial use Neighbors want low noise regardless of airplane weight: Goal should be cum noise as to Stage 3 minus XX

STOL to Reduce Noise Footprints Rapid Climb Out Steep Approach Take Off The BWB configurations studied have inherently much lower approach noise. The take-off noise benefits from no wing noise reflection.. Sideline 2000m Approach

. TO . Sideline Approach Low Sideline Noise would be of high value at Burke Lakefront Airport

Long Beach, CA Airport 10PM to 7AM curfew 41 flight/day limit can be raised if aircraft noise decreased

El Toro Marine Air Base in SoCal could not be converted to relieve congestion at LAX because of neighborhood opposition

2025+ Summary Traffic Growth Forecasts generally for next 20 years For 2025+, extrapolate trends from Boeing Current Market Outlook Noise sensitive regions are U.S. and Europe Twin aisles and large airplanes for trans oceanic flights Single aisle dominates size and generally with many more take-off and landing operations/day than twin aisle and large aircraft Reducing noise for greatest noise growth is thus single aisle 90-175 passenger size Focus on high end for growth, 170 passenger size, but with BWB, It becomes multiple aisle airplane Study for use at regional airports for air traffic expansion that may provide dual use technology for multi-role military applications

BLENDED WING BODY IS FUTURE CONCEPT FOR IMPROVED EFFICIENCY AND LOWER NOISE LOW NOISE FEATURES: Forward noise shielding No aft noise reflection No flap noise Low approach thrust Body suppression of landing gear noise

Benefits From Embedded Distributed Propulsion Embedded engines for quiet powered lift Close coupled engine to slot with cold low pressure fan bleed Smaller nozzle diameters for improved jet noise shielding More rapid mixing moving jet noise source forward Longer flap chord shielding / nozzle diameter Increased atmospheric attenuation form higher frequency jet noise Reducing engine size enables embedding in mid wing sections for more forward Cp and Cg Reduces the thrust of individual engines reducing engine out thrust yaw control moments

Distributed propulsion: Forward Fan Noise Shielding Aft Turbo-machinery and Combustion Noise Shielding Jet Noise Shielding Chevrons for mixing Fan Bleed IBF Freestream Inlet Distributed propulsion: Smaller exhaust diameters enhances jet noise shielding Smaller engines enable direct fan bleed for low pressure powered IBF Slotted ejector reduces powered lift noise Minimal engine out rolling moment with powered lift

Concept Development Process SOW 2025 technology for traffic growth using untapped regional airspace Cruise efficient configuration with Embedded Wing Propulsion Review/Summarize Previous Studies IBF most efficient powered lift for STOL Mission Requirements for CESTOL 170 pax, 3,000 nmi, Mach 0.8 Very low noise Minimum 5,000 ft TOFL Define Configuration with STOL characteristics WingMOD planform development Digital configuration development Assess System Benefits of Distributed Propulsion on CESTOL Boeing Integrated Vehicle Design System (BIVDS) synthesis Very low noise features on Quiet Powered Lift Concept Foundational Technology Needs Outlined

WingMOD: Multidisciplinary Optimization Configuration Estimate Hard Constraints Payload Range Approach Speed etc. Design Constraints Running Loads Buffet Characteristics DFMA etc. Optimized Config. WingMOD Optimizer Baseline Config. Closed. Balanced. Trimmed. Min. OEW Aerodynamics Vortex Lattice Model Empirical Profile Drag, Compressibility Drag, & Sectional Maximum Lift CFD, Wind Tunnel Calibration Structures Monocoque Beam Model Stress & Buckling Sizing Static Aeroelastics Controls Elevon Model Balance Analysis Configuration Layout

Quiet Distributed Propulsion Starting Point Fan bleed slot ejector IBF for quiet powered lift Short inlet diffuser w/AFC Inlet and exhaust noise shielding IBF sizing 12 x 6 K lb thrust engines Slot width per engine = 68.1 in Slot height = 2.36 in Fan pressure ratio = 1.69 4 engines 4 engines 4 engines Injection Slots 272.4 in 272.4 in 137 ft 100 optimization runs to evolve controllable planform

Configuration Components – All Basic Airframe Upper Deck Avionics Air Conditioning Lower Deck Landing Gear Furnishings & Standard Items Anti-Icing Operational Items Propulsion Electrical Inboard Fuel Instruments Outboard Fuel Fuel System Surface Controls Hydraulic, Pneumatic, APU

Control Surface Usage Lift effectors geared to pitch effectors -0.64:1 for trim, 0.44:1 for control 10.2 deg flap deflection on lift effectors Transition flap geared to pitch effectors -0.29:1 for trim, 0.16:1 for control Lift effect, pitch and roll control Yaw and roll control Pitch and roll control Pitch control

BIVDS Evaluation Mission Performance EWP Design 500 nm 150 nm Range (nm) 3,000 500 150 Payload (lb) 40,000 Takeoff Gross Weight (lb) 189,140 157,874 152,835 Landing Weight (lb) 152,548 151,052 150,866 Total Fuel (lb) 44,098 12,832 8,793 Block Fuel (lb) 37,723 7,946 4,098 Block Time (h) 6.92 1.48 0.68 Initial Cruise Altitude (ft) 39,000 43,000 31,000 Takeoff Field Length (ft) 2,452 1,772 1,694 Landing Field Length (ft) 3,477 3,457 3,454 Takeoff CLmax Liftoff 1.66 1.80 1.83 Takeoff CLmax Obstacle 1.57 1.65 Landing CLmax 1.06

Segment Climb 1st and 2nd Accel to Final Climb Speed TO Performance analyses resulted in about the same take-off flight paths with the same altitude over the take-off measuring point at 6,500 m or 21,325 ft from brake release

Very Low Noise Features 3,500 ft TOFL Embedded Distributed propulsion enables quiet powered lift with jet noise shielding Rapid Climb (3000+ ft over T.0. noise point) Could Use Cutback or Higher Altitude Before Acceleration to Climb Speed Steep Descent (6 degree glide slope) Forward Noise Shielded Aft Noise Shielded Consider Part Span Verticals to Improve Sideline Shielding if Necessary Note: Powered lift is off during climb Differential elevons positions could be optimized for noise shielding Boeing Technology/Phantom Works Huntington Beach provides mission data for very low noise concept for NASA to make noise assessment

Foundational Technologies Needed Noise Shielding Codes Reflections Turbo-machinery noise Jet noise Inlet/airframe Aero Integration Inlets in high Mach flow field Quiet Powered Lift: Low Pressure IBF performance and noise Revolutionary Engine Concepts Short Cruise Efficient Variable Geometry Noise Reflection Nozzles Forward noise source Flow Control Inlets Active, Passive and Hybrid Evaluations

Reduce Nozzle Height and Create Vortices to Move Jet Noise Source Forward

Need Small Turbofan for X-48B Foundational Technology for Jet Noise Shielding Shielded Jet Noise Nozzle CFD Development Shielding Code Development Calibration Wind Tunnel Tests Model Tests Flight Validations Small Turbofan(s) Current X-48B program to validate low speed characteristics Modify with quiet turbofan for very low noise and IR validation

Conclusions Continuing growth in air travel demand is forecast. This growth is expected to increase daily departures operating from an increasing number of city pairs. This growth is forecast to go with increasing GDP providing a need for very quiet airplane operating from regional airports which can have current economics Studies have shown eliminating noise reflections while providing noise shielding can significantly reduce flyover noise Extending these principals to jet noise source downstream in the exhaust wake should provide more dramatic noise reductions Large surface area planforms such as the BWB provides opportunities for increased source noise shielding Embedded distributed propulsion offers the potential for quiet powered lift with jet noise shielding for small noise footprints operating from regional airports Configuration studies were made to evolve a BWB STOL planform that is trimmable with total noise shielding Low noise footprints would also have low IR footprints for passive protection from terrorists Development of foundational technologies are needed that would be generic and dual use