Breaking the Real Sound Barrier: Achieving Quiet Supersonic Flight

Aircraft Builders Conference Montreal Canada Peter Coen NASA Low Boom Flight Demonstration Mission Manager www.nasa.gov www.nasa.gov1 Presentation topics

• NASA Aeronautics • Commercial supersonic flight background • What is a sonic boom anyway? • From boom to thump: Designing for quiet flight • How will we know if it’s quiet enough • NASA’s Low Boom Flight Demonstration • Concluding remarks

2 www.nasa.gov NASA: The National AERONAUTICS and Space Administration “The Big ”A” in NASA”

3 www.nasa.gov NASA Aeronautics NASA Aeronautics Vision for Aviation in the 21st Century

U.S. leadership for a new era of flight

4 www.nasa.gov Innovation in Commercial Supersonic Flight Commercial supersonic flight represents a potentially large new market for aircraft WHY? manufacturers and operators world-wide

The government plays a central role in • Global demand for air travel is growing, which places a demand on speed developing the data • Supersonic aircraft manufacturing offer the opportunity to establish a new needed for the market segment with significant export opportunity and high-tech job growth regulation change that is – Large potential market predicted: - business aircraft followed by larger essential to enabling commercial aircraft this new market – Technology leadership established through initial products will lead to development of larger, more capable airliners • Technologies reducing the environmental impact of supersonic aircraft may www.nasa.gov benefit subsonic aircraft as well The Vision for Commercial Supersonic Flight Overland Flight Restrictions based The emerging potential market has generated renewed interest in on unacceptable civil supersonic aircraft sonic boom noise • Evidenced by the appearance of several commercial programs even with are viewed as the existing restrictions on overland flight and other challenges main barrier to this vision

The vision of the Supersonics Community is a future where fast air travel is available for a broad spectrum of the traveling public. • Future supersonic aircraft will not only be able to fly overland without creating an “unacceptable situation” but compared to Concorde and SST will be efficient, affordable and environmentally responsible www.nasa.gov Credit :Lockheed Martin Supersonic flight and sonic boom: A brief hhistory

1947 First supersonic flight Bell X-1 Sonic boom a novelty

1950s Rapid development of supersonic military aircraft F-100 Noise and damage concerns Extensive research into sonic boom XB-70 1960s Supersonic Commercial aircraft proposed Community studies determine sonic boom exposure is unacceptable to people 1973 US Federal ban, International limits Concorde 1976 – 2003 Concorde commercial service Supersonic operation only over the ocean 2003 DARPA-NASA Shaped Sonic Boom Demonstration SSBD First flight demonstration of theory for ”shaping” boom signature 2011 Breakthrough! Shaped signature in a practical aircraft design New approaches demonstrated by analysis and model testing

Quiet Supersonic Concept www.nasa.gov What is a sonic boom?

• Not the sound of an aircraft ”breaking the sound” barrier • Caused by instantaneous pressure changes called shock waves • Occurs continuously during supersonic flight

www.nasa.gov 8 Why is a sonic boom so loud?

What makes it annoying?

Duration

Pressure Change

Rise Time Rounding

www.nasa.gov 9 From ”Boom” to “Thump”: How is it done?

www.nasa.gov 10 That doesn’t sound too hard…. Almost 50 years of research to solve the sonic boom noise problem Minimum 1960’s 2-D Geometry Overpressure Original math connecting the shape of the aircraft Minimum to the shape of the signature on the ground Initial Shock 1970’s-80’s 3-D Geometry Front Math improved to allow representation of actual aircraft geometry. Experimental validation Shaping Only

1980’s-90’s Segmented Nose Multiple, Computational models, new approaches to Similar breaking up shock waves, Experimental and flight Shocks validation

Detailed Model of All Features Fully Shaped, Rounded Shocks 2000’s Fast, high fidelity computations New approach to selecting design goals. Maximized effects of the atmosphere

11 www.nasa.gov Quiet supersonic designs are within reach

Breakthrough knowledge advancement • New methods for the design of aircraft with shaped sonic boom signatures • Shaping incorporated into practical, balanced designs • Design performance validated by wind tunnel tests • Sound level targets met for small airliner type aircraft; but methods are applicable to larger and smaller vehicles. www.nasa.gov 12 How will we know if it’s quiet enough? Studying response to sonic boom – Part 1: Laboratory studies

• Sophisticated boom simulators - Laboratory reproduction of sonic boom sounds Simulation of - Consistent, repeatable test conditions boom sound • Study elements of boom that create annoyance as heard indoors - Goal: Understand how annoyance is related to spectrum, level, rattle, vibration

Simulation of boom sound as heard outdoors

www.nasa.gov 13 How will we know if it’s quiet enough? Studying response to sonic boom Part 2: Simulation with conventional aircraft

• Current aircraft cannot generate low booms during straight and level flight • Sonic boom is generated during supersonic dive of an F/A 18 aircraft

• Long propagation distance, significant attenuation, rounding Subsonic • Boom amplitude observed at house is adjusted by moving dive location relative to the house

Boom Amplitude .1-.5 PSF Subsonic Boom Loudness 60-80 PLdB

House

Ground 10 to 20 miles www.nasa.gov 14 How will we know if it’s quiet enough? Studying response to sonic boom – Part 3: Limited community Studies • Dive maneuver creates new research opportunities • Realistic, varied structures and environments - Living & working conditions • Test conducted under approved supersonic flight corridors and a coastal city

Galveston community test 2018 Structural & Acoustic Response Subjective Reaction www.nasa.gov 15 What do you think?

Gunshot recorded “Thermometer” of Impulsive Sound Levels Firework Balloon pop Concorde sonic boom Nearby thunder Golf ball struck by driver Car door slam Hand clap

Nail struck by hammer Perceived Level (dB) Level Perceived Car door slam outside the car Basketball bounce Range of sound level exposures in recent Distant thunder community tests Sonic “thump” design target Car door slam at neighbor’s house www.nasa.gov 16 16 Overcoming the Barrier to supersonic overland flight

The Low-Boom Flight Demonstration Mission is specifically planned to generate key data for success in NASA’s Critical Commitment to support development of en route certification standards based on acceptable sound levels

• New Environmental Standards are needed to open the market to supersonic flight • An En route Noise Standard is the biggest challenge – Requires proof of new design approaches – Must replace current prohibitions – No relevant data on exists to define limits • Community data from large, diverse population is a requirement – Standard must be accepted internationally

www.nasa.gov NASA’s Low-Boom Flight Demonstration Mission

Design Parameters • Length:96 ft • Span: 29.5 ft X-plane approach • Speed: Mach 1.42 (940 mph) focuses efforts on • Altitude: 55,000 ft defining minimum set of key requirements Timeline that can be met in the •2018 - Contract award most cost effective •2021 - First Flight design •2022 - Mission and Acoustic Validation •2023-25 - Community tests

X-59 QueSST (Quiet SuperSonic Technology) Key Requirements Derived Requirements • The acoustic signal of the X-plane must effectively •New airframe design to achieve desired acoustic signal, with smallest size that meets replicate that of future larger supersonic commercial key acoustic requirements aircraft. •Use of components from existing aircraft to reduce cost (F-18 engine, T-38 canopy • The X-plane must conduct community overflight tests in and cockpit, F-16 landing gear, etc.) a manner representative of typical flight operations of •Payload capacity: single pilot/flight test instrumentation www.nasa.govfuture aircraft. 18 Concluding Remarks

• NASA’s Strategic Plan for Aeronautics calls for leadership in Innovation in Commercial Supersonic Flight • Technical barriers to quiet supersonic flight have been overcome • Regulatory barriers in terms of prohibitions to overland flight need to be replaced with certification standards that enable innovation, but protect the public • NASA Aeronautics has made a commitment to deliver data on community response to quiet overflight sounds that will support the development of standards • The development of a new supersonic X-plane is the core of the NASA’s Low Boom Flight Demonstration Mission • Planning for community overflight tests is underway - NASA seeks to engage the international community to insure broadest applicability of data • Success in standards development will help industry realize a supersonic commercial market • NASA’s strategy also recognizes the importance of continued development to insure that future supersonic aircraft are compatible with developing aviation environmental initiatives