Dr. David Hunn

Director Technology and Senior Fellow Emeritus

Lockheed Martin Missiles and Fire Control

The Road to Hypersonics - Key Challenges, Advantages and Disadvantages

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2

•In this context, controlled and precise flight within the atmosphere with speeds in excess of Mach 5/3800 mph/6100 kph

•Maneuvers may occur in all phases of flight

•Comprised of air-breathing systems and boosted “glide bodies”

•Aerodynamic environment not fully understood (hypersonic boundary layers, leading edge physics, unsteady flow…..)

•Structural heating rates significant, especially at the leading edges (thousands degrees Celsius)

•Extreme heating in novel propulsion systems

What Do We Mean By “Hypersonics”?

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What Hypersonics Offer

• Survivability: Offset air defenses • Weapon survival as it seeks the target

• Afford global target access:

• Mach 5+ missile goes 1,000 nm in

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AF Studies Board, NRC, 2006

Air Vehicle Iso-Survivability

Conceptual simulations showing speed & observability combinations that yield iso-survivability against 2018 threat

“High”

Survivability

“Medium”

Survivability

“Low”

Survivability

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“Atmospheric hypersonic flight is only three years away…and always will be.”

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Renewed interest in hypersonics has significantly increased in the past decade, entering a new paradigm*

1951 X-7

1980-1990 National Aero-Space Plane

2010 Falcon HypersonicTest Vehicle-2

Future Reusable Hypersonic Vehicle

201X Tactical Boost Glide

1959 X-15

2010 X-51

2004 X-43 2012 HiFire

1980s-2000s Shuttle2007 CKEM

1950s 1960s 1970s 1980s 1990s 2000s 2010s 2020s

202X ARRW

202X HCSW

202X HAWC

202X HCSW

*”It was the best of times, it was the worst of times.”

ARRW: Air-launched Rapid Response WeaponHCSW: Hypersonic Conventional Strike WeaponHAWC: Hypersonic Air-breathing Weapon ConceptIR-CPS: Intermediate Range-Conventional Prompt Strike LRHW: Long Range Hypersonic Weapon

202X IR-CPS

202X LRHW

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Hypersonics Challenges: Physics, Aero, Engineering

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• Air can no longer be assumed to be “air”, and the constituents change across the flow field

• Leading Edge “bluntness” drives drag

• Boundary layer transition from laminar to turbulent flow affects drag, heating, and stability; aerodynamic coupling in all axes likely

• Pressure rises across shocks are similar to a “detonation” and can interact with the boundary layer

• Propulsion systems need to compress, dissemble, mix, react, and exert thrust in only a few milliseconds

• The engine needs to keep the ignition process going similar to “keeping a match lit in a hurricane”

• Everything happens quickly (heat transfer, controls, navigation, etc.)

• Ground testing at the correct conditions is almost impossible

Developing a Relevant Hypersonic System “Ain’t Easy”*

*Uttered by anonymous Lockheed Chief Engineer in Dallas ~1997

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Hypersonics Siren Song: Speed Matters!

“Speed is imperative for effective action [and] safety against enemy counter-measures.”

Theodore von Kármán, Science: Key to Air Supremacy, 1946.

“Hypersonics promises most favorable access-to-space” US Science Advisory Board, 2000

“Imagine flying from Dallas to London in less time than it takes to drive from London to Heathrow..that’s just cool” Hunn, 2019

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Hypersonics Siren Song: Speed Matters!

“Speed is imperative for effective action [and] safety against enemy counter-measures.”

Theodore von Kármán, Science: Key to Air Supremacy, 1946.

“Hypersonics promises most favorable access-to-space” US Science Advisory Board, 2000

“Imagine flying from Dallas to London in less time than it takes to drive from London to Heathrow..that’s just cool” Hunn, 2019

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The Hypersonic “Extreme Challenges”1. Sustained Hypersonic Flight Limited by Materials

• Extraordinarily high heat flux over a small area• Very high surface temperatures, oxidation, catalysis effects• Changing material properties during flight• High temperature gradients, high thermal shock• Limited options for sensor and communication apertures/antennas

2. Dramatically Changing Flow Physics with Mach Number• Non linear aerodynamics, unstable boundary layers, varying shock locations• Desired high aerodynamic efficiency drives very sharp and noneroding wing

leading edges• Guidance and control complicated by unsteady aerodynamics• Navigation and communication complicated by plasma effects

3. Development of Highly Integrated Flight Architectures• Minimisation of subsystem size/weight/power required, complicating

internal thermal management• Coupled optimisation of propulsion, airframe, and control surfaces necessary• Validation and verification of performance very difficult

Photo credit: NASA

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The Hypersonic “Extreme Challenges”1. Sustained Hypersonic Flight Limited by Materials

• Extraordinarily high heat flux over a small area• Very high surface temperatures, oxidation, catalysis effects• Changing material properties during flight• High temperature gradients, high thermal shock• Limited options for sensor and communication apertures/antennas

2. Dramatically Changing Flow Physics with Mach Number• Non linear aerodynamics, unstable boundary layers, varying shock locations• Desired high aerodynamic efficiency drives very sharp and noneroding wing

leading edges• Guidance and control complicated by unsteady aerodynamics• Navigation and communication complicated by plasma effects

3. Development of Highly Integrated Flight Architectures• Minimisation of subsystem size/weight/power required, complicating

internal thermal management• Coupled optimisation of propulsion, airframe, and control surfaces necessary• Validation and verification of performance very difficult

Photo credit: NASA

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The Hypersonic “Extreme Challenges”1. Sustained Hypersonic Flight Limited by Materials

• Extraordinarily high heat flux over a small area• Very high surface temperatures, oxidation, catalysis effects• Changing material properties during flight• High temperature gradients, high thermal shock• Limited options for sensor and communication apertures/antennas

2. Dramatically Changing Flow Physics with Mach Number• Non linear aerodynamics, unstable boundary layers, varying shock locations• Desired high aerodynamic efficiency drives very sharp and noneroding wing

leading edges• Guidance and control complicated by unsteady aerodynamics• Navigation and communication complicated by plasma effects

3. Development of Highly Integrated Flight Architectures• Minimisation of subsystem size/weight/power required, complicating

internal thermal management• Coupled optimisation of propulsion, airframe, and control surfaces necessary• Validation and verification of performance very difficult

Photo credit: NASA

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The Hypersonic Materials Challenge

Leading edge temperatures expected to exceed 2000 °C at hypersonic speeds in the atmosphere

“Missile Design and System Engineering” , E. Fleeman, ISBN 978-1-60086-908-2

Recovery (adiabatic wall) temperature

for a turbulent boundary layer

(recovery factor r = 0.9)

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Hypersonics: Hot Stuff

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• Radiation Cooled Structure – also known as “Hot Structure”Depends upon the conduction and radiation of the thermal energy away from the structure to maintain a balance with the thermal input; passive and shape stable

• Insulated Structure – also known as a Thermal Protection System (TPS)

The primary structural elements are protected from the direct effect of the hot environment by a “shield”. The TPS can be passive, ablative, or semi-active.

• Internally Cooled StructureThe structural system employs a coolant which circulates through the structure and is either recovered or jettisoned after use.

Approaches to Handle the Heat

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• Radiation Cooled Structure – also known as “Hot Structure”Depends upon the conduction and radiation of the thermal energy away from the structure to maintain a balance with the thermal input; passive and shape stable

• Insulated Structure – also known as a Thermal Protection System (TPS)

The primary structural elements are protected from the direct effect of the hot environment by a “shield”. The TPS can be passive, active, or ablative.

• Internally Cooled StructureThe structural system employs a coolant which circulates through the structure and is either recovered or jettisoned after use.

Approaches to Handle the Heat

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The Hypersonic Materials Challenge

Leading edge temperatures expected to exceed 2000 °C at hypersonic speeds in the atmosphere

Unless actively cooled, metals aren’t the answer

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What Materials Might Be the Answer?

From “Materials Selection in Mechanical Design”, Ashby, ISBN 0-08-041907-0, 1992

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Materials To Consider For >1600°C….Limited

From “Materials Selection in Mechanical Design”, Ashby, ISBN 0-08-041907-0, 1992

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Materials To Consider For >1600°C….Limited

High temp hypersonic materials likely composed of some combination of these

From “Materials Selection in Mechanical Design”, Ashby, ISBN 0-08-041907-0, 1992

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Materials To Consider For >1600°C….Limited

High temp hypersonic materials likely composed of some combination of these

From “Materials Selection in Mechanical Design”, Ashby, ISBN 0-08-041907-0, 1992

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Current Research Focusing on Carbon-Carbon and Ceramic Composites for Hypersonic Structure

(3600 °F) (2700 °F) (1800 °F) (900 °F) Carbon-carbon: Carbon fibers in a carbon matrixCeramic Matrix Composites (CMC): Ceramic fibers in a ceramic matrix “Advanced Structural Ceramics in Aerospace Propulsion”;

Nature Materials 15, 804-809 (2016) Nitin P. Padture

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Current Research Focusing on Carbon-Carbon and Ceramic Composites for Hypersonic Structure

(3600 °F) (2700 °F) (1800 °F) (900 °F) Carbon-carbon: Carbon fibers in a carbon matrixCeramic Matrix Composites (CMC): Ceramic fibers in a ceramic matrix “Advanced Structural Ceramics in Aerospace Propulsion”;

Nature Materials 15, 804-809 (2016) Nitin P. Padture

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Silicon Carbide Coatings Have Proven Successful For

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Coatings For >1700°C Focusing On Novel Carbides and Borides

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Fundamental Materials Science Being Applied To Develop New High Temp Materials

• Multiscale framework to explore new materials:• Ab initio: Fundamental chemistry, electronic

properties• Atomistic: Thermal/mechanical properties,

thermal resistance• Continuum: Macro properties,

thermal/mechanical analysis of microstructure

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Extending the Art of the Possible for Future Hypersonic Systems

Dr. Bill Carter, DARPA DSO, MACH Proposers Day Presentation, January 22, 2019

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Representative Materials Verification Also Critical

Dr. David Glass, NASA, MACH Proposers Day Presentation, January 22, 2019

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X-43A (1997-2004)

Mach 9.6, ~ 10 seconds, 2004

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X-51A (2004-2011)

Mach 5.1, ~ 210 seconds, 2013

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DARPA HTV-2 (2004-2011)1st flight April 2010

2nd flight August 2011

Mach ~16, ~ 540 seconds, 2011

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HIFiRE: Hypersonic International Flight Research Experimentation

1st

ScramjetFlight

Mach ~8, ~12 seconds, 2017

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• China has emerged as a peer strategic and technological competitor

• China Ministry of S&T has listed hypersonics as one of 16 national “megaprojects”

• Building wind tunnels, including world’s largest shock tunnel, capable of Mach 5-9

• Research heavily focused on Mach 6-7 cruise missiles and > Mach 8 glide weapons

Call to Action Catalyst: China

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• Russia defining itself through renewed strategic military competition with the West

• Near-Peer Competitor’s advancement in hypersonic strike and A2AD capabilities • Hypersonic Threat Characteristics

• Long Range• High Speed• Highly Maneuverable• Challenging Glide Altitude

• Increasingly Sophisticated Adversary IAMD• BMD, Air Defense and ASAT

A2AD: Anti-access/Area Denial IAMD: Integrated Air and Missile DefenseBMD: Ballistic Missile DefenseASAT: Anti-Satellite

Call to Action Catalyst: Russia

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Hypersonic Vehicle Development and MaturationTruly a “Manhattan Project” Class Effort

• Will Require…• The development of new test facilities, capabilities, techniques and analytical

methods• Close collaboration between domestic and international research, development,

and test communities• Significant capital investment in all the above

Yes…Huge Challenges…But Also Huge Dividends

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We Are on the Verge of a Hypersonic Revolution

Questions?