The Road to Hypersonics - Key Challenges, Advantages and Disadvantages

Dr. David Hunn Director Technology and Senior Fellow Emeritus Lockheed Martin Missiles and Fire Control 2 What Do We Mean By “Hypersonics”?

•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

Hypersonics 2 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 <20 min • Provide “4th dimension” effects … Time warfare: • Compresses a foe’s decision-making window, effectively enabling the hypersonic attacker to get inside an adversary’s Command, Control, Battle Management, and Communications (C2BMC) • Afford unprecedented rapid reach: • Shrink the “time to target” window • 6X swifter than a conventional cruise missile • Demands a more effective intel & targeting cycle The Economist

Hypersonics 3 Air Vehicle Iso-Survivability

“High” Survivability

“Medium” Survivability

“Low” Survivability

Conceptual simulations showing speed & observability combinations that yield iso-survivability against 2018 threat AF Studies Board, NRC, 2006

Hypersonics 4 “Atmospheric hypersonic flight is only three years away…and always will be.”

Hypersonics 5 Renewed interest in hypersonics has significantly increased in the past decade, 202X ARRW entering a new paradigm* 201X Tactical Boost Glide 2010 Falcon Hypersonic Test Vehicle-2

Future Reusable Hypersonic Vehicle

2007 CKEM 1980s-2000s Shuttle 2010 X-51 1951 X-7 202X LRHW 1950s 1960s 1970s 1980s 1990s 2000s 2010s 2020s

202X HCSW

1959 X-15 1980-1990 National Aero-Space Plane 2004 X-43 2012 HiFire ARRW: Air-launched Rapid Response Weapon 202X HAWC HCSW: Hypersonic Conventional Strike Weapon HAWC: Hypersonic Air-breathing Weapon Concept IR-CPS: Intermediate Range-Conventional Prompt Strike *”It was the best of times, it was the worst of times.” 202X IR-CPS LRHW: Long Range Hypersonic Weapon

Hypersonics 6 Hypersonics Challenges: Physics, Aero, Engineering

Hypersonics 7 Developing a Relevant Hypersonic System “Ain’t Easy”*

• 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.) *Uttered by anonymous Lockheed • Ground testing at the correct conditions is almost impossible Chief Engineer in Dallas ~1997

Hypersonics 8 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

Hypersonics 9 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 10 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 Photo credit: NASA 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

Hypersonics 11 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 Photo credit: NASA 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

Hypersonics 12 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 Photo credit: NASA 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

Hypersonics 13 The Hypersonic Materials Challenge

Recovery (adiabatic wall) temperature for a turbulent boundary layer (recovery factor r = 0.9)

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

Hypersonics 14 Hypersonics: Hot Stuff

Hypersonics 15 Approaches to Handle the Heat

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

Hypersonics 16 Approaches to Handle the Heat

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

Hypersonics 17 The Hypersonic Materials Challenge Unless actively cooled, metals aren’t the answer

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

Hypersonics 18 What Materials Might Be the Answer?

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

Hypersonics 19 Materials To Consider For >1600°C….Limited

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

Hypersonics 20 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

Hypersonics 21 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

Hypersonics 22 Current Research Focusing on Carbon-Carbon and Ceramic Composites for Hypersonic Structure

Carbon-carbon: Carbon fibers in a carbon (900 °F) (1800 °F) (2700 °F) (3600 °F) matrix Ceramic Matrix Composites (CMC): Ceramic fibers in a ceramic matrix “Advanced Structural Ceramics in Aerospace Propulsion”; Nature Materials 15, 804-809 (2016) Nitin P. Padture

Hypersonics 23 Current Research Focusing on Carbon-Carbon and Ceramic Composites for Hypersonic Structure

Hypersonics 24 Silicon Carbide Coatings Have Proven Successful For <1700°C Use

SiC Coated C-C On Space Shuttle Developed and Manufactured by Lockheed Martin in Texas

Hypersonics 25 Coatings For >1700°C Focusing On Novel Carbides and Borides

Hypersonics 26 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

Hypersonics 27 Extending the Art of the Possible for Future Hypersonic Systems

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

Hypersonics 28 Representative Materials Verification Also Critical

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

Hypersonics 29 X-43A (1997-2004)

Mach 9.6, ~ 10 seconds, 2004

Hypersonics 30 X-51A (2004-2011)

Mach 5.1, ~ 210 seconds, 2013

Hypersonics 31 DARPA HTV-2 (2004-2011) 1st flight April 2010 2nd flight August 2011

Mach ~16, ~ 540 seconds, 2011

Hypersonics 32 HIFiRE: Hypersonic International Flight Research Experimentation

1st Scramjet Flight

Mach ~8, ~12 seconds, 2017

Hypersonics 33 Call to Action Catalyst: China • 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

Hypersonics 34 Call to Action Catalyst: Russia

• 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 Defense BMD: Ballistic Missile Defense ASAT: Anti-Satellite

Hypersonics 35 Hypersonic Vehicle Development and Maturation Truly 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

Hypersonics 36 Questions?

We Are on the Verge of a Hypersonic Revolution

Hypersonics 37