Learning to Fly Beyond Mach 5 Hypersonics 101: Learning to Fly Beyond Mach 5 Dr. Mark J. Lewis Department of Aerospace Engineering University of Maryland HIT Industry Day May 24, 2011

What Is “Hypersonic”? No fixed definition, but Usually means flight in  excess of Mach 5 (or 6 or 4…) Shock waves pressed close to surface Heating rates significant, especially at edges, transition Chemistry may be important (inside and outside) In modern use, typically powered by airbreathing engines, but could be rocket powered or gliding. Airbreathing at Mach 5+ is hard!

Future Hypersonic Vehicles Weapons -Blunt-body reentry High-lift (maneuvering) reentry Cruise missiles LRS missiles Aircraft Recce/strike Transatmospheric Airbreathing global cruise Access-to-Space Two-stage-to-orbit hybrid airbreathing Two-stage-to-orbit fully airbreathing Single-Stage-to-Orbit (NASP)

Key Hypersonics Programs X-51 Scramjet testbed Long duration, hydrocarbon fuel Waverider forebody Building on X-43 experience X-51A+ follow-on? Falcon HTV-2 Unpowered maneuvering reentry vehicle Materials and lifting-body aerodynamics Significant NASA support Initially mismanaged, questionable goals; now on track Hypersonic International Flight Research and Experimentation (HiFire) Sounding rocket flights in Australia Emphasis on acceptance of risk, fundamental science Australian DSTO matching dollar-for-dollar AFRL Robust Scramjet Build on X-51 efforts Scale up for larger craft, access-to-space AFOSR/NASA Fundamental Program – Steady Basic Research

An historic accomplishment X-51A - First Flight May 26, 2010 An historic accomplishment Success (!): 200 Secs powered flight Thermally balanced Successful boost a= 0.17g uphill to Mach ~5 Ethylene to JP-7

X-51A - Second Flight Status Cause of Flight 1 anomalies identified (maybe…) Seal reinforced Fuel schedule logic changed Scheduled for June, 2011 Delayed by weather Attempted flight aborted Failure on B-52 Cause for concern? 70% new personnel including flight crew New (very old) airplane

Hypersonic Accomplishments First hypersonic object: Bumper-WAC, 1948 Fastest earth entry: Mach 43, NASA Stardust Fastest human flight: Mach 36, Apollo entry Fastest man-made hypersonic object: Mach 65, Galileo Fastest accelerating human flight: Mach 6.7, X-15 Fastest airbreathing flight: Mach 9.8, X-43A Fastest human jet-powered flight: Mach 3.4+, SR-71 Frank Malina with 5th WAC Corporal

75 Years of Mixed Efforts The “Hallion” Chronology V-2/A-4b Atlas Mercury The Confluence of Air and Space Gemini Bumper-WAC Titan Apollo X-17 ASSET SPACE BGRV Alpha Draco PRIME X-24C/ NHFRF X-51 Sänger-Bredt HSFS X-20 X-15 STS-1 NASP DC-X X-33 X-43 H-Soar Tsien Ames ASP M2F HL-10 X-24A X-24B X-7 AIR X-2 Missile/Space Projects XB-70A D-558-2 Aeronautics R & D Projects SM-64 Hypersonic Test Projects A-12 X-1 Hypersonic Studies 1940 1950 1960 1970 1980 1990 2000 2010 courtesy Dr Richard P. Hallion

Hypersonics Has Followed a ~15-yr Cycle 1950’s Most research in blunt-body reentry flows, lifting bodies marginal 1960’s Aerospace Plane - cancelled on SAB recommendation. X-15 Rocketplane - 199 flights, ended before scramjets, delta wing X-20 DynaSoar - canceled after metal parts fabricated 1970’s Shuttle development focus on blunt flows, X-24C canceled 1980’s X-30 NASP - Mach 25 SSTO, canceled after $2.6B spent. 1990’s NASA’s X-33 SSTO, canceled. 2000’s Australian HyShot - success for a few $ million. NASA’s X-43A, one failure, two successful flights, then canceled. X-43B, X-43C canceled 2010’s Navy HyFly - three failures, program canceled DARPA HTV-2, flight 1 lost after 9 min. X-51A mostly successful, more flights planned X-37 successful, but doesn’t push SOA

Global Missions and Concepts Long Range & Prompt Global Strike Reconnaissance Responsive Launch (Inc. TacSats) Forward Based CONUS Based Global Hypersonic Ground Launchers Hypersonic Missiles Hypersonic Aircraft RBCC RBS

Relevant Air Force Board Studies SAB Why and Whither Hypersonics (2000) Most favorable for access-to-space. Weapons also favorable as an off-ramp on the way. Rocket and airbreathing options are both promising. SAB Immediate Attack Deep Into Hostile Territory (2002) Rapid prosecution of theater attack Only options are loiter, Mach 106 (laser), or hypersonics SAB Long Range Strike From CONUS (2003) Hypersonic cruisers won’t work well- insufficient range. Missiles very attractive, but no “knee” in the Mach curve. Don’t sacrifice range for speed. NRC Future AF Needs for Survivability (2007). Considered combination of stealth and speed Hypersonic global aircraft traded poorly, missiles did well. SAB Future Launch Vehicles (2010) Hypersonics traded as a promising future launch technology.

Important Past Success: X-15 Total 199 flights 12 pilots Max Speed Mach 6.7 (Pete Knight) Max Altitude 67 mi. (Joe Walker) 1350oF, q=2200 lb./ft2 High-speed fuel tank jettison. 765 technical documents. Robust, incremental approach. NOT RISK AVERSE! X-15-2 broke in half, back in flight within 3 months, fuselage extension added.

Some Significant Failures X-30 National Aerospace Plane (NASP) 1986-1990 Intended as SSTO, canceled after $2B spent.

Why is X-51A so Important? Hydrocarbon fuel - practical, easily handled Missile-scale – direct path to an early product Thermally balanced – engine runs as long as it has fuel Air launched – integrates with existing platforms Proved that scramjets work – positive net acceleration (uphill) But…Still lots to do to make it practical: Starting mechanism, booster, controls, guidance, warhead, etc.

We Already Knew that Scramjets Work But Total Flight Time Before X-51 ~35 seconds NACA TN 4386 An Analysis of Ramjet Engines Using Supersonic Combustion R.J. Weber and J. S. McKay National Advisory Committee on Aeronautics September 1958 HyShot X-15A July 30, 2002 5 sec. Mach 7.6 flown in Australia Initial concept: 1958 Dummy HRE engine: 1968 program cancelled. X-43A Finally, modern acquisition programs are dramatically influenced by changes in technology and the external world (think, for example, of changes in both in just the last two decades). To give but one example of this… X-51 Engine NASA ground tests >50 seconds duration flight weight active cooling with HC fuel, 2007. Flight 2: March 27, 2004 11 sec. at Mach 6.8 Flight 3: Nov. 16, 2004 10 sec. at Mach 9.8

A Laundry List of Basic/Early Applied Research Issues Downrange, in Mm Alt. In km Trajectory selection Periodic cruise Multi-staging Off-design optimization Transonic drag Landing/takeoff Stage and store separation Guidance and Control Engine/airframe integration High efficiency inlet Starting/unstarting Unsteady flows Leading edge physics Shock location Off-design aerodynamics Sharp leading edge heating/cooling Advanced materials/TPS Plasma and telemetry Sensing and communication Navigation and guidance Boundary layers – transition, etc. Surface interactions (roughness) CH4+3/2 CO2->CO+ 2H2O CO+1/2O2 ->CO2 Kf=1.2x10e10 Kb=5x10e8 SiH4 + 5O2 -> SiO2 + 4H2O Coupled Optimization Base closure Targeting and communication Sensing Operability Aeroelasticity Health monitoring Testing and Evaluation Finite-rate chemistry Fuel selection and handling Piloting and enhancers Nozzle reactions Engine/attitude coupling Engines, combined cycles Internal flows Fuel injection and mixing Multimode operation Plasmadynamics/MHD

Fundamental Knowledge to Enable Future Capabilities HiFire Affordable Flight Research exploring critical fundamental phenomena AFRL/Australian DSTO Collaborative Effort Joint effort significantly reduces cost to USAF, provides access to Woomera Test Range 10 Sounding Rocket Flights Planned (FY09-12), Mach 8-12 NASA Aeronautics program is providing analysis, building a payload Utilizing All Resources- Ground Test, Numerical Simulation and Flight Research – to build a strong technical foundation ORS Detailed Flowfield Information and Analysis Direction for future fundamental research X-51 LRS Fundamental Knowledge to Enable Future Capabilities Ground Test and CFD Provide the Foundation

Highlighted Basic Fluids Issues Hypersonic boundary layers Transition at high speeds poorly understood Surface coupling including roughness effects Thinning and three-dimensional effects Influence on freestream – compound flow phenomena Leading edge physics Shocks on sharp geometries – analysis is lacking Rarefied effects – challenging computational solutions Strong interactions – especially at small scale Unsteady flow Shocks at high-speed – steady or unsteady, and why? Shock interactions – extreme heating rates possible Internal flows – especially important for scramjet mixing. Why did X-51 unstart? And why did it re-start??

Nonweiler caret waverider Coupled Aerodynamics Aerodynamics must be fully coupled to engine Need high L/D for cruisers and access to space Inverse design techniques, but optimal designs uncertain Stability, control issues Sharp leading edge and heating Transition, rarefied effects Nonweiler caret waverider

Rocket-Based or Turbine-Based? Which to Do? Best Engine Cycle Scramjets Turbines Complex integration Ram/Scramjet operation from Mach 2+ to Mach 6 Mach 4 turbine for acceleration to Ram/Scramjet takeover / overlap? Inlet / exhaust flowpath integration and hypersonic engine operability? Role of rockets? Rocket-Based or Turbine-Based? Which to Do?

Answering Our Questions Step one - minutes-long flights of fully-integrated positive thrust hydrocarbon-fueled scramjets: X-51A, B, ATK-GASL, etc. Step two - platform elements that take propulsion testbed to operational level (navigation, sensing, warheads, etc.): X-5n? Step three - combined-cycle or parallel-cycle systems (both rocket and turbine): i.e. Boeing Phantom Works concepts. In parallel - fundamental programs: HiFire, AFOSR-NASA MURI To do this, we need repeated access into the hypersonics regime: Adaptive, recoverable platform, but not necessarily reusable Ground T&E infrastructure and comparison to flight (learn from flight) Willingness to take RISK, but don’t repeat mistakes of NASP, X-33, etc.

Following a Logical Progression Step one - minutes-long flights of fully-integrated positive thrust hydrocarbon-fueled scramjets: X-51A, B, ATK-GASL, etc. Step two - platform elements that take propulsion testbed to operational level (navigation, sensing, warheads, etc.): X-5n? Step three - combined-cycle or parallel-cycle systems (both rocket and turbine): i.e. Boeing Phantom Works concepts. In parallel - fundamental programs: HiFire, AFOSR-NASA MURI To do this, we need repeated access into the hypersonics regime: Adaptive, recoverable platform, but not necessarily reusable Ground T&E infrastructure and comparison to flight (learn from flight) Willingness to take RISK, but don’t repeat mistakes of NASP, X-33, etc.

Following a Logical Progression Step one - minutes-long flights of fully-integrated positive thrust hydrocarbon-fueled scramjets: X-51A, B, ATK-GASL, etc. Step two - platform elements that take propulsion testbed to operational level (navigation, sensing, warheads, etc.): X-5n? Step three - combined-cycle or parallel-cycle systems (both rocket and turbine): i.e. Boeing Phantom Works concepts. In parallel - fundamental programs: HiFire, AFOSR-NASA MURI To do this, we need repeated access into the hypersonics regime: Adaptive, recoverable platform, but not necessarily reusable Ground T&E infrastructure and comparison to flight (learn from flight) Willingness to take RISK, but don’t repeat mistakes of NASP, X-33, etc.

Following a Logical Progression Step one - minutes-long flights of fully-integrated positive thrust hydrocarbon-fueled scramjets: X-51A, B, ATK-GASL, etc. Step two - platform elements that take propulsion testbed to operational level (navigation, sensing, warheads, etc.): X-5n? Step three - combined-cycle or parallel-cycle systems (both rocket and turbine): i.e. Boeing Phantom Works concepts. In parallel - fundamental programs: HiFire, AFOSR-NASA MURI To do this, we need repeated access into the hypersonics regime: Adaptive, recoverable platform, but not necessarily reusable Ground T&E infrastructure and comparison to flight (learn from flight) Willingness to take RISK, but don’t repeat mistakes of NASP, X-33, etc.

Following a Logical Progression Step one - minutes-long flights of fully-integrated positive thrust hydrocarbon-fueled scramjets: X-51A, B, ATK-GASL, etc. Step two - platform elements that take propulsion testbed to operational level (navigation, sensing, warheads, etc.): X-5n? Step three - combined-cycle or parallel-cycle systems (both rocket and turbine): i.e. Boeing Phantom Works concepts. In parallel - fundamental programs: HiFire, AFOSR-NASA MURI To do this, we need repeated access into the hypersonics regime: Adaptive, recoverable platform, but not necessarily reusable Ground T&E infrastructure and comparison to flight (learn from flight) Willingness to take RISK, but don’t repeat mistakes of NASP, X-33, etc. CRITICAL

Hypersonic Nations (and Wannabe’s) Australia (first scramjet flight, sort of) China (shadow program, possibly > $1B) India Russia (especially plasmas, T&E) France (leading in materials) Germany Japan (leading in ground test) England (interest waning) Iran Italy (reentry) Sweden (rockets, ramjets?)

Summing Up Hypersonic flight has been a realistic concept for > 60 years “It’s not that hard” - R. Voland, NASA Langley, Nov. 16, 2004. BUT…first practical flight only happened last year. This past year has seen tremendous progress. AFRL’s X-51 is a historic step - flying testbed. HiFire is exploring the fundamental problems. We have also been reminded of what we don’t know HTV-2 – lost due to heating? Boundary layer? Instability? HyFly – failure of systems-level thinking. X-51 – does a seal failure explain it all? Inlet unstart? In order to progress, we must advance in the air, but also stay focused on fundamentals.

“Speed is imperative for effective action [and] safety against enemy counter-measures.” Theodore von Kármán, Science: Key to Air Supremacy, 1946. “If the Air Force is to execute faster than an enemy in the 21st century... the only alternative is to go faster.” SAB, New World Vistas, 1995. “Speed is THE critical issue” UK Air Chief Marshall Sir Jock Stirrup, RUSI 2005

QUESTIONS?