AF T&E Days High Speed Weapons What is Different Today 2 February 2010

1. AF T&E Days High Speed Weapons What is Different Today 2 February 2010 Maj Gen Curt Bedke Commander Air Force Research Laboratory Approved for Public Release; 88ABW-2010-0007

2. Starts…and Stops

3. Hypersonic Capabilities • Persistent and Responsive Precision Engagement • On-Demand Force Projection, Anywhere • Globally Deliver Full Spectrum of Kinetic Effects • Global Delivery of Selected Effects Against Time-Sensitive and High-Value Targets • Clandestinely, Globally Deliver Autonomous, Unattended Payloads • Responsively Deliver Payloads Into, or Through, Space Global Reach Regional Reach

4. “Man’s got to know his limitations”.– Harry Callahan, Magnum Force National Aerospace Plane cancelled FY95 for primary technical shortfalls: • Boundary Layer Transition flow field uncertainty • Scramjet Engine immaturity

5. Scientific Challenges in Hypersonics Courtsey: R. Baurle, NASA Hypersonics: High-speed flow regime where thermodynamic and chemical processes dominate energy transfer between the vehicle and flow Ground simulation cannot match enthalpy, noise, Reynolds number, scale, and nonequilibrium chemistry contributing to friction and catalytic heating in flight Boundary Layer Physics Gas-Surface Interactions High-Temperature Materials Internal Thermal Management Thermal Protection Propulsion Issues Shock Interactions Combustion

6. Flow Instability Laminar Transitional Turbulent image courtesy Hornung, Cal Tech • When Boundary Layer • Transition Occurs… • Skin Friction Increases Vehicle Drag • Surface Heat Transfer Rate Increases Structural Thermal Load • Boundary Layer Thickness is Fuller Control Surface Effectiveness Pull-Out ALT Cold Wall Heating Rate Turbulent Time Laminar Cruise Time ~6x difference between peak turbulent and laminar heating rates. Boost-Glide Trajectory

7. Scramjet Propulsion • Light a Match and keep it burning in a “Hurricane” • Burn fuel quickly (1 millisecond) • Control shock generation • Optimize fuel/air utilization

8. High Temperature Materials Reinforced Carbon/Carbon Leading Edge Oxidation Failure Spalling Cracking and debonding of coating Oxidation and burn-through

9. What is Different Today? Advances in Science & Technology are resolving crucial challenges to hypersonic flight: • Predictive computational tools that simulate the flight environment with high fidelity • Material systems that perform across the high speed flight regime • Better understanding of wind tunnel environment and correlation to flight

10. Foundation for Hypersonic System Development Flight Test ORS Computations Ground Test Must do an effective, efficient job of tying together all three elements

11. Scramjet Flow Diagnostics Variable Geometry Inlet Combustion Monitoring • Rationale • Inlet Control / Variable Geometry • Fuel Control / Equivalence Ratio • Monitor Performance • Thrust and ISP Impact • Objectives • Characterize internal flow field • Measure mass flux • Monitor combustion • Validate computational data Axial Velocity Radial Velocity Pressure Vorticity

12. Broad Program Portfolio • X-51A Scramjet Engine Demonstrator • Falcon Hypersonic Test Vehicle 2 (HTV-2) • Hypersonic International Flight Research Experimentation (HIFiRE)

13. X-51A Scramjet Engine Demo (SED) Milestones 2004 Program Initiated 2009 B-52 Captive Carry Flight 2010 Flight Tests 1-4 Free-flying technology demonstrator for hydrocarbon-fueled scramjet propulsion. Air-launched from B-52 aircraft with modified ATACMS rocket booster.

14. Hypersonic X-51AScramjet Engine Demonstrator X-51A - Hydrocarbon fuel (JP-7), M=4.5 to Mach 6+ flight

15. X-51A Scramjet Engine Demo • Flight demonstration of scramjet engine • Thrust > Drag • Engine On Mach 4.5 – 6.0+ • Fixed geometry flowpath • 12 minute durability • Affordable, high lift Waverider airframe • Logistic-friendly hydrocarbon JP-7 fuel • ATACMS booster (modified) • Before 2020: Affordable fast reaction standoff weapon • Time sensitive targets: rapid response, long range standoff • Deeply buried targets • Modular payload (penetrator, explosive, or submunition) • Reduced vulnerability to air defenses • 2030: Affordable on-demand access to space with aircraft-like operations

16. X-51A SED First Flight Preparation • 4 Flight Tests Feb-May 2010 • Engine start • Cruiser acceleration • Scramjet engine transients • Power-on & power-off parameter identification maneuvers

17. Falcon Hypersonic Test Vehicle 2(HTV-2) Free-flying technology demonstrator for aerodynamic performance and advanced structures

18. Quiet Flow Windtunnel Helps Extrapolate HTV-2 Flight Prediction Transition NASA Langley Mach 6 Noisy flow Purdue Mach 6 Quiet Flow Purdue Mach 6 Quiet Tunnel Developed 95-05 AFOSR Demonstrated Boundary Layer Transition Reynolds #’s at least twice those of conventional tunnels

19. PSE Analysis Provides Best HTV-2 Flight Transition Estimates PSE Correlation of Wind Tunnel Transition Contractor Transition Criterion Parabolized Stability Equations (PSE) Most advanced correlation method AFOSR – developed mid 90’s Straight-In Crossrange Design Correlated Ground Test Transition Estimate Altitude Velocity PSE method provides order-of-magnitude improvement in predicting transition

20. Applying Basic Science Technologies to System Demonstrators Critical assessment of transition and heating issues allows certification of HTV-2 design and trajectories Quiet Tunnel measurements counter indications of early transition obtained in conventional facilities Advanced Numerical Simulations Provide Revolutionary Insight: Identify Source of Near-Centerline Hot Streaks Temp measurements G. Candler, U. of Minnesota S. Schneider, Purdue Langley Mach 10 Empirical Thickening of boundary layer results in less surface heat flux Streamline Convergence Computational Streamline Divergence Increased surface pressure due to nose/leading edge shock interactions

21. HIFiRE Hypersonic International Flight Research Experimentation Captive-booster and free-flying research experiments in fundamental sciences. Low-cost sounding rocket approach provides a flying wind tunnel to build “hypersonic tool kit”. 1 Flight in FY09 9 Flights Scheduled FY10-11

22. HIFiRE Program M=8, h=50kft, a=0, b=0 ORS HIFiRE Flight Research Provides Focus LRS PGS Fundamental Knowledge to Enable Future Capabilities Ground Test and CFD Provide the Foundation

23. Aerodynamics & Aerothermodynamics Propulsion & Aeropropulsion Integration HIFiRE Experiments • Aerosciences: • Boundary layer transition • Shock/shock interactions/separations • Aerodynamic heating • Propulsion: • Combustion limit of HC fuels • Engine mode transition • Radical farming • Guidance and Control: • Vehicle dynamics and aerodynamics • Integrative, Adaptive Guidance & Control w/ gain adaptation • Sensors and Instrumentation: • GPS translation • Aero-optical wave front aberrations • Tunable Diode Laser Absorption Spectroscopy flow field measurements • Scramjet engine and boundary layers • High data rate, high sensor density measurements Integrated NG&C

24. HIFiRE Flight 0 Launched from Woomera Test Range, South Australia: 07 May 09 We found it!

25. A Reminder… • Hypersonics is not a problem to be solved, it is a lot of problems to be solved! • Accelerate through jet – ramjet – scramjet – and back • Aerodynamics • Thermodynamics • Sensors • Configuration changes • …

26. Looking ForwardT&E Challenges for Large Scale Applications Scale: Missile & Ground Test (1x) 14’ long, 9” wide Inlet Combustor Nozzle Scale: Space Access (100x) 100’ long, 10’ wide Inlet Nozzle Combustor

27. Summary • Air Force on threshold of truly operating scramjet-powered hypersonic test vehicles for 10s and 100s of seconds • Hypersonic flight test is inherently expensive and high risk • The risk comes down dramatically with: • High fidelity modeling and simulation tools • Realistic ground test • We need a sustained, steady effort… • Focused on solving real science problems… • Driven by practical mission requirements