AF T E Days High Speed Weapons What is

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; 88 ABW-2010 -0007 1

Starts…and Stops 2

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

“Man’s got to know his limitations”. – Harry Callahan, Magnum Force National Aerospace Plane cancelled FY 95 for primary technical shortfalls: 1. Boundary Layer Transition flow field uncertainty 2. Scramjet Engine immaturity 4

Scientific Challenges in 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 Courtsey: R. Baurle, NASA Shock Interactions Combustion

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

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

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

What is Different Today? Advances in Science & Technology are resolving crucial challenges to hypersonic flight: 1. Predictive computational tools that simulate the flight environment with high fidelity 2. Material systems that perform across the high speed flight regime 3. Better understanding of wind tunnel environment and correlation to flight 9

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

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

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

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

Hypersonic X-51 A Scramjet Engine Demonstrator X-51 A - Hydrocarbon fuel (JP-7), M=4. 5 to Mach 6+ flight

X-51 A 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 15

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

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

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

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

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 S. Schneider, Purdue Temp measurements Thickening of boundary layer results in less surface heat flux Advanced Numerical Simulations Provide Revolutionary Insight: Identify Source of Near-Centerline Hot Streaks G. Candler, U. of Minnesota Langley Mach 10 Empirical Streamline Convergence Computational Streamline Divergence Increased surface pressure due to nose/leading edge shock interactions

HIFi. RE 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 FY 09 9 Flights Scheduled FY 10 -11

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

HIFi. RE Experiments Aerosciences: § Boundary layer transition § Shock/shock interactions/separations § Aerodynamic heating Aerodynamics & Aerothermodynamics Propulsion: § Combustion limit of HC fuels § Engine mode transition § Radical farming Guidance and Control: Propulsion & Aeropropulsion Integrated NG&C § 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

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

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 –… 25

Looking Forward T&E Challenges for Large Scale Applications Scale: Missile & Ground Test (1 x) 14’ long, 9” wide Inlet Combustor Nozzle Scale: Space Access (100 x) 100’ long, 10’ wide Inlet Nozzle Combustor

Summary 1. Air Force on threshold of truly operating scramjetpowered hypersonic test vehicles for 10 s and 100 s of seconds 2. Hypersonic flight test is inherently expensive and high risk 3. 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 27