What is Different Today 4/23/2017 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

Starts…and Stops 4/23/2017 Clockwise from Upper Right: X-33 orbital lifting body (Single Stage to Orbit) [1996-2001] X-23 PRIME maneuvering re-entry body [1966-67] X-43A Hypersonic Experiment Vehicle [2001-04] X-20 Dyna-Soar spaceplane [1957-63] X-30 National Aerospace Plane [~1986-93] X-15 [1955-1968] with Dummy RAM payload suspended underneath before shock-wave interaction heating burned it off. ASSET lifting reentry body [1960-65] Center: Advanced Strategic Air Launched Missile (ASALM) Propulsion Test Vehicle [1976-80]

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 FLTC 4: Persistent and responsive precision engagement 4.2 Globally deliver full spectrum of kinetic effects 4.3 Global delivery of selected effects against time-sensitive and high-value targets 4.4 Clandestinely, globally deliver autonomous, unattended payloads FLTC 7: On-demand force projection, anywhere 7.3 Responsively deliver payloads into, or through, space The re-entry payload in the photo for Global Reach is called a MHV – Maneuvering Hypersonic Vehicle Regional Reach

“Man’s got to know his limitations”. – Harry Callahan, Magnum Force 4/23/2017 National Aerospace Plane cancelled FY95 for primary technical shortfalls: Boundary Layer Transition flow field uncertainty Scramjet Engine immaturity Title quote personally verified with DVD. Full scale experiments initiated after NaSP: Photo Left: NASA HyBoLT [2005-2008] (Hypersonic Boundary Layer Transition) Flight Experiment – Launch terminated in boost stage, August 2008. Designed to address aerodynamics uncertainty. Photo Right: AFRL HyTech [1995-present (X-51A)] Scramjet Ground Demonstration Engine (GDE) tests – designed to address propulsion maturity risk

Scientific Challenges in Hypersonics 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 High speed flow chemical processes: primarily ionization of the gases Gas-surface interactions drive the ability to conduct heat across the mediums through chemical reactions and heat transfer mechanisms There are a number of critical issues for hypersonic flows 4 areas emphasized in the hypersonic thrust in my program are shown in this cartoon Nonequilibrium flows - high-Temperature, low-Density flows High-speed boundary layers - substantial influence of the incoming boundary layer Shock-dominated flows - local flow frequently dominated by geometry specific shock interactions Plasmas -cross-cutting potential as another method to control critical phenomena in the other areas of emphasis Internal Thermal Management Thermal Protection Propulsion Issues Courtsey: R. Baurle, NASA Shock Interactions Combustion

Flow Instability When Boundary Layer Transition Occurs… image courtesy Hornung, Cal Tech Laminar Transitional Turbulent 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 The boost-glide pullout is a high-g maneuver (+ 10-25 g’s) creating lots of heat. Laminar Cruise Time ~6x difference between peak turbulent and laminar heating rates. Boost-Glide Trajectory

Scramjet Propulsion Light a Match and keep it burning in a “Hurricane” This schematic illustrates the transition from laminar to turbulent flow in the boundary layer. The isolator does the job of a diffuser 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: 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

Foundation for Hypersonic System Development 4/23/2017 ORS Flight Test Computations Blue triangle symbolizes the relationship of our full arsenal of tools employed in hypersonic research Ground test and CFD form the base, signifying the fact that they will provide the foundation for future system development Flight research at the apex – provides the focus to ground test and CFD Ground Test Must do an effective, efficient job of tying together all three elements

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

Broad Program Portfolio 4/23/2017 X-51A Scramjet Engine Demonstrator Falcon Hypersonic Test Vehicle 2 (HTV-2) Hypersonic International Flight Research Experimentation (HIFiRE)

X-51A Scramjet Engine Demo (SED) 4/23/2017 Milestones 2004 Program Initiated 2009 B-52 Captive Carry Flight 2010 Flight Tests 1-4 Picture is a screen shot from a promotional simulation video. Free-flying technology demonstrator for hydrocarbon-fueled scramjet propulsion. Air-launched from B-52 aircraft with modified ATACMS rocket booster.

Hypersonic X-51A Scramjet Engine Demonstrator X-51A - Hydrocarbon fuel (JP-7), M=4.5 to Mach 6+ flight The overall objective of the X-51A program is to test the scramjet engine developed by the HyTech program by accelerating a vehicle from an approximate boosted Mach 4.5 to Mach 6.5 Specifically the intent is to gather ground and flight data on an actively cooled endothermically fueled scramjet in order to correlate “rules and tools” and demonstrate the viability of an actively cooled, self controlled operating scramjet. Detailed Objectives Demonstrate clean air performance Correlate flight test data with ground test data and simulation/analyses Investigate acceleration/operation through Mach transients (compare to analysis) Investigate boost/free-flight transition & starting (compare to analytical predictions)

X-51A Scramjet Engine Demo 4/23/2017 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) JP-7 - a high heat capacity fuel (the same used by the SR-71). Far easier to handle than hydrogen. It's a liquid hydrocarbon fuel. 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

X-51A SED First Flight Preparation 4/23/2017 If the first two flights are fully successful, the USAF is looking at the option of pursuing both envelope expansion and waypoint guidance demonstrations for flights 3 & 4. If this option is selected, the X-51 test team would stand down for several/many months to source funds, recode and verify software, coordinate new test objectives with both AFFTC and Pt Mugu, and maintain the contractor test cadre. 4 Flight Tests Feb-May 2010 Engine start Cruiser acceleration Scramjet engine transients Power-on & power-off parameter identification maneuvers

Falcon Hypersonic Test Vehicle 2 (HTV-2) 4/23/2017 HTV 2 started in 2006 by DARPA and we initially joined as an executing agent. That said, it does help expand our S&T base in support of both our FLTC 4.2.3 Responsive Invulnerable Global Delivery Against Time Critical Targets as well as 7.3.2 - Fully Reusable Responsive Space Access. It also laid the groundwork for the terminated Blackswift program.  Along the prompt global strike train of thought AFSPC/SMC is very interested in how it might advance their understanding for the conventional strike missile concept, and they are pursuing an HTV-2 follow-on flight test in the 2012 to 2013 timeframe. Free-flying technology demonstrator for aerodynamic performance and advanced structures

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

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 Design Correlated Ground Test Transition Estimate Altitude Contractor Transition Criterion Velocity PSE method provides order-of-magnitude 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 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

Hypersonic International Flight Research Experimentation HIFiRE Hypersonic International Flight Research Experimentation 4/23/2017 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”. HIFiRE 0 Flight Successful March 2009 1 Flight in FY09 9 Flights Scheduled FY10-11

Fundamental Knowledge to Enable Future Capabilities HIFiRE Program HIFiRE Flight Research Provides Focus ORS Computation, Ground Test, and Flight Test provide the underpinnings for successful evaluation of hypersonic capabilities: PGS: Prompt Global Strike (boost/glide re-entry vehicle to drop payload anywhere on globe) LRS: Long Range Strike (hypersonic cruise vehicle) ORS: Operationally Responsive Space access (1st stage to orbit) LRS M=8, h=50kft, a=0, b=0 PGS Fundamental Knowledge to Enable Future Capabilities Ground Test and CFD Provide the Foundation

HIFiRE Experiments Aerosciences: Propulsion: Guidance and Control: 4/23/2017 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 Aerodynamics & Aerothermodynamics Propulsion & Aeropropulsion Integration Boundary Layer Transition: trip from ‘low heating’ smooth air flow to ‘high heating’ turbulent air flow Shock/shock interactions: pressure waves colliding from different parts of vehicle geometry and generating high heating areas Aerodynamic heating: produced by moving an object through a gas, non-linear increasing with object velocity Combustion limit of Hydrocarbon fuels: Engine mode transition: internal flow through engine accelerating from transonic to supersonic fuel combustion (ramjet-scramjet) Radical Farming: Using relatively cool and hot zones of shock/shock interactions to ignite and control fuel combustion Vehicle dynamics and aerodynamics: investigating vehicle stability and affects of mold-line shape changes Integrated, Adaptive Guidance & Control: investigating reduced control surface authority at hypersonic speeds or low-density (high altitude) flows GPS translation: investigating high velocity effects Aero-optical wave-front abberations: sensors investigations Tunable Diode Laser Absorption Spectroscopy Flow Field measurements: derive flow rates by passing beams through flow field and evaluating changes Integrated NG&C

Launched from Woomera Test Range, South Australia: 07 May 09 HIFiRE Flight 0 Launched from Woomera Test Range, South Australia: 07 May 09 Successes: Vehicle attitude sensing system flight validated Attitude Control Maneuver system pushed vehicle nose over into small angle-of-attack re-entry attitude High speed data acquisition, processing, and telemetry systems flight validated Recovering the experimental payload downrange Combined US/AUS flight test 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 …

Looking Forward T&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 This is a photo of the X-51A engine in NASA Langley’s 8 Foot Wind Tunnel. That hardware is essentially full scale for a missile-size application, and fills the test section area of the facility. Our research is moving from the missile scale, which consumes about 10 pounds of air every second, to the much larger scale that is necessary for space access (100x size). In between, we’ll enable mid-scale propulsion systems (10x size) for large missiles and small launch systems. This chart graphically illustrates the two extreme scales, and identifies some of the key components. Note that the large scale engine concept illustrated will consume about 1000 pounds of air, along with 30 to 60 pounds of fuel, every second. This is comparable to a rocket engine that can produce 50,000 to 100,000 pounds of thrust. Inlet Nozzle Combustor

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

4/23/2017