AF T&E DaysHigh Speed WeaponsWhat is Different Today2 February 2010Maj Gen Curt BedkeCommander Air Force Research Laboratory

*Approved for Public Release; 88ABW-2010-0007

Startsand Stops*

Hypersonic CapabilitiesRegional ReachGlobally Deliver Full Spectrum of Kinetic EffectsGlobal Delivery of Selected Effects Against Time-Sensitive and High-Value TargetsClandestinely, Globally Deliver Autonomous, Unattended PayloadsResponsively Deliver Payloads Into, or Through, Space

Mans got to know his limitations. Harry Callahan, Magnum ForceNational Aerospace Plane cancelled FY95 for primary technical shortfalls:Boundary Layer Transition flow field uncertaintyScramjet Engine immaturity*

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 flightScientific Challenges in HypersonicsCombustionBoundary Layer PhysicsHigh-Temperature MaterialsInternal Thermal ManagementGas-Surface InteractionsShock InteractionsPropulsion IssuesThermal Protection

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 EffectivenessFlow Instability ~6x difference between peak turbulent and laminar heating rates.Cold Wall Heating RateTurbulentLaminarPull-OutCruiseTimeALTTimeBoost-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

Cracking and debonding of coatingHigh Temperature MaterialsOxidation andburn-throughSpallingReinforced Carbon/Carbon Leading Edge Oxidation Failure

What is Different Today?Predictive computational tools that simulate the flight environment with high fidelityMaterial systems that perform across the high speed flight regimeBetter understanding of wind tunnel environment and correlation to flight

*Advances in Science & Technology are resolving crucial challenges to hypersonic flight:

Foundation for HypersonicSystem DevelopmentORSMust do an effective, efficient job of tying together all three elementsFlight TestComputationsGround Test

Scramjet Flow Diagnostics*Pressure VorticityAxial Velocity Radial VelocityObjectivesCharacterize internal flow fieldMeasure mass fluxMonitor combustionValidate computational dataRationaleInlet Control / Variable GeometryFuel Control / Equivalence RatioMonitor PerformanceThrust and ISP Impact

X-51A Scramjet Engine DemonstratorFalcon Hypersonic Test Vehicle 2 (HTV-2)Hypersonic International Flight Research Experimentation (HIFiRE)*Broad Program Portfolio

X-51A Scramjet Engine Demo (SED)*Free-flying technology demonstrator for hydrocarbon-fueled scramjet propulsion. Air-launched from B-52 aircraft with modified ATACMS rocket booster. Milestones2004 Program Initiated2009 B-52 Captive Carry Flight2010 Flight Tests 1-4

Hypersonic X-51A Scramjet Engine DemonstratorX-51A - Hydrocarbon fuel (JP-7), M=4.5 to Mach 6+ flight

X-51A Scramjet Engine Demo*Flight demonstration of scramjet engineThrust > DragEngine On Mach 4.5 6.0+Fixed geometry flowpath12 minute durabilityAffordable, high lift Waverider airframeLogistic-friendly hydrocarbon JP-7 fuelATACMS booster (modified) Before 2020: Affordable fast reaction standoff weaponTime sensitive targets: rapid response, long range standoffDeeply buried targetsModular 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 Flight Tests Feb-May 2010Engine start Cruiser accelerationScramjet engine transientsPower-on & power-off parameter identification maneuvers

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

Quiet Flow Windtunnel Helps Extrapolate HTV-2 Flight PredictionPurdue Mach 6 Quiet TunnelDeveloped 95-05 AFOSRDemonstrated Boundary Layer Transition Reynolds #s at least twice those of conventional tunnels

PSE Analysis Provides Best HTV-2 Flight Transition EstimatesPSE method provides order-of-magnitude improvement in predicting transitionParabolized Stability Equations (PSE)Most advanced correlation methodAFOSR developed mid 90sCorrelated Ground Test Transition EstimateVelocityStraight-InCrossrangeDesign

Critical assessment of transition and heating issues allows certification of HTV-2 design and trajectoriesApplying Basic Science Technologiesto System DemonstratorsQuiet Tunnel measurements counter indications of early transition obtained in conventional facilitiesTemp measurementsS. Schneider, PurdueAdvanced Numerical Simulations Provide Revolutionary Insight: Identify Source of Near-Centerline Hot StreaksG. Candler, U. of MinnesotaLangley Mach 10EmpiricalComputationalIncreased surface pressure due to nose/leading edge shock interactionsStreamline ConvergenceStreamline DivergenceThickening of boundary layer results in less surface heat flux

1 Flight in FY099 Flights Scheduled FY10-11HIFiREHypersonic International Flight Research ExperimentationCaptive-booster and free-flying research experiments in fundamental sciences. Low-cost sounding rocket approach provides a flying wind tunnel to build hypersonic tool kit.

Ground Test and CFD Provide the Foundation HIFiRE ProgramFundamental Knowledgeto Enable Future CapabilitiesHIFiRE Flight Research Provides Focus PGSLRS

Aerosciences:Boundary layer transitionShock/shock interactions/separationsAerodynamic heating

Propulsion:Combustion limit of HC fuelsEngine mode transitionRadical farming

Guidance and Control:Vehicle dynamics and aerodynamicsIntegrative, Adaptive Guidance & Control w/ gain adaptation

Sensors and Instrumentation:GPS translationAero-optical wave front aberrationsTunable Diode Laser Absorption Spectroscopy flow field measurementsScramjet engine and boundary layersHigh data rate, high sensor density measurementsHIFiRE Experiments

HIFiRE Flight 0

A ReminderHypersonics is not a problem to be solved, it is a lot of problems to be solved!Accelerate through jet ramjet scramjet and backAerodynamicsThermodynamicsSensorsConfiguration changes*

Looking ForwardT&E Challenges for Large Scale ApplicationsScale: Missile & Ground Test (1x)14 long, 9 wideScale: Space Access (100x)100 long, 10 wideInletCombustorNozzleInletCombustorNozzle

SummaryAir Force on threshold of truly operating scramjet-powered hypersonic test vehicles for 10s and 100s of secondsHypersonic flight test is inherently expensive and high riskThe risk comes down dramatically with:High fidelity modeling and simulation toolsRealistic ground test*We need a sustained, steady effortFocused on solving real science problemsDriven by practical mission requirements

**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]

***FLTC 4: Persistent and responsive precision engagement4.2 Globally deliver full spectrum of kinetic effects4.3 Global delivery of selected effects against time-sensitive and high-value targets4.4 Clandestinely, globally deliver autonomous, unattended payloadsFLTC 7: On-demand force projection, anywhere7.3 Responsively deliver payloads into, or through, space

The re-entry payload in the photo for Global Reach is called a MHV Maneuvering Hypersonic VehicleTitle 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***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 flows4 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 layerShock-dominated flows - local flow frequently dominated by geometry specific shock interactionsPlasmas -cross-cutting potential as another method to control critical phenomena in the other areas of emphasis*The boost-glide pullout is a high-g maneuver (+ 10-25 gs) creating lots of heat. *This schematic illustrates the transition from laminar to turbulent flow in the boundary layer.

The isolator does the job of a diffuser*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****Picture is a screen shot from a promotional simulation video.***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)

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.**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.

**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.

**HIFiRE 0 Flight Successful March 2009

***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)

Boundary Layer Transition: trip from low heating smooth air flow to high heating turbulent air flowShock/shock interactions: pressure waves colliding from different parts of vehicle geometry and generating high heating areasAerodynamic heating: produced by moving an object through a gas, non-linear increasing with object velocityCombustion 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 combustionVehicle dynamics and aerodynamics: investigating vehicle stability and affects of mold-line shape changesIntegrated, Adaptive Guidance & Control: investigating reduced control surface authority at hypersonic speeds or low-density (high altitude) flowsGPS translation: investigating high velocity effectsAero-optical wave-front abberations: sensors investigationsTunable Diode Laser Absorption Spectroscopy Flow Field measurements: derive flow rates by passing beams through flow field and evaluating changes

***Successes: Vehicle attitude sensing system flight validatedAttitude Control Maneuver system pushed vehicle nose over into small angle-of-attack re-entry attitudeHigh speed data acquisition, processing, and telemetry systems flight validatedRecovering the experimental payload downrangeCombined US/AUS flight test

*This is a photo of the X-51A engine in NASA Langleys 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, well 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.**