AF T&E DaysAF T&E DaysHigh Speed WeaponsHigh Speed Weapons

What is Different TodayWhat is Different Today2 February 20102 February 2010

Maj Gen Curt BedkeMaj Gen Curt Bedke

CommanderCommander

Air Force Research LaboratoryAir Force Research Laboratory1

Approved for Public Release; 88ABW-2010-0007

Starts…and Stops

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Persistent and Responsive Precision EngagementOn-Demand Force Projection, Anywhere

Hypersonic Capabilities

Regional Reach

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

“Man’s got to know his limitations”.– Harry Callahan, Magnum Force

National Aerospace Plane cancelled FY95 for primary technical shortfalls:

1. Boundary Layer Transition flow field uncertainty

2. Scramjet Engine immaturity

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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

Scientific Challenges in Hypersonics

Combustion

Boundary Layer Physics

High-Temperature Materials

Internal Thermal Management

Gas-Surface Interactions

Courtsey: R. Baurle, NASA

Shock Interactions

Propulsion Issues

Thermal 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 Effectiveness

Flow Instability

Time (sec)

Co

ldW

all

He

atin

gR

ate

(Btu

/ft2

sec)

0 500 1000

0

50

100

150

200

250

300

Laminar FlowLORN TransitionTurbulent Flow

Pull-Out Maneuver

Hypersonic Cruise

~6x difference between peak turbulent and laminar heating rates.

Co

ld W

all

He

ati

ng

Ra

te

Turbulent

Laminar

Pull-Out

Cruise

Time

ALT

Time

Boost-Glide Trajectory

image courtesy Hornung, Cal TechLaminar Transitional Turbulent

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

coating

High Temperature Materials

Oxidation andburn-through

Spalling

Reinforced Carbon/Carbon Leading Edge Oxidation Failure

What is Different Today?

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

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

Foundation for HypersonicSystem Development

ORS

Must do an effective, efficient job of tying together all three elements

Flight Test

ComputationsGround Test

Scramjet Flow Diagnostics

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Pressure Vorticity

Axial Velocity Radial Velocity

Objectives

• Characterize internal flow field

• Measure mass flux

• Monitor combustion

• Validate computational data

Variable GeometryInlet

Combustion Monitoring

Rationale

• Inlet Control / Variable Geometry

• Fuel Control / Equivalence Ratio

• Monitor Performance

• Thrust and ISP Impact

•X-51A Scramjet Engine Demonstrator

•Falcon Hypersonic Test Vehicle 2 (HTV-2)

•Hypersonic International Flight Research Experimentation (HIFiRE)

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Broad Program Portfolio

X-51A Scramjet Engine Demo (SED)

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Free-flying technology demonstrator for hydrocarbon-fueled scramjet propulsion. Air-launched from B-52 aircraft with modified ATACMS rocket booster.

Milestones

2004 Program Initiated

2009 B-52 Captive Carry Flight

2010 Flight Tests 1-4

Hypersonic X-51AScramjet Engine Demonstrator

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

X-51A Scramjet Engine Demo

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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

X-51A SED First Flight Preparation

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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)

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Free-flying technology demonstrator for aerodynamic performance and advanced structures

Quiet Flow Windtunnel Helps Extrapolate HTV-2 Flight Prediction

NASA Langley Mach 6Noisy flow

Transition

Purdue Mach 6Quiet Flow

Purdue Mach 6 Quiet Tunnel

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

PSE method provides order-of-magnitude improvement in

predicting transition

PSE Correlation of Wind Tunnel Transition

Parabolized Stability Equations (PSE)Most advanced correlation methodAFOSR – developed mid 90’s

Contractor Transition Criterion

Correlated Ground Test Transition Estimate

Velocity

Straight-In

Crossrange

Design

Critical assessment of transition and heating issues allows certification of HTV-2 design and trajectories

Applying Basic Science Technologiesto System Demonstrators

Quiet Tunnel measurements counter indications of early transition obtained in conventional facilities Temp

measurementsS. Schneider, Purdue

Advanced Numerical Simulations Provide Revolutionary Insight: Identify Source of Near-Centerline Hot Streaks

G. Candler, U. of Minnesota

Langley Mach 10Empirical

Computational

Increased surface pressure due to nose/leading edge shock interactions

Streamline Convergence

Streamline Divergence

Thickening of boundary layer results in less surface heat flux

1 Flight in FY09

9 Flights Scheduled FY10-11

HIFiREHypersonic 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”.

Ground Test and CFD Provide the Foundation

HIFiRE Program

Fundamental Knowledgeto Enable Future Capabilities

HIFiRE Flight Research Provides Focus

PGS

ORS

LRS M=8, h=50kft, =0, =0

Integrated NG&C

Propulsion &Aeropropulsion Integration

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

HIFiRE Experiments

HIFiRE 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

–…

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Looking ForwardT&E Challenges for Large Scale Applications

Scale: Missile & Ground Test (1x)14’ long, 9” wide

Scale: Space Access (100x)100’ long, 10’ wide

Inlet

Combustor

Nozzle

Inlet

CombustorNozzle

Summary

1. Air Force on threshold of truly operating scramjet-powered hypersonic test vehicles for 10s and 100s 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

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We need a sustained, steady effort…Focused on solving real science problems…

Driven by practical mission requirements