AF T&E Days
High Speed Weapons
What is Different Today
2 February 2010
Maj Gen Curt Bedke
Commander
Air Force Research Laboratory
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Approved for Public Release; 88ABW-2010-0007
Starts…and Stops
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Hypersonic Capabilities

Persistent and Responsive Precision Engagement
On-Demand Force Projection, Anywhere
Global 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
Regional 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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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
Internal Thermal Management
Thermal Protection
Propulsion Issues
Courtsey: R. Baurle, NASA
Shock Interactions
Combustion
Flow Instability
Transitional
When Boundary Layer
Transition Occurs…
Turbulent
image courtesy Hornung, Cal Tech
Pull-OutManeuver
Pull-Out
300
Cold Wall Heating Rate (Btu/ft2sec)
Cold Wall Heating Rate
Laminar
ALT
250
•Skin Friction Increases
Vehicle Drag
•Surface Heat Transfer Rate Increases
Structural Thermal Load
Turbulent
150
Laminar
100
•Boundary Layer Thickness is Fuller
Control Surface Effectiveness
~6x difference between peak
turbulent and laminar heating rates.
Laminar Flow
LORN
TimeTransition
Turbulent Flow
200
Cruise Cruise
Hypersonic
50
Time
0
0
500
1000
Time (sec)
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
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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
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
Axial Velocity Radial Velocity
Variable Geometry
Inlet
Pressure
Vorticity
Combustion Monitoring
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Broad Program Portfolio
•X-51A Scramjet Engine Demonstrator
•Falcon Hypersonic Test Vehicle 2
(HTV-2)
•Hypersonic International Flight
Research Experimentation (HIFiRE)
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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 hydrocarbonfueled scramjet propulsion. Air-launched from B-52
aircraft with modified ATACMS rocket booster.
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Hypersonic X-51A
Scramjet Engine Demonstrator
X-51A - Hydrocarbon fuel (JP-7), M=4.5 to Mach 6+ flight
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
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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
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Falcon Hypersonic Test Vehicle 2
(HTV-2)
Free-flying technology demonstrator for
aerodynamic performance and
advanced structures
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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
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
HIFiRE Program
HIFiRE Flight Research Provides Focus
ORS
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:
 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 Integration
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
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 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
Inlet
Nozzle
Combustor
Summary
1. Air Force on threshold of truly operating scramjetpowered 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
We need a sustained, steady effort…
Focused on solving real science problems…
Driven by practical mission requirements
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