1. 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

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

3. 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

4. “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 [ ] (Hypersonic Boundary Layer Transition) Flight Experiment – Launch terminated in boost stage, August 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

5. 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

6. 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 ( g’s) creating lots of heat.
Laminar
Cruise
Time
~6x difference between peak turbulent and laminar heating rates.
Boost-Glide Trajectory

7. 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

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

9. 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

10. 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

11. 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

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

13. 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.

14. 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)

15. 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

16. 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

17. 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 Responsive Invulnerable Global Delivery Against Time Critical Targets as well as 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

18. 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 AFOSR
Demonstrated Boundary Layer Transition Reynolds #’s at least twice those of conventional tunnels

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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!

25. 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 …

26. 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

27. 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

28. 4/23/2017