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Fixing the Sound Barrier
The DARPA/NASA/Northrop-Grumman
Shaped Sonic Boom Flight Demonstration
Peter G. Coen, NASA
&
Roy Martin, Northrop Grumman
EAA AirVenture
Oshkosh, Wisconsin
July 2004
Shaped Sonic Boom Demonstration
SSBD
First ever FLIGHT demonstration of sonic boom
Shaping
Design, fabrication and test using a surrogate
aircraft
Nose modification of an F-5E Fighter
Primarily funded by DARPA, Northrop and NASA
Extremely successful government/industry
collaboration
5 U.S. Government agencies
8 U.S. aerospace companies
Sonic Boom Basics
Multiple Shock
Waves of Differing
Strengths
Shocks
begin to
merge
Overpressure Dp
Impulse
Duration All Shocks merged into “N-wave”
Rise Time
Sonic Boom Calculation Approaches
Whitham-Walkden Theoretical Computational
Equivalent Area AE
Equivalent Length AE
Theory of Minimum Initial Shock
Equivalent Area
Sonic Boom Lift
Minimization Volume
Minimum Overpressure
Through Length
Aircraft Shaping George and Seebass, 1969
Multiple Shocks Shock Strength
of Differing and Position
Strengths Controlled
Coalescence
Prevented
Shocks
begin to
Coalesce
Shocks Coalesce into “N-wave” Shaped Boom at the Ground
SSBD Background: Key Elements of
Theory Validated in Previous Programs
A
A = 1.3. psf
B
8
7 Rise Time
6
0.25
5 0.5
Mean
0.75
Loudness 4 1
Rating
3 B/A
2
1
0
1 2 3
Rise Time, ms
Noise Acceptability Benefit Verified: Sullivan 1990
Vehicle Design Approach Verified: Darden and Mack, 1979
SSBD Provides a Missing Piece of the Puzzle
Design
… Through Ground
Measurement of
Booms from
Modified and
Unmodified F-5Es
Demonstrate
Design Mach 1.4
Shaped Boom Shock Thickening Adjusted
Ground Boom Signature Comparisons
Propagation in 1.4
1.2
1.0
M = 1.40
h = 32 kft.
Tanh 1/P Modification
Real
0.8
0.6
0.4
Atmosphere…
0.2
DP - psf
0.0
-0.2
-0.4
-0.6
F-5SSBD
SBD-24b @ 12,700 lbs.
-0.8 F-5E
F-5E @ 11,200 lbs.
-1.0
-1.2
-1.4
0 10 20 30 40 50 60 70 80 90 100
Time - msec
Noise Acceptability
Key to SSBD Success: F-5E
Aircraft Configuration Is Very Amenable to the Type of Forebody Modifications
Required to Produce a Shaped Boom Signature
Long Nose, Blended Canopy, and
Inlets Relatively Far Back
F-5E
Very High Overall Fineness Ratio
Lightweight
RF-5E
Modification Is Relatively Low Risk
Due to Similarity with F-5 Family
Extensive Database of Modified F-5F
Forebodies with Comprehensive
Wind Tunnel and Flight Testing
F-5 Aircraft Forebodies
Cost-Effective Test Approach
Limited Wind Tunnel Testing and CFD
Analysis Required for F-5 Mod Initial Design
Low Aircraft Operating Cost
Supersonic Performance Capability
with Margin
Final Design
FOR PUBLIC RELEASE
Build-Up Approach To
Development & Validation
Extensive CFD Inlet Shock Flight Test Boom Tunnel Tests
NASA Dryden NASA Glenn
Feb 02 Mar & May 02
Mod Shape Defined Jan 02
Correlations Completed
SSBD WTM-2 Near-Field Pressures S&C Tunnel Test Force Tunnel Test
M = 1.367, CN = 0.132, h/L = 1.5, = 0
o
0.04
0.03
0.02
0.01
DPlocal / P local freestream
0.00
-0.01
-0.02
-0.03
Euler - 24b WTM-2 @ MFR = 0.76
-0.04
-0.05
24b4 WT Data @ MFR = 0.76 - 0.80 - Rdg. 143 (P3)
24b4 WT Data @ MFR = 0.76 - 0.80 - Rdg. 157 (P4)
NGC LSWT AEDC 4T
-0.06
Aug 02 Oct 02
35 40 45 50 55 60 65 70 75
Along Track (Model) - inches
IDRs - 12/01 & 2/02 PDR - 3/02 CDR - 7/02 Pre-FRR - 1/03
FOR PUBLIC RELEASE
SSBD F-5E Handling Qualities
Engineering Predictions
Longitudinal Stability Comparable F-5F, Minor Reduction Dynamic
Stability Damping
Directional Stability of F-5SSBD is Comparable to F-5F with 275
Gallon Centerline Tank
Directional Stability is Positive for AOA of Planned Flight
Envelope
Subsonic and Supersonic Handling Qualities Satisfactory and
Comparable to other F-5 Configurations (with Stability
Augmentaion Engaged)
Use Aft CG Limit of F-5F (More Forward than F-5E)
25% MAC
L.E. MAC
Design C.G.
FOR PUBLIC RELEASE
Test Aircraft Selection
Arranged Loan of Navy F-5E
- Destined for “Boneyard” - Extended 50 Flight Hrs
Navy Assumed Safety of Flight Risk
- Navy Flight Clearance Review
- Navy Test Pilot Participation ( CDR “Spike” Long)
FOR PUBLIC RELEASE
FOR PUBLIC RELEASE
Fabrication & Flight Operations
USN F-5E Arrives NGSA Mod Nose Attached Fairings Attached
Jan 03 Mar 03 Apr 03
Pre-Flight Prep First Taxi First Flight
May 03 9 Jun 03 24 Jul O3
Envelope Expansion Back-to-Back & 21 Flawless Flights
& Ferry Flights Probe Flights Over 1 Month!
FOR PUBLIC RELEASE
FOR PUBLIC RELEASE
SSBD F-5E Cockpit Modifications
Preparation for First Flight
Test Plan Approved by NAVAIR
Civil Landing Permits from USAF, USN, US Army
F-5E Spare Parts from Marines at YUMA MCAS
Flight Readiness Reviews: NAVAIR, DARPA, Northrop
Grumman, NASA Dryden, NASA Langley
Aircraft Prep, EMC, Low and High Speed Taxi
Real Time Telemetry for First Flight and Envelope
Expansion Flight Tests
Pre-position T-38 Chase from Seattle to St. Augustine
- Extremely Useful for Test Pilot Proficiency
FOR PUBLIC RELEASE
FOR PUBLIC RELEASE
First Flight of SSBD F-5E
Takeoff from St. Augustine (8000 Ft Rwy)
Test Area Over the Atlantic (W-158)
Boeing T-38 Chase (Mike Bryan)
Landing at Cecil Field (12,500 Ft Rwy)
Envelope Expansion Flights
Maneuver Block:
Pitch Doublet
Yaw Doublet
Steady Sideslips
30 Bank to Bank
Windup Turn
(Augs-On then Off)
FOR PUBLIC RELEASE
FOR PUBLIC RELEASE
Cross Country Ferry Flights
FOR PUBLIC RELEASE
Back-to-Back Data Flight
27 August 2003
(45 Second Separation Between Aircraft During Supersonic Run)
NAS Fallon VFC-13 F-5E and
F-5 SSBD at Palmdale, CA
F-5 SSBD Takes Off
at Dawn Enroute to
EAFB Supersonic Corridor
F-5 Pilots
Roy Martin
CDR Darryl “Spike” Long LCDR Dwight “Tricky” Dick
FOR PUBLIC RELEASE
FOR PUBLIC RELEASE
SSBD Flight Path
Edwards AFB
Supersonic Corridor
32
FOR PUBLIC RELEASE
FOR PUBLIC RELEASE
Ground Recording Array Setup
FOR PUBLIC RELEASE
First-Ever Shaped Sonic Boom
Recorded 27 August 2003
Signatures recorded
during SSBD back-
to-back data flights
in the Edwards AFB
supersonic flight
corridor early
morning
Flight conditions:
Mach 1.36+,
Altitude 32,000 ft
Design Mach 1.4
Shock Thickening Adjusted
Ground Boom Signature Comparisons
1.4
1.2
M = 1.40
1.0 Tanh 1/P Modification
h = 32 kft.
0.8
0.6
0.4
0.2
DP - psf
0.0
-0.2
-0.4
-0.6
F-5SSBD
SBD-24b @ 12,700 lbs.
-0.8 F-5E
F-5E @ 11,200 lbs.
-1.0
-1.2
-1.4
0 10 20 30 40 50 60 70 80 90 100
Time - msec
FOR PUBLIC RELEASE
Lessons Learned from Initial Tests
Florida in July has BIG Thunderstorms in PM!
Navy Flight Clearances Are Difficult and
Expensive, but Great Confidence Builders
Don’t Depend on Using Ground References for
Early Morning Flights into a Rising Sun!
Program Will Cost Twice Your Initial Estimate
Good Programs Attract Interest & Support
Shaped Sonic Boom Theory is Valid
FOR PUBLIC RELEASE
FOR PUBLIC RELEASE
Test Background/Objectives Shaped Sonic Boom
Experiment
Based on the Success of the DARPA SSBD Program,
NASA Created a Follow-On Program to Further Explore
the Characteristics and Robustness of Shaped Sonic
Booms Using the F-5 SSBD Test Aircraft
Up to 21 Test Flights Planned
Achieve M1.4, 32k ft. Design Condition
Collect Data at Off-Design Conditions
Collect Back-to-Back Data with Navy F-5E
Collect Near-Field Probing Data with NASA F-15
Collect Data Above Ground Turbulence Layer with
USAF TPS Glider
Attempt to Record Focused Boom
FOR PUBLIC RELEASE
Shaped Sonic Boom Experiment
SSBE Experiment Designed to Collect Quality Data from Many Sources
Test Summary Test Schematic
• 21 flights in 9 days
• 8 flights back to back with baseline F- 5E F-5 SSBD operated by Northrop
• 4 flights with F-15 probe aircraft Grumman generates shaped
• 45 probe data sets boom over sensor array
• 13 flights with glider
• 1300 boom recordings Unmodified F-5E from
• 2 focus booms recorded USN VFC-13 used to
generate baseline
boom signature
Microphone on USAF Test
Pilot School glider measures DFRC F-15 probes
30,000 ft boom above turbulence layer pressure field below
F-5 SSBD
Boom senor array
8,000 ft (42 sensors total), on
& off the flight track
North Edwards AFB Runway NASA, Wyle Labs, NGC,
Gulfstream, Eagle
FOR PUBLIC RELEASE
Revised Ground Track Shaped Sonic Boom
Experiment
FOR PUBLIC RELEASE
FOR PUBLIC RELEASE
SSBE Test Summary Shaped Sonic Boom
Experiment
Met or Exceeded All Flight Test Goals
21 Test Flights Conducted January 12–22, 2004
1 Functional Check Flight
8 F-5 SSBD Solo Flights
8 F-5 SSBD / F-5E Back-to-Back Flights
4 F-5 SSBD / F-15B Probing Flights
Repeatable Data Collected Between M1.35 and M1.45
Well Over 1300 Sonic Boom Signatures Recorded by Ground
Sensor Array at EAFB North Base
USAF TPS Glider Obtained Excellent Data Above Ground
Turbulence Layer on 14 Flights
45 Near-Field Probing Measurements Obtained with F-15
Successfully Recorded Focused Boom on 2 Flights
Excellent Weather for Meaningful Data Collection Experienced
Throughout Test Phase
FOR PUBLIC RELEASE
FOR PUBLIC RELEASE
Initial SSBE Flight Test Results Shaped Sonic Boom
Experiment
F-15B Probe Data
Glider Data
Ground Data
FOR PUBLIC RELEASE
FOR PUBLIC RELEASE
SSBD/SSBE Program Summary Shaped Sonic Boom
Experiment
Shaped Sonic Boom Persistence Theory was Proven in
Actual Flight Conditions
Sonic Boom Intensity Can Be Reduced Through Aircraft Shaping
Shaped Ground Boom Signature for a Supersonic Aircraft Can Be
Predicted
DARPA and NASA Were Delighted with the Quantity and
Quality of the Supersonic Data
Mapped Shockwave Propagation Around the Near-Field of SSBD
Aircraft, at the Mid-Field Using a Glider, and at the Ground Level in
Various Atmospheric Conditions
Recorded Boom Focus Data Using ¼ G Pushover
Program Data Will be Invaluable to Future Supersonic
Aircraft Designs – Allows Designers to Go Forward with
Confidence in Ability to Predict Boom Signatures
FOR PUBLIC RELEASE
A Tribute To The SSBD Team
SSBD/SSBE Test and Support Team
NAVY •
• US W
SA YL
• NA E
RPA LA
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N • DA •E
A
UMM AG
P GR LE
TH RO SSBD AE
R RO
NO
USA AM
F•
US SHAPED SONIC T RE
AR FS
MY
• BO BOOM DEMO UL
EIN •G
G • LO ON
CK T HE
HEE AY
DM
ART I N • R
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