FAA CENTER OF EXCELLENCE FOR ALTERNATIVE JET FUELS & ENVIRONMENT
Supersonic En-route Noise
- a.k.a. Sonic Boom
Vic Sparrow, Director and Professor of Acoustics
Graduate Program in Acoustics, Penn State
vws1@psu.edu
April 21, 2017
ANERS 2017, Alexandria, VA, USA
Opinions, findings, conclusions and recommendations expressed in this material are those of the author
and do not necessarily reflect the views of ASCENT sponsor organizations.
Acknowledgments
The ANERS organizers
Wonderful sponsors: FAA & NASA
– Particularly FAA managers Sandy Liu, Bao Tong, Becky Cointin
– Particularly NASA managers Peter Coen, Ed Haering, Alexandra
Loubeau
Wonderful partners
– Aerion
– Boeing
– Gulfstream
– KBRwyle
– Lockheed Martin
– Volpe
Faculty and students at Penn State
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Sonic booms are coming!
Purpose:
– Describe sonic booms and methods to enable
the return of routine civilian supersonic flight
Reminders:
– Supersonic: Faster than the speed of sound
– Mach number: airplane speed relative to speed
of sound,
Outline:
– Background
– 2 approaches for overland supersonics
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Need for speed
People want to get from place to place as fast as
possible, so aircraft are helpful
Faster transportation brings the peoples of the world
closer together
– Trade and commerce: key for international
business
– Mutual understanding: world peace
You don’t always need speed, but when you need it,
you really want it
– Federal Express versus U.S. mail
For many people, time is money.
– Supersonic flight can be twice as fast as subsonic.
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Why a small supersonic jet (SSJ)?
It’s a stepping stone to get to supersonic airliners.
– Easier to overcome technical hurdles for small aircraft
– Learn lessons so can build larger vehicles
People are willing to pay for them.
– Affluent individuals are usually the first to pay high
prices for technology until the price comes down for
everyone else (subsonic aircraft in 1940’s and 50’s,
cellphones in 1980’s . . . )
Can do a lot of good right away.
– Organ donations
(double the range of potential donor/recipient
matches)
– Fast travel to natural disasters, etc.
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Shock waves: continuously made
Power boat on lake
[Edmont, Creative commons.]
Sonic boom
[L. Weinstein, NASA Langley]
Common misunderstanding:
– There is no singular boom from “breaking the sound barrier”
– The boom is carried around by the aircraft whenever it is
supersonic!
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pressure
Typical “N-wave”
~100 Pa
“N-wave”
what you hear
boom
~300 ms
time
boom
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Geometry
Mach Cone:
θM
1⎞
= sin ⎜ ⎟ , the Mach angle
⎝ M⎠
−1 ⎛
8
Boom “carpet” on a typical flight
[Maglieri &
Plotkin, 1991.]
Primary carpet about 30 to 50 miles wide (50 to 80 km).
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Projected flight routes over U.S.
(one day, fleet of 400 aircraft)
[Salamone, 2009.]
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Current U.S. regulation
Overland, civil supersonic
flight is currently prohibited:
FAA is interested in
reevaluating regulations in
light of
– new research findings
– current direction of NASA and
industry
Data is needed to
reevaluate the regulations.
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The only civilian supersonic airliner to
date: The Concorde
Statistics:
– Regular flights between 1976 and 2003.
– Speed peaked at Mach 2, height 59,000 ft!
Concorde was restricted to over-water routes because of
the sonic boom
Concorde was [P. Henne, 2005]
– Technical success
– Economic failure
– Environmental failure
But now we know a lot more know about
– Computational fluid dynamics
– Human perception, for example . . .
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2 paths to overland supersonic flight
“Shape” the aircraft to make it quieter
– Low boom technology
When overland, fly the aircraft slower so sonic
booms never reach the ground
– Mach cut-off technology
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Current industry choices
Low-Boom
Gulfstream
Lockheed Martin
Spike Aerospace
[Maglieri, et al., 2014.]
Mach Cut-off
or N-wave
Wait and See
Aerion
Boeing
Boom
Technology
Cessna
Dassault
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Calculated Loudness of
Shaped Booms
Slide courtesy of
Brenda Sullivan,
NASA Langley
1 psf peak
initial shock
all booms have 1 ms initial rise time
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Metrics for sonic boom
Peak pressure doesn’t work very well
– pascals [Pa] or poundforce per square foot [psf]
Steven’s Mark VII Perceived Loudness, PL
A-weighted SEL
C-weighted SEL (but not for quiet booms)
Glasberg and Moore loudness metrics
Hybrid Metrics
– Example “Indoor sonic boom annoyance predictor”
ISBAP = a0 + a1*PL + a2*(ASEL - CSEL)
[Loubeau, et al., (2015)]
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Outdoor subjective
testing with N-wave
aircraft
Photo: Hodgdon
Retouch: Leith
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Sonic booms can cause rattle indoors
Low-frequency content in sonic booms will likely make
houses vibrates, and this can create rattles.
Americans spend 90% of their time indoors (EPA).
Researchers
at NASA are
conducting
studies on
rattle’s effects
on subjective
annoyance.
[Mr. Jorge Cruz,
Pinterest]
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Attempt at a smoother waveform
Gulfstream’s Quiet Spike, 2006-2007
– F-15 with extendable forward spike
– Make multiple small shocks instead of one big shock
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NASA’s planned demonstrator
2015 stated they are working to develop an X-plane to
demonstrate low-boom technology.
– Called Quiet SuperSonic Technology (QueSST) aircraft
– Designed for cruise at Mach 1.6
– Waiting on Congress for funding
– Really need this aircraft to move forward
Lockheed Martin/
NASA
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Aerion’s announcement
In 2015 stated they are working with Airbus Military to
build a supersonic aircraft with first flight in 2021.
– Not a low-boom aircraft; makes an N-wave
– Fly like Concorde over water
– Will ask FAA to fly over land in Mach-Cut Off
configuration: M < 1.15
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Speed of sound varies with height
Relies on temperature
dependence of
atmosphere
Speed of sound varies
with temperature
And temperature varies
with height
Typical lapse condition:
(afternoon)
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Concept of Mach cut-off
At altitude, airplane achieves Mach 1 velocity at a lower
speed than if near ground.
Aircraft is supersonic at altitude, but not at ground.
Rays bend upwards, so no boom on the ground.
Approximate range: 1 < M < 1.15
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Ray theory does not explain all
Zoom in to see a wave structure near caustic:
Caustic line
Evanescent wave
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ASCENT research on Mach cut-off
Dusting off all the theories and data that were available
in the early 1970s
Current work focused on finding
– “Safe altitudes” for Mach cut-off flight, incorporating real world
atmospheres
– Annoyance thresholds for Mach cut-off sounds
Summary:
§ Mach cut-off could work much of the time
§52F/@8??;->/1=?-5:
- How often Mach cut-off sounds will be heard
- What the public will think of the sounds
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What does the future hold?
Look into the crystal ball . . .
its very likely we will see:
Demonstration aircraft assembled in 2-3 years
Flying demonstration aircraft in 3-5 years
Prototype N-wave aircraft in 4-5 years
Routine service of N-wave aircraft in 7-10 years
Routine service of low-boom aircraft overland in 10-15
years
Note: V. Sparrow’s best guesses; no one else’s.
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Summary
Sonic booms are coming to you in a few years
– N-wave
– Mach cut-off (keep boom off the ground)
– Low boom (shape the aircraft)
Want to learn more?
– Download your free copy of an amazing 535 page book
prepared by NASA
– It is *FREE* and available online: NASA/SP-2014-622
– Get from ntrs.nasa.gov
Thanks for listening!
vws1@psu.edu
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References
Master reference: D. Maglieri, P. Bobbitt, K. Plotkin, K. Shepherd, P. Coen, and D. Richwine, Sonic Boom: Six
Decades of Research, NASA/SP-2014-622 (NASA Langley Research Center, Hampton, VA, USA, 2015).
Boom Technology, boomsupersonic.com
H. Carlson, “Experimental and analytical research on sonic boom generation at NASA,” in Sonic Boom Research,
NASA SP-147, A. R. Seebass, Ed. (1967).
L. Cliatt, et al., “Mach cutoff analysis and results from NASA’s farfield investigation of no-boom thresholds,” AIAA
2016-3011, 22nd AIAA/CEAS Aeroacoustics Conf., Lyon, France, 30 May – 1 June, 2016.
G. Haglund and E. Kane, "Flight test measurements and analysis of sonic boom phenomena near the shock wave
extremity," NASA Report CR-2167 (1973).
P. Henne, “Case for a small supersonic civil aircraft,” J. of Aircraft 42(3) 765-774 (2005).
S. Horinouchi, “Conceptual design for a low sonic boom SSBJ,” 43rd AIAA Aerospace Sciences Meeting, AIAA
2005-1018.
“JAXA validates sonic boom reduction technology: Towards realizing future supersonic civil transport,” http://
global.jaxa.jp/press/2015/10/20151027_dsend2.html , retrieved October 2015.
A. Loubeau, Y. Naka, B. Cook, V. Sparrow, and J. Morgenstern, “A new evaluation of noise metrics for sonic
booms using existing data,” AIP Conf. Proc. 1685 (2015).
D. Maglieri and K. Plotkin, Chap. 10 “Sonic Boom,” in Aeroacoustics of Flight Vehicles: Theory and Practice, H.
Hubbard (Ed.) (NASA Ref. Pub. 1258, Vol. 1 WRDC Tech. Rept. 90-3052, NASA Langley Research Center, 1991)
R. Perley, “Design and demonstration of a system for routine, boomless, supersonic flights,” FAA Report No. FAARD-77-72 (1977).
J. Salamone,”Recent sonic boom propagation studies at Gulfsteam Aerospace,” AIAA 2009-3388, (2009).
Spike Aerospace, spikeaerospace.com
B. M. Sullivan, “Research on subjective response to simulated sonic booms at NASA Langley Research Center,”
presentation FrAM108 at International Sonic Boom Forum, 18-22 July 2005, State College, PA. Proceedings paper
written and will appear in 2006.
W. Shurcliff, "S/S/T and sonic boom handbook," (Ballantine, 1970), p. 63.
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Backup Slides
29
Alternative representations
Steady supersonic flight assumed:
[Maglieri &
Plotkin, 1991.]
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How shocks become an N-wave
shocks
Result from nonlinear
acoustics: higher amplitude
portions of the wave travel
faster
Multiple shocks become the
N-wave during the
propagation to the ground:
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Effects of atmospheric turbulence
The hypothesis is that lowboom waveforms will be less
affected by turbulence than
N-waves. To be tested . . .
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Recent research by JAXA
Japanese Aviation eXploration Agency
Drop an unpowered low-boom model from 30 km
Success, July 2015!
[JAXA, 2015]
JAXA
id
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Does boom shaping really work?
Back-to-Back Data Flight
27 August 2003
DARPA
QSP
Northrop Grumman
USN Fallon F-5E
With F-5 SSBD
At Palmdale
Preparing For
Flight
F-5E SSBD Aircraft
Takes-Off Followed
USN F-5E
45-Seconds
Later
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Yes, boom shaping works
First-Ever Shaped Sonic Boom
Recorded 27 August 2003
DARPA
QSP
Northrop Grumman
Signatures recorded
during SSBD backto-back data flights
in the Edwards AFB
supersonic flight
corridor early
morning
Estimated
conditions:
Mach 1.36+,
Altitude 32,000 ft
[Benson, 2013.]
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Subjective testing via simulators
NASA Langley
Gulfstream
Lockheed-Martin
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Spectrum of N-wave
Both low & high frequencies important
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Indoor subjective testing
[KlosF3@=1
Haering idea.]
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