Mach Cutoff Analysis and Results from NASA's Farfield Investigation of No-boom Thresholds

Cliatt, Larry J.; Haering, Edward A.; Arnac, Sarah R.; Hill, Michael A.

doi:10.2514/6.2016-3011

Cited by 9 publications

(9 citation statements)

References 8 publications

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“…Illustration of Mach cutoff. 2 coordinate system for the data processing in the study was defined with the x-y plane as the ground plane, the +z-axis pointing up, broadside to the array, and the origin at the center of the array as shown in Figure 3. The direction from which the propagating wave is arriving is given by the azimuthal angle y, and the elevation angle ', forming the unit vectorr.…”

Section: Methodsmentioning

confidence: 99%

“…The purpose of the Farfield Investigation of No-boom Thresholds (FaINT) test was to investigate lateral and Mach cutoff conditions. 1,2 Lateral cutoff is the ground point where the sonic boom ray is refracted upward and thus no shock wave is observed past that point, although evanescent waves may be detected. 3 Lateral cutoff is demonstrated in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

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Finding the boom: Phased array processing applied to sonic boom direction of arrival estimation

Schultz

Underbrink

Hunting

et al. 2017

International Journal of Aeroacoustics

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, 73 supersonic passes of an F-18 aircraft were observed over a dry lake bed at Edwards Air Force Base as part of NASA's Farfield Investigation of No-boom Thresholds project, which was conceived to measure the characteristics of sonic booms at the boundaries of their decay, where overpressure is exceptionally low, thereby stretching the limits of current prediction methods. Each pass was recorded by a 55-microphone phased array sensor system with a circular aperture diameter of 2000 ft (609.6 m). The data were processed using a novel time domain array processing algorithm to estimate the direction of arrival and trace speed of the sonic boom wave front along the plane of the phased array. The results from the phased array processing are consistent with the known location of the test aircraft for each processed flight and are consistent with expectations for direction of arrival due to atmospheric refraction. Near real-time estimation of the sonic boom direction of arrival, trace speed along the ground, and visualization of the propagation of the sonic boom wave front are possible. This could allow the test team to assess the data and determine if the target of the test point has been met while the test aircraft is still in flight. This would enable improved test efficiency and efficacy, ultimately improving the value of the test campaign. The measured direction of arrival also provides sonic boom propagation numerical prediction code validation. Most sonic boom prediction codes provide the propagation path of the sonic boom and thus the direction of arrival of the sonic boom at a point on the ground. Thus for predictions made

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Finding the boom: Phased array processing applied to sonic boom direction of arrival estimation

Schultz

Underbrink

Hunting

et al. 2017

International Journal of Aeroacoustics

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“…5,000 ft were again taken as the basic cutoff altitude. For each of the 365 atmospheres, 1000 geographic locations over land were picked at random 10 . At each location, eastward as well as westward flight was considered.…”

Section: Figure 7 Distribution Of Cutoff Mach Numbers Flown In Cruisementioning

confidence: 99%

Supersonic Overland Without a Sonic Boom – Quantifying the Speed Advantage of Mach-Cutoff Flight

Liebhardt

Linke²,

Knaack³

2021

Aiaa Aviation 2021 Forum

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When flying at low supersonic speeds, rising temperatures and convenient winds can deflect the sonic boom shock waves so that they do not reach the ground. This work presents a computation methodology that incorporates atmospheric sonic ray tracing, topography, and realistic 3-D atmospheres in order to optimize supersonic overland cruise with respect to speed. Flight missions are simulated on several suitable city pairs using numerous atmospheric conditions. Flight times and fuel consumption are compared to subsonic high-speed missions.

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“…During the above-mentioned FaINT project, a second flight campaign was conducted to measure the loudness of evanescent waves below the cutoff altitude [20]. Using the results, an empirical equation was developed that describes the relationship between on-ground loudness, cutoff altitude, threshold Mach number, and flight Mach number.…”

Section: Altitude Cutoffmentioning

confidence: 99%

“…The presented methodologies have to be validated with the help of actual flight tests. Looking back at NASA's FaINT project [18,20], this seems to be a challenging task. Atmospheric conditions have to be predicted as accurately as possible, considering the actual duration of the flight, and the effect of unpredictable turbulence has to be quantified statistically.…”

Section: Validation Of Simulated Boom Carpetsmentioning

confidence: 99%

Sonic Boom Carpet Computation as a Basis for Supersonic Flight Routing

Liebhardt

2019

AIAA Aviation 2019 Forum

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Mach Cutoff Analysis and Results from NASA's Farfield Investigation of No-boom Thresholds

Cited by 9 publications

References 8 publications

Finding the boom: Phased array processing applied to sonic boom direction of arrival estimation

Finding the boom: Phased array processing applied to sonic boom direction of arrival estimation

Supersonic Overland Without a Sonic Boom – Quantifying the Speed Advantage of Mach-Cutoff Flight

Sonic Boom Carpet Computation as a Basis for Supersonic Flight Routing

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