Recording sonic booms with the Romanian infrasound arrays

<p>Two infrasound stations are currently in operation on the Romanian territory: IPLOR 4-element array of 0.6 km aperture, in the central part, and BURARI 6-element array of 0.7 km aperture, in the northern region.</p><p>Automatic processing of continuous data recorded by the two arrays has revealed many impulsive signals generated by repeating sources confined in certain directions, i.e., sonic booms induced by supersonic aircraft activity. The approximate origins of the infrasound found by cross bearing the detections of IPLOR and BURARI arrays are typically pointed to the military air bases located in Romania and across Europe and Near East region. In some cases, the observed azimuths need to be corrected for the deviating effects of zonal cross-winds as the direction of stratospheric winds changes seasonally.</p><p>The distances to the sources of sonic booms range from 140 km (Romania) to 2200 km (North Sea, Northern Norway, Germany, France, Ukraine-Russia border, Aegean Sea, Turkey etc.). The signal characteristics varies when time and spatial distance increase: from short-spiked to long-pulsed shape, from higher amplitudes (1 Pa) to lower ones (0.01 Pa). In case of short-range propagation, high frequencies (above 1 Hz) predominate, while for long-range propagation, the lower frequency drops below 1 Hz and higher frequency components are attenuated.</p>

Effects of Atmospheric Uncertainties on Sonic Boom Perceived Level

This work quantifies the uncertainty in Stevens Mark VII Perceived Level of sonic booms due to uncertainties in atmospheric profiles. The influence of temperature, humidity, and wind profiles, at six cities around the globe, on the sonic boom loudness is calculated. The flow field around an aircraft was obtained by solving the three-dimensional (3D), compressible Euler equations using the UNS3D solver. The near-field pressure signature is then propagated through the atmosphere by solving the augmented Burgers equation using the sBOOM solver. The uncertainty is modeled using a nonintrusive polynomial chaos approach. A sensitivity analysis is performed to identify the altitude range and the atmospheric variable to which the Perceived Level is most sensitive. It was shown that the Perceived Level is not sensitive to any particular altitude but rather the atmospheric profiles. It was also seen that the Perceived Level is highly sensitive to humidity and temperature profiles and less sensitive to the wind profiles.

Estimating Flight Characteristics of Anomalous Unidentified Aerial Vehicles in the 2004 Nimitz Encounter

A number of Unidentified Aerial Phenomena (UAP) encountered by military, commercial, and civilian aircraft have been reported to be structured craft that exhibit `impossible’ flight characteristics. We consider the 2004 UAP encounters with the Nimitz Carrier Group off the coast of California, and estimate lower bounds on the accelerations exhibited by the craft during the observed maneuvers. Estimated accelerations range from 75 g to more than 5000 g with no observed air disturbance, no sonic booms, and no evidence of excessive heat commensurate with even the minimal estimated energies. In accordance with observations, the estimated parameters describing the behavior of these craft are both anomalous and surprising. The extreme estimated flight characteristics reveal that these observations are either fabricated or seriously in error, or that these craft exhibit technology far more advanced than any known craft on Earth. In the case of the Nimitz encounters the number and quality of witnesses, the variety of roles they played in the encounters, and the equipment used to track and record the craft favor the latter hypothesis that these are technologically advanced craft.