Physical effects from the Yushu meteoroid. 1

1Chernogor, LF
1V.N. Karazin Kharkiv National University, Kharkiv, Ukraine
Kinemat. fiz. nebesnyh tel (Online) 2022, 38(3):20-46
https://doi.org/10.15407/kfnt2022.03.020
Start Page: Dynamics and Physics of Solar System Bodies
Language: Ukrainian
Abstract: 

The purpose of this work is to estimate effects in gas dynamics as well as mechanical and optical effects from the Yushu meteoroid that entered the terrestrial atmosphere and exploded over a sparsely populated area near the City of Yushu, the Province of Quinghai (the Tibetan Plateau, the People’s Republic of China). According to the NASA, the initial kinetic energy of the celestial body was estimated to be about 9.5 kt of TNT or 40 TJ, of which 4.9 TJ, i.e., 12.25 %, were transformed into the energy of light flash. The velocity components have been estimated to be vx = –2.6 km/s, vy = 5.9 km/s, vz = –12.1 km/s, which yield an estimate of about 5° for the inclination angle, the angle that the trajectory makes with the horizontal plane. The altitude of the explosion, 35.5 km and the angle, 5°, give an estimate of the material density of approximately 3.5 t/m3, close to the chondrite density. The kinetic energy and the velocity yield an estimate of the meteoroid mass to be 432 t and its characteristic size scale of 6.2 m. The energy of the processes and effects in gas dynamics as well as mechanical and optical effects from the celestial body have been analyzed. The main release of energy associated with the deceleration of the fragments of the celestial body, which was defragmented under a dynamical pressure of ~1 MPa, took place in the region of 3.6 km in length at an altitude of about 35 km. A quasi-continuous defragmentation was suggested to produce a mass distribution that follows a power law. The main parameters of the ballistic and explosive shock waves have been estimated. For the Mach number of 45, the radius of the ballistic shock wave was estimated to be about 280 m and the fundamental period to be 2.6 s, which showed a dispersive increase from 9.5 s to 30.1 s with the propagation path length increasing from 50 km to 5,000 km. The radii of cylindric and spherical wavefront shock wave were approximately to 0.8 km and 2 km respectively, and fundamental period was about 7.5 s and 18.8 s respectively. This period had been increased from 21.1 s to 66.7 s and from 42 s to 132.9 s with the propagation path length increasing from 50 km to 5,000 km. In the vicinity of the meteoroid terminal point, the excess pressure was a maximum on a relative scale. It decreased with decreasing altitude, and increased with increasing altitude up to an altitude of approximately 120...150 km where it attained values of ~10...20 of percent, and further it decreased down to a few percent. The absolute value of the excess pressure for spherical wavefront was estimated to be near the altitude of the explosion, subsequently it decreased with decreasing altitude down to 15 km, and further it again increased. At the epicenter of the explosion, it was estimated to be about 310 Pa for cylindrical wavefront and ~ 48.5 Pa for spherical wavefront, which is not enough to damage objects on the ground. The excess pressure decreased with increasing altitude from many tens of pascals to micropascals. Given the average duration of the light flash of 1.26 s, the average power of the fireball was estimated to be 3.9 TW, the flux of power near the fireball (or more precisely, the cone of 3.4 km in length and of 18.6 m in diameter) to be 19.5 MW/m2. At the same time, the temperature was estimated to be about 4,300 K, and Wien wavelength to be 6.7*10–7 m.

Keywords: ballistic shock wave, excess pressure, fundamental period, gas dynamics effect, mechanical effect, meteoroid, optical effect, spherical shock wave