After the trial of 78 years ago today, it was on October 15, 1947, (Calendar 2 September 1947) the world's first ultrasonic aircraft¡ªthe heavy jet flight trial. The initial aircraft, was a spiral jet, this aircraft, although after scientists continuously explore and improve, but until 1939, its flight speed reached only 755 km per hour. When the flight speed exceeds this kilometer, the aircraft's spike rotating speed and the aircraft sinking down from the sky will become faster, and the speed of sound spread will be almost the same, i.e. about 1227 km. Thus, the aircraft's front aircraft will cause intense fluctuations, causing the aircraft to increase resistance, the aircraft will tremble, and the aircraft will be badly shattered, causing