求翻译：高超音速飞行马赫数范围很宽，要跨域亚音速，音速，超音速3个阶段，才能进入高超音速阶段。当飞行器从稠密大气层冲进稀薄大气层时，空气密度的巨大变化会给飞行器设计带来巨大的困难，所以必须突破四大关键技术。是什么意思？

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hypersonic flight Mach was very broad scope, it is necessary to cross-domain subsonic, supersonic speed of sound, which would be able to enter into three stages, hypersonic stage. When an aircraft crashed into the dense layers of the atmosphere of the rarefied atmosphere, great changes batter will r

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Hypersonic Flight Mach number range is very wide, cross-domain subsonic, Sonic, supersonic 3 stages, before they enter the Hypersonic phase. When aircraft from the dense atmosphere into rarefied atmosphere, great changes in air density will pose great difficulties for aircraft design, so you must br

The Mach number scope of the hypersonic flight is very wide, should step the land subsonically, the velocity, at supersonic 3 stages, could enter hypersonic stage. When the aircraft rushes into the thin atmosphere from the dense atmosphere, the enormous change of the air density will design bringing