求翻译：高超音速推进技术。目前各国发展高超音速技术，主要选用超然冲压发动机作为推进系统。其中，超然冲压发动机的一个技术困难就是飞行器必须到达一定速度才能启动，这要有助推器提供初速才行。因此，对于高超音速飞机，跨大气层飞行器和空天飞机而言，如何是实现固体助推火箭与超然冲压发动机的最佳组合变成唯一大关键。是什么意思？

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hypersonic propulsion technology. The current national development, primarily a hypersonic technology chosen as transcendent ram engine propulsion system. Of these, transcendent ram engine aircraft is a technical difficulties must reach a certain speed to start, this should have a booster provide in

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Hypersonic propulsion technology. Current national development of hypersonic technology, mainly use transcendent Ramjet propulsion systems. Among them, transcendent technical difficulty is Ramjet aircraft must reach a certain speed to start, the boosters provide a muzzle velocity to lines. Therefore

The hypersonic speed advances the technology. Various countries develop hypersonic technology at present, mainly select for use and press the engine detachedly as the propulsion system. Among them, detached a technical difficulty of pressing the engine is that an aircraft must reach certain speed to