但其排气速度却异常惊人，大约为化学燃料火箭的十倍—这使得离子推进器的效率非常高。
The exhaust velocity, though, is enormous—more than ten times that of a chemical rocket—and this makes ion propulsion extremely efficient.
并进一步分析了基岩厚度、采高、推进速度对顶板破断的影响。
The effect of basic rock thickness, mining height and advancing speed on roof breaking is analyzed.
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