另外还有地理因素：这些国家彼此都非常接近，从发射到目标，一个带核弹头的导弹的飞行时间只要几分钟。

There's also the geographic factor: These countries are very close to one another; a nuclear-armed missile's flight time, from launcher to target, is a few minutes.

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首先，基于微分几何理论，得到了导弹运动的微分几何描述方程，无需估计剩余飞行时间。

First, a differential geometrical description equation is obtained based on differential geometry theory without the need to estimate the parameter of available time-to-go.

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