弹道导弹从东经120北纬20高度30公里打目标东经150北纬30高度0的目标，关机点及飞行时间计算。还介绍了惯性导航的内容。 对于弹道式导弹：目标作为地球上的某一点，它是随地球一起在惯性空间运动的，因此需要迭代求解需要速度和自由飞行时间。按照给出的程序进行多次迭代解算即可得出考虑地球自转时的关机点参数解算和飞行时间计算。-20 ballistic missile from a high degree of north latitude and 120 east longitude hit targets 30 kilometers north latitude and east longitude 150 0 30 a high target, off points and flight time calculations. Also describes the contents of inertial navigation. For ballistic missile: target as a point on the earth, it is together with the Earth' s movement in inertial space, and therefore requires iterative solving the need for speed, and free flight time. Several times in accordance with the procedures given iteration can be derived when considering the earth' s rotation off point parameters, and calculating time of flight calculations.