On the optimum mass ratios of two-stage rocket in the practical permissible region, we get the results analytic expression.

本文考虑二级火箭在实际允许区域内的最佳质量比问题，得到解的解析表达式。

youdao

South Korea launched a multi-stage rocket Tuesday in the country's first space shot, but the satellite it was carrying separated a few seconds later than planned and didn't reach the proper orbit.

韩国周二在该国的首次太空发射中发射了一枚多级运载火箭，但所携带卫星与火箭的分离时间比计划晚了几秒钟，卫星未能进入预定轨道。

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The two-stage rocket, called Korea Space Launch Vehicle I or KSLV-I, blasted off at 5 p.m. into blue skies from the seaside Naro Space Center, near the city of Goheung on the country's south coast.

被称作“韩国航天运载器一号”的两级火箭是周二下午5时从韩国南部海岸高兴郡的罗老宇航中心发射升空的。

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Two-and-one-half minutes after the Apollo Eleven launch, the first-stage rocket separated from the spacecraft.

VOA: special.2009.07.15

They fired the third-stage rocket.

VOA: special.2009.07.15

He adds that the newer version has a shorter launch time, better deterrent capability, and that it is a two-stage rocket using solid fuel that is highly maneuverable.

VOA: standard.2009.12.18

The firm, established by Amazon entrepreneur Jeff Bezos, has a design for a capsule and two-stage rocket.

BBC: US firms target astronaut flights

The concept calls for a two-stage rocket that would be powered by engines burning liquid oxygen and kerosene.

BBC: Science & Environment

Our scientists and technicians have succeeded in launching the first artificial satellite aboard a multi-stage rocket into orbit.

BBC: Satellite 'transmitting revolutionary hymns'