这样，当普通燃料火箭到达地球轨道约800公里高度时，核反应堆舱会脱离化学燃料火箭，并开始工作。

Then, once the vehicle had ascended to high-Earth orbit, above about 800 kilometers, the nuclear reactor module would detach from the chemical rocket and start up.

youdao

这一假设认为，地球运行的变化，特别是绕太阳轨道的变化，会导致太阳到达地球能量的不同。

It says that variations in earth's movements, specifically in its orbit around the sun, these variations lead to differences in the amount of solar energy that reaches the earth.

youdao

目前“信使号”探测器已经到达了地球、金星、水星多重引力助力飞行的最后一个阶段，并将于2009年9月29号进行第三次飞越最终将在2011年3月正式进入水星轨道。

MESSENGER is now in the last stages of multiple gravity-assist flybys of Earth, Venus and Mercury, en route to an insertion into orbit around Mercury in March of 2011.

youdao