Once you're in orbit, you are two thirds of the way, energetically, to anywhere -- the moon, to Mars. And today, there's only three vehicles -- the U.S. shuttle, the Russian Soyuz and the Chinese vehicle -- that gets you there.
一旦你上了轨道，从能量的角度来讲你已经完成了去往任何地方的三分之二过程了 无论是月球或者还是火星。目前， 只有3种运输工具能把你送上太空－美国的太空梭， 俄国的联盟号太空船以及中国的运载火箭。