Electric propulsion systems are so simple that really there's just nothing that you really need to be that concerned about.

电力推进系统非常简单，没有什么真的需要担心的地方。

The first electric propulsion engines were actually developed in the 50s and 60s.

最初的电力推进引擎，是在上世纪五六十年代发展起来的。

Other new technologies needed are solar electric propulsion for power and a vehicle that could land people on Mars.

其他所需的技术包括动力方面的太阳能电子推进器和能够让人在火星登陆的火星车。

To move the Earth more efficiently, we'd have to consider electric propulsion.

为了更有效地移动地球，我们必须考虑电力推进。

Unlike the chemical one used in most rockets, electric propulsion doesn't require a lot of mass.

与大多数火箭使用的化学物质不同，电力推进不需要很大的质量。