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Rocket scientists agree that we have about reached the limit of our ability to travel in space using chemical rockets. To achieve anything near the speed of light we will need a new energy source and a new propellant. Nuclear fission is not an option.

火箭科学家一致认为，我们使用化学火箭在太空旅行的能力已接近极限。为了达到接近光速的速度，我们需要一种新的能源和一种新的推进剂。核裂变不是一个选择。

— Wilson Greatbatch 格雷特巴奇