Aiming for space is about more than understanding flight paths and knowing the best rockets to use: moon shots are about taking risks.

太空计划不止是熟知飞行轨道和用什么样的火箭最好：载人登月是有巨大风险的。

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Sometimes the stakeholders who set requirements gain better understanding of their needs and update requirements in flight; sometimes their needs actually change because of changes of their context.

有时设置需求的出资方更加了解俄他们的需要，并且随时更新需求；有时他们的需求是由于上下文的变化而发生改变。

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"The major barrier to resuming flight has been understanding tolerance levels of aircraft to ash, " the CAA said.

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Prior efforts had been a mixture of trial and error and hard work mixed with a basic understanding of the mechanics of flight.

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"Understanding how our bodies prepare for fight or flight is just one of the applications of their work, which has also opened the door for a wide range of new, more effective drug treatments with fewer side effects, " Poliakoff added.

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