核心问题
New Concept English, Book 3, L.9 有这么一句话：
By now, a rocket will have set off on its 35 million mile trip to Mars and scientists must be waiting anxiously for the results.
为什么 by now 与将来完成时连用?
词典解答
在上面的句子里 will have set off 并不是将来完成时。其中的 will 在这里是表示现在对业已完成的动作的推测。请与下列实例进行对比：
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You will have received an invitation to the meeting. 你可能已经收到了会议的邀请了。
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I knew his father, Professor Harold C. Pile — you'll have heard of him? (Greene) 我认识他父亲哈罗德·C·派尔教授，你可能听人谈到过他了吧？
will have done
would 也有此种用法, 见 would have done 。