什么破书,扔掉算了,根本不是状语.
你说的倒是差不多,语法的表述是：
to travel the quarter of a million miles from the Moon to Earth-orbit 是实际的主语；
it 是形式主语,指代的就是to travel the quarter of a million miles from the Moon to Earth-orbit
如果不用形式主语,句子就是：
To travel the quarter of a million miles from the Moon to Earth-orbit requires 97 per cent less energy than the 200 mile-journey from Earth's surface into orbit!
由于主语过长,句子显得头重脚轻,所以用形式主语it,用不定式作实际主语,使句子结构平衡.