Fast fill of the external fuel tank began at 8:15 a.m. with the liquid oxygen and one minute later for the liquid hydrogen. The propellants are used by the shuttle's three main engines during the launch into orbit. The fueling process is expected to be finished at about 10:25 a.m. From there, propellants will be trickled into the tank to replace the portion of the chemicals that evaporate during the countdown.
基于1个网页-相关网页
Site Map of the three major factors: the text, links, key words, are extremely beneficial to the search engines crawl the main page content.
网站地图的三大因素：文本、连结、关键词，都极其有利于搜寻引擎抓取主要页面内容。
A major exception, the space shuttle orbiter, USES three onboard liquid-fuel main engines supplied by a disposable external tank and a pair of solid-fuel boosters to reach space.
一个主要的例外是航天飞机轨道飞行器，它使用三个随之携带的液体燃料的重要引擎到达宇宙，而这又是由一个可任意使用的外部箱和一对固体燃料后援器来供给的。
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