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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Nuclear energy may overtake oil as the main fuel.

核能可能会超过石油成为主要燃料。

《牛津词典》

Fuel cells have three main applications: transportation, portable USES, and stationary installations.

燃料电池有三种主要用途：运输工具、携带用电源、固定装置。

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Indeed, coal would be the main fuel of the British economy for the next 350 years.

FORBES: Magazine Article

Petroleum caught on early as the main fuel source for internal combustion engines because it was plentiful and cheap to refine.

FORBES: Veggie Oil Smells Better Than Diesel, But It's No Slam Dunk

But the main fuel is local anger over crime and migration.

ECONOMIST: Central Europe��s Roma