As for the space shuttle main engines, those are now free.
航天飞机的主发动机现在是免费的。
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It is mainly used on board for starting main engines.
在船上主要用于启动主机。
It is mainly used on board ship for staring main engines.
France and Germany helped found the European Union and are still considered the main engines driving the 27-member bloc.
VOA: standard.2009.11.11
They could power electrically driven wheels, letting an aircraft taxi without using its main engines.
ECONOMIST: Electric planes
They are one of the main engines that drive job creation and economic growth in our country.
FORBES: Washington D.C. Needs More Entrepreneurs
To do this, the computers on board the ISS ignite two of the freighter's four main engines, generating a total thrust of 1, 000 newtons.
BBC: Freighter boosts altitude of ISS
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