NASA calls this a gravity assist, and exploits it to save fuel in missions to outer planets such as Jupiter and Saturn.

美国航空航天局称这是一个重力辅助，并利用它来节省执行去木星和土星等外行星的任务时消耗的燃料。

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All these spacecraft have used sling-shot style gravity assist maneuvers to increase their speeds through the outer solar system.

这些航天器全都使用了射弹弓式的引力辅助方法，从而在外太阳系中提高速度。

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The MESSENGER spacecraft is zeroing in on Venus for the most significant gravity assist maneuver of its long journey to Mercury.

为此次“信使”号在前往水星的长途旅程中最重要的引力机动，飞船正在对金星进行校正。

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The gravity assist would allow a safe return to Earth even if the spacecraft's main rocket engine failed, Professor Longuski said.

BBC: Manned flight to Mars in 2014?

If that happened, the Martian gravity would change the spacecraft's trajectory, hurling it toward Venus, where another gravity assist would return the spacecraft back to Earth.

BBC: Manned flight to Mars in 2014?