Theinvestigation showed that low temperatures on the day of the launch caused arubber “O-ring” seal on one of the rocket boosters to fail, which led to a leakof explosive gases.

调查显示，挑战者号发射当日低温，导致火箭推进器上橡胶O行环密封圈失效，进而引起爆炸性气体泄露。

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There have been two failures: The shuttle Challenger and seven astronauts were lost just after launch in January 1986 due to an O-ring seal leak in a solid rocket booster that led to an explosion.

有两次失败的教训：1986年1月刚刚发射过后，一个固体火箭助推器的O型圈密封泄漏导致的爆炸，使我们失去了挑战者号和7名宇航员。

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Remove the pressed in relief valve seat and seat O-ring.

拆卸压进去的安全阀阀座和阀座o形环。

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Exult o shores, and ring o bells!

VOA: special.2009.12.31

Amongst the updates are a more textured backing for the cover, which should help it stay in small hands and some more subtle choices, like the inclusion of tiny X's, corresponding to the O ring at top, in keeping with the product name.

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Some of those Thiokol engineers expected o-ring failures at liftoff.

NPR: Challenger: Reporting a Disaster's Cold, Hard Facts

In the case of the Challenger, the culprit was a simple O-ring that had become too brittle to do its job after a freezing night waiting on the launch pad.

FORBES: BP Oil Spill Investigation Will Focus On Blowout Preventers