While technicians took core samples of the spacecraft's heat shield around that time, in February Orion's back shell and heat shield were removed for further testing.

技术人员在大约那个时候拿到了该航天器热盾的核心样品，二月份，为了进一步测试，猎户座的背壳和热盾被移除。

youdao

A tortoise has a shell on his back.

乌龟背上有硬壳。

《新英汉大辞典》

Put the pie shell back into the freezer for 1 hour to firm up.

把饼皮冻回冰箱约1个钟头左右、使其紧实。

youdao

"I though it was a good response from the team, we did not just fall back into our shell and just let it all go out the window,"

VOA: standard.2009.06.07

And he gave a very good analogy in saying, "It was almost as incredible as if you'd fired a 15 inch shell at a piece of tissue paper, and it came back and hit you."

他还打过一个很好的比方：,“这就像是,你用个15英寸果壳,打到面巾纸上被弹回来打到你，一样不可思议，“

麻省理工公开课 - 化学原理课程节选

The investing class has instead pulled its collective head back into its weathered shell and mentally retreated back to the (relative) safety of looking at their own homes as a preferred investment class.

FORBES: Americans Hate Stocks

Here are three places, however, where Samsung has changed the game and will tempt Apple to shrink back into it shell.

FORBES: These Three Game Changers Define the Apple vs Samsung Battle

I'm like a little hermit crab who retreats back into his shell.

WSJ: Lingering Insecurities | John Grant | Pale Green Ghosts | By Jim Fusilli