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NASA 2024 年 8 月科普

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保护极冷望远镜

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为何不用一块厚板？

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工程师偏偏选择

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把五层轻薄的遮阳膜彼此隔开

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Webb 是红外望远镜

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镜面和传感器必须低温

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才能测到微弱红外信号

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被动遮阳罩要隔绝太阳、地球、月球

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及航天器自身的光和热

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若用一整块厚板

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底面的热更容易顺着固体内部直接传到上表面

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而五层薄膜彼此分离

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层间真空抑制接触传导

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但仍有热辐射

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靠特定形状和间隔

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热量从侧边向太空辐射出去

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越往望远镜一层越冷

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它们不是实体金属板

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膜材是 Kapton 镀铝涂层

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最热两层向阳面还有处理硅涂层

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兼顾反射与耐热设计

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NASA 曾对 2 到 7 层建模

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层数过多反而增加重量和复杂度

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五层是冷却与冗余、重量和复杂度的折中

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给热量留出侧向出路