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BBC地平线 火星旅行者指南(Mars-A Traveller's Guide) 第06期

航天器结构工程师艾比·赫蒂 Spacecraft structures engineer Abbie Hutty 负责确保欧洲第一辆火星车 is responsible for making sure Europe's first rover, 火星生命探测计划 ExoMars, 完好无缺地着陆 stays in one piece. 着陆永远都是探测火星任务 Landing's always going to be one of the trickiest parts 艾比·赫蒂 空中客车防务与航天公司 最难的部分 of getting a mission to Mars safely. 很难预测探测车 It's very hard to predict exactly 掉落的具体位置 what you're going to be dropping down through 因为风速变化很大 because the wind speeds vary dramatically. 还有沙尘暴 会大幅改变大气密度 You get dust storms, which really change the atmospheric density. 最根本的原因是 And fundamentally, 从进入大气顶部 you don't have that much thickness of atmosphere 到撞击地面 between entering it at the top 之间的大气厚度不够 and hitting the ground at the bottom, 因此没有足够的阻力来让探测车减速 so you've not got very much to actually slow yourself down. 刚进入火星大气表面时 When you first hit the top of Mars' atmosphere, 你的速度过快 you are going so fast 你能做的其实只是躲在一块挡热板后面 that really all you can do is just hide behind a heat shield 祈求上天 and hope for the best. 在进入大气层的过程中 During atmospheric entry, 探测车需要承受 the lander will need to withstand temperatures 高达1750摄氏度的温度 reaching up to 1750 Celsius. 最终你会到达一个临界点 So eventually you'll get to the point 那时你就可以释放一顶大得多的降落伞 where you can deploy a much larger parachute, 这样你就能更有效地降低你的速度 so you have a lot more acting to slow yourself down 此时 你的速度已经足够低 and, at this point, you're going slow enough 其实不再需要挡热板了 that you don't really need this heat shield any more, 你就可以将挡热板分离 so you jettison your heat shield. 下一阶段 你可以发射制动火箭 The next stage is you can fire retrorockets, 来自:VOA英语网 文章地址: http://www.tingvoa.com/html/20180213/Mars-A-Travellers-Guide-6.html