5 This exponential increase is the centralproblem of rocketry: The fuel required to increase your speed by 1 km/smultiplies your weight by about 1.4. To get into orbit, you need to increaseyour speed to 8 km/s, which means you 8217;ll need a lot of fuel: 1.4 ×1.4 ×1.4 ×1.4 ×1.4 ×1.4 ×1.4 ×1.4 ≈15 times the originalweight of your ship.Using a rocket to slow down carries the same problem: Every1 km/s decrease in speed multiplies your starting mass by that same factor of1.4. If you want to slow all the way down to zero 8211; and drop gently
5．指数式增长是火箭科学中的核心问题：速度每秒提升1千米，就需要自身质量×1.4千克的燃料。进入轨道要加速到每秒8千米，这需要1.48≈15倍自身重量的燃料。用火箭减速也会面临相同的问题，速度每减少每秒1千米，就需要1.4倍自身质量的燃料。如果想要减速到零，并轻柔地再入大气层，那么还需要额外的15倍自身质量的燃料。
6 There are some good apps and online toolsto help you spot the station, along with other neat satellites.
6．网上有许多软件可以帮你找到国际空间站和其他一些卫星的位置。
7 Either kind.
7．足球或橄榄球都行。
8 This type of play is legal in Australianrules football.
8．这么玩在澳大利亚是被允许的。
9 Using song beats to help measure the passage of timeis a technique also used in CPR training, where the song “Stayin 8217; Alive”is used.
9． 心肺复苏也会用歌曲的节拍计算时间，使用的歌曲是Stayin 8217; Alive（活下去）。