ORBITAL SPEED
轨道速度
Q. What if a spacecraft slowed down onreentry to just a few miles per hour using rocket boosters like the Mars skycrane? Would it negate the need for a heat shield?
Q．在宇宙飞船返回再入大气层时，如果用一个像“好奇号”降落火星表面时所用的“天空起重机”，把飞船的速度降到每小时只有几千米，那是不是就可以不用热防护罩了？
Brian
——布赖恩
Q. Is it possible for a spacecraft tocontrol its reentry in such a way that it avoids the atmospheric compressionand thus would not require the expensive (and relatively fragile) heat shieldon the outside?
Q．有没有一种办法可以让飞船在冲入大气层的时候避免压缩大气，这样就不再需要昂贵而又脆弱的外部热防护罩了？
Christopher Mallow
——克里斯托弗•马洛
Q. Could a (small) rocket (with payload) belifted to a high point in the atmosphere where it would only need a smallrocket to get to escape velocity?
Q．可不可以把一个小火箭（载有货物）提升到一个很高的地方，然后在那里只需要很小的火箭就能达到逃逸速度？
Kenny Van de Maele
——肯尼•范德梅勒
A. THE ANSWERS TO THESE questions all hingeon the same idea. It 8217;s an idea I 8217;ve touched on in other answers, but right nowI want to focus on it specifically:
A．这三个问题问的东西本质上是一样的，而且我在其他几篇文章中也讲到过，不过现在我把它们特别拿出来讲一下：
The reason it 8217;s hard to get to orbit isn 8217;tthat space is high up.
进入地球轨道之所以困难并不是因为太空太高。
It 8217;s hard to get to orbit because you haveto go so fast.
进入轨道很困难是因为你必须达到足够快的速度。
Space isn 8217;t like this:
太空并不是像这样：
Not actual size.
未按真实比例绘制
Space is like this:
太空其实是这样的：
You know what, sure, actual size.
你知道的，按真实比例绘制。
Space is about 100 kilometers away. That 8217;sfar away-I wouldn 8217;t want to climb a ladder to get there-but it isn 8217;t that faraway. If you 8217;re in Sacramento, Seattle, Canberra, Kolkata, Hyderabad, PhnomPenh, Cairo, Beijing, central Japan, central Sri Lanka, or Portland, space iscloser than the sea.
太空大约距离我们有100千米远。它确实很遥远——至少我不想爬100千米高的梯子——但它又没有想象中的远。如果你在萨克拉门托、西雅图、堪培拉、加尔各答、海得拉巴、金边、开罗、北京、日本中部、斯里兰卡中部或者波特兰，那么你离大海的距离比你离太空的距离还要远。