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Launching a satellite is not as simple as pointing the rocket up and counting to zero.
发射卫星可不只是竖起火箭然后倒数到零那么简单。
I wish it was. Because Earth doesn’t sit still. It’s constantly spinning.
真希望能这样。因为地球不是静止不动的。它在不停旋转。
And like we’ve talked about before, rockets get a boost from that spin if they launch in the direction of Earth’s rotation.
就像我们之前说过的，如果火箭按照地球自转的方向发射，火箭就会从地球的旋转中获得动力。
But Earth’s rotation might help some launches, but it doesn’t help all of them.
但地球的自转可能对某些发射有利，但并不是对所有的发射都有利。
Like, over half of satellites have orbits that are harder to reach because of Earth’s spin.
因为地球的自转，超过一半的卫星难以到达既定的轨道。
So, what are we supposed to do about those?!
那我们该怎么办呢?!
Well, at least in the U.S., part of the answer is simple: You move your rocket to California.
至少在美国，答案的一部分是很简单的：你把火箭移到加州就可以了。
Obviously the ground and everything on it is constantly moving around Earth’s axis, including us, launch pads, and the rockets sitting on top of them, so when a rocket launches, it starts out with that horizontal motion.
显然，地面和地面上的所有东西都在不断地绕着地轴运动，包括我们、发射台和上面的火箭，所以当火箭发射时，它一开始是水平运动。
Up near the poles, this doesn’t mean a lot, since the ground is moving more slowly there.
在靠近两极的地方，这并无太大影响，因为那里的地面移动速度更慢。
But at low latitudes, closer to the equator, like, say, at NASA’s Kennedy Space Center in Florida, ground is really truckin.
但是在低纬度地区，更靠近赤道的地方，比如，在美国宇航局位于佛罗里达的肯尼迪航天中心，地面移速很快。
Since Earth spins west-to-east, if you launch your rocket eastward, you can get an extra speed boost without burning any fuel.
由于地球自西向东旋转，如果你向东发射火箭，你可以在不燃烧任何燃料的情况下获得额外的加速。
This can be great if you’re launching a satellite that orbits Earth in the same direction the planet rotates.
如果你发射的卫星与地球旋转的方向相同，那就太好了。
Because to orbit, you need to be going fast.
因为要绕轨道运行，你的速度必须得快。
The thing is, though, the vast majority of satellites have orbits where a low-latitude, eastbound launch isn’t ideal.
但问题是，低纬度、向东发射对绝大多数卫星的运转轨道而言并不理想。
Including the International Space Station. That is thanks to the inclination of their orbits.
包括国际空间站。那是因为它们的轨道有倾角。
Inclination is the angle between an orbit and a reference plane, like Earth’s equator.
倾角是指轨道与参考平面(如地球赤道)之间的夹角。
A satellite that travels directly above the equator and is moving west to east, the same direction as Earth's rotation, has an inclination of zero degrees.
卫星在赤道正上方由西向东运行，与地球自转方向相同，其倾角为0度。
And a satellite that travels from north to south is in a polar orbit, with an inclination of around 90 degrees.
一颗从北到南的卫星在极地轨道上运行，倾角约为90度。
So a satellite that travels from east to west, the opposite direction of the Earth's rotation, is in a retrograde orbit, with an inclination higher than 90 degrees.
因此，自东向西运行的卫星与地球自转方向相反，处于逆行轨道，其倾角大于90度。
The ISS has an inclination of about 51 degrees, which is considered high, and just over half of all satellites have polar ones.
国际空间站的倾角大约为51度，这已经很高了，而且略超过一半的卫星有极地倾角（90度）。
So, why would you fly a more complicated orbit like this, and how does that even work?
那么，为什么要在这么复杂的轨道上飞行呢？它又是如何实现的呢？
Well, the why is actually pretty easy.
原因其实很简单。
One big reason is that, when a satellite is in a highly inclined orbit, it passes over more of the planet.
一个重要的原因是，当卫星在高度倾斜的轨道上运行时，它会经过地球上更多的地方。
Like, as the ISS moves, the Earth is still rotating underneath it.
就像，当国际空间站移动时，地球仍然在它下方旋转。
So it gets to see huge parts of Earth’s surface a couple of times a day.
所以它一天能有好几次看到地球表面的大片区域。
Meanwhile, in a truly polar orbit, a satellite might get to see the whole planet.
而在真正的极地轨道上，卫星可能可以看到整个星球。
Which is great for communication, photos, taking measurements, staring longingly out the Space Station’s window, you know, that kind of thing.
这对交流、拍照、测量、满怀憧憬地凝视空间站窗外之类的事情都很有利。
The problem with reaching these orbits is that the satellites in them don’t go east relative to the Earth’s surface, so they’re not helped by the boost from the planet’s spin.
到达这些轨道的问题是，这些卫星相对于地球表面而言并不是向东移动，所以它们不能从地球自转中获得助力。
Instead, at some point, their rockets need to cancel out that purely eastward motion of the launch pad.
相反，在某个时刻，这些卫星的火箭还要抵消掉发射台纯粹向东运动的影响。
And if they’re launching from a place closer to the equator like in Florida, they have to cancel a lot of eastward motion.
如果它们是在赤道附近发射的，比如在佛罗里达，它们就需要抵消很多向东的运动力。
On the up side, doing that is pretty straightforward: You just point your rocket a little bit to the west.
从积极面来说，实现这一点非常简单：你只需把火箭稍微向西一点。
But like lots of things in engineering, that’s easier said than done.
但就像工程中的很多事情一样，说起来容易做起来难。
For one, it takes more fuel, since these rockets can’t devote all their energy to flying north and getting into orbit; they have to use more of it to fly west as well.
首先，它需要更多的燃料，因为这些火箭不能把所有的能量都用于向北飞行和进入轨道；它们还需要更多的能量向西飞行。
This is one reason Florida is kind of a crummy place to launch a polar satellite.
这就是为什么佛罗里达非常不适合发射极地卫星的原因。
Somewhere farther north would be more efficient, like the launch pad in Alaska.
更北的地方效率会更高，比如阿拉斯加的发射台。
That said though, the boost from Earth’s spin is nice when you can use it, but it’s not a mission-killer to fight against it.
尽管如此，如果可以利用的话，来自地球自转的推力还是很不错的，但也不需要把它当成任务杀手来对待。
I mean, if you started from the equator and wanted a polar or retrograde orbit, it would definitely take more fuel.
我的意思是，如果你从赤道出发，想要一个极地或逆行轨道，这肯定会需要更多燃料。
And to keep more fuel on board, you’d have to reduce the number of scientific instruments on your mission.
为了在卫星上装载更多燃料，就必须减少任务中携带的科学仪器。
You might even have to upgrade to a bigger, more expensive rocket.
你甚至可能需要升级到更大、更贵的火箭。
For some missions, those are big sacrifices.
对于一些任务来说，这是巨大的牺牲。
But for a whole space program, those costs are still a lot less than the cost of building and maintaining a whole new facility at a snowy, windy location closer to the poles.
但就整个太空计划而言，这些成本仍然远远低于在靠近极地、多雪、多风的地方建造和维护一个全新设施的成本。
So, the real problem is that pointing your rocket west, well, it requires a bunch of empty space to the west.
所以，真正的问题是向西发射火箭，它需要有更多空间。
Otherwise, if something goes wrong, you run the risk of hitting people and buildings and cows with debris.
否则，如果出了故障，可能会有碎片砸到人、建筑物或牛。
It’s true. We’ve hit cows before.
这是真的。我们以前砸到过牛。
Today, this is mainly why the U.S. doesn’t typically launch satellites with polar orbits from Florida.
所以，现在美国一般不从佛罗里达发射极地轨道卫星。
Instead, they launch at Vandenberg Air Force Base, way up north in… southern California.
相反，他们选择在加利福尼亚州南部的范登堡空军基地发射。
It’s not that much farther north, but its big advantage is that the ocean is to the west.
它并没有往北去那么远，但它最大的优势是西边是海洋。
So rockets don’t have to go over populated areas, and as a nice bonus, they save a little fuel, too.
所以火箭不必经过人口稠密的地区，而且还有一个很棒的优点是可以节省一点燃料。
At the end of the day, spaceflight is complicated, but hey:
总而言之，太空飞行是复杂的，但是，嘿:
When you get to put people in space, or launch a satellite that helps us understand our home and the universe; it’s all worth it.
当你把人送入太空，或者发射卫星帮助我们了解自己的家园和宇宙；这一切都值得。
Thanks for watching this episode of SciShow Space!
感谢收看本期《太空科学秀》!
And a huge shoutout to our patrons on Patreon for making this episode and everything we do possible.
非常感谢粉丝们对本集以及我们所做的一切的赞助。
If you want to learn about supporting more episodes like this, you can find the details at patreon.com/scishow.
如果你想了解更多这样的节目，可以去patreon.com/scishow查看更多细节。
