字幕列表 影片播放 列印英文字幕 NASA's most important rocket launches – the Mercury program, the Moon missions, and the space shuttles – lifted off from the Kennedy Space Center in Cape Canaveral, Florida. But why there? Florida doesn't seem to have a lot going for it. The state gets hit by lightning more than anywhere else in the U.S., plus there's monster hurricanes that blow through almost every year. It's not impossible to launch rockets from somewhere else, but NASA has a need for speed. And because of Florida's latitude, rockets get a big speed boost from the Earth's rotation. Let's say you want to get up to the International Space Station. It's in low-Earth orbit, about 400 kilometers up. Distance-wise, that's not so bad. Like, the Moon is over 350,000 kilometers away when it's closest to us, and we've been there too! The real problem is that the ISS is orbiting the Earth at speeds of over 27,000 kilometers per hour. So to get your flight to the ISS, you have to match its altitude and its speed. By launching rockets from places on Earth that are close to the equator, like in Florida, you'll get an extra speed boost. All thanks to our planet's rotation. See, imagine a flat, spinning disc, like a record, or a CD. The whole disc finishes one rotation at the same time. But a point on the edge is actually moving faster than a point near the center, because it has farther to go. A rotating sphere works the same way, and we're pretty much just a rotating sphere! This means a point near one of the poles on Earth travels along a much smaller circle than a point at the equator. So the closer to the equator you are – or the lower your latitude – the faster you're moving. But you can't really feel how fast you're moving when you're standing on Earth's surface, because you're rotating with the planet. Someone right on the equator in Ecuador, for example, is moving at around 1,670 kilometers per hour. So when your rocket lifts off in Cape Canaveral, Florida, at around 28 degrees north, your speedometer is already reading 1,470 kilometers per hour. Even though it's only a fraction of the speed you need, that extra oomph is energy you don't have to spend in fuel. And if you spend a little less fuel speeding your rocket up, you could bring along some heavier experiments or satellites. So speed was a big factor, but not the only one, when the US government picked Cape Canaveral as a rocket launch site. In the late 1940s, a team of engineers, scientists, and military analysts that would eventually become part of NASA was test firing rockets and missiles in the New Mexico desert. And they were running out of room. Their rockets were going faster and higher than ever before, and they were landing farther away. They needed a new launch site – one that was big enough to handle more powerful rockets that could enter space, and far enough away from people in case something went wrong. Enter Cape Canaveral, Florida. The area was pretty empty except for the Banana River Naval Aviation Station, which was already owned by the US government. This meant there were already roads to the rest of civilization, and they didn't have to worry as much about the costs of making the site livable for everyone working on the rockets. Plus, to take advantage of the speed boost from Earth's rotation, rockets need to be launched toward the east. And the only thing that's east of Florida? Thousands of kilometers of the Atlantic Ocean. So there's much less danger of a wayward rocket or a spent first stage landing in a densely packed city, like there was in the New Mexico desert. And while Florida's weather might not be perfect, other parts of the country have their storms too. Now, this isn't to say you can't launch a rocket safely somewhere else, or at a higher latitude – it just means you'll need more fuel, or a smaller payload. The Soyuz space capsules that ferry astronauts up to the ISS, for example, have been launched for decades from the Baikonur Cosmodrome in Kazakhstan. It's at about 46 degrees north, near the same latitude as us here in Missoula, Montana. Now, with the retirement of the space shuttle in 2011, NASA isn't launching astronauts from Florida anymore. But lots of unmanned rockets, carrying important satellites and spacecraft, are still launched there regularly. Even private companies like SpaceX are using Cape Canaveral launch pads to test their rockets, and will probably continue when they start having manned missions. So even as rocket technology keeps improving, many of them still depend on that speed boost from the Earth's rotation, as they fly to low Earth orbit and beyond. Thanks for watching this episode of SciShow Space, and especially to our patrons on Patreon. If you'd like to support more content like this, just go to Patreon dot com slash SciShow. And don't forget to go to YouTube dot com slash SciShow Space and subscribe!