Name: 我們是如何把東西發射上外太空的？（How Do We Launch Things into Space?）
Uploaded: 2021-11-02T02:30:35.000Z
Duration: 2 min 44 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

情態副詞

You've probably seen beautiful photos of Earth and other planets in our solar system.

基礎被動語態

Those photos were often captured by spacecraft – robotic explorers doing their work far

But how exactly do we send these spacecraft so far away?

A spacecraft – and basically everything else on Earth – is held down by Earth's

However, a rocket burns fuel – called propellant – to push away from Earth and against gravity.

A rocket needs enough fuel – and thrust – to speed up to at least 17,800 miles per

That's how fast you have to get going to fly above most of Earth's atmosphere and

Next, the rocket will release the spacecraft.

But when that happens depends on where you're going.

A spacecraft that orbits Earth is sometimes called a satellite.

A satellite is released from a rocket at a specific distance from Earth.

There, it keeps going around Earth in a circular path – an orbit.

This happens because there is a balance between the energy the satellite picked up from the

rocket – called momentum – and the pull of Earth's gravity.

The balance of these two forces can keep a satellite in orbit for many years!

But what happens if you want to go farther than Earth?

If you're trying to get to another planet, you'll need a fast rocket to overcome Earth's

And you'll still need to release the spacecraft from the rocket.

But you'll also need to figure out the best time to leave Earth to get to that planet.

Every two years or so, Mars and Earth are closest together.

This is the best time to go to Mars, since it will require the least amount of fuel and

And if you want to explore even farther planets like Saturn,

For example, will your spacecraft want to encounter Mars or Jupiter on its way to Saturn?

But don't worry, all the planning is worth it when you end up with a view like this one.

Find out more about our solar system at NASA Space Place.