Why does a rocket need to travel 25,000 miles per hour to flee Earth?

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Why does a rocket need to travel 25,000 miles per hour (about 40,000 kilometers per hour) to flee Earth? – Bo H., age 10, Durham, New Hampshire

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There's a reason why a rocket has to go so fast to flee Earth. It's about gravity – something for all of us Experience every moment of daily.

Gravity is the force that pulls you towards the bottom. And that's a superb thing. Gravity keeps you grounded; otherwise you’ll float into space.

But gravity also makes it difficult to go away Earth when flying into space as a rocket. Escaping our planet's gravitational pull is difficult – gravity isn't just strong, it's strong extends removed from Earth.

Like a balloon

As a rocket scientistOne of the things I teach students is how rockets overcome gravity. This is how it really works:

Essentially, the rocket must generate thrust – that’s, generate force burning propellant to supply hot gases. It then shoots these hot gases out of a nozzle. It's like blowing up a balloon, releasing it, and watching it fly away because the air rushes out.

More specifically, the rocket fuel consists of each fuel and oxidizer. The fuel is usually something flammable, often hydrogen, methane or kerosene. The oxidizer is frequently liquid oxygen, which reacts with the fuel and causes it to burn.

When flying into space and escaping from Earth, rockets require plenty of power, so that they use up fuel in a short time. That's an issue since the rocket can't carry enough fuel to maintain pushing endlessly; The amount of fuel required would make the rocket too heavy to get off the bottom.

So what happens while you run out of fuel? The thrust stops and gravity slows the rocket until it step by step falls back to Earth.

Luckily, scientists can launch the rocket with some sideways momentum in order that it misses Earth when it returns. You may even do that in order that it falls across the Earth repeatedly endlessly. In other words, it goes into orbitand begins to orbit the planet.

Many launches intentionally don’t leave Earth completely behind. Thousands of satellites are currently orbiting our planet. They make phones and TVs work, show weather patterns to meteorologists, and even can help you pay with a bank card on the food market or refill on the gas pump. Sometimes you possibly can see these satellites within the night sky, including the International Space Station.

Escape from the earth

Suppose the goal is to let the rocket escape Earth's gravity endlessly so it could actually fly into the depths of space. That's when scientists do it a neat trick called staging. They launch with a big rocket after which, once in space, throw it away to make use of a smaller rocket. This allows the journey to proceed without the load of the larger rocket and requires less fuel.

But even the staging shouldn’t be enough; At some point the rocket will run out of fuel. But if the rocket goes fast enough, it could actually run out of fuel and still roll away from Earth endlessly without gravity pulling it back. It's like riding a motorcycle: construct up enough speed and eventually you'll have the opportunity to roll up a hill without having to pedal.

And just as there’s a minimum speed required to coast the bike, there’s also a minimum speed required for a rocket to coast into space: 25,020 miles per hour (approx. 40,000 kilometers per hour).

Scientists call this speed the escape velocity. A rocket must fly so fast that the momentum pushing it away from Earth is stronger than the force of gravity pulling it back. If you decelerate, you’ll enter Earth orbit.

Escape from Jupiter

Larger or more massive objects have a stronger gravitational pull. A rocket launching from a planet larger than Earth would have to realize the next escape velocity.

Jupiter, for instance, is probably the most massive planet in our solar system. It is so big that it could swallow 1,000 Earths. Therefore, a really high escape velocity is required: 133,100 miles per hour (about 214,000 kilometers per hour), greater than five times the escape velocity of Earth.

But the acute example is a black holean object so massive that its escape velocity is exceptionally high. So high, actually, that even light – which travels at 370 million miles per hour (about 600 million kilometers per hour) – shouldn’t be fast enough to flee. That's why it's called a black hole.

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