What is a gravity assist?

Uploaded on September 21, 2017

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What is a gravity assist?

2017-09-21 - Did you know that a spacecraft can use a planet's gravity to change its orbit?

For example, on September 22, 2017, the OSIRIS-REx spacecraft will use Earth's gravity to change its orbit and help put it on course to asteroid Bennu, its target destination.

With the help of this gravity assist, OSIRIS-REx is due to arrive at the asteroid in August 2018.

Learn more about the OSIRIS-REx asteroid-sample return mission: https://www.asc-csa.gc.ca/eng/satellites/osiris-rex/.   (Credit: Canadian Space Agency)

Hi, I’m Tim and I like science.

Did you know that a spacecraft can use a planet’s gravity to change its orbit?

It does this by using something called a gravity assist. But what exactly is it and why would we ever need to use one?

Well, first of all, getting anything off the surface of the Earth is really hard, but reaching some faraway destinations in the solar system is even harder. This is where gravity assists come in!

Conceptually, it’s really pretty simple. As a spacecraft gets closer and closer to a planet, it starts to be affected by the planet’s gravitational pull. The closer it gets, the stronger the pull.

But… don’t forget, though… the planet isn’t just sitting still. It’s moving through space, and so it’s carrying momentum along with it.

Essentially, as the spacecraft moves through the planet’s gravity field, it “steals” some of this momentum, curving its path and changing its orbit.

For example, when the OSIRIS-REx spacecraft launched in September 2016, the rocket wasn’t powerful enough to send it straight to asteroid Bennu, its target destination. So we needed to find a way to use nature to help get it there.

In this case, it had to go all the way around the sun and come back to the Earth a year later. We’re then using Earth’s gravity to change its orbit and help put it on course to Bennu.

With the help of this Gravity Assist, OSIRIS-REx is due to arrive at the asteroid in August of 2018.

In the meantime, keep following the adventure on the Web and get set for what’s sure to be an incredible mission.

And I’m late, and I’ve got to catch a Gravity Assist. We’ve got to go.

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