• Question: how do rockets fly?

    Asked by thomas1814 to Nat, Nate, Roberto, Sam, Sarah on 23 Jun 2014.
    • Photo: Sarah Casewell

      Sarah Casewell answered on 23 Jun 2014:

      Rockets burn fuel and the exhaust gasses come out of the bottom of the rocket allowing it to escape the gravity pulling it down.
      The more fuel the rocket burns the lighter it is and the faster it can accelerate.

      In space – where there is less gravity acting on the rocket, because of Newton’s second law which says that each force has an equal and opposite force, when the rocket fires in one direction, the spaceship keeps moving in that direction until we stop it by firing the rocket in the other direction!

    • Photo: Nate Bastian

      Nate Bastian answered on 23 Jun 2014:

      For every action there is an equal, and opposite reaction. If you sit on a chair with wheels, and you push off a wall, you slide across the floor. That’s the same principle as a rocket. A rocket shoots out material (burning gas) from one end, which pushes the rocket in the opposite direction.

    • Photo: Sam Connolly

      Sam Connolly answered on 23 Jun 2014:

      If you think about a hose that has water squirting out of it, and how it gets pushed back by the water that’s squirting out of it, in the opposite direction to the way the water is going, that’s how rockets work. The more stuff you squirt out the back, and the faster you squirt it out, the faster you can push yourself forwards. Planes work in a similar way, by blowing air which is sucked in the front of their engines out the back at very high speeds. This doesn’t work with rockets though, because there’s no air to suck in! So you have to bring the stuff you blow out the back with you, which is why rockets are usually very big – most of the space is just for fuel!

    • Photo: Roberto Trotta

      Roberto Trotta answered on 23 Jun 2014:

      Rockets fly thanks to a principle of physics that says that if you throw a ball in a certain direction your body gets thrown in the opposite direction with equal force (in reality of course you don’t move because your feet oppose resistance thanks to friction on the ground — but you would move in the opposite direction if you threw a ball while ice-skating — try it!)

      So rockets burn fuel to give out hot, fast gases that go out from the back of the rocket. As they do so, the entire rocket is pushed forward because of the above effect. We call it “conservation of momentum”.

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