Question: do you know how the fire comes out from the bottom of a rocket ship

Gary Munnelly answered on 9 Nov 2018:

The main idea behind any engine is that you have fuel which contains energy. You need to release the energy from that fuel in order to turn it into motion (we call this kinetic energy). One way that you can do this is by burning the fuel. However, when you burn fuel, you also release a load of energy in the form of heat and noise.

It takes a huge amount of energy to lift a rocket straight up off the ground and into the sky, so you have to burn a lot of fuel. This gives us the kinetic energy we need to lift the rocket, but it also results in a lot of heat being released. We see that as the flames which come out the bottom of the rocket and help to propel it into the sky.

Energy is a really interesting thing to talk about. The main idea is that you can never create or destroy energy. You can just change it from one form to another (e.g. the potential energy in fuel turning into kinetic energy, heat and noise). So a big challenge for engineers is to make sure that we reduce the amount of energy we lose through heat and noise and turn it into the energy that we need in order to do what we want to do.