What is rocket science?

It’s all about using rocket propulsion to move anything from a firework to a manned spaceship. At the heart of rocketry is Isaac Newton’s Third Law of Motion, something that’s been established for over 300 years. It says that every action has an equal and opposite reaction. If you stand in front of a wall and push it hard, you will move backwards. Similarly if you stand on a skateboard and throw a heavy object away from you as hard as you can (don’t try this at home), you’ll roll in the opposite direction. As you push an object forwards, the object pushes back on you with the same amount of force. In a rocket, the ‘object’ being pushed is the end product of burning fuel, which shoots out of the back of the rocket as the fuel burns, forcing the rocket to move in the opposite direction. these depends on physics that has been known since Newton’s day.

Rocketry in empty space is easy, but on Earth we have to overcome our planet’s gravity. This is where a rocket is so much better than a cannon. Sci-fi writer Jules Verne suggested using the latter to fire a shell containing three passengers to the Moon in the 19th Century. But a cannon has to get its payload up to the speed needed to leave Earth’s gravity – the escape velocity – by the time it leaves the barrel, because after that the only forces acting on it are gravity and air resistance, which both slow it down. The acceleration to get Verne’s shell to the required 11.2km per second would squish the passengers. But a rocket can accelerate more gently for as long as its fuel lasts, gradually climbing out of the Earth’s gravity.

When it comes to plotting a course, once again, all we need is Newton’s physics, which allows us to understand how the flight path will be affected by the gravitational pulls of the Earth, the Sun and the Moon (the planets will have influences too but these are small in a local flight), plus any ‘burns’ of the rocket engine. What makes successful rocketry so difficult isn’t so much the science as the engineering. There’s so much complex technology in a rocket that it’s incredibly tough to be sure that everything is going to work.