Physics Behind Rocket Launch

Things are launched into space by loading them onto rockets with enough propellant. But what physics is behind the rocket launch? The propellant provides enough energy to push the rocket away from Earth’s surface. The heaviest spacecraft require the largest rockets and the greatest propellant due to Earth’s gravity. Lifting an object is not simple; several factors like as thrust, lift, weight, and drag are involved.

Physics behind Rocket Launch

The publication of Newton’s laws of motion proved to be greatly advantageous for scientists and engineers across the globe. His laws have found applications in everything with moving parts whether it is the design for machines and scientific equipment or clocks and wheeled devices. 

On the basis of these laws, it was possible to predict whether a machine would work even before it was built. In the nineteenth century British engineer Isambard Kingdom Brunel, built huge steam ships and suspension bridges using Newton’s laws. James Watt couldn’t have made the first working steam engine without the laws of motion. We use these laws even today to solve the problems related to the construction of modern structures and tall buildings. Newton‘s laws of motion are still the basis of modern mechanical engineering. Its application is spread across different fields. Everyone from technicians to space engineers and car designers to satellite constructors utilize these laws.

Laws Of Motion


Rockets come in different shapes and sizes, from little pyrotechnics to huge Saturn Vs that once transported cargoes to the Moon. Newton’s third law of motion explains the propulsion of all rockets, jet engines, deflating balloons, and even the movement of squids and octopuses. The engines of rockets need to overcome both the pull of gravity and the inertia of the rocket as stated in the first law.

According to Newton’s Third Law, “Every action has an equal and opposite reaction“. A rocket is pushed forward by the push of the burning fuel at its front. This also the creates an equal and opposite push on the exhaust gas backwards. Once they’re in motion, they won’t stop until a force is applied.

As per Newton’s second law, as mass of the object increases, the force needed to move it also increases. The larger a rocket, the stronger the force (for instance, more fuel) to make it accelerate. A space shuttle requires around three liters or kg of fuel for every kilogram of payload it carries.

Inside Rocket

The Pencil Puzzle

Astronauts in space must also keep the laws of motion in mind. In 1961, Yuri Gagarin made history by being the first person to orbit the Earth. Russian cosmonaut Yuri Gagarin was the first to experience the practical effects. Gagarin put down his pencil while writing his log. In keeping with Newton’s first law, by which the planets. move around the Sun, the pencil floated out of reach. He ended up completing the log using a tape recorder. Now astronauts keep their equipment tethered to a surface with Velcro or bungee straps.

Astronauts in Space

The laws of motion are applicable even in outer space. Newton’s Second Law states that force is needed to increase or decrease the speed of a body. This implies that astronauts must learn to push themselves through their spacecraft, or else they will float around helplessly. They also need to remember to stop themselves as they near their destination or else they’ll keep moving till they hit something. During their first attempt, astronauts usually end up a little worse for the wear after stumbling around the spacecraft. Unlike humans, animals flown to space often fail to learn this. A set of new-born quails aboard Russia’s Mir space station couldn’t adapt to life in space and died in a few days.


Newton’s Third Law too has application for astronauts. While turning a Screw, astronauts have to anchor themselves to a wall, or else they’ll be the ones twisting. Even the mildest action like typing at a computer keyboard will send an astronaut floating away. To remedy this problem, workstations on the international space station has restraining loops for the crew to anchor their feet. 

Motion in Space

Though it may seem like the laws of motion are different in space and on Earth, that is not the case. The overwhelming force of Earth’s gravitational field simply makes its exact effects. Gravity plays an astonishing part in many phenomena we take for granted. For instance, hot air (which is lighter than cool air) rises, and a convection current is formed which enables natural air circulation in our houses.

International Space Station

 In space however, nothing is lighter than anything else and ordinary convection currents do not exist. Thus, to make sure that the astronauts don’t suffocate due to carbon dioxide accumulation, a ventilation fan is installed to facilitate air circulation. The International Space Station is the best example of the laws of motion

What speed is required to beat Gravity?

Newton realized that a bullet shot from a gun should continue to move indefinitely. On Earth, atmospheric friction slows the projectile while gravitational force pulls it to the ground. But the faster the bullet is shot, the farther it will travel before falling. And if you can manage to shoot something at a speed of around 11.2 km/s, it will never finish its trajectory. It will instead orbit the Earth in a state of perpetual free fall. This particular velocity (11.2 km/s) cancels the pull of Earth’s gravity and is used to launch spacecraft. Even fire is not exempt from the laws of motion in space. Behavior of weight less flames is rather different from those on Earth. However, such a fire is best limited to the lab as fire aboard a spacecraft can have catastrophic effects.

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