NEWTON LAWS

In order to get to Venus and to ascertain how much fuel will be needed and what type of rocket engine fuel, we have to start first and foremost with Newton’s Laws of motion. There are three types of fuel for rocket launching. Solid fuel burns like an explosive and you cannot control acceleration/deceleration. It is the heaviest as it occupies 93% of the rocket and it is mainly used for launching spaceship to space. Liquid fuel helps controlling the acceleration, stop, start or speed and helps control velocity once the rocket is launched into space. It occupies 77% of the rocket. Ion fuel is still under research but if used, will save a lot of weight while launching from Earth. The goal is to have a smaller mass of gas that pushes at same speed of thrust so that rocket is lighter and gets same speed as using solid fuel. Mass of “ion gas” can push thrust through a magnetic acceleration process and can replace chemical gas. If used, 20% of the rocket would be occupied by this type of fuel, reaching a speed of 30 km/s In determining acceleration, we use Newton laws.

Newton’s First Law

Newton’s First Law simply explains that an object will remain inactive or in uniform movement unless an external force affects its state and changes the motion, also including the phenomenon of acceleration. An external force comes from outside an object rather than a force internal to an object, because an internal force within an object can’t modify the object’s movement. This law is usually named the law of inertia. Inertia represents the property of a body to stay at rest or in motion with constant velocity –a vector that indicates both speed and the direction of the motion. By measuring mass of an object we determine the inertia. The bigger the mass, the harder is it to set it in motion. Therefore, it is easy for us to understand that some objects have more inertia than others (for example, it is definitely tougher to change the motion of a desk than that of a notebook). In order to have a better insight into this law, here is an example: Assuming that the spacecraft is in deep space and not surrounded by any planets, once it has fired its engines for a period of time, the ship accelerates and reaches a level of speed. After the engines are stopped, there is no force acting on the spacecraft. So, what happens to the spacecraft? As a consequence of Newton’s First Law, the craft will keep coasting at the same speed and in the same direction, until an external action will modify its state. We understand that coasting has an important role when it comes to space travel. The astronauts only need to fire their engines to then coast the rest of their way to a planet. When the spacecraft reaches the proximity of that planet, they must use fuel to slow down, also using Newton’s Laws to create an opposing force in order to land safely.

Newton’s Second Law

Newton’s Second Law of motion is applicable only if the force is an external one. Therefore, this law focuses on how much an object will accelerate when forces act upon it. We observe that the acceleration is proportional to the net force and is inversely proportional to the mass. Using the same amount of force on a small object – a fruit – will produce a bigger acceleration than a heavier object – a chair – which will accelerate slower.

Putting this law in practice means that the astronauts have to learn how to push themselves through their spacecraft and when to stop so as to prevent floating around helplessly and also hitting something or someone. Now when you think about this process, it seems like a piece of cake, when in reality, the unexperienced astronauts always collect many bruises from simply moving. In an animal’s case, this situation gets worse as it can’t adapt to the microgravity environment and for some of them, it ends tragically (an example is a set of new-born quails who couldn’t adapt to life aboard the space station and died after a few days).

Newton’s Third Law

Newton’s Third Law states that if a body exerts a force on another body then that other body is going to exert an equal force on the first one. This law is the key to rocket propulsion for space travel. Rockets move forward by expelling fuel backward at high velocity. So, when the rocket exerts a backward force on the gas, the gas reacts with the same force but in the opposite direction. As an application of Newton’s Third Law, even the simple action of typing at a computer in a spacecraft will send an astronaut floating away. This is a reason why many space stations are provided with restraining loops where the astronauts can fix their feet.

ACTION – REACTION: Equal in magnitude - Opposite in their directions

The laws of motion don’t behave differently in space than they do on Earth. The difference is that the Earth’s gravitational field changes their precise effects. A crew travelling in space has to put up with every tiny detail and action that we would normally consider absurd, but that makes their entire experience much more exciting. We never understand the power of gravity and we take it for granted. For example, on Earth, because of gravity, the air in our houses circulates in a normal way: hot air rises because it is lighter than cool air. In space, nothing is lighter than anything else, so this process doesn’t work. Therefore, with no ventilation fan, an astronaut could suffocate while sleeping due to the carbon dioxide that accumulates around his face.