Rocket Science

To fly a rocket, there are many factors to consider and one of them is force. As we or some of us know, force is a vector quantity as it has both a magnitude and a direction and there are four types of forces to which rocket flight is subjected to such as weight, thrust as well as lift and drag which are aerodynamic forces. Weight is a gravitational forces while thrust and aerodynamics forces are mechanical force. The main difference between these two types of forces acting on the rocket is the latter requires physical contact with the medium that generates the force.

The magnitude of the gravitational force or the weight depends on the mass of the parts of the rocket, the amount of fuel and payloads such as satellites or space crafts. Have you seen a full scale rocket launch already, may it be on videos or in real life? Sometimes we see a rocket gets broken down into smaller rockets or staged where a smaller rocket rides a bigger rocket. I’ve researched that its actually engineers way to increase the rocket’s performance as the weight of the rocket changes when it exhausts fuel therefore having a constantly changing mass.

The thrust is the force responsible for moving the rocket through air and space. An application of Newton’s Law of Motion, particular the third law which is “For every action, there is an equal and opposite reaction”, which manifests through a propulsion system. This propulsion system accelerates a “working fluid” which is either a liquid or gas and expels this in one direction. The reaction to this expulsion is that it produces a thrust force which is then applied to the opposite direction to which the working fluid is expelled. The simplest rocket engine uses air as working fluid. There are many more factors to consider in thrust force but we’re not going to delve into that.

Lastly, the aerodynamics force which is broken down into two components: lift and drag, acts and is generated as rocket flies through the air. Drag is considered as aerodynamic friction and as we know friction opposes the direction of motion, therefore a source of drag is when solid surface of moving rockets comes in contact with the molecules of the air. Lift, on the other hand, is another application of Newton’s third law wherein the flow of gas is steered or turned by a solid object such as the nose cone or fins of a rocket in one direction, and the lift is generated in the opposite direction which is inclined to the flight direction. Aerodynamics force, however, is pretty negligible when it comes to full scale rockets but are very important in model rockets.

As they say, the only thing that is constant is change and this applies to rockets too. Magnitude of the four forces constantly changes as it flies through the air and sometimes the direction too. Adding up these forces, we gain a net external force and the resulting motion which is also a vector quantity in terms of displacement, velocity and acceleration, is explained by Newton’s laws of motion

rktfor

Sources: https://spaceflightsystems.grc.nasa.gov/education/rocket/vectors.html

https://spaceflightsystems.grc.nasa.gov/education/rocket/rktfor.html

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