• Shalmali

What is Rocket Aerodynamics?

Updated: Apr 23

Are Rockets even affected by Aerodynamic Force?


Table of Contents:

  1. Introduction

  2. Aerodynamic Force

  3. Definition of Aerodynamic Force

  4. Summary

  5. Short Video

Green grass & windmills
Aerodynamics
A beautiful landscape, green grass, colorful flowers, huge trees, big blue sky what a great scene isn’t it!

You walk through it and come across a pretty structure — a windmill. The wind cresses your hair as the blades of the windmill. Your hair sway with the air as the blades of the windmill move. Why did your hair or the blade move due to the air? Does it mean the air applied force on your hair or the blades? But wait, no one could see the point of application of force, did you?

Aerodynamic Force:


Why is Aerodynamic Force different than other forces?


Imagine, you are re-decorating your room. You try to shift the position of the fridge. You and the fridge are solid bodies. When you push the fridge, you can see the point of contact of the force that is been transmitted. You can visualize the point of contact and the direction of force applied on the fridge by you. But on similar lines, you could not imagine the windmill scene, right? Is there even any force acting on it? Where is the point of contact of force? So, we have a problem here, and obviously, there is a solution to it.


Understanding Aerodynamics:


In the case of the windmill, the force is acting on the blades at each and every point, as the blades are surrounded by air at every point. Air is fluid, and the blades of the windmill are solid.

When there is relative velocity between fluid and solid molecules, Aerodynamic force acts on the body.

This force acts on a point called the Centre of Pressure. The Centre of Pressure is simply the point at which the pressure of the whole body can be balanced. Wait!!! Where did this word pressure come from now, because we were talking about force right?


Yes! We were talking about force. But in the scenario where you were pushing the fridge, you could visualize the direction of force acting on the fridge. This means the quantity is a vector, isn’t it? Indeed, force is a vector quantity. Conversely, we could not visualize the direction of the force in the windmill example. This means the quantity here is a scalar. That scalar quantity is pressure. That's why the Aerodynamic Force is applied at 'Center of Pressure' and not 'Center of Force'.



The Aerodynamic Force that is acting at the Centre of Pressure, is further resolved into two components, namely, Lift force and Drag force. Now do these forces affect the rocket? Surely, these forces act on the rocket too!

But... what do you think there exists an exception? Well... Yes! The rocket should be in the atmosphere so that there is a presence of air, in space, or more precisely in the vacuum, Aerodynamic force will act not on the Rocket.

Summary:

  • When there is a relative velocity between fluid and solid molecules, Aerodynamic Force acts on the body.

  • Aerodynamic Force acts on a point called Center of Pressure.

  • Aerodynamic Force does act on rockets!

  • Aerodynamic Force is resolved into two components namely: Lift Force and Drag Force.


How does this drag force and lift force act on the rocket? Want to know more about the topic in detail? Follow me for similar topics!


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