# Which components do we calculate for center of pressure? Where is the distance of components while computing the cp and cg of a rocket?

everybody!

I have 4 questions about center or pressure (cp) and center of gravity (cg) of a rocket system.

### Questions

1) While computing the center of pressure of rocket system, which components do we account? Are these components only components that come in contact with air or all components of a rocket system (including componenets that inside the structure of rocket)?

2) In the above figure, we have a rocket with it's values about calculating it's center of gravity. The question is, the d-payload, d-ox, d-structure, d-fuel, d-wings values are where of the component's body? Is center of gravity or the component or most close side of the component or where?

3) The same question with 2. question but it's about center of pressure. Where is?

4) In the above figure, we see a rocket system with it's 6 Degrees of Freedom except Thrust and Drag Aerodynamic Force. How the movement in x-axis (roll or rolling maneuver) affects rocket's flight path negatively?

Thanks!

• The coordinate frame in the second figure looks off. Assuming that the "axis" labels are in the axis "positive" directions, the "roll" and "pitch" rotational arrows seem to be in the wrong directions.
– RLH
Jun 22 at 21:10

1) Look at the answer to this question Testing flight characteristics before actual flight in model rockets? for simple ways to estimate the center of pressure. Make sure to look at the linked references.

2) Assuming X is the axis that points down the long dimension of the rocket, it looks like you are calculating the X location of the center of gravity for the overall rocket. So use the X location of each component's center of gravity in the equation.

3) Again, see the reference in #1.

4) Rolling doesn't do much negative, except that it can make it harder to turn the rocket's flight path...in other words, it stabilizes it. You can read about spin stabilization here Why does spinning help stabilisation? (Especially Puffin's answer)

• thanks so much! You are so fast to give answers to my questions! I got 15 reputations and i gave you pozitive feedbacks for old answers and referenced link's answers. Have a good day sir! You are a monster! May 1, 2019 at 21:08

Imagine, yes, the rocket is a "surface" or shell with infinite "thinness" or a complete solid of homogeneous material, surface-model, solid-model, the resemblance is the volumetric constituents are the same. Solidworks will generate a "c.g.", which will be the same for each. THIS IS THE C.P. .

New contributor
edward sunday is a new contributor to this site. Take care in asking for clarification, commenting, and answering. Check out our Code of Conduct.