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API Reference: CalculateCOP

The CalculateCOP class implements the Barrowman equations to calculate the Center of Pressure (COP) for a subsonic rocket. It accounts for contributions from the nose cone, transition (if present), and fins.

All length-based units must be consistent (e.g., all in inches or all in centimeters).

For a diagram and detailed explanation of each variable, see the Barrowman Equations page.

See example.py for a complete usage example.

CalculateCOP Class

Module: calculator

Initialization

Create an instance by providing your rocket's geometric parameters:

from calculator import CalculateCOP

params = {
    'nose_type': 'ogive',
    'Ln': 12.5,
    'd': 5.54,
    'dF': 5.54,
    'dR': 5.54,
    'Lt': 0.0,
    'Xp': 0.0,
    'CR': 10.0,
    'CT': 0.0,
    'S': 5.25,
    'LF': 6.5,
    'R': 2.77,
    'XR': 9.0,
    'XB': 27.0,
    'N': 3,
}
cop = CalculateCOP(**params)

Parameters

Parameter Type Description
nose_type str Nose cone shape: 'ogive' or 'cone'
Ln float Length of nose cone
d float Diameter at base of nose cone
dF float Diameter at front of transition (set equal to d if no transition)
dR float Diameter at rear of transition (set equal to d if no transition)
Lt float Length of transition (set to 0.0 if no transition)
Xp float Distance from nose tip to front of transition (set to 0.0 if no transition)
CR float Fin root chord
CT float Fin tip chord
S float Fin semispan (height of one fin)
LF float Length of fin mid-chord line
R float Radius of body at aft end
XR float Fin sweep distance (root leading edge to tip leading edge, parallel to body)
XB float Distance from nose tip to fin root chord leading edge
N int Number of fins

For a diagram and detailed explanation of each variable, see the Barrowman Equations page.

Methods

net_COP()

Calculates the overall Center of Pressure (COP) for the entire rocket by combining all component contributions. Returns the distance from the tip of the nose cone.

cop_location = cop.net_COP()
print(f"The net Center of Pressure is {cop_location:.2f} units from the nose tip.")

Returns: - float: The final Center of Pressure location.

visualize_rocket(show_plot=True, save_path=None)

Generates an interactive 3D visualization of the rocket with the calculated Center of Pressure location.

# Display interactive 3D plot
cop.visualize_rocket()

# Save plot to file
cop.visualize_rocket(save_path="rocket.png")

# Generate plot without displaying
fig = cop.visualize_rocket(show_plot=False)

Parameters: - show_plot (bool): Whether to display the plot (default: True) - save_path (str): Path to save the plot image (optional)

Returns: - matplotlib.figure.Figure: The generated figure object

Visualization Features: - Complete 3D rocket body (nose cone, transition, body tube) - 3D fin geometry with proper positioning - Center of Pressure marked as blue dot - Interactive controls (rotate, zoom, pan)

Visualization Screenshot:

3D Rocket Visualization

nose_contribution()

Calculates the location of the center of pressure for the nose cone alone. - Returns: float

transition_contribution()

Calculates the location of the center of pressure for the transition section. If no valid transition exists, returns 0. - Returns: float

fin_contribution()

Calculates the location of the center of pressure for the fin set alone. - Returns: float

constant_calculations()

Calculates the normal force coefficient derivatives (CN) for the nose, transition, and fins. - Returns: tuple of three floats: (cnn, cnt, cnf)

References