EllipticalFins Class#

class rocketpy.EllipticalFins[source]#

Class that defines and holds information for an elliptical fin set.

This class inherits from the Fins class.

Note

Local coordinate system: Z axis along the longitudinal axis of symmetry, positive downwards (top -> bottom). Origin located at the top of the root chord.

See also

Fins

Variables:

  • EllipticalFins.n (int) – Number of fins in fin set.

  • EllipticalFins.rocket_radius (float) – The reference rocket radius used for lift coefficient normalization, in meters.

  • EllipticalFins.airfoil (tuple) – Tuple of two items. First is the airfoil lift curve. Second is the unit of the curve (radians or degrees)

  • EllipticalFins.cant_angle (float) – Fins cant angle with respect to the rocket centerline, in degrees.

  • EllipticalFins.changing_attribute_dict (dict) – Dictionary that stores the name and the values of the attributes that may be changed during a simulation. Useful for control systems.

  • EllipticalFins.cant_angle_rad (float) – Fins cant angle with respect to the rocket centerline, in radians.

  • EllipticalFins.root_chord (float) – Fin root chord in meters.

  • EllipticalFins.span (float) – Fin span in meters.

  • EllipticalFins.name (string) – Name of fin set.

  • EllipticalFins.sweep_length (float) – Fins sweep length in meters. By sweep length, understand the axial distance between the fin root leading edge and the fin tip leading edge measured parallel to the rocket centerline.

  • EllipticalFins.sweep_angle (float) – Fins sweep angle with respect to the rocket centerline. Must be given in degrees.

  • EllipticalFins.d (float) – Reference diameter of the rocket, in meters.

  • EllipticalFins.ref_area (float) – Reference area of the rocket.

  • EllipticalFins.Af (float) – Area of the longitudinal section of each fin in the set.

  • EllipticalFins.AR (float) – Aspect ratio of each fin in the set.

  • EllipticalFins.gamma_c (float) – Fin mid-chord sweep angle.

  • EllipticalFins.Yma (float) – Span wise position of the mean aerodynamic chord.

  • EllipticalFins.roll_geometrical_constant (float) – Geometrical constant used in roll calculations.

  • EllipticalFins.tau (float) – Geometrical relation used to simplify lift and roll calculations.

  • EllipticalFins.lift_interference_factor (float) – Factor of Fin-Body interference in the lift coefficient.

  • EllipticalFins.cp (tuple) – Tuple with the x, y and z local coordinates of the fin set center of pressure. Has units of length and is given in meters.

  • EllipticalFins.cpx (float) – Fin set local center of pressure x coordinate. Has units of length and is given in meters.

  • EllipticalFins.cpy (float) – Fin set local center of pressure y coordinate. Has units of length and is given in meters.

  • EllipticalFins.cpz (float) – Fin set local center of pressure z coordinate. Has units of length and is given in meters.

  • EllipticalFins.cl (Function) – Function which defines the lift coefficient as a function of the angle of attack and the Mach number. Takes as input the angle of attack in radians and the Mach number. Returns the lift coefficient.

  • EllipticalFins.clalpha (float) – Lift coefficient slope. Has units of 1/rad.

__init__(n, root_chord, span, rocket_radius, cant_angle=0, airfoil=None, name='Fins')[source]#

Initialize EllipticalFins class.

Parameters:

  • n (int) – Number of fins, from 2 to infinity.

  • root_chord (int, float) – Fin root chord in meters.

  • span (int, float) – Fin span in meters.

  • rocket_radius (int, float) – Reference radius to calculate lift coefficient, in meters.

  • cant_angle (int, float, optional) – Fins cant angle with respect to the rocket centerline. Must be given in degrees.

  • sweep_length (int, float, optional) – Fins sweep length in meters. By sweep length, understand the axial distance between the fin root leading edge and the fin tip leading edge measured parallel to the rocket centerline. If not given, the sweep length is assumed to be equal the root chord minus the tip chord, in which case the fin is a right trapezoid with its base perpendicular to the rocket’s axis. Cannot be used in conjunction with sweep_angle.

  • sweep_angle (int, float, optional) – Fins sweep angle with respect to the rocket centerline. Must be given in degrees. If not given, the sweep angle is automatically calculated, in which case the fin is assumed to be a right trapezoid with its base perpendicular to the rocket’s axis. Cannot be used in conjunction with sweep_length.

  • airfoil (tuple, optional) – Default is null, in which case fins will be treated as flat plates. Otherwise, if tuple, fins will be considered as airfoils. The tuple’s first item specifies the airfoil’s lift coefficient by angle of attack and must be either a .csv, .txt, ndarray or callable. The .csv and .txt files can contain a single line header and the first column must specify the angle of attack, while the second column must specify the lift coefficient. The ndarray should be as [(x0, y0), (x1, y1), (x2, y2), …] where x0 is the angle of attack and y0 is the lift coefficient. If callable, it should take an angle of attack as input and return the lift coefficient at that angle of attack. The tuple’s second item is the unit of the angle of attack, accepting either “radians” or “degrees”.

  • name (str) – Name of fin set.

Return type:

None

evaluate_center_of_pressure()[source]#

Calculates and returns the center of pressure of the fin set in local coordinates. The center of pressure position is saved and stored as a tuple.

Return type:

None

evaluate_geometrical_parameters()[source]#

Calculates and saves fin set’s geometrical parameters such as the fins’ area, aspect ratio and parameters for roll movement.

Return type:

None

info()[source]#

Prints and plots summarized information of the aerodynamic surface.

Return type:

None

all_info()[source]#

Prints and plots all the available information of the aero surface.

Return type:

None