ENH: move weathercocking_coeff to PointMassRockt

MateusStano · MateusStano · commit e4314905bafd · 2026-03-19T23:35:22.000-03:00
diff --git a/docs/user/three_dof_simulation.rst b/docs/user/three_dof_simulation.rst
@@ -381,7 +381,7 @@ The ``weathercock_coeff`` Parameter
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 The weathercocking behavior is controlled by the ``weathercock_coeff`` parameter
-in the :class:`rocketpy.Flight` class:
+in the :class:`rocketpy.PointMassRocket` class:
 
 .. jupyter-execute::
 
@@ -407,18 +407,18 @@ in the :class:`rocketpy.Flight` class:
         center_of_mass_without_motor=0.0,
         power_off_drag=0.43,
         power_on_drag=0.43,
+        weathercock_coeff=1.0,  # Example with weathercocking enabled
     )
     rocket.add_motor(motor, position=0)
 
-    # Flight with weathercocking enabled
+    # Flight uses the weathercocking configured on the point-mass rocket
     flight = Flight(
         rocket=rocket,
         environment=env,
         rail_length=4.2,
         inclination=85,
         heading=45,
         simulation_mode="3 DOF",
-        weathercock_coeff=1.0,  # Example with weathercocking enabled
     )
 
     print(f"Apogee: {flight.apogee - env.elevation:.2f} m")
@@ -540,6 +540,7 @@ accuracy.
         center_of_mass_without_motor=0,
         power_off_drag=0.43,
         power_on_drag=0.43,
+        weathercock_coeff=0.0,
     )
     rocket_3dof.add_motor(motor_3dof, -1.1356)
 
@@ -561,6 +562,7 @@ accuracy.
 
     # 3-DOF with no weathercocking
     start = time.time()
+    rocket_3dof.weathercock_coeff = 0.0
     flight_3dof_0 = Flight(
         rocket=rocket_3dof,
         environment=env,
@@ -569,12 +571,12 @@ accuracy.
         heading=45,
         terminate_on_apogee=True,
         simulation_mode="3 DOF",
-        weathercock_coeff=0.0,
     )
     time_3dof_0 = time.time() - start
 
     # 3-DOF with default weathercocking
     start = time.time()
+    rocket_3dof.weathercock_coeff = 1.0
     flight_3dof_1 = Flight(
         rocket=rocket_3dof,
         environment=env,
@@ -583,12 +585,12 @@ accuracy.
         heading=45,
         terminate_on_apogee=True,
         simulation_mode="3 DOF",
-        weathercock_coeff=1.0,
     )
     time_3dof_1 = time.time() - start
 
     # 3-DOF with high weathercocking
     start = time.time()
+    rocket_3dof.weathercock_coeff = 5.0
     flight_3dof_5 = Flight(
         rocket=rocket_3dof,
         environment=env,
@@ -597,7 +599,6 @@ accuracy.
         heading=45,
         terminate_on_apogee=True,
         simulation_mode="3 DOF",
-        weathercock_coeff=5.0,
     )
     time_3dof_5 = time.time() - start
 
diff --git a/rocketpy/rocket/point_mass_rocket.py b/rocketpy/rocket/point_mass_rocket.py
@@ -31,6 +31,10 @@ class PointMassRocket(Rocket):
         as :class:`rocketpy.Rocket`, including 1D (Mach-only) and 7D
         (alpha, beta, mach, reynolds, pitch_rate, yaw_rate, roll_rate)
         definitions.
+    weathercock_coeff : float, optional
+        Proportionality coefficient for the alignment rate of the point-mass
+        rocket body axis with the relative wind direction in 3-DOF
+        simulations. Must be non-negative. Default is 0.0.
 
     Attributes
     ----------
@@ -63,6 +67,9 @@ class PointMassRocket(Rocket):
         Convenience wrapper for power-off drag as a Mach-only function.
     power_on_drag_by_mach : Function
         Convenience wrapper for power-on drag as a Mach-only function.
+    weathercock_coeff : float
+        Proportionality coefficient for weathercocking alignment in 3-DOF
+        simulations.
     """
 
     def __init__(
@@ -72,6 +79,7 @@ def __init__(
         center_of_mass_without_motor: float,
         power_off_drag,
         power_on_drag,
+        weathercock_coeff: float = 0.0,
     ):
         self._center_of_mass_without_motor_pointmass = center_of_mass_without_motor
         self._center_of_dry_mass_position = center_of_mass_without_motor
@@ -84,6 +92,8 @@ def __init__(
         self.dry_I_13 = 0.0
         self.dry_I_23 = 0.0
 
+        self.weathercock_coeff = float(weathercock_coeff)
+
         # Call base init with safe defaults
         super().__init__(
             radius=radius,
diff --git a/rocketpy/simulation/flight.py b/rocketpy/simulation/flight.py
@@ -504,7 +504,6 @@ def __init__(  # pylint: disable=too-many-arguments,too-many-statements
         equations_of_motion="standard",
         ode_solver="LSODA",
         simulation_mode="6 DOF",
-        weathercock_coeff=0.0,
     ):
         """Run a trajectory simulation.
 
@@ -588,16 +587,6 @@ def __init__(  # pylint: disable=too-many-arguments,too-many-statements
             A custom ``scipy.integrate.OdeSolver`` can be passed as well.
             For more information on the integration methods, see the scipy
             documentation [1]_.
-        weathercock_coeff : float, optional
-            Proportionality coefficient (rate coefficient) for the alignment rate of the rocket's body axis
-            with the relative wind direction in 3-DOF simulations, in rad/s. The actual angular velocity
-            applied to align the rocket is calculated as ``weathercock_coeff * sin(angle)``, where ``angle``
-            is the angle between the rocket's axis and the wind direction. A higher value means faster alignment
-            (quasi-static weathercocking). This parameter is only used when simulation_mode is '3 DOF'.
-            Default is 0.0 to mimic a pure 3-DOF simulation without any weathercocking (fixed attitude).
-            Set to a positive value to enable quasi-static weathercocking behaviour.
-
-
         Returns
         -------
         None
@@ -627,7 +616,6 @@ def __init__(  # pylint: disable=too-many-arguments,too-many-statements
         self.equations_of_motion = equations_of_motion
         self.simulation_mode = simulation_mode
         self.ode_solver = ode_solver
-        self.weathercock_coeff = weathercock_coeff
 
         # Controller initialization
         self.__init_controllers()
@@ -2310,7 +2298,8 @@ def u_dot_generalized_3dof(self, t, u, post_processing=False):
         r_dot = [vx, vy, vz]
         # Weathercocking: evolve body axis direction toward relative wind
         # The body z-axis (attitude vector) should align with -freestream_velocity
-        if self.weathercock_coeff > 0 and free_stream_speed > 1e-6:
+        weathercock_coeff = getattr(self.rocket, "weathercock_coeff", 0.0)
+        if weathercock_coeff > 0 and free_stream_speed > 1e-6:
             # Current body z-axis in inertial frame (attitude vector)
             # From rotation matrix: column 3 gives the body z-axis in inertial frame
             body_z_inertial = Vector(
@@ -2342,7 +2331,7 @@ def u_dot_generalized_3dof(self, t, u, post_processing=False):
                 sin_angle = min(1.0, max(-1.0, rotation_axis_mag))
 
                 # Angular velocity magnitude proportional to misalignment angle
-                omega_mag = self.weathercock_coeff * sin_angle
+                omega_mag = weathercock_coeff * sin_angle
 
                 # Angular velocity in inertial frame, then transform to body frame
                 omega_body = Kt @ (rotation_axis * omega_mag)
@@ -2363,7 +2352,7 @@ def u_dot_generalized_3dof(self, t, u, post_processing=False):
                             )
                     rotation_axis = perp_axis.unit_vector
                     # 180 degree rotation: sin(angle) = 1
-                    omega_mag = self.weathercock_coeff * 1.0
+                    omega_mag = weathercock_coeff * 1.0
                     omega_body = Kt @ (rotation_axis * omega_mag)
                 # else: aligned (dot > 0.999) - no rotation needed, omega_body stays None
 
diff --git a/tests/acceptance/test_3dof_flight.py b/tests/acceptance/test_3dof_flight.py
@@ -202,7 +202,7 @@ def test_3dof_weathercocking_coefficient_stored(flight_3dof_with_weathercock):
     flight_3dof_with_weathercock : rocketpy.Flight
         A 3 DOF flight simulation with weathercocking enabled.
     """
-    assert flight_3dof_with_weathercock.weathercock_coeff == 1.0
+    assert flight_3dof_with_weathercock.rocket.weathercock_coeff == 1.0
 
 
 def test_3dof_flight_post_processing_attributes(flight_3dof_no_weathercock):
@@ -399,6 +399,8 @@ def test_3dof_flight_reproducibility(
     acceptance_point_mass_rocket : rocketpy.PointMassRocket
         Rocket fixture for testing.
     """
+    acceptance_point_mass_rocket.weathercock_coeff = 0.5
+
     # Run simulation twice with same parameters
     flight1 = Flight(
         rocket=acceptance_point_mass_rocket,
@@ -407,7 +409,6 @@ def test_3dof_flight_reproducibility(
         inclination=LAUNCH_INCLINATION,
         heading=LAUNCH_HEADING,
         simulation_mode="3 DOF",
-        weathercock_coeff=0.5,
     )
 
     flight2 = Flight(
@@ -417,7 +418,6 @@ def test_3dof_flight_reproducibility(
         inclination=LAUNCH_INCLINATION,
         heading=LAUNCH_HEADING,
         simulation_mode="3 DOF",
-        weathercock_coeff=0.5,
     )
 
     # Results should be identical
@@ -452,14 +452,14 @@ def test_3dof_flight_different_weathercock_coefficients(
     flights = []
 
     for coeff in coefficients:
+        acceptance_point_mass_rocket.weathercock_coeff = coeff
         flight = Flight(
             rocket=acceptance_point_mass_rocket,
             environment=example_spaceport_env,
             rail_length=5.0,
             inclination=LAUNCH_INCLINATION,
             heading=LAUNCH_HEADING,
             simulation_mode="3 DOF",
-            weathercock_coeff=coeff,
         )
         flights.append(flight)
 
diff --git a/tests/fixtures/flight/flight_fixtures.py b/tests/fixtures/flight/flight_fixtures.py
@@ -352,6 +352,7 @@ def acceptance_point_mass_rocket(acceptance_point_mass_motor):
         center_of_mass_without_motor=0,
         power_off_drag=0.43,
         power_on_drag=0.43,
+        weathercock_coeff=0.0,
     )
     rocket.add_motor(acceptance_point_mass_motor, position=0)
     return rocket
@@ -376,14 +377,14 @@ def flight_3dof_no_weathercock(example_spaceport_env, acceptance_point_mass_rock
     rocketpy.Flight
         A 3 DOF flight simulation with weathercock_coeff=0.0.
     """
+    acceptance_point_mass_rocket.weathercock_coeff = 0.0
     return Flight(
         rocket=acceptance_point_mass_rocket,
         environment=example_spaceport_env,
         rail_length=5.0,
         inclination=LAUNCH_INCLINATION,
         heading=LAUNCH_HEADING,
         simulation_mode="3 DOF",
-        weathercock_coeff=0.0,
     )
 
 
@@ -406,12 +407,12 @@ def flight_3dof_with_weathercock(example_spaceport_env, acceptance_point_mass_ro
     rocketpy.Flight
         A 3 DOF flight simulation with weathercock_coeff=1.0.
     """
+    acceptance_point_mass_rocket.weathercock_coeff = 1.0
     return Flight(
         rocket=acceptance_point_mass_rocket,
         environment=example_spaceport_env,
         rail_length=5.0,
         inclination=LAUNCH_INCLINATION,
         heading=LAUNCH_HEADING,
         simulation_mode="3 DOF",
-        weathercock_coeff=1.0,
     )
diff --git a/tests/integration/simulation/test_flight_3dof.py b/tests/integration/simulation/test_flight_3dof.py
@@ -59,12 +59,12 @@ def flight_weathercock_zero(example_plain_env, point_mass_rocket):
     rocketpy.simulation.flight.Flight
         A Flight object configured for 3-DOF with zero weathercock coefficient.
     """
+    point_mass_rocket.weathercock_coeff = 0.0
     return Flight(
         rocket=point_mass_rocket,
         environment=example_plain_env,
         rail_length=1,
         simulation_mode="3 DOF",
-        weathercock_coeff=0.0,
     )
 
 
@@ -94,12 +94,12 @@ def flight_weathercock_pos(example_plain_env, point_mass_rocket):
     rocketpy.simulation.flight.Flight
         A Flight object configured for 3-DOF with weathercocking enabled.
     """
+    point_mass_rocket.weathercock_coeff = 1.0
     return Flight(
         rocket=point_mass_rocket,
         environment=example_plain_env,
         rail_length=1,
         simulation_mode="3 DOF",
-        weathercock_coeff=1.0,
     )
 
 
@@ -169,24 +169,16 @@ def test_invalid_simulation_mode(example_plain_env, calisto):
         )
 
 
-def test_weathercock_coeff_stored(example_plain_env, point_mass_rocket):
-    """Tests that the weathercock_coeff parameter is correctly stored.
+def test_weathercock_coeff_stored(point_mass_rocket):
+    """Tests that weathercock coefficient is stored in PointMassRocket.
 
     Parameters
     ----------
-    example_plain_env : rocketpy.Environment
-        A basic environment fixture for flight simulation.
     point_mass_rocket : rocketpy.PointMassRocket
         A point mass rocket fixture for 3-DOF simulation.
     """
-    flight = Flight(
-        rocket=point_mass_rocket,
-        environment=example_plain_env,
-        rail_length=1,
-        simulation_mode="3 DOF",
-        weathercock_coeff=2.5,
-    )
-    assert flight.weathercock_coeff == 2.5
+    point_mass_rocket.weathercock_coeff = 2.5
+    assert point_mass_rocket.weathercock_coeff == 2.5
 
 
 def test_weathercock_coeff_default(flight_3dof):
@@ -197,7 +189,7 @@ def test_weathercock_coeff_default(flight_3dof):
     flight_3dof : rocketpy.Flight
         A Flight object for a 3-DOF simulation, provided by the flight_3dof fixture.
     """
-    assert flight_3dof.weathercock_coeff == 0.0
+    assert flight_3dof.rocket.weathercock_coeff == 0.0
 
 
 def test_point_mass_rocket_3dof_uses_7d_drag_inputs(
