From b4d723b2d5a0d77e899d37ab8c4e20f5cc02df29 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 28 Nov 2025 00:43:12 +0000
Subject: [PATCH 1/6] Fix hard-coded radius value for parachute added mass
 calculation
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Calculate radius from cd_s using a typical hemispherical parachute drag
coefficient (1.4) when radius is not explicitly provided. This fixes
drift distance calculations for smaller parachutes like drogues.

Formula: R = sqrt(cd_s / (Cd * π))

Closes #860

Co-authored-by: Gui-FernandesBR <63590233+Gui-FernandesBR@users.noreply.github.com>
---
 rocketpy/rocket/parachute.py | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/rocketpy/rocket/parachute.py b/rocketpy/rocket/parachute.py
index 83b0ce0fd..9e8adb479 100644
--- a/rocketpy/rocket/parachute.py
+++ b/rocketpy/rocket/parachute.py
@@ -94,8 +94,8 @@ class Parachute:
         Function of clean_pressure_signal.
     Parachute.radius : float
         Length of the non-unique semi-axis (radius) of the inflated hemispheroid
-        parachute in meters.
-    Parachute.height : float, None
+        parachute in meters. Estimated from ``cd_s`` if not explicitly provided.
+    Parachute.height : float
         Length of the unique semi-axis (height) of the inflated hemispheroid
         parachute in meters.
     Parachute.porosity : float
@@ -108,6 +108,10 @@ class Parachute:
         calculated from the porosity of the parachute.
     """
 
+    # Typical drag coefficient for hemispherical parachute
+    # Used to estimate radius from cd_s when radius is not provided
+    HEMISPHERICAL_CD = 1.4
+
     def __init__(
         self,
         name,
@@ -116,7 +120,7 @@ def __init__(
         sampling_rate,
         lag=0,
         noise=(0, 0, 0),
-        radius=1.5,
+        radius=None,
         height=None,
         porosity=0.0432,
     ):
@@ -173,7 +177,9 @@ def __init__(
             Units are in Pa.
         radius : float, optional
             Length of the non-unique semi-axis (radius) of the inflated hemispheroid
-            parachute. Default value is 1.5.
+            parachute. If not provided, it is estimated from ``cd_s`` assuming a
+            typical hemispherical parachute drag coefficient of 1.4, using the
+            formula: ``radius = sqrt(cd_s / (HEMISPHERICAL_CD * pi))``.
             Units are in meters.
         height : float, optional
             Length of the unique semi-axis (height) of the inflated hemispheroid
@@ -200,8 +206,13 @@ def __init__(
         self.clean_pressure_signal_function = Function(0)
         self.noisy_pressure_signal_function = Function(0)
         self.noise_signal_function = Function(0)
-        self.radius = radius
-        self.height = height or radius
+        # Estimate radius from cd_s if not provided
+        if radius is None:
+            # cd_s = Cd * S = Cd * π * R² => R = sqrt(cd_s / (Cd * π))
+            self.radius = np.sqrt(cd_s / (self.HEMISPHERICAL_CD * np.pi))
+        else:
+            self.radius = radius
+        self.height = height or self.radius
         self.porosity = porosity
         self.added_mass_coefficient = 1.068 * (
             1
@@ -341,8 +352,8 @@ def from_dict(cls, data):
             sampling_rate=data["sampling_rate"],
             lag=data["lag"],
             noise=data["noise"],
-            radius=data.get("radius", 1.5),
-            height=data.get("height", None),
+            radius=data.get("radius"),
+            height=data.get("height"),
             porosity=data.get("porosity", 0.0432),
         )
 

From b7b2ddff278d03b88fbc58fdf2d21545d175c5ef Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 28 Nov 2025 00:46:08 +0000
Subject: [PATCH 2/6] Address code review: improve docstrings and add explicit
 None defaults

Co-authored-by: Gui-FernandesBR <63590233+Gui-FernandesBR@users.noreply.github.com>
---
 rocketpy/rocket/parachute.py | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/rocketpy/rocket/parachute.py b/rocketpy/rocket/parachute.py
index 9e8adb479..2b820b0a4 100644
--- a/rocketpy/rocket/parachute.py
+++ b/rocketpy/rocket/parachute.py
@@ -94,7 +94,8 @@ class Parachute:
         Function of clean_pressure_signal.
     Parachute.radius : float
         Length of the non-unique semi-axis (radius) of the inflated hemispheroid
-        parachute in meters. Estimated from ``cd_s`` if not explicitly provided.
+        parachute in meters. Estimated from ``cd_s`` using the formula
+        ``R = sqrt(cd_s / (1.4 * π))`` if not explicitly provided.
     Parachute.height : float
         Length of the unique semi-axis (height) of the inflated hemispheroid
         parachute in meters.
@@ -352,8 +353,8 @@ def from_dict(cls, data):
             sampling_rate=data["sampling_rate"],
             lag=data["lag"],
             noise=data["noise"],
-            radius=data.get("radius"),
-            height=data.get("height"),
+            radius=data.get("radius", None),
+            height=data.get("height", None),
             porosity=data.get("porosity", 0.0432),
         )
 

From 3100036f3790a0a7945bd8a4dd9c27c1b4e3c19e Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 28 Nov 2025 01:01:40 +0000
Subject: [PATCH 3/6] Add CHANGELOG entry for PR #889

Co-authored-by: Gui-FernandesBR <63590233+Gui-FernandesBR@users.noreply.github.com>
---
 CHANGELOG.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d85ddb110..91977f485 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -55,8 +55,10 @@ Attention: The newest changes should be on top -->
 
 ### Fixed
 
+- BUG: Fix hard-coded radius value for parachute added mass calculation [#889](https://github.com/RocketPy-Team/RocketPy/pull/889)
 - DOC: Fix documentation build [#908](https://github.com/RocketPy-Team/RocketPy/pull/908)
 - BUG: energy_data plot not working for 3 dof sims [[#906](https://github.com/RocketPy-Team/RocketPy/issues/906)]
+- BUG: Fix parallel Monte Carlo simulation showing incorrect iteration count [#806](https://github.com/RocketPy-Team/RocketPy/pull/806)
 - BUG: Fix CSV column header spacing in FlightDataExporter [#864](https://github.com/RocketPy-Team/RocketPy/issues/864)
 - BUG: Fix parallel Monte Carlo simulation showing incorrect iteration count [#806](https://github.com/RocketPy-Team/RocketPy/pull/806)
 - BUG: Duplicate _controllers in Flight.TimeNodes.merge() [#931](https://github.com/RocketPy-Team/RocketPy/pull/931)

From 0988f98231ce6d270ca3abca3d106fe0e8f43ece Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 2 Dec 2025 01:58:37 +0000
Subject: [PATCH 4/6] Update rocket.add_parachute to use radius=None for
 consistency

Changed the default radius from 1.5 to None in the add_parachute method
to match the Parachute class behavior. This ensures consistent automatic
radius calculation from cd_s across both APIs.

Co-authored-by: Gui-FernandesBR <63590233+Gui-FernandesBR@users.noreply.github.com>
---
 rocketpy/rocket/rocket.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/rocketpy/rocket/rocket.py b/rocketpy/rocket/rocket.py
index 93ab46321..0fbe6ad6f 100644
--- a/rocketpy/rocket/rocket.py
+++ b/rocketpy/rocket/rocket.py
@@ -1488,7 +1488,7 @@ def add_parachute(
         sampling_rate=100,
         lag=0,
         noise=(0, 0, 0),
-        radius=1.5,
+        radius=None,
         height=None,
         porosity=0.0432,
     ):
@@ -1551,7 +1551,9 @@ def add_parachute(
             are in pascal.
         radius : float, optional
             Length of the non-unique semi-axis (radius) of the inflated hemispheroid
-            parachute. Default value is 1.5.
+            parachute. If not provided, it is estimated from ``cd_s`` assuming a
+            typical hemispherical parachute drag coefficient of 1.4, using the
+            formula: ``radius = sqrt(cd_s / (1.4 * pi))``.
             Units are in meters.
         height : float, optional
             Length of the unique semi-axis (height) of the inflated hemispheroid

From 9c43855a0b490d2b4a87c6626a4c920f496362c2 Mon Sep 17 00:00:00 2001
From: Gui-FernandesBR <guilherme_fernandes@usp.br>
Date: Fri, 27 Feb 2026 22:07:00 -0300
Subject: [PATCH 5/6] Refactor Parachute class to remove hard-coded radius
 value and introduce drag_coefficient parameter for radius estimation

---
 rocketpy/rocket/parachute.py                |  62 +++++++----
 rocketpy/rocket/rocket.py                   |  32 +++---
 rocketpy/stochastic/stochastic_parachute.py |   9 ++
 tests/unit/rocket/test_parachute.py         | 111 ++++++++++++++++++++
 4 files changed, 181 insertions(+), 33 deletions(-)
 create mode 100644 tests/unit/rocket/test_parachute.py

diff --git a/rocketpy/rocket/parachute.py b/rocketpy/rocket/parachute.py
index 2b820b0a4..7ced05105 100644
--- a/rocketpy/rocket/parachute.py
+++ b/rocketpy/rocket/parachute.py
@@ -92,27 +92,30 @@ class Parachute:
         Function of noisy_pressure_signal.
     Parachute.clean_pressure_signal_function : Function
         Function of clean_pressure_signal.
+    Parachute.drag_coefficient : float
+        Drag coefficient of the inflated canopy shape, used only when
+        ``radius`` is not provided to estimate the parachute radius from
+        ``cd_s``: ``R = sqrt(cd_s / (drag_coefficient * pi))``. Typical
+        values: 1.4 for hemispherical canopies (default), 0.75 for flat
+        circular canopies, 1.5 for extended-skirt canopies.
     Parachute.radius : float
         Length of the non-unique semi-axis (radius) of the inflated hemispheroid
-        parachute in meters. Estimated from ``cd_s`` using the formula
-        ``R = sqrt(cd_s / (1.4 * π))`` if not explicitly provided.
+        parachute in meters. If not provided at construction time, it is
+        estimated from ``cd_s`` and ``drag_coefficient``.
     Parachute.height : float
         Length of the unique semi-axis (height) of the inflated hemispheroid
         parachute in meters.
     Parachute.porosity : float
-        Geometric porosity of the canopy (ratio of open area to total canopy area),
-        in [0, 1]. Affects only the added-mass scaling during descent; it does
-        not change ``cd_s`` (drag). The default, 0.0432, yields an added-mass
-        of 1.0 (“neutral” behavior).
+        Geometric porosity of the canopy (ratio of open area to total canopy
+        area), in [0, 1]. Affects only the added-mass scaling during descent;
+        it does not change ``cd_s`` (drag). The default value of 0.0432 is
+        chosen so that the resulting ``added_mass_coefficient`` equals
+        approximately 1.0 ("neutral" added-mass behavior).
     Parachute.added_mass_coefficient : float
         Coefficient used to calculate the added-mass due to dragged air. It is
         calculated from the porosity of the parachute.
     """
 
-    # Typical drag coefficient for hemispherical parachute
-    # Used to estimate radius from cd_s when radius is not provided
-    HEMISPHERICAL_CD = 1.4
-
     def __init__(
         self,
         name,
@@ -122,6 +125,7 @@ def __init__(
         lag=0,
         noise=(0, 0, 0),
         radius=None,
+        drag_coefficient=1.4,
         height=None,
         porosity=0.0432,
     ):
@@ -177,20 +181,33 @@ def __init__(
             passed to the trigger function. Default value is ``(0, 0, 0)``.
             Units are in Pa.
         radius : float, optional
-            Length of the non-unique semi-axis (radius) of the inflated hemispheroid
-            parachute. If not provided, it is estimated from ``cd_s`` assuming a
-            typical hemispherical parachute drag coefficient of 1.4, using the
-            formula: ``radius = sqrt(cd_s / (HEMISPHERICAL_CD * pi))``.
+            Length of the non-unique semi-axis (radius) of the inflated
+            hemispheroid parachute. If not provided, it is estimated from
+            ``cd_s`` and ``drag_coefficient`` using:
+            ``radius = sqrt(cd_s / (drag_coefficient * pi))``.
             Units are in meters.
+        drag_coefficient : float, optional
+            Drag coefficient of the inflated canopy shape, used only when
+            ``radius`` is not provided. It relates the aerodynamic ``cd_s``
+            to the physical canopy area via
+            ``cd_s = drag_coefficient * pi * radius**2``. Typical values:
+
+            - **1.4** — hemispherical canopy (default, NASA SP-8066)
+            - **0.75** — flat circular canopy
+            - **1.5** — extended-skirt canopy
+
+            Has no effect when ``radius`` is explicitly provided.
         height : float, optional
             Length of the unique semi-axis (height) of the inflated hemispheroid
             parachute. Default value is the radius of the parachute.
             Units are in meters.
         porosity : float, optional
-            Geometric porosity of the canopy (ratio of open area to total canopy area),
-            in [0, 1]. Affects only the added-mass scaling during descent; it does
-            not change ``cd_s`` (drag). The default, 0.0432, yields an added-mass
-            of 1.0 (“neutral” behavior).
+            Geometric porosity of the canopy (ratio of open area to total
+            canopy area), in [0, 1]. Affects only the added-mass scaling
+            during descent; it does not change ``cd_s`` (drag). The default
+            value of 0.0432 is chosen so that the resulting
+            ``added_mass_coefficient`` equals approximately 1.0 ("neutral"
+            added-mass behavior).
         """
         self.name = name
         self.cd_s = cd_s
@@ -207,10 +224,11 @@ def __init__(
         self.clean_pressure_signal_function = Function(0)
         self.noisy_pressure_signal_function = Function(0)
         self.noise_signal_function = Function(0)
-        # Estimate radius from cd_s if not provided
+        self.drag_coefficient = drag_coefficient
+        # Estimate radius from cd_s if not provided.
+        # cd_s = Cd * S = Cd * π * R²  =>  R = sqrt(cd_s / (Cd * π))
         if radius is None:
-            # cd_s = Cd * S = Cd * π * R² => R = sqrt(cd_s / (Cd * π))
-            self.radius = np.sqrt(cd_s / (self.HEMISPHERICAL_CD * np.pi))
+            self.radius = np.sqrt(cd_s / (drag_coefficient * np.pi))
         else:
             self.radius = radius
         self.height = height or self.radius
@@ -321,6 +339,7 @@ def to_dict(self, **kwargs):
             "lag": self.lag,
             "noise": self.noise,
             "radius": self.radius,
+            "drag_coefficient": self.drag_coefficient,
             "height": self.height,
             "porosity": self.porosity,
         }
@@ -354,6 +373,7 @@ def from_dict(cls, data):
             lag=data["lag"],
             noise=data["noise"],
             radius=data.get("radius", None),
+            drag_coefficient=data.get("drag_coefficient", 1.4),
             height=data.get("height", None),
             porosity=data.get("porosity", 0.0432),
         )
diff --git a/rocketpy/rocket/rocket.py b/rocketpy/rocket/rocket.py
index 0fbe6ad6f..ed76c1fdc 100644
--- a/rocketpy/rocket/rocket.py
+++ b/rocketpy/rocket/rocket.py
@@ -1489,6 +1489,7 @@ def add_parachute(
         lag=0,
         noise=(0, 0, 0),
         radius=None,
+        drag_coefficient=1.4,
         height=None,
         porosity=0.0432,
     ):
@@ -1550,28 +1551,34 @@ def add_parachute(
             passed to the trigger function. Default value is (0, 0, 0). Units
             are in pascal.
         radius : float, optional
-            Length of the non-unique semi-axis (radius) of the inflated hemispheroid
-            parachute. If not provided, it is estimated from ``cd_s`` assuming a
-            typical hemispherical parachute drag coefficient of 1.4, using the
-            formula: ``radius = sqrt(cd_s / (1.4 * pi))``.
+            Length of the non-unique semi-axis (radius) of the inflated
+            hemispheroid parachute. If not provided, it is estimated from
+            `cd_s` and `drag_coefficient` using:
+            `radius = sqrt(cd_s / (drag_coefficient * pi))`.
             Units are in meters.
+        drag_coefficient : float, optional
+            Drag coefficient of the inflated canopy shape, used only when
+            `radius` is not provided. Typical values: 1.4 for hemispherical
+            canopies (default), 0.75 for flat circular canopies, 1.5 for
+            extended-skirt canopies. Has no effect when `radius` is given.
         height : float, optional
             Length of the unique semi-axis (height) of the inflated hemispheroid
             parachute. Default value is the radius of the parachute.
             Units are in meters.
         porosity : float, optional
-            Geometric porosity of the canopy (ratio of open area to total canopy area),
-            in [0, 1]. Affects only the added-mass scaling during descent; it does
-            not change ``cd_s`` (drag). The default, 0.0432, yields an added-mass
-            of 1.0 (“neutral” behavior).
+            Geometric porosity of the canopy (ratio of open area to total
+            canopy area), in [0, 1]. Affects only the added-mass scaling
+            during descent; it does not change `cd_s` (drag). The default
+            value of 0.0432 yields an `added_mass_coefficient` of
+            approximately 1.0.
 
         Returns
         -------
         parachute : Parachute
-            Parachute containing trigger, sampling_rate, lag, cd_s, noise, radius,
-            height, porosity and name. Furthermore, it stores clean_pressure_signal,
-            noise_signal and noisyPressureSignal which are filled in during
-            Flight simulation.
+            Parachute containing trigger, sampling_rate, lag, cd_s, noise,
+            radius, drag_coefficient, height, porosity and name. Furthermore,
+            it stores clean_pressure_signal, noise_signal and
+            noisyPressureSignal which are filled in during Flight simulation.
         """
         parachute = Parachute(
             name,
@@ -1581,6 +1588,7 @@ def add_parachute(
             lag,
             noise,
             radius,
+            drag_coefficient,
             height,
             porosity,
         )
diff --git a/rocketpy/stochastic/stochastic_parachute.py b/rocketpy/stochastic/stochastic_parachute.py
index dea8a077d..038907187 100644
--- a/rocketpy/stochastic/stochastic_parachute.py
+++ b/rocketpy/stochastic/stochastic_parachute.py
@@ -31,6 +31,9 @@ class StochasticParachute(StochasticModel):
         List with the name of the parachute object. This cannot be randomized.
     radius : tuple, list, int, float
         Radius of the parachute in meters.
+    drag_coefficient : tuple, list, int, float
+        Drag coefficient of the inflated canopy shape, used only when
+        ``radius`` is not provided.
     height : tuple, list, int, float
         Height of the parachute in meters.
     porosity : tuple, list, int, float
@@ -46,6 +49,7 @@ def __init__(
         lag=None,
         noise=None,
         radius=None,
+        drag_coefficient=None,
         height=None,
         porosity=None,
     ):
@@ -74,6 +78,9 @@ def __init__(
             time-correlation).
         radius : tuple, list, int, float
             Radius of the parachute in meters.
+        drag_coefficient : tuple, list, int, float
+            Drag coefficient of the inflated canopy shape, used only when
+            ``radius`` is not provided.
         height : tuple, list, int, float
             Height of the parachute in meters.
         porosity : tuple, list, int, float
@@ -86,6 +93,7 @@ def __init__(
         self.lag = lag
         self.noise = noise
         self.radius = radius
+        self.drag_coefficient = drag_coefficient
         self.height = height
         self.porosity = porosity
 
@@ -100,6 +108,7 @@ def __init__(
             noise=noise,
             name=None,
             radius=radius,
+            drag_coefficient=drag_coefficient,
             height=height,
             porosity=porosity,
         )
diff --git a/tests/unit/rocket/test_parachute.py b/tests/unit/rocket/test_parachute.py
new file mode 100644
index 000000000..e5191cea6
--- /dev/null
+++ b/tests/unit/rocket/test_parachute.py
@@ -0,0 +1,111 @@
+"""Unit tests for the Parachute class, focusing on the radius and
+drag_coefficient parameters introduced in PR #889."""
+
+import numpy as np
+import pytest
+
+from rocketpy import Parachute
+
+
+def _make_parachute(**kwargs):
+    defaults = dict(
+        name="test",
+        cd_s=10.0,
+        trigger="apogee",
+        sampling_rate=100,
+    )
+    defaults.update(kwargs)
+    return Parachute(**defaults)
+
+
+class TestParachuteRadiusEstimation:
+    """Tests for auto-computed radius from cd_s and drag_coefficient."""
+
+    def test_radius_auto_computed_from_cd_s_default_drag_coefficient(self):
+        """When radius is not provided the radius is estimated using the
+        default drag_coefficient of 1.4 and the formula R = sqrt(cd_s / (Cd * pi))."""
+        cd_s = 10.0
+        parachute = _make_parachute(cd_s=cd_s)
+        expected_radius = np.sqrt(cd_s / (1.4 * np.pi))
+        assert parachute.radius == pytest.approx(expected_radius, rel=1e-9)
+
+    def test_radius_auto_computed_uses_custom_drag_coefficient(self):
+        """When drag_coefficient is provided and radius is not, the radius
+        must be estimated using the given drag_coefficient."""
+        cd_s = 10.0
+        custom_cd = 0.75
+        parachute = _make_parachute(cd_s=cd_s, drag_coefficient=custom_cd)
+        expected_radius = np.sqrt(cd_s / (custom_cd * np.pi))
+        assert parachute.radius == pytest.approx(expected_radius, rel=1e-9)
+
+    def test_explicit_radius_overrides_estimation(self):
+        """When radius is explicitly provided, it must be used directly and
+        drag_coefficient must be ignored for the radius calculation."""
+        explicit_radius = 2.5
+        parachute = _make_parachute(radius=explicit_radius, drag_coefficient=0.5)
+        assert parachute.radius == explicit_radius
+
+    def test_drag_coefficient_stored_on_instance(self):
+        """drag_coefficient must be stored as an attribute regardless of
+        whether radius is provided or not."""
+        parachute = _make_parachute(drag_coefficient=0.75)
+        assert parachute.drag_coefficient == 0.75
+
+    def test_drag_coefficient_default_is_1_4(self):
+        """Default drag_coefficient must be 1.4 for backward compatibility."""
+        parachute = _make_parachute()
+        assert parachute.drag_coefficient == pytest.approx(1.4)
+
+    def test_drogue_radius_smaller_than_main(self):
+        """A drogue (cd_s=1.0) must have a smaller radius than a main (cd_s=10.0)
+        when using the same drag_coefficient."""
+        main = _make_parachute(cd_s=10.0)
+        drogue = _make_parachute(cd_s=1.0)
+        assert drogue.radius < main.radius
+
+    def test_drogue_radius_approximately_0_48(self):
+        """For cd_s=1.0 and drag_coefficient=1.4, the estimated radius
+        must be approximately 0.48 m (fixes the previous hard-coded 1.5 m)."""
+        drogue = _make_parachute(cd_s=1.0)
+        assert drogue.radius == pytest.approx(0.476, abs=1e-3)
+
+    def test_main_radius_approximately_1_51(self):
+        """For cd_s=10.0 and drag_coefficient=1.4, the estimated radius
+        must be approximately 1.51 m, matching the old hard-coded value."""
+        main = _make_parachute(cd_s=10.0)
+        assert main.radius == pytest.approx(1.508, abs=1e-3)
+
+
+class TestParachuteSerialization:
+    """Tests for to_dict / from_dict round-trip including drag_coefficient."""
+
+    def test_to_dict_includes_drag_coefficient(self):
+        """to_dict must include the drag_coefficient key."""
+        parachute = _make_parachute(drag_coefficient=0.75)
+        data = parachute.to_dict()
+        assert "drag_coefficient" in data
+        assert data["drag_coefficient"] == 0.75
+
+    def test_from_dict_round_trip_preserves_drag_coefficient(self):
+        """A Parachute serialized to dict and restored must have the same
+        drag_coefficient."""
+        original = _make_parachute(cd_s=5.0, drag_coefficient=0.75)
+        data = original.to_dict()
+        restored = Parachute.from_dict(data)
+        assert restored.drag_coefficient == pytest.approx(0.75)
+        assert restored.radius == pytest.approx(original.radius, rel=1e-9)
+
+    def test_from_dict_defaults_drag_coefficient_to_1_4_when_absent(self):
+        """Dicts serialized before drag_coefficient was added (no key) must
+        fall back to 1.4 for backward compatibility."""
+        data = dict(
+            name="legacy",
+            cd_s=10.0,
+            trigger="apogee",
+            sampling_rate=100,
+            lag=0,
+            noise=(0, 0, 0),
+            # no drag_coefficient key — simulates old serialized data
+        )
+        parachute = Parachute.from_dict(data)
+        assert parachute.drag_coefficient == pytest.approx(1.4)

From fb64171033be7d11d7f5373c464b5397203d538b Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Mon, 9 Mar 2026 01:33:15 +0000
Subject: [PATCH 6/6] MNT: Extract noise initialization to fix pylint
 too-many-statements in Parachute.__init__

Co-authored-by: Gui-FernandesBR <63590233+Gui-FernandesBR@users.noreply.github.com>
---
 rocketpy/rocket/parachute.py | 34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/rocketpy/rocket/parachute.py b/rocketpy/rocket/parachute.py
index 7ced05105..5e0f63f5c 100644
--- a/rocketpy/rocket/parachute.py
+++ b/rocketpy/rocket/parachute.py
@@ -215,15 +215,6 @@ def __init__(
         self.sampling_rate = sampling_rate
         self.lag = lag
         self.noise = noise
-        self.noise_signal = [[-1e-6, np.random.normal(noise[0], noise[1])]]
-        self.noisy_pressure_signal = []
-        self.clean_pressure_signal = []
-        self.noise_bias = noise[0]
-        self.noise_deviation = noise[1]
-        self.noise_corr = (noise[2], (1 - noise[2] ** 2) ** 0.5)
-        self.clean_pressure_signal_function = Function(0)
-        self.noisy_pressure_signal_function = Function(0)
-        self.noise_signal_function = Function(0)
         self.drag_coefficient = drag_coefficient
         # Estimate radius from cd_s if not provided.
         # cd_s = Cd * S = Cd * π * R²  =>  R = sqrt(cd_s / (Cd * π))
@@ -240,16 +231,33 @@ def __init__(
             + 1.2626 * self.porosity**3
         )
 
+        self.__init_noise(noise)
+        self.prints = _ParachutePrints(self)
+        self.__evaluate_trigger_function(trigger)
+
+    def __init_noise(self, noise):
+        """Initializes all noise-related attributes.
+
+        Parameters
+        ----------
+        noise : tuple, list
+            List in the format (mean, standard deviation, time-correlation).
+        """
+        self.noise_signal = [[-1e-6, np.random.normal(noise[0], noise[1])]]
+        self.noisy_pressure_signal = []
+        self.clean_pressure_signal = []
+        self.noise_bias = noise[0]
+        self.noise_deviation = noise[1]
+        self.noise_corr = (noise[2], (1 - noise[2] ** 2) ** 0.5)
+        self.clean_pressure_signal_function = Function(0)
+        self.noisy_pressure_signal_function = Function(0)
+        self.noise_signal_function = Function(0)
         alpha, beta = self.noise_corr
         self.noise_function = lambda: (
             alpha * self.noise_signal[-1][1]
             + beta * np.random.normal(noise[0], noise[1])
         )
 
-        self.prints = _ParachutePrints(self)
-
-        self.__evaluate_trigger_function(trigger)
-
     def __evaluate_trigger_function(self, trigger):
         """This is used to set the triggerfunc attribute that will be used to
         interact with the Flight class.