From 0873d217bc31c87fd5b5af173105e1a67840292c Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Thu, 19 Jun 2025 12:01:00 -0400
Subject: [PATCH 01/22] ENH: added radius and porosity to parachute

---
 rocketpy/rocket/parachute.py  |  8 ++++++++
 rocketpy/simulation/flight.py | 30 +++++++++++++++++++++++-------
 2 files changed, 31 insertions(+), 7 deletions(-)

diff --git a/rocketpy/rocket/parachute.py b/rocketpy/rocket/parachute.py
index a18cb4793..11bdce63e 100644
--- a/rocketpy/rocket/parachute.py
+++ b/rocketpy/rocket/parachute.py
@@ -102,6 +102,8 @@ def __init__(
         sampling_rate,
         lag=0,
         noise=(0, 0, 0),
+        parachute_radius=1.5,
+        porosity=0.0432,
     ):
         """Initializes Parachute class.
 
@@ -161,6 +163,8 @@ def __init__(
         self.sampling_rate = sampling_rate
         self.lag = lag
         self.noise = noise
+        self.parachute_radius = parachute_radius
+        self.porosity = porosity
         self.noise_signal = [[-1e-6, np.random.normal(noise[0], noise[1])]]
         self.noisy_pressure_signal = []
         self.clean_pressure_signal = []
@@ -264,6 +268,8 @@ def to_dict(self, include_outputs=False):
             "sampling_rate": self.sampling_rate,
             "lag": self.lag,
             "noise": self.noise,
+            "parachute_radius": self.parachute_radius,
+            "porosity": self.porosity,
         }
 
         if include_outputs:
@@ -290,6 +296,8 @@ def from_dict(cls, data):
             sampling_rate=data["sampling_rate"],
             lag=data["lag"],
             noise=data["noise"],
+            parachute_radius=data["parachute_radius"],
+            porosity=data["porosity"],
         )
 
         return parachute
diff --git a/rocketpy/simulation/flight.py b/rocketpy/simulation/flight.py
index ce728dafe..9c3b1b9d3 100644
--- a/rocketpy/simulation/flight.py
+++ b/rocketpy/simulation/flight.py
@@ -767,7 +767,13 @@ def __simulate(self, verbose):
                         callbacks = [
                             lambda self, parachute_cd_s=parachute.cd_s: setattr(
                                 self, "parachute_cd_s", parachute_cd_s
-                            )
+                            ),
+                            lambda self, parachute_radius=parachute.radius: setattr(
+                                self, "parachute_radius", parachute_radius
+                            ),
+                            lambda self, parachute_porosity=parachute.porosity: setattr(
+                                self, "parachute_porosity", parachute_porosity
+                            ),
                         ]
                         self.flight_phases.add_phase(
                             node.t + parachute.lag,
@@ -1013,7 +1019,13 @@ def __simulate(self, verbose):
                                             lambda self,
                                             parachute_cd_s=parachute.cd_s: setattr(
                                                 self, "parachute_cd_s", parachute_cd_s
-                                            )
+                                            ),
+                                            lambda self, parachute_radius=parachute.radius: setattr(
+                                                self, "parachute_radius", parachute_radius
+                                            ),
+                                            lambda self, parachute_porosity=parachute.porosity: setattr(
+                                                self, "parachute_porosity", parachute_porosity
+                                            ),
                                         ]
                                         self.flight_phases.add_phase(
                                             overshootable_node.t + parachute.lag,
@@ -1961,13 +1973,15 @@ def u_dot_parachute(self, t, u, post_processing=False):
 
         # Get Parachute data
         cd_s = self.parachute_cd_s
+        R = self.parachute_radius
+        porosity = self.parachute_porosity
+
 
         # Get the mass of the rocket
         mp = self.rocket.dry_mass
 
         # Define constants
-        ka = 1  # Added mass coefficient (depends on parachute's porosity)
-        R = 1.5  # Parachute radius
+        ka = 1.068 * (1 - 1.465 * porosity - 0.25975 * porosity**2 + 1.2626 * porosity**3)
         # to = 1.2
         # eta = 1
         # Rdot = (6 * R * (1 - eta) / (1.2**6)) * (
@@ -1975,8 +1989,10 @@ def u_dot_parachute(self, t, u, post_processing=False):
         # )
         # Rdot = 0
 
+        # tf = 8 * nominal diameter / velocity at line stretch
+
         # Calculate added mass
-        ma = ka * rho * (4 / 3) * np.pi * R**3
+        ma = ka * rho * (4 / 3) * np.pi * R**3 # ma = ka * rho * (4 / 3) * np.pi * R**2 * height
 
         # Calculate freestream speed
         freestream_x = vx - wind_velocity_x
@@ -1985,9 +2001,9 @@ def u_dot_parachute(self, t, u, post_processing=False):
         free_stream_speed = (freestream_x**2 + freestream_y**2 + freestream_z**2) ** 0.5
 
         # Determine drag force
-        pseudo_drag = -0.5 * rho * cd_s * free_stream_speed
+        pseudo_drag = -0.5 * rho * cd_s * free_stream_speed # * Area
         # pseudo_drag = pseudo_drag - ka * rho * 4 * np.pi * (R**2) * Rdot
-        Dx = pseudo_drag * freestream_x
+        Dx = pseudo_drag * freestream_x # add eta efficiency for wake
         Dy = pseudo_drag * freestream_y
         Dz = pseudo_drag * freestream_z
         ax = Dx / (mp + ma)

From 02ddd1b638c79ca9c650b2871d7d554e945190f3 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Wed, 25 Jun 2025 20:57:52 -0400
Subject: [PATCH 02/22] ENH: added parachute radius

---
 rocketpy/rocket/parachute.py  | 19 +++++++++++++++++--
 rocketpy/simulation/flight.py | 15 +++++++++++----
 2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/rocketpy/rocket/parachute.py b/rocketpy/rocket/parachute.py
index 11bdce63e..a1f96f912 100644
--- a/rocketpy/rocket/parachute.py
+++ b/rocketpy/rocket/parachute.py
@@ -103,6 +103,7 @@ def __init__(
         lag=0,
         noise=(0, 0, 0),
         parachute_radius=1.5,
+        parachute_height=None,
         porosity=0.0432,
     ):
         """Initializes Parachute class.
@@ -156,6 +157,15 @@ def __init__(
             The values are used to add noise to the pressure signal which is
             passed to the trigger function. Default value is ``(0, 0, 0)``.
             Units are in Pa.
+        parachute_radius : float, optional
+            Radius of the inflated parachute in meters. Default value is 1.5.
+            Units are in meters.
+        parachute_height : float, optional
+            Height of the inflated parachute in meters.
+            Default value is the radius parachute. Units are in meters.
+        porosity : float, optional
+            Porosity of the parachute material, which is a measure of how much air can
+            pass through the parachute material. Default value is 0.0432.
         """
         self.name = name
         self.cd_s = cd_s
@@ -164,6 +174,9 @@ def __init__(
         self.lag = lag
         self.noise = noise
         self.parachute_radius = parachute_radius
+        if parachute_height is None:
+            parachute_height = parachute_radius
+        self.parachute_height = parachute_height
         self.porosity = porosity
         self.noise_signal = [[-1e-6, np.random.normal(noise[0], noise[1])]]
         self.noisy_pressure_signal = []
@@ -269,6 +282,7 @@ def to_dict(self, include_outputs=False):
             "lag": self.lag,
             "noise": self.noise,
             "parachute_radius": self.parachute_radius,
+            "parachute_height": self.parachute_height,
             "porosity": self.porosity,
         }
 
@@ -296,8 +310,9 @@ def from_dict(cls, data):
             sampling_rate=data["sampling_rate"],
             lag=data["lag"],
             noise=data["noise"],
-            parachute_radius=data["parachute_radius"],
-            porosity=data["porosity"],
+            parachute_radius=data.get("parachute_radius", 1.5),
+            parachute_height=data.get("parachute_height", None),
+            porosity=data.get("porosity", 0.0432),
         )
 
         return parachute
diff --git a/rocketpy/simulation/flight.py b/rocketpy/simulation/flight.py
index 9c3b1b9d3..f5b6edc18 100644
--- a/rocketpy/simulation/flight.py
+++ b/rocketpy/simulation/flight.py
@@ -771,6 +771,9 @@ def __simulate(self, verbose):
                             lambda self, parachute_radius=parachute.radius: setattr(
                                 self, "parachute_radius", parachute_radius
                             ),
+                            lambda self, parachute_height=parachute.height: setattr(
+                                self, "parachute_height", parachute_height
+                            ),
                             lambda self, parachute_porosity=parachute.porosity: setattr(
                                 self, "parachute_porosity", parachute_porosity
                             ),
@@ -1023,6 +1026,9 @@ def __simulate(self, verbose):
                                             lambda self, parachute_radius=parachute.radius: setattr(
                                                 self, "parachute_radius", parachute_radius
                                             ),
+                                            lambda self, parachute_height=parachute.height: setattr(
+                                                self, "parachute_height", parachute_height
+                                            ),
                                             lambda self, parachute_porosity=parachute.porosity: setattr(
                                                 self, "parachute_porosity", parachute_porosity
                                             ),
@@ -1973,7 +1979,8 @@ def u_dot_parachute(self, t, u, post_processing=False):
 
         # Get Parachute data
         cd_s = self.parachute_cd_s
-        R = self.parachute_radius
+        parachute_radius = self.parachute_radius
+        parachute_height = self.parachute_height
         porosity = self.parachute_porosity
 
 
@@ -1992,7 +1999,7 @@ def u_dot_parachute(self, t, u, post_processing=False):
         # tf = 8 * nominal diameter / velocity at line stretch
 
         # Calculate added mass
-        ma = ka * rho * (4 / 3) * np.pi * R**3 # ma = ka * rho * (4 / 3) * np.pi * R**2 * height
+        ma = ka * rho * (4 / 3) * np.pi * parachute_radius**2 * parachute_height
 
         # Calculate freestream speed
         freestream_x = vx - wind_velocity_x
@@ -2001,14 +2008,14 @@ def u_dot_parachute(self, t, u, post_processing=False):
         free_stream_speed = (freestream_x**2 + freestream_y**2 + freestream_z**2) ** 0.5
 
         # Determine drag force
-        pseudo_drag = -0.5 * rho * cd_s * free_stream_speed # * Area
+        pseudo_drag = -0.5 * rho * cd_s * free_stream_speed
         # pseudo_drag = pseudo_drag - ka * rho * 4 * np.pi * (R**2) * Rdot
         Dx = pseudo_drag * freestream_x # add eta efficiency for wake
         Dy = pseudo_drag * freestream_y
         Dz = pseudo_drag * freestream_z
         ax = Dx / (mp + ma)
         ay = Dy / (mp + ma)
-        az = (Dz - 9.8 * mp) / (mp + ma)
+        az = (Dz - mp * self.env.gravity.get_value_opt(z)) / (mp + ma)
 
         if post_processing:
             self.__post_processed_variables.append(

From 1119ef8d581c3fd1616041a3e35140fdea677c0a Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Wed, 25 Jun 2025 21:12:21 -0400
Subject: [PATCH 03/22] ENH: fixing radius and height attribute in flight class

---
 rocketpy/simulation/flight.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/rocketpy/simulation/flight.py b/rocketpy/simulation/flight.py
index f5b6edc18..0e0bc597c 100644
--- a/rocketpy/simulation/flight.py
+++ b/rocketpy/simulation/flight.py
@@ -768,10 +768,10 @@ def __simulate(self, verbose):
                             lambda self, parachute_cd_s=parachute.cd_s: setattr(
                                 self, "parachute_cd_s", parachute_cd_s
                             ),
-                            lambda self, parachute_radius=parachute.radius: setattr(
+                            lambda self, parachute_radius=parachute.parachute_radius: setattr(
                                 self, "parachute_radius", parachute_radius
                             ),
-                            lambda self, parachute_height=parachute.height: setattr(
+                            lambda self, parachute_height=parachute.parachute_height: setattr(
                                 self, "parachute_height", parachute_height
                             ),
                             lambda self, parachute_porosity=parachute.porosity: setattr(
@@ -1023,10 +1023,10 @@ def __simulate(self, verbose):
                                             parachute_cd_s=parachute.cd_s: setattr(
                                                 self, "parachute_cd_s", parachute_cd_s
                                             ),
-                                            lambda self, parachute_radius=parachute.radius: setattr(
+                                            lambda self, parachute_radius=parachute.parachute_radius: setattr(
                                                 self, "parachute_radius", parachute_radius
                                             ),
-                                            lambda self, parachute_height=parachute.height: setattr(
+                                            lambda self, parachute_height=parachute.parachute_height: setattr(
                                                 self, "parachute_height", parachute_height
                                             ),
                                             lambda self, parachute_porosity=parachute.porosity: setattr(

From 413503fc3a3669df1e03943413e6995c27cff4c8 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Thu, 26 Jun 2025 12:31:44 -0400
Subject: [PATCH 04/22] STY: ruff formatting

---
 rocketpy/simulation/flight.py | 34 +++++++++++++++++++++++-----------
 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/rocketpy/simulation/flight.py b/rocketpy/simulation/flight.py
index 0e0bc597c..c78c961bd 100644
--- a/rocketpy/simulation/flight.py
+++ b/rocketpy/simulation/flight.py
@@ -768,10 +768,12 @@ def __simulate(self, verbose):
                             lambda self, parachute_cd_s=parachute.cd_s: setattr(
                                 self, "parachute_cd_s", parachute_cd_s
                             ),
-                            lambda self, parachute_radius=parachute.parachute_radius: setattr(
+                            lambda self,
+                            parachute_radius=parachute.parachute_radius: setattr(
                                 self, "parachute_radius", parachute_radius
                             ),
-                            lambda self, parachute_height=parachute.parachute_height: setattr(
+                            lambda self,
+                            parachute_height=parachute.parachute_height: setattr(
                                 self, "parachute_height", parachute_height
                             ),
                             lambda self, parachute_porosity=parachute.porosity: setattr(
@@ -1023,14 +1025,23 @@ def __simulate(self, verbose):
                                             parachute_cd_s=parachute.cd_s: setattr(
                                                 self, "parachute_cd_s", parachute_cd_s
                                             ),
-                                            lambda self, parachute_radius=parachute.parachute_radius: setattr(
-                                                self, "parachute_radius", parachute_radius
+                                            lambda self,
+                                            parachute_radius=parachute.parachute_radius: setattr(
+                                                self,
+                                                "parachute_radius",
+                                                parachute_radius,
                                             ),
-                                            lambda self, parachute_height=parachute.parachute_height: setattr(
-                                                self, "parachute_height", parachute_height
+                                            lambda self,
+                                            parachute_height=parachute.parachute_height: setattr(
+                                                self,
+                                                "parachute_height",
+                                                parachute_height,
                                             ),
-                                            lambda self, parachute_porosity=parachute.porosity: setattr(
-                                                self, "parachute_porosity", parachute_porosity
+                                            lambda self,
+                                            parachute_porosity=parachute.porosity: setattr(
+                                                self,
+                                                "parachute_porosity",
+                                                parachute_porosity,
                                             ),
                                         ]
                                         self.flight_phases.add_phase(
@@ -1983,12 +1994,13 @@ def u_dot_parachute(self, t, u, post_processing=False):
         parachute_height = self.parachute_height
         porosity = self.parachute_porosity
 
-
         # Get the mass of the rocket
         mp = self.rocket.dry_mass
 
         # Define constants
-        ka = 1.068 * (1 - 1.465 * porosity - 0.25975 * porosity**2 + 1.2626 * porosity**3)
+        ka = 1.068 * (
+            1 - 1.465 * porosity - 0.25975 * porosity**2 + 1.2626 * porosity**3
+        )
         # to = 1.2
         # eta = 1
         # Rdot = (6 * R * (1 - eta) / (1.2**6)) * (
@@ -2010,7 +2022,7 @@ def u_dot_parachute(self, t, u, post_processing=False):
         # Determine drag force
         pseudo_drag = -0.5 * rho * cd_s * free_stream_speed
         # pseudo_drag = pseudo_drag - ka * rho * 4 * np.pi * (R**2) * Rdot
-        Dx = pseudo_drag * freestream_x # add eta efficiency for wake
+        Dx = pseudo_drag * freestream_x  # add eta efficiency for wake
         Dy = pseudo_drag * freestream_y
         Dz = pseudo_drag * freestream_z
         ax = Dx / (mp + ma)

From f09a4b0fa8bffad56e4f5cd1be322fee06850155 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Mon, 30 Jun 2025 15:45:55 -0400
Subject: [PATCH 05/22] TST: updated test value due to gravity update in
 u_dot_parachute

---
 tests/unit/test_flight.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/unit/test_flight.py b/tests/unit/test_flight.py
index 260a2b138..a2cc1012a 100644
--- a/tests/unit/test_flight.py
+++ b/tests/unit/test_flight.py
@@ -252,7 +252,7 @@ def test_aerodynamic_moments(flight_calisto_custom_wind, flight_time, expected_v
         ("t_initial", (1.654150, 0.659142, -0.067103)),
         ("out_of_rail_time", (5.052628, 2.013361, -1.75370)),
         ("apogee_time", (2.339424, -1.648934, -0.938867)),
-        ("t_final", (0, 0, 159.2210)),
+        ("t_final", (0, 0, 159.0800)),
     ],
 )
 def test_aerodynamic_forces(flight_calisto_custom_wind, flight_time, expected_values):

From 78ef92e76c00210c64660a6b3b90d231520d0d65 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Tue, 1 Jul 2025 11:07:29 -0400
Subject: [PATCH 06/22] ENH: added new parameters into add_parachute method in
 Rocket class

---
 rocketpy/rocket/parachute.py | 26 ++++++++++++++++---------
 rocketpy/rocket/rocket.py    | 37 ++++++++++++++++++++++++++++++++----
 2 files changed, 50 insertions(+), 13 deletions(-)

diff --git a/rocketpy/rocket/parachute.py b/rocketpy/rocket/parachute.py
index a1f96f912..7d5212c61 100644
--- a/rocketpy/rocket/parachute.py
+++ b/rocketpy/rocket/parachute.py
@@ -92,6 +92,13 @@ class Parachute:
         Function of noisy_pressure_signal.
     Parachute.clean_pressure_signal_function : Function
         Function of clean_pressure_signal.
+    Parachute.parachute_radius : float
+        Radius of the inflated parachute in meters.
+    Parachute.parachute_height : float
+        Height of the inflated parachute in meters.
+    Parachute.porosity : float
+        Porosity of the parachute material, which is a measure of how much air can
+        pass through the parachute material.
     """
 
     def __init__(
@@ -158,14 +165,15 @@ def __init__(
             passed to the trigger function. Default value is ``(0, 0, 0)``.
             Units are in Pa.
         parachute_radius : float, optional
-            Radius of the inflated parachute in meters. Default value is 1.5.
+            Radius of the inflated parachute. Default value is 1.5.
             Units are in meters.
         parachute_height : float, optional
-            Height of the inflated parachute in meters.
-            Default value is the radius parachute. Units are in meters.
+            Height of the inflated parachute. Default value is the radius parachute.
+            Units are in meters.
         porosity : float, optional
             Porosity of the parachute material, which is a measure of how much air can
-            pass through the parachute material. Default value is 0.0432.
+            pass through the parachute material.
+            Default value is 0.0432 (for consistency with previous versions).
         """
         self.name = name
         self.cd_s = cd_s
@@ -173,11 +181,6 @@ def __init__(
         self.sampling_rate = sampling_rate
         self.lag = lag
         self.noise = noise
-        self.parachute_radius = parachute_radius
-        if parachute_height is None:
-            parachute_height = parachute_radius
-        self.parachute_height = parachute_height
-        self.porosity = porosity
         self.noise_signal = [[-1e-6, np.random.normal(noise[0], noise[1])]]
         self.noisy_pressure_signal = []
         self.clean_pressure_signal = []
@@ -187,6 +190,11 @@ def __init__(
         self.clean_pressure_signal_function = Function(0)
         self.noisy_pressure_signal_function = Function(0)
         self.noise_signal_function = Function(0)
+        self.parachute_radius = parachute_radius
+        if parachute_height is None:
+            parachute_height = parachute_radius
+        self.parachute_height = parachute_height
+        self.porosity = porosity
 
         alpha, beta = self.noise_corr
         self.noise_function = lambda: alpha * self.noise_signal[-1][
diff --git a/rocketpy/rocket/rocket.py b/rocketpy/rocket/rocket.py
index bf938d4be..c0f91b744 100644
--- a/rocketpy/rocket/rocket.py
+++ b/rocketpy/rocket/rocket.py
@@ -1434,7 +1434,16 @@ def add_free_form_fins(
         return fin_set
 
     def add_parachute(
-        self, name, cd_s, trigger, sampling_rate=100, lag=0, noise=(0, 0, 0)
+        self,
+        name,
+        cd_s,
+        trigger,
+        sampling_rate=100,
+        lag=0,
+        noise=(0, 0, 0),
+        parachute_radius=1.5,
+        parachute_height=None,
+        porosity=0.0432,
     ):
         """Creates a new parachute, storing its parameters such as
         opening delay, drag coefficients and trigger function.
@@ -1493,16 +1502,36 @@ def add_parachute(
             The values are used to add noise to the pressure signal which is
             passed to the trigger function. Default value is (0, 0, 0). Units
             are in pascal.
+        parachute_radius : float, optional
+            Radius of the inflated parachute. Default value is 1.5.
+            Units are in meters.
+        parachute_height : float, optional
+            Height of the inflated parachute. Default value is the radius parachute.
+            Units are in meters.
+        porosity : float, optional
+            Porosity of the parachute material, which is a measure of how much air can
+            pass through the parachute material.
+            Default value is 0.0432 (for consistency with previous versions).
 
         Returns
         -------
         parachute : Parachute
-            Parachute  containing trigger, sampling_rate, lag, cd_s, noise
-            and name. Furthermore, it stores clean_pressure_signal,
+            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 = Parachute(name, cd_s, trigger, sampling_rate, lag, noise)
+        parachute = Parachute(
+            name,
+            cd_s,
+            trigger,
+            sampling_rate,
+            lag,
+            noise,
+            parachute_radius,
+            parachute_height,
+            porosity,
+        )
         self.parachutes.append(parachute)
         return self.parachutes[-1]
 

From 7defc38ceabb689e886d1acbba07d85571e5caaf Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Thu, 3 Jul 2025 10:35:18 -0400
Subject: [PATCH 07/22] DOC: added new parameters to the documentation

---
 README.md                         | 6 ++++++
 docs/user/first_simulation.rst    | 6 ++++++
 docs/user/rocket/rocket_usage.rst | 6 ++++++
 3 files changed, 18 insertions(+)

diff --git a/README.md b/README.md
index 15127e966..52f5985bd 100644
--- a/README.md
+++ b/README.md
@@ -261,6 +261,9 @@ main = calisto.add_parachute(
     sampling_rate=105,
     lag=1.5,
     noise=(0, 8.3, 0.5),
+    parachute_radius=1.5,
+    parachute_height=1.5,
+    porosity=0.0432,
 )
 
 drogue = calisto.add_parachute(
@@ -270,6 +273,9 @@ drogue = calisto.add_parachute(
     sampling_rate=105,
     lag=1.5,
     noise=(0, 8.3, 0.5),
+    parachute_radius=1.5,
+    parachute_height=1.5,
+    porosity=0.0432,
 )
 ```
 
diff --git a/docs/user/first_simulation.rst b/docs/user/first_simulation.rst
index 5624ed926..e3ff65724 100644
--- a/docs/user/first_simulation.rst
+++ b/docs/user/first_simulation.rst
@@ -276,6 +276,9 @@ Finally, we can add any number of Parachutes to the ``Rocket`` object.
         sampling_rate=105,
         lag=1.5,
         noise=(0, 8.3, 0.5),
+        parachute_radius=1.5,
+        parachute_height=1.5,
+        porosity=0.0432,
     )
 
     drogue = calisto.add_parachute(
@@ -285,6 +288,9 @@ Finally, we can add any number of Parachutes to the ``Rocket`` object.
         sampling_rate=105,
         lag=1.5,
         noise=(0, 8.3, 0.5),
+        parachute_radius=1.5,
+        parachute_height=1.5,
+        porosity=0.0432,
     )
 
 We can then see if the rocket is stable by plotting the static margin:
diff --git a/docs/user/rocket/rocket_usage.rst b/docs/user/rocket/rocket_usage.rst
index 1b4d2bbd5..349471463 100644
--- a/docs/user/rocket/rocket_usage.rst
+++ b/docs/user/rocket/rocket_usage.rst
@@ -302,6 +302,9 @@ apogee and another that will be deployed at 800 meters above ground level:
         sampling_rate=105,
         lag=1.5,
         noise=(0, 8.3, 0.5),
+        parachute_radius=1.5,
+        parachute_height=1.5,
+        porosity=0.0432,
     )
 
     drogue = calisto.add_parachute(
@@ -311,6 +314,9 @@ apogee and another that will be deployed at 800 meters above ground level:
         sampling_rate=105,
         lag=1.5,
         noise=(0, 8.3, 0.5),
+        parachute_radius=1.5,
+        parachute_height=1.5,
+        porosity=0.0432,
     )
 
 .. seealso::

From c5ce166fa42aaf69a0daf3fb4f3bcb2dcc3bee14 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Tue, 15 Jul 2025 07:41:02 -0400
Subject: [PATCH 08/22] TST: updated test values to match the right gravity
 model

---
 tests/unit/test_flight.py    | 2 +-
 tests/unit/test_utilities.py | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/unit/test_flight.py b/tests/unit/test_flight.py
index 04bd97c40..31e27de42 100644
--- a/tests/unit/test_flight.py
+++ b/tests/unit/test_flight.py
@@ -252,7 +252,7 @@ def test_aerodynamic_moments(flight_calisto_custom_wind, flight_time, expected_v
         ("t_initial", (1.654150, 0.659142, -0.067103)),
         ("out_of_rail_time", (5.052628, 2.013361, -1.75370)),
         ("apogee_time", (2.321838, -1.613641, -0.962108)),
-        ("t_final", (-0.025792, 0.012030, 159.202481)),
+        ("t_final", (-0.025792, 0.012030, 159.061515)),
     ],
 )
 def test_aerodynamic_forces(flight_calisto_custom_wind, flight_time, expected_values):
diff --git a/tests/unit/test_utilities.py b/tests/unit/test_utilities.py
index 55d45de95..2bb8608b5 100644
--- a/tests/unit/test_utilities.py
+++ b/tests/unit/test_utilities.py
@@ -114,7 +114,7 @@ def test_fin_flutter_analysis(flight_calisto_custom_wind):
     assert np.isclose(flutter_mach(np.inf), 1.0048188594647927, atol=5e-3)
     assert np.isclose(safety_factor(0), 64.78797, atol=5e-3)
     assert np.isclose(safety_factor(10), 2.1948620401502072, atol=5e-3)
-    assert np.isclose(safety_factor(np.inf), 61.64222220697017, atol=5e-3)
+    assert np.isclose(safety_factor(np.inf), 61.669562809629035, atol=5e-3)
 
 
 def test_flutter_prints(flight_calisto_custom_wind):

From f84459d7e78ca081f9dcd205d4674c359a7fb12f Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Tue, 15 Jul 2025 07:49:17 -0400
Subject: [PATCH 09/22] DOC: improved descriptions of the new parameters

---
 rocketpy/rocket/parachute.py | 23 +++++++++++++----------
 rocketpy/rocket/rocket.py    | 11 ++++++-----
 2 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/rocketpy/rocket/parachute.py b/rocketpy/rocket/parachute.py
index 7d5212c61..90c457393 100644
--- a/rocketpy/rocket/parachute.py
+++ b/rocketpy/rocket/parachute.py
@@ -9,7 +9,7 @@
 
 
 class Parachute:
-    """Keeps parachute information.
+    """Keeps information of the parachute, which is modeled as a hemispheroid.
 
     Attributes
     ----------
@@ -93,12 +93,14 @@ class Parachute:
     Parachute.clean_pressure_signal_function : Function
         Function of clean_pressure_signal.
     Parachute.parachute_radius : float
-        Radius of the inflated parachute in meters.
+        Length of the non-unique semi-axis (radius) of the inflated hemispheroid
+        parachute in meters.
     Parachute.parachute_height : float
-        Height of the inflated parachute in meters.
+        Length of the unique semi-axis (height) of the inflated hemispheroid
+        parachute in meters.
     Parachute.porosity : float
-        Porosity of the parachute material, which is a measure of how much air can
-        pass through the parachute material.
+        Porosity of the parachute is the ratio of open space in the canopy to total
+        canopy area.
     """
 
     def __init__(
@@ -165,15 +167,16 @@ def __init__(
             passed to the trigger function. Default value is ``(0, 0, 0)``.
             Units are in Pa.
         parachute_radius : float, optional
-            Radius of the inflated parachute. Default value is 1.5.
+            Length of the non-unique semi-axis (radius) of the inflated hemispheroid
+            parachute. Default value is 1.5.
             Units are in meters.
         parachute_height : float, optional
-            Height of the inflated parachute. Default value is the radius parachute.
+            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
-            Porosity of the parachute material, which is a measure of how much air can
-            pass through the parachute material.
-            Default value is 0.0432 (for consistency with previous versions).
+            Porosity of the parachute is the ratio of open space in the canopy to total
+            canopy area. Default value is 0.0432 (for consistency with previous versions).
         """
         self.name = name
         self.cd_s = cd_s
diff --git a/rocketpy/rocket/rocket.py b/rocketpy/rocket/rocket.py
index 3b3b5655a..0324250c1 100644
--- a/rocketpy/rocket/rocket.py
+++ b/rocketpy/rocket/rocket.py
@@ -1502,15 +1502,16 @@ def add_parachute(
             passed to the trigger function. Default value is (0, 0, 0). Units
             are in pascal.
         parachute_radius : float, optional
-            Radius of the inflated parachute. Default value is 1.5.
+            Length of the non-unique semi-axis (radius) of the inflated hemispheroid
+            parachute. Default value is 1.5.
             Units are in meters.
         parachute_height : float, optional
-            Height of the inflated parachute. Default value is the radius parachute.
+            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
-            Porosity of the parachute material, which is a measure of how much air can
-            pass through the parachute material.
-            Default value is 0.0432 (for consistency with previous versions).
+            Porosity of the parachute is the ratio of open space in the canopy to total
+            canopy area. Default value is 0.0432 (for consistency with previous versions).
 
         Returns
         -------

From 4fcb40692af1e0dcbbf94fb62e6528c583f65e05 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Tue, 12 Aug 2025 09:39:09 -0400
Subject: [PATCH 10/22] ENH: added new parameters to the stochastic parachute

---
 rocketpy/stochastic/stochastic_parachute.py | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/rocketpy/stochastic/stochastic_parachute.py b/rocketpy/stochastic/stochastic_parachute.py
index 4cf7746d7..3cfa80647 100644
--- a/rocketpy/stochastic/stochastic_parachute.py
+++ b/rocketpy/stochastic/stochastic_parachute.py
@@ -39,6 +39,9 @@ def __init__(
         sampling_rate=None,
         lag=None,
         noise=None,
+        parachute_radius=None,
+        parachute_height=None,
+        porosity=None,
     ):
         """Initializes the Stochastic Parachute class.
 
@@ -70,6 +73,9 @@ def __init__(
         self.sampling_rate = sampling_rate
         self.lag = lag
         self.noise = noise
+        self.parachute_radius = parachute_radius
+        self.parachute_height = parachute_height
+        self.porosity = porosity
 
         self._validate_trigger(trigger)
         self._validate_noise(noise)
@@ -81,6 +87,9 @@ def __init__(
             lag=lag,
             noise=noise,
             name=None,
+            parachute_radius=parachute_radius,
+            parachute_height=parachute_height,
+            porosity=porosity
         )
 
     def _validate_trigger(self, trigger):

From 159cce8ed02706906e022302cf559c0d425996ac Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Tue, 12 Aug 2025 09:48:46 -0400
Subject: [PATCH 11/22] ENH: implementing previous comments

---
 rocketpy/rocket/parachute.py  |  4 +---
 rocketpy/simulation/flight.py | 12 +++---------
 2 files changed, 4 insertions(+), 12 deletions(-)

diff --git a/rocketpy/rocket/parachute.py b/rocketpy/rocket/parachute.py
index 90c457393..e637f1d51 100644
--- a/rocketpy/rocket/parachute.py
+++ b/rocketpy/rocket/parachute.py
@@ -194,9 +194,7 @@ def __init__(
         self.noisy_pressure_signal_function = Function(0)
         self.noise_signal_function = Function(0)
         self.parachute_radius = parachute_radius
-        if parachute_height is None:
-            parachute_height = parachute_radius
-        self.parachute_height = parachute_height
+        self.parachute_height = parachute_height or parachute_radius
         self.porosity = porosity
 
         alpha, beta = self.noise_corr
diff --git a/rocketpy/simulation/flight.py b/rocketpy/simulation/flight.py
index 036224d94..2606c7b06 100644
--- a/rocketpy/simulation/flight.py
+++ b/rocketpy/simulation/flight.py
@@ -1992,18 +1992,12 @@ def u_dot_parachute(self, t, u, post_processing=False):
         wind_velocity_x = self.env.wind_velocity_x.get_value_opt(z)
         wind_velocity_y = self.env.wind_velocity_y.get_value_opt(z)
 
-        # Get Parachute data
-        cd_s = self.parachute_cd_s
-        parachute_radius = self.parachute_radius
-        parachute_height = self.parachute_height
-        porosity = self.parachute_porosity
-
         # Get the mass of the rocket
         mp = self.rocket.dry_mass
 
         # Define constants
         ka = 1.068 * (
-            1 - 1.465 * porosity - 0.25975 * porosity**2 + 1.2626 * porosity**3
+            1 - 1.465 * self.parachute_porosity - 0.25975 * self.parachute_porosity**2 + 1.2626 * self.parachute_porosity**3
         )
         # to = 1.2
         # eta = 1
@@ -2015,7 +2009,7 @@ def u_dot_parachute(self, t, u, post_processing=False):
         # tf = 8 * nominal diameter / velocity at line stretch
 
         # Calculate added mass
-        ma = ka * rho * (4 / 3) * np.pi * parachute_radius**2 * parachute_height
+        ma = ka * rho * (4 / 3) * np.pi * self.parachute_radius**2 * self.parachute_height
 
         # Calculate freestream speed
         freestream_x = vx - wind_velocity_x
@@ -2024,7 +2018,7 @@ def u_dot_parachute(self, t, u, post_processing=False):
         free_stream_speed = (freestream_x**2 + freestream_y**2 + freestream_z**2) ** 0.5
 
         # Determine drag force
-        pseudo_drag = -0.5 * rho * cd_s * free_stream_speed
+        pseudo_drag = -0.5 * rho * self.parachute_cd_s * free_stream_speed
         # pseudo_drag = pseudo_drag - ka * rho * 4 * np.pi * (R**2) * Rdot
         Dx = pseudo_drag * freestream_x  # add eta efficiency for wake
         Dy = pseudo_drag * freestream_y

From 0c434f8993c08646f0338a6a5926d4c6e0158125 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Tue, 12 Aug 2025 10:04:24 -0400
Subject: [PATCH 12/22] ENH: fixing formatting and adding docs

---
 rocketpy/rocket/parachute.py                |  2 +-
 rocketpy/simulation/flight.py               | 14 ++++++++++++--
 rocketpy/stochastic/stochastic_parachute.py |  8 +++++++-
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/rocketpy/rocket/parachute.py b/rocketpy/rocket/parachute.py
index e637f1d51..3997769cd 100644
--- a/rocketpy/rocket/parachute.py
+++ b/rocketpy/rocket/parachute.py
@@ -95,7 +95,7 @@ class Parachute:
     Parachute.parachute_radius : float
         Length of the non-unique semi-axis (radius) of the inflated hemispheroid
         parachute in meters.
-    Parachute.parachute_height : float
+    Parachute.parachute_height : float, None
         Length of the unique semi-axis (height) of the inflated hemispheroid
         parachute in meters.
     Parachute.porosity : float
diff --git a/rocketpy/simulation/flight.py b/rocketpy/simulation/flight.py
index 2606c7b06..9c8c8cb89 100644
--- a/rocketpy/simulation/flight.py
+++ b/rocketpy/simulation/flight.py
@@ -1997,7 +1997,10 @@ def u_dot_parachute(self, t, u, post_processing=False):
 
         # Define constants
         ka = 1.068 * (
-            1 - 1.465 * self.parachute_porosity - 0.25975 * self.parachute_porosity**2 + 1.2626 * self.parachute_porosity**3
+            1
+            - 1.465 * self.parachute_porosity
+            - 0.25975 * self.parachute_porosity**2
+            + 1.2626 * self.parachute_porosity**3
         )
         # to = 1.2
         # eta = 1
@@ -2009,7 +2012,14 @@ def u_dot_parachute(self, t, u, post_processing=False):
         # tf = 8 * nominal diameter / velocity at line stretch
 
         # Calculate added mass
-        ma = ka * rho * (4 / 3) * np.pi * self.parachute_radius**2 * self.parachute_height
+        ma = (
+            ka
+            * rho
+            * (4 / 3)
+            * np.pi
+            * self.parachute_radius**2
+            * self.parachute_height
+        )
 
         # Calculate freestream speed
         freestream_x = vx - wind_velocity_x
diff --git a/rocketpy/stochastic/stochastic_parachute.py b/rocketpy/stochastic/stochastic_parachute.py
index 3cfa80647..5a74f02ff 100644
--- a/rocketpy/stochastic/stochastic_parachute.py
+++ b/rocketpy/stochastic/stochastic_parachute.py
@@ -66,6 +66,12 @@ def __init__(
         noise : list
             List of tuples in the form of (mean, standard deviation,
             time-correlation).
+        parachute_radius : tuple, list, int, float
+            Radius of the parachute in meters.
+        parachute_height : tuple, list, int, float
+            Height of the parachute in meters.
+        porosity : tuple, list, int, float
+            Porosity of the parachute.
         """
         self.parachute = parachute
         self.cd_s = cd_s
@@ -89,7 +95,7 @@ def __init__(
             name=None,
             parachute_radius=parachute_radius,
             parachute_height=parachute_height,
-            porosity=porosity
+            porosity=porosity,
         )
 
     def _validate_trigger(self, trigger):

From f136ffbaace3000a26a6671fe8c3e325ef2da946 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Tue, 12 Aug 2025 15:23:16 -0400
Subject: [PATCH 13/22] ENH: added ka property to Parachute class

---
 rocketpy/rocket/parachute.py  |  6 ++++++
 rocketpy/simulation/flight.py | 15 +++++++--------
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/rocketpy/rocket/parachute.py b/rocketpy/rocket/parachute.py
index 3997769cd..f4b07a927 100644
--- a/rocketpy/rocket/parachute.py
+++ b/rocketpy/rocket/parachute.py
@@ -196,6 +196,12 @@ def __init__(
         self.parachute_radius = parachute_radius
         self.parachute_height = parachute_height or parachute_radius
         self.porosity = porosity
+        self.ka = 1.068 * (
+            1
+            - 1.465 * self.parachute_porosity
+            - 0.25975 * self.parachute_porosity**2
+            + 1.2626 * self.parachute_porosity**3
+        )
 
         alpha, beta = self.noise_corr
         self.noise_function = lambda: alpha * self.noise_signal[-1][
diff --git a/rocketpy/simulation/flight.py b/rocketpy/simulation/flight.py
index 9c8c8cb89..13dd0eb9e 100644
--- a/rocketpy/simulation/flight.py
+++ b/rocketpy/simulation/flight.py
@@ -777,6 +777,9 @@ def __simulate(self, verbose):
                             lambda self, parachute_porosity=parachute.porosity: setattr(
                                 self, "parachute_porosity", parachute_porosity
                             ),
+                            lambda self, ka=parachute.ka: setattr(
+                                self, "parachute_ka", ka
+                            ),
                         ]
                         self.flight_phases.add_phase(
                             node.t + parachute.lag,
@@ -1041,6 +1044,9 @@ def __simulate(self, verbose):
                                                 "parachute_porosity",
                                                 parachute_porosity,
                                             ),
+                                            lambda self, ka=parachute.ka: setattr(
+                                                self, "parachute_ka", ka
+                                            ),
                                         ]
                                         self.flight_phases.add_phase(
                                             overshootable_node.t + parachute.lag,
@@ -1995,13 +2001,6 @@ def u_dot_parachute(self, t, u, post_processing=False):
         # Get the mass of the rocket
         mp = self.rocket.dry_mass
 
-        # Define constants
-        ka = 1.068 * (
-            1
-            - 1.465 * self.parachute_porosity
-            - 0.25975 * self.parachute_porosity**2
-            + 1.2626 * self.parachute_porosity**3
-        )
         # to = 1.2
         # eta = 1
         # Rdot = (6 * R * (1 - eta) / (1.2**6)) * (
@@ -2013,7 +2012,7 @@ def u_dot_parachute(self, t, u, post_processing=False):
 
         # Calculate added mass
         ma = (
-            ka
+            self.ka
             * rho
             * (4 / 3)
             * np.pi

From 112b75aa5b85a511fc4b7a582ba60afb90f16aa3 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Mon, 18 Aug 2025 16:39:53 -0400
Subject: [PATCH 14/22] ENH: fixing variable name

---
 rocketpy/rocket/parachute.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/rocketpy/rocket/parachute.py b/rocketpy/rocket/parachute.py
index f4b07a927..7c55a7ff2 100644
--- a/rocketpy/rocket/parachute.py
+++ b/rocketpy/rocket/parachute.py
@@ -198,9 +198,9 @@ def __init__(
         self.porosity = porosity
         self.ka = 1.068 * (
             1
-            - 1.465 * self.parachute_porosity
-            - 0.25975 * self.parachute_porosity**2
-            + 1.2626 * self.parachute_porosity**3
+            - 1.465 * self.porosity
+            - 0.25975 * self.porosity**2
+            + 1.2626 * self.porosity**3
         )
 
         alpha, beta = self.noise_corr

From 40d10c5069439032343550f0e9118529d4d86187 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Mon, 18 Aug 2025 17:18:17 -0400
Subject: [PATCH 15/22] ENH: fixed attribute name

---
 rocketpy/simulation/flight.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rocketpy/simulation/flight.py b/rocketpy/simulation/flight.py
index 13dd0eb9e..48fa7c75c 100644
--- a/rocketpy/simulation/flight.py
+++ b/rocketpy/simulation/flight.py
@@ -1045,7 +1045,7 @@ def __simulate(self, verbose):
                                                 parachute_porosity,
                                             ),
                                             lambda self, ka=parachute.ka: setattr(
-                                                self, "parachute_ka", ka
+                                                self, "ka", ka
                                             ),
                                         ]
                                         self.flight_phases.add_phase(

From 1e2a2fdd997b3c9c4c6ec9af009946ca3a3040f6 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Tue, 19 Aug 2025 16:59:41 -0400
Subject: [PATCH 16/22] ENH: simplifying variable names

---
 rocketpy/rocket/parachute.py                | 24 ++++++++++-----------
 rocketpy/rocket/rocket.py                   | 12 +++++------
 rocketpy/simulation/flight.py               |  4 ++--
 rocketpy/stochastic/stochastic_parachute.py | 16 +++++++-------
 4 files changed, 28 insertions(+), 28 deletions(-)

diff --git a/rocketpy/rocket/parachute.py b/rocketpy/rocket/parachute.py
index 7c55a7ff2..b5a8dd729 100644
--- a/rocketpy/rocket/parachute.py
+++ b/rocketpy/rocket/parachute.py
@@ -92,10 +92,10 @@ class Parachute:
         Function of noisy_pressure_signal.
     Parachute.clean_pressure_signal_function : Function
         Function of clean_pressure_signal.
-    Parachute.parachute_radius : float
+    Parachute.radius : float
         Length of the non-unique semi-axis (radius) of the inflated hemispheroid
         parachute in meters.
-    Parachute.parachute_height : float, None
+    Parachute.height : float, None
         Length of the unique semi-axis (height) of the inflated hemispheroid
         parachute in meters.
     Parachute.porosity : float
@@ -111,8 +111,8 @@ def __init__(
         sampling_rate,
         lag=0,
         noise=(0, 0, 0),
-        parachute_radius=1.5,
-        parachute_height=None,
+        radius=1.5,
+        height=None,
         porosity=0.0432,
     ):
         """Initializes Parachute class.
@@ -166,11 +166,11 @@ def __init__(
             The values are used to add noise to the pressure signal which is
             passed to the trigger function. Default value is ``(0, 0, 0)``.
             Units are in Pa.
-        parachute_radius : float, optional
+        radius : float, optional
             Length of the non-unique semi-axis (radius) of the inflated hemispheroid
             parachute. Default value is 1.5.
             Units are in meters.
-        parachute_height : float, optional
+        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.
@@ -193,8 +193,8 @@ def __init__(
         self.clean_pressure_signal_function = Function(0)
         self.noisy_pressure_signal_function = Function(0)
         self.noise_signal_function = Function(0)
-        self.parachute_radius = parachute_radius
-        self.parachute_height = parachute_height or parachute_radius
+        self.radius = radius
+        self.height = height or radius
         self.porosity = porosity
         self.ka = 1.068 * (
             1
@@ -296,8 +296,8 @@ def to_dict(self, include_outputs=False):
             "sampling_rate": self.sampling_rate,
             "lag": self.lag,
             "noise": self.noise,
-            "parachute_radius": self.parachute_radius,
-            "parachute_height": self.parachute_height,
+            "radius": self.radius,
+            "height": self.height,
             "porosity": self.porosity,
         }
 
@@ -325,8 +325,8 @@ def from_dict(cls, data):
             sampling_rate=data["sampling_rate"],
             lag=data["lag"],
             noise=data["noise"],
-            parachute_radius=data.get("parachute_radius", 1.5),
-            parachute_height=data.get("parachute_height", None),
+            radius=data.get("radius", 1.5),
+            height=data.get("height", None),
             porosity=data.get("porosity", 0.0432),
         )
 
diff --git a/rocketpy/rocket/rocket.py b/rocketpy/rocket/rocket.py
index 0324250c1..752d33896 100644
--- a/rocketpy/rocket/rocket.py
+++ b/rocketpy/rocket/rocket.py
@@ -1440,8 +1440,8 @@ def add_parachute(
         sampling_rate=100,
         lag=0,
         noise=(0, 0, 0),
-        parachute_radius=1.5,
-        parachute_height=None,
+        radius=1.5,
+        height=None,
         porosity=0.0432,
     ):
         """Creates a new parachute, storing its parameters such as
@@ -1501,11 +1501,11 @@ def add_parachute(
             The values are used to add noise to the pressure signal which is
             passed to the trigger function. Default value is (0, 0, 0). Units
             are in pascal.
-        parachute_radius : float, optional
+        radius : float, optional
             Length of the non-unique semi-axis (radius) of the inflated hemispheroid
             parachute. Default value is 1.5.
             Units are in meters.
-        parachute_height : float, optional
+        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.
@@ -1528,8 +1528,8 @@ def add_parachute(
             sampling_rate,
             lag,
             noise,
-            parachute_radius,
-            parachute_height,
+            radius,
+            height,
             porosity,
         )
         self.parachutes.append(parachute)
diff --git a/rocketpy/simulation/flight.py b/rocketpy/simulation/flight.py
index 48fa7c75c..57e8a3b72 100644
--- a/rocketpy/simulation/flight.py
+++ b/rocketpy/simulation/flight.py
@@ -1027,13 +1027,13 @@ def __simulate(self, verbose):
                                                 self, "parachute_cd_s", parachute_cd_s
                                             ),
                                             lambda self,
-                                            parachute_radius=parachute.parachute_radius: setattr(
+                                            parachute_radius=parachute.radius: setattr(
                                                 self,
                                                 "parachute_radius",
                                                 parachute_radius,
                                             ),
                                             lambda self,
-                                            parachute_height=parachute.parachute_height: setattr(
+                                            parachute_height=parachute.height: setattr(
                                                 self,
                                                 "parachute_height",
                                                 parachute_height,
diff --git a/rocketpy/stochastic/stochastic_parachute.py b/rocketpy/stochastic/stochastic_parachute.py
index 5a74f02ff..8fc0a82bf 100644
--- a/rocketpy/stochastic/stochastic_parachute.py
+++ b/rocketpy/stochastic/stochastic_parachute.py
@@ -39,8 +39,8 @@ def __init__(
         sampling_rate=None,
         lag=None,
         noise=None,
-        parachute_radius=None,
-        parachute_height=None,
+        radius=None,
+        height=None,
         porosity=None,
     ):
         """Initializes the Stochastic Parachute class.
@@ -66,9 +66,9 @@ def __init__(
         noise : list
             List of tuples in the form of (mean, standard deviation,
             time-correlation).
-        parachute_radius : tuple, list, int, float
+        radius : tuple, list, int, float
             Radius of the parachute in meters.
-        parachute_height : tuple, list, int, float
+        height : tuple, list, int, float
             Height of the parachute in meters.
         porosity : tuple, list, int, float
             Porosity of the parachute.
@@ -79,8 +79,8 @@ def __init__(
         self.sampling_rate = sampling_rate
         self.lag = lag
         self.noise = noise
-        self.parachute_radius = parachute_radius
-        self.parachute_height = parachute_height
+        self.radius = radius
+        self.height = height
         self.porosity = porosity
 
         self._validate_trigger(trigger)
@@ -93,8 +93,8 @@ def __init__(
             lag=lag,
             noise=noise,
             name=None,
-            parachute_radius=parachute_radius,
-            parachute_height=parachute_height,
+            radius=radius,
+            height=height,
             porosity=porosity,
         )
 

From 65530fd175f5e95b7bdfa306a011d15d52cf3ed1 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Tue, 19 Aug 2025 17:01:43 -0400
Subject: [PATCH 17/22] DOC: adding parameters documentation into
 StochasticParachute description

---
 rocketpy/stochastic/stochastic_parachute.py | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/rocketpy/stochastic/stochastic_parachute.py b/rocketpy/stochastic/stochastic_parachute.py
index 8fc0a82bf..dea8a077d 100644
--- a/rocketpy/stochastic/stochastic_parachute.py
+++ b/rocketpy/stochastic/stochastic_parachute.py
@@ -29,6 +29,12 @@ class StochasticParachute(StochasticModel):
         time-correlation).
     name : list[str]
         List with the name of the parachute object. This cannot be randomized.
+    radius : tuple, list, int, float
+        Radius of the parachute in meters.
+    height : tuple, list, int, float
+        Height of the parachute in meters.
+    porosity : tuple, list, int, float
+        Porosity of the parachute.
     """
 
     def __init__(

From 363bfc80a022fda377fff2d292483174f001990e Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Fri, 5 Sep 2025 09:18:32 -0400
Subject: [PATCH 18/22] ENH: changing ma calculation and porosity documentation
 from previous comments

---
 rocketpy/rocket/parachute.py  | 12 ++++++++----
 rocketpy/rocket/rocket.py     |  6 ++++--
 rocketpy/simulation/flight.py |  2 +-
 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/rocketpy/rocket/parachute.py b/rocketpy/rocket/parachute.py
index b5a8dd729..cdf943901 100644
--- a/rocketpy/rocket/parachute.py
+++ b/rocketpy/rocket/parachute.py
@@ -99,8 +99,10 @@ class Parachute:
         Length of the unique semi-axis (height) of the inflated hemispheroid
         parachute in meters.
     Parachute.porosity : float
-        Porosity of the parachute is the ratio of open space in the canopy to total
-        canopy area.
+        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).
     """
 
     def __init__(
@@ -175,8 +177,10 @@ def __init__(
             parachute. Default value is the radius of the parachute.
             Units are in meters.
         porosity : float, optional
-            Porosity of the parachute is the ratio of open space in the canopy to total
-            canopy area. Default value is 0.0432 (for consistency with previous versions).
+            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).
         """
         self.name = name
         self.cd_s = cd_s
diff --git a/rocketpy/rocket/rocket.py b/rocketpy/rocket/rocket.py
index 752d33896..c421f6abc 100644
--- a/rocketpy/rocket/rocket.py
+++ b/rocketpy/rocket/rocket.py
@@ -1510,8 +1510,10 @@ def add_parachute(
             parachute. Default value is the radius of the parachute.
             Units are in meters.
         porosity : float, optional
-            Porosity of the parachute is the ratio of open space in the canopy to total
-            canopy area. Default value is 0.0432 (for consistency with previous versions).
+            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).
 
         Returns
         -------
diff --git a/rocketpy/simulation/flight.py b/rocketpy/simulation/flight.py
index 57e8a3b72..040287ed1 100644
--- a/rocketpy/simulation/flight.py
+++ b/rocketpy/simulation/flight.py
@@ -2014,7 +2014,7 @@ def u_dot_parachute(self, t, u, post_processing=False):
         ma = (
             self.ka
             * rho
-            * (4 / 3)
+            * (2 / 3)
             * np.pi
             * self.parachute_radius**2
             * self.parachute_height

From 53b09401f11c0027766847df568aa9318caeb451 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Fri, 5 Sep 2025 15:49:13 -0400
Subject: [PATCH 19/22] TST: updated test value due to change in ma calculation

---
 tests/unit/test_flight.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/unit/test_flight.py b/tests/unit/test_flight.py
index 31e27de42..1bd9384e2 100644
--- a/tests/unit/test_flight.py
+++ b/tests/unit/test_flight.py
@@ -252,7 +252,7 @@ def test_aerodynamic_moments(flight_calisto_custom_wind, flight_time, expected_v
         ("t_initial", (1.654150, 0.659142, -0.067103)),
         ("out_of_rail_time", (5.052628, 2.013361, -1.75370)),
         ("apogee_time", (2.321838, -1.613641, -0.962108)),
-        ("t_final", (-0.025792, 0.012030, 159.061515)),
+        ("t_final", (-0.019802, 0.012030, 159.051604)),
     ],
 )
 def test_aerodynamic_forces(flight_calisto_custom_wind, flight_time, expected_values):

From 87216caf5eb8686a8ff2715330bac8a9d3a259f7 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Fri, 12 Sep 2025 11:13:19 -0400
Subject: [PATCH 20/22] ENH: changing parameter ka to added_mass_coefficient

---
 rocketpy/rocket/parachute.py  | 5 ++++-
 rocketpy/simulation/flight.py | 7 ++++---
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/rocketpy/rocket/parachute.py b/rocketpy/rocket/parachute.py
index cdf943901..732f16e1f 100644
--- a/rocketpy/rocket/parachute.py
+++ b/rocketpy/rocket/parachute.py
@@ -103,6 +103,9 @@ class Parachute:
         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).
+    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.
     """
 
     def __init__(
@@ -200,7 +203,7 @@ def __init__(
         self.radius = radius
         self.height = height or radius
         self.porosity = porosity
-        self.ka = 1.068 * (
+        self.added_mass_coefficient = 1.068 * (
             1
             - 1.465 * self.porosity
             - 0.25975 * self.porosity**2
diff --git a/rocketpy/simulation/flight.py b/rocketpy/simulation/flight.py
index 040287ed1..d8b69e84a 100644
--- a/rocketpy/simulation/flight.py
+++ b/rocketpy/simulation/flight.py
@@ -777,7 +777,7 @@ def __simulate(self, verbose):
                             lambda self, parachute_porosity=parachute.porosity: setattr(
                                 self, "parachute_porosity", parachute_porosity
                             ),
-                            lambda self, ka=parachute.ka: setattr(
+                            lambda self, ka=parachute.added_mass_coefficient: setattr(
                                 self, "parachute_ka", ka
                             ),
                         ]
@@ -1044,7 +1044,8 @@ def __simulate(self, verbose):
                                                 "parachute_porosity",
                                                 parachute_porosity,
                                             ),
-                                            lambda self, ka=parachute.ka: setattr(
+                                            lambda self,
+                                            ka=parachute.added_mass_coefficient: setattr(
                                                 self, "ka", ka
                                             ),
                                         ]
@@ -2012,7 +2013,7 @@ def u_dot_parachute(self, t, u, post_processing=False):
 
         # Calculate added mass
         ma = (
-            self.ka
+            self.added_mass_coefficient
             * rho
             * (2 / 3)
             * np.pi

From 4f20568f6579aee6195178e59c81db0724bf20b6 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Fri, 12 Sep 2025 11:17:05 -0400
Subject: [PATCH 21/22] DOC: updating the CHANGELOG

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f78b34edb..f3393aeb5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -33,6 +33,7 @@ Attention: The newest changes should be on top -->
 ### Added
 
 -  ENH: Add the Coriolis Force to the Flight class [#799](https://github.com/RocketPy-Team/RocketPy/pull/799)
+-  ENH: Improve parachute geometric parametrization [#835](https://github.com/RocketPy-Team/RocketPy/pull/835)
 
 ### Changed
 

From 9a03c01cd305b68f46f1a308955448304d564ce2 Mon Sep 17 00:00:00 2001
From: ArthurJWH <arthurjwhwang@gmail.com>
Date: Fri, 12 Sep 2025 13:23:31 -0400
Subject: [PATCH 22/22] ENH: properly substituted all ka parameters for
 added_mass_coefficient

---
 rocketpy/simulation/flight.py | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/rocketpy/simulation/flight.py b/rocketpy/simulation/flight.py
index d8b69e84a..11e737b5a 100644
--- a/rocketpy/simulation/flight.py
+++ b/rocketpy/simulation/flight.py
@@ -777,8 +777,11 @@ def __simulate(self, verbose):
                             lambda self, parachute_porosity=parachute.porosity: setattr(
                                 self, "parachute_porosity", parachute_porosity
                             ),
-                            lambda self, ka=parachute.added_mass_coefficient: setattr(
-                                self, "parachute_ka", ka
+                            lambda self,
+                            added_mass_coefficient=parachute.added_mass_coefficient: setattr(
+                                self,
+                                "parachute_added_mass_coefficient",
+                                added_mass_coefficient,
                             ),
                         ]
                         self.flight_phases.add_phase(
@@ -1045,8 +1048,10 @@ def __simulate(self, verbose):
                                                 parachute_porosity,
                                             ),
                                             lambda self,
-                                            ka=parachute.added_mass_coefficient: setattr(
-                                                self, "ka", ka
+                                            added_mass_coefficient=parachute.added_mass_coefficient: setattr(
+                                                self,
+                                                "parachute_added_mass_coefficient",
+                                                added_mass_coefficient,
                                             ),
                                         ]
                                         self.flight_phases.add_phase(
@@ -2013,7 +2018,7 @@ def u_dot_parachute(self, t, u, post_processing=False):
 
         # Calculate added mass
         ma = (
-            self.added_mass_coefficient
+            self.parachute_added_mass_coefficient
             * rho
             * (2 / 3)
             * np.pi