ENH: added ka property to Parachute class

Author: ArthurJWH

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][

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