MNT: improve parallel_axis_theorem_from_com documentation

rocketpy/motors/hybrid_motor.py

@@ -1,4 +1,4 @@
-from rocketpy.tools import parallel_axis_theorem
+from rocketpy.tools import parallel_axis_theorem_from_com
 
 from ..mathutils.function import Function, funcify_method, reset_funcified_methods
 from ..plots.hybrid_motor_plots import _HybridMotorPlots
@@ -468,9 +468,11 @@ def propellant_I_11(self):
         solid_prop_inertia = self.solid.propellant_I_11
         liquid_prop_inertia = self.liquid.propellant_I_11
 
-        I_11 = parallel_axis_theorem(
+        I_11 = parallel_axis_theorem_from_com(
             solid_prop_inertia, solid_mass, solid_cm_to_cm
-        ) + parallel_axis_theorem(liquid_prop_inertia, liquid_mass, liquid_cm_to_cm)
+        ) + parallel_axis_theorem_from_com(
+            liquid_prop_inertia, liquid_mass, liquid_cm_to_cm
+        )
 
         return I_11
 

rocketpy/motors/liquid_motor.py

@@ -7,7 +7,7 @@
     funcify_method,
     reset_funcified_methods,
 )
-from rocketpy.tools import parallel_axis_theorem
+from rocketpy.tools import parallel_axis_theorem_from_com
 
 from ..plots.liquid_motor_plots import _LiquidMotorPlots
 from ..prints.liquid_motor_prints import _LiquidMotorPrints
@@ -390,7 +390,9 @@ def propellant_I_11(self):
             tank = positioned_tank.get("tank")
             tank_position = positioned_tank.get("position")
             distance = tank_position + tank.center_of_mass - center_of_mass
-            I_11 += parallel_axis_theorem(tank.inertia, tank.fluid_mass, distance)
+            I_11 += parallel_axis_theorem_from_com(
+                tank.inertia, tank.fluid_mass, distance
+            )
 
         return I_11
 

rocketpy/motors/motor.py

@@ -7,7 +7,7 @@
 from ..mathutils.function import Function, funcify_method
 from ..plots.motor_plots import _MotorPlots
 from ..prints.motor_prints import _MotorPrints
-from ..tools import parallel_axis_theorem, tuple_handler
+from ..tools import parallel_axis_theorem_from_com, tuple_handler
 
 try:
     from functools import cached_property
@@ -520,8 +520,10 @@ def I_11(self):
         prop_to_cm = self.center_of_propellant_mass - self.center_of_mass
         dry_to_cm = self.center_of_dry_mass_position - self.center_of_mass
 
-        prop_I_11 = parallel_axis_theorem(prop_I_11, self.propellant_mass, prop_to_cm)
-        dry_I_11 = parallel_axis_theorem(dry_I_11, self.dry_mass, dry_to_cm)
+        prop_I_11 = parallel_axis_theorem_from_com(
+            prop_I_11, self.propellant_mass, prop_to_cm
+        )
+        dry_I_11 = parallel_axis_theorem_from_com(dry_I_11, self.dry_mass, dry_to_cm)
 
         return prop_I_11 + dry_I_11
 

rocketpy/rocket/rocket.py

@@ -18,7 +18,7 @@
 )
 from rocketpy.rocket.components import Components
 from rocketpy.rocket.parachute import Parachute
-from rocketpy.tools import parallel_axis_theorem
+from rocketpy.tools import parallel_axis_theorem_from_com
 
 
 class Rocket:
@@ -634,13 +634,17 @@ def evaluate_dry_inertias(self):
         )
 
         # Compute dry inertias
-        self.dry_I_11 = parallel_axis_theorem(
+        self.dry_I_11 = parallel_axis_theorem_from_com(
             self.I_11_without_motor, mass, noMCM_to_CDM
-        ) + parallel_axis_theorem(self.motor.dry_I_11, motor_dry_mass, motorCDM_to_CDM)
+        ) + parallel_axis_theorem_from_com(
+            self.motor.dry_I_11, motor_dry_mass, motorCDM_to_CDM
+        )
 
-        self.dry_I_22 = parallel_axis_theorem(
+        self.dry_I_22 = parallel_axis_theorem_from_com(
             self.I_22_without_motor, mass, noMCM_to_CDM
-        ) + parallel_axis_theorem(self.motor.dry_I_22, motor_dry_mass, motorCDM_to_CDM)
+        ) + parallel_axis_theorem_from_com(
+            self.motor.dry_I_22, motor_dry_mass, motorCDM_to_CDM
+        )
 
         self.dry_I_33 = self.I_33_without_motor + self.motor.dry_I_33
         self.dry_I_12 = self.I_12_without_motor + self.motor.dry_I_12
@@ -698,13 +702,13 @@ def evaluate_inertias(self):
         CM_to_CPM = self.center_of_mass - self.center_of_propellant_position
 
         # Compute inertias
-        self.I_11 = parallel_axis_theorem(
+        self.I_11 = parallel_axis_theorem_from_com(
             self.dry_I_11, dry_mass, CM_to_CDM
-        ) + parallel_axis_theorem(self.motor.I_11, prop_mass, CM_to_CPM)
+        ) + parallel_axis_theorem_from_com(self.motor.I_11, prop_mass, CM_to_CPM)
 
-        self.I_22 = parallel_axis_theorem(
+        self.I_22 = parallel_axis_theorem_from_com(
             self.dry_I_22, dry_mass, CM_to_CDM
-        ) + parallel_axis_theorem(self.motor.I_22, prop_mass, CM_to_CPM)
+        ) + parallel_axis_theorem_from_com(self.motor.I_22, prop_mass, CM_to_CPM)
 
         self.I_33 = self.dry_I_33 + self.motor.I_33
         self.I_12 = self.dry_I_12 + self.motor.I_12

rocketpy/tools.py

@@ -382,25 +382,31 @@ def check_requirement_version(module_name, version):
     return True
 
 
-def parallel_axis_theorem(initial_inertia_moment, mass, distance):
-    """Converts the moment of inertia from one axis to another using the
-    parallel axis theorem. The axes must be parallel to each other.
+def parallel_axis_theorem_from_com(com_inertia_moment, mass, distance):
+    """Calculates the moment of inertia of a object relative to a new axis using
+    the parallel axis theorem. The new axis is parallel to and at a distance
+    'distance' from the original axis, which *must* passes through the object's
+    center of mass.
 
     Parameters
     ----------
-    initial_inertia_moment : float
-        Initial moment of inertia.
+    com_inertia_moment : float
+        Moment of inertia relative to the center of mass of the object.
     mass : float
         Mass of the object.
     distance : float
-        Distance between the two points.
+        Perpendicular distance between the original and new axis.
 
     Returns
     -------
     float
-        New moment of inertia.
+        Moment of inertia relative to the new axis.
+
+    Reference
+    ---------
+    https://en.wikipedia.org/wiki/Parallel_axis_theorem
     """
-    return initial_inertia_moment + mass * distance**2
+    return com_inertia_moment + mass * distance**2
 
 
 # Flight