Merge branch 'develop' into mnt/modularize-rocket-draw

.coveragerc

@@ -0,0 +1,4 @@
+[report]
+exclude_also=
+    ; Don't complain about exceptions or warnings not being covered by tests
+    warnings.warn*

CHANGELOG.md

@@ -38,8 +38,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 
 - MNT: Modularize Rocket Draw [#580](https://github.com/RocketPy-Team/RocketPy/pull/580)
+- DOC: Improvements of Environment docstring phrasing [#565](https://github.com/RocketPy-Team/RocketPy/pull/565)
 - MNT: Refactor flight prints module [#579](https://github.com/RocketPy-Team/RocketPy/pull/579)
 - DOC: Convert CompareFlights example notebooks to .rst files [#576](https://github.com/RocketPy-Team/RocketPy/pull/576)
+- MNT: Refactor inertia calculations using parallel axis theorem [#573] (https://github.com/RocketPy-Team/RocketPy/pull/573)
 - ENH: Optional argument to show the plot in Function.compare_plots [#563](https://github.com/RocketPy-Team/RocketPy/pull/563)
 
 ### Fixed

rocketpy/environment/environment.py

@@ -57,8 +57,7 @@ class Environment:
     Environment.datum : string
         The desired reference ellipsoid model, the following options are
         available: "SAD69", "WGS84", "NAD83", and "SIRGAS2000". The default
-        is "SIRGAS2000", then this model will be used if the user make some
-        typing mistake
+        is "SIRGAS2000".
     Environment.initial_east : float
         Launch site East UTM coordinate
     Environment.initial_north :  float
@@ -74,7 +73,7 @@ class Environment:
         Launch site E/W hemisphere
     Environment.elevation : float
         Launch site elevation.
-    Environment.date : datetime
+    Environment.datetime_date : datetime
         Date time of launch in UTC.
     Environment.local_date : datetime
         Date time of launch in the local time zone, defined by
@@ -276,49 +275,70 @@ def __init__(
         timezone="UTC",
         max_expected_height=80000.0,
     ):
-        """Initialize Environment class, saving launch rail length,
-        launch date, location coordinates and elevation. Note that
-        by default the standard atmosphere is loaded until another
+        """Initializes the Environment class, capturing essential parameters of
+        the launch site, including the launch date, geographical coordinates,
+        and elevation. This class is designed to calculate crucial variables
+        for the Flight simulation, such as atmospheric air pressure, density,
+        and gravitational acceleration.
+
+        Note that the default atmospheric model is the International Standard
+        Atmosphere as defined by ISO 2533 unless specified otherwise in
+        :meth:`Environment.set_atmospheric_model`.
 
         Parameters
         ----------
         gravity : int, float, callable, string, array, optional
             Surface gravitational acceleration. Positive values point the
-            acceleration down. If None, the Somigliana formula is used to
-        date : array, optional
-            Array of length 4, stating (year, month, day, hour (UTC))
-            of rocket launch. Must be given if a Forecast, Reanalysis
+            acceleration down. If None, the Somigliana formula is used.
+            See :meth:`Environment.set_gravity_model` for more information.
+        date : list or tuple, optional
+            List or tuple of length 4, stating (year, month, day, hour) in the
+            time zone of the parameter ``timezone``.
+            Alternatively, can be a ``datetime`` object specifying launch
+            date and time. The dates are stored as follows:
+
+            - :attr:`Environment.local_date`: Local time of launch in
+              the time zone specified by the parameter ``timezone``.
+
+            - :attr:`Environment.datetime_date`: UTC time of launch.
+
+            Must be given if a Forecast, Reanalysis
             or Ensemble, will be set as an atmospheric model.
+            Default is None.
+            See :meth:`Environment.set_date` for more information.
         latitude : float, optional
             Latitude in degrees (ranging from -90 to 90) of rocket
             launch location. Must be given if a Forecast, Reanalysis
             or Ensemble will be used as an atmospheric model or if
-            Open-Elevation will be used to compute elevation.
+            Open-Elevation will be used to compute elevation. Positive
+            values correspond to the North. Default value is 0, which
+            corresponds to the equator.
         longitude : float, optional
-            Longitude in degrees (ranging from -180 to 360) of rocket
+            Longitude in degrees (ranging from -180 to 180) of rocket
             launch location. Must be given if a Forecast, Reanalysis
             or Ensemble will be used as an atmospheric model or if
-            Open-Elevation will be used to compute elevation.
+            Open-Elevation will be used to compute elevation. Positive
+            values correspond to the East. Default value is 0, which
+            corresponds to the Greenwich Meridian.
         elevation : float, optional
             Elevation of launch site measured as height above sea
             level in meters. Alternatively, can be set as
             'Open-Elevation' which uses the Open-Elevation API to
             find elevation data. For this option, latitude and
             longitude must also be specified. Default value is 0.
-        datum : string
+        datum : string, optional
             The desired reference ellipsoidal model, the following options are
             available: "SAD69", "WGS84", "NAD83", and "SIRGAS2000". The default
-            is "SIRGAS2000", then this model will be used if the user make some
-            typing mistake.
+            is "SIRGAS2000".
         timezone : string, optional
             Name of the time zone. To see all time zones, import pytz and run
-            print(pytz.all_timezones). Default time zone is "UTC".
+            ``print(pytz.all_timezones)``. Default time zone is "UTC".
         max_expected_height : float, optional
             Maximum altitude in meters to keep weather data. The altitude must
             be above sea level (ASL). Especially useful for visualization.
             Can be altered as desired by doing `max_expected_height = number`.
             Depending on the atmospheric model, this value may be automatically
-            mofified.
+            modified.
 
         Returns
         -------
@@ -396,15 +416,57 @@ def set_date(self, date, timezone="UTC"):
 
         Parameters
         ----------
-        date : Datetime
-            Datetime object specifying launch date and time.
+        date : list, tuple, datetime
+            List or tuple of length 4, stating (year, month, day, hour) in the
+            time zone of the parameter ``timezone``. See Notes for more
+            information.
+            Alternatively, can be a ``datetime`` object specifying launch
+            date and time.
         timezone : string, optional
             Name of the time zone. To see all time zones, import pytz and run
-            print(pytz.all_timezones). Default time zone is "UTC".
+            ``print(pytz.all_timezones)``. Default time zone is "UTC".
 
         Returns
         -------
         None
+
+        Notes
+        -----
+        - If the ``date`` is given as a list or tuple, it should be in the same
+          time zone as specified by the ``timezone`` parameter. This local
+          time will be available in the attribute :attr:`Environment.local_date`
+          while the UTC time will be available in the attribute
+          :attr:`Environment.datetime_date`.
+
+        - If the ``date`` is given as a ``datetime`` object without a time zone,
+          it will be assumed to be in the same time zone as specified by the
+          ``timezone`` parameter. However, if the ``datetime`` object has a time
+          zone specified in its ``tzinfo`` attribute, the ``timezone``
+          parameter will be ignored.
+
+        Examples
+        --------
+
+        Let's set the launch date as an list:
+
+        >>> date = [2000, 1, 1, 13] # January 1st, 2000 at 13:00 UTC+1
+        >>> env = Environment()
+        >>> env.set_date(date, timezone="Europe/Rome")
+        >>> print(env.datetime_date) # Get UTC time
+        2000-01-01 12:00:00+00:00
+        >>> print(env.local_date)
+        2000-01-01 13:00:00+01:00
+
+        Now let's set the launch date as a ``datetime`` object:
+
+        >>> from datetime import datetime
+        >>> date = datetime(2000, 1, 1, 13, 0, 0)
+        >>> env = Environment()
+        >>> env.set_date(date, timezone="Europe/Rome")
+        >>> print(env.datetime_date) # Get UTC time
+        2000-01-01 12:00:00+00:00
+        >>> print(env.local_date)
+        2000-01-01 13:00:00+01:00
         """
         # Store date and configure time zone
         self.timezone = timezone
@@ -458,23 +520,66 @@ def set_location(self, latitude, longitude):
                 self.atmospheric_model_file, self.atmospheric_model_dict
             )
 
-        # Return None
-
-    def set_gravity_model(self, gravity):
-        """Sets the gravity model to be used in the simulation based on the
-        given user input to the gravity parameter.
+    def set_gravity_model(self, gravity=None):
+        """Defines the gravity model based on the given user input to the
+        gravity parameter. The gravity model is responsible for computing the
+        gravity acceleration at a given height above sea level in meters.
 
         Parameters
         ----------
-        gravity : None or Function source
-            If None, the Somigliana formula is used to compute the gravity
-            acceleration. Otherwise, the user can provide a Function object
-            representing the gravity model.
+        gravity : int, float, callable, string, list, optional
+            The gravitational acceleration in m/s² to be used in the
+            simulation, this value is positive when pointing downwards.
+            The input type can be one of the following:
+
+            - ``int`` or ``float``: The gravity acceleration is set as a\
+              constant function with respect to height;
+
+            - ``callable``: This callable should receive the height above\
+              sea level in meters and return the gravity acceleration;
+
+            - ``list``: The datapoints should be structured as\
+              ``[(h_i,g_i), ...]`` where ``h_i`` is the height above sea\
+              level in meters and ``g_i`` is the gravity acceleration in m/s²;
+
+            - ``string``: The string should correspond to a path to a CSV file\
+              containing the gravity acceleration data;
+
+            - ``None``: The Somigliana formula is used to compute the gravity\
+              acceleration.
+
+            This parameter is used as a :class:`Function` object source, check\
+            out the available input types for a more detailed explanation.
 
         Returns
         -------
         Function
             Function object representing the gravity model.
+
+        Notes
+        -----
+        This method **does not** set the gravity acceleration, it only returns
+        a :class:`Function` object representing the gravity model.
+
+        Examples
+        --------
+        Let's prepare a `Environment` object with a constant gravity
+        acceleration:
+
+        >>> g_0 = 9.80665
+        >>> env_cte_g = Environment(gravity=g_0)
+        >>> env_cte_g.gravity([0, 100, 1000])
+        [9.80665, 9.80665, 9.80665]
+
+        It's also possible to variate the gravity acceleration by defining
+        its function of height:
+
+        >>> R_t = 6371000
+        >>> g_func = lambda h : g_0 * (R_t / (R_t + h))**2
+        >>> env_var_g = Environment(gravity=g_func)
+        >>> g = env_var_g.gravity(1000)
+        >>> print(f"{g:.6f}")
+        9.803572
         """
         if gravity is None:
             return self.somigliana_gravity.set_discrete(
@@ -500,7 +605,7 @@ def max_expected_height(self, value):
 
     @funcify_method("height (m)", "gravity (m/s²)")
     def somigliana_gravity(self, height):
-        """Computes the gravity acceleration with the Somigliana formula.
+        """Computes the gravity acceleration with the Somigliana formula [1]_.
         An height correction is applied to the normal gravity that is
         accurate for heights used in aviation. The formula is based on the
         WGS84 ellipsoid, but is accurate for other reference ellipsoids.
@@ -514,6 +619,10 @@ def somigliana_gravity(self, height):
         -------
         Function
             Function object representing the gravity model.
+
+        References
+        ----------
+        .. [1] https://en.wikipedia.org/wiki/Theoretical_gravity#Somigliana_equation
         """
         a = 6378137.0  # semi_major_axis
         f = 1 / 298.257223563  # flattening_factor

rocketpy/environment/environment_analysis.py

@@ -441,7 +441,7 @@ def __localize_input_dates(self):
 
     def __find_preferred_timezone(self):
         if self.preferred_timezone is None:
-            # Use local timezone based on lat lon pair
+            # Use local time zone based on lat lon pair
             try:
                 timezonefinder = import_optional_dependency("timezonefinder")
                 tf = timezonefinder.TimezoneFinder()

rocketpy/motors/hybrid_motor.py

@@ -1,3 +1,5 @@
+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
 from ..prints.hybrid_motor_prints import _HybridMotorPrints
@@ -455,22 +457,21 @@ def propellant_I_11(self):
         ----------
         .. [1] https://en.wikipedia.org/wiki/Moment_of_inertia#Inertia_tensor
         """
-        solid_correction = (
-            self.solid.propellant_mass
-            * (self.solid.center_of_propellant_mass - self.center_of_propellant_mass)
-            ** 2
-        )
-        liquid_correction = (
-            self.liquid.propellant_mass
-            * (self.liquid.center_of_propellant_mass - self.center_of_propellant_mass)
-            ** 2
-        )
 
-        I_11 = (
-            self.solid.propellant_I_11
-            + solid_correction
-            + self.liquid.propellant_I_11
-            + liquid_correction
+        solid_mass = self.solid.propellant_mass
+        liquid_mass = self.liquid.propellant_mass
+
+        cm = self.center_of_propellant_mass
+        solid_cm_to_cm = self.solid.center_of_propellant_mass - cm
+        liquid_cm_to_cm = self.liquid.center_of_propellant_mass - cm
+
+        solid_prop_inertia = self.solid.propellant_I_11
+        liquid_prop_inertia = self.liquid.propellant_I_11
+
+        I_11 = parallel_axis_theorem_from_com(
+            solid_prop_inertia, solid_mass, solid_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

@@ -7,6 +7,7 @@
     funcify_method,
     reset_funcified_methods,
 )
+from rocketpy.tools import parallel_axis_theorem_from_com
 
 from ..plots.liquid_motor_plots import _LiquidMotorPlots
 from ..prints.liquid_motor_prints import _LiquidMotorPrints
@@ -388,10 +389,9 @@ def propellant_I_11(self):
         for positioned_tank in self.positioned_tanks:
             tank = positioned_tank.get("tank")
             tank_position = positioned_tank.get("position")
-            I_11 += (
-                tank.inertia
-                + tank.fluid_mass
-                * (tank_position + tank.center_of_mass - center_of_mass) ** 2
+            distance = tank_position + tank.center_of_mass - center_of_mass
+            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 tuple_handler
+from ..tools import parallel_axis_theorem_from_com, tuple_handler
 
 try:
     from functools import cached_property
@@ -513,25 +513,19 @@ def I_11(self):
         ----------
         .. [1] https://en.wikipedia.org/wiki/Moment_of_inertia#Inertia_tensor
         """
-        # Propellant inertia tensor 11 component wrt propellant center of mass
-        propellant_I_11 = self.propellant_I_11
 
-        # Dry inertia tensor 11 component wrt dry center of mass
+        prop_I_11 = self.propellant_I_11
         dry_I_11 = self.dry_I_11
 
-        # Steiner theorem the get inertia wrt motor center of mass
-        propellant_I_11 += (
-            self.propellant_mass
-            * (self.center_of_propellant_mass - self.center_of_mass) ** 2
-        )
+        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
 
-        dry_I_11 += (
-            self.dry_mass
-            * (self.center_of_dry_mass_position - self.center_of_mass) ** 2
+        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)
 
-        # Sum of inertia components
-        return propellant_I_11 + dry_I_11
+        return prop_I_11 + dry_I_11
 
     @funcify_method("Time (s)", "Inertia I_22 (kg m²)")
     def I_22(self):