From 39c97f02e776544b8d5ad50bb58ba5d8a284205d Mon Sep 17 00:00:00 2001
From: Lucas Prates <lucasdelprates@gmail.com>
Date: Thu, 17 Oct 2024 11:15:51 -0300
Subject: [PATCH 01/10] ENH: add structural to total mass ratio for motor and
 rocket

---
 rocketpy/prints/rocket_prints.py      | 2 ++
 rocketpy/prints/solid_motor_prints.py | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/rocketpy/prints/rocket_prints.py b/rocketpy/prints/rocket_prints.py
index c9f5585ac..ef5e850c0 100644
--- a/rocketpy/prints/rocket_prints.py
+++ b/rocketpy/prints/rocket_prints.py
@@ -36,6 +36,8 @@ def inertia_details(self):
         print(f"Rocket Mass: {self.rocket.mass:.3f} kg (without motor)")
         print(f"Rocket Dry Mass: {self.rocket.dry_mass:.3f} kg (with unloaded motor)")
         print(f"Rocket Loaded Mass: {self.rocket.total_mass(0):.3f} kg")
+        mass_ratio = self.rocket.dry_mass / self.rocket.total_mass(0)
+        print(f"Rocket Structural to total mass ratio: {mass_ratio:.3f}")
         print(
             f"Rocket Inertia (with unloaded motor) 11: {self.rocket.dry_I_11:.3f} kg*m2"
         )
diff --git a/rocketpy/prints/solid_motor_prints.py b/rocketpy/prints/solid_motor_prints.py
index c37a9b69e..31c50e6e8 100644
--- a/rocketpy/prints/solid_motor_prints.py
+++ b/rocketpy/prints/solid_motor_prints.py
@@ -65,6 +65,8 @@ def motor_details(self):
         print(
             f"Total Propellant Mass: {self.solid_motor.propellant_initial_mass:.3f} kg"
         )
+        mass_ratio = self.solid_motor.dry_mass / self.solid_motor.total_mass(0)
+        print(f"Structural to total mass ratio: {mass_ratio:.3f}")
         average = self.solid_motor.exhaust_velocity.average(*self.solid_motor.burn_time)
         print(f"Average Propellant Exhaust Velocity: {average:.3f} m/s")
         print(f"Average Thrust: {self.solid_motor.average_thrust:.3f} N")

From 4633584a8284dad0b7761e64172c04dabd00ee90 Mon Sep 17 00:00:00 2001
From: Lucas de Oliveira Prates <lucasdelprates@gmail.com>
Date: Tue, 29 Oct 2024 19:08:52 -0300
Subject: [PATCH 02/10] ENH: adding structural mass ratio as an attribute of
 Motor

---
 rocketpy/motors/motor.py               | 15 +++++++++++++++
 rocketpy/prints/hybrid_motor_prints.py |  1 +
 rocketpy/prints/liquid_motor_prints.py |  1 +
 rocketpy/prints/motor_prints.py        |  1 +
 rocketpy/prints/solid_motor_prints.py  |  3 +--
 5 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/rocketpy/motors/motor.py b/rocketpy/motors/motor.py
index 5fa154d88..ea495e524 100644
--- a/rocketpy/motors/motor.py
+++ b/rocketpy/motors/motor.py
@@ -49,6 +49,8 @@ class Motor(ABC):
     Motor.propellant_mass : Function
         Total propellant mass in kg as a function of time, including solid,
         liquid and gas phases.
+    Motor.structural_mass_ratio: float
+        Initial ratio between the dry mass and the total mass.
     Motor.total_mass_flow_rate : Function
         Time derivative of propellant total mass in kg/s as a function
         of time as obtained by the thrust source.
@@ -497,6 +499,19 @@ def propellant_initial_mass(self):
             Propellant initial mass in kg.
         """
 
+    @property
+    def structural_mass_ratio(self):
+        """Calculates the structural mass ratio. The ratio is defined as
+        the dry mass divided by the initial total mass.
+
+        Returns
+        -------
+        float
+            Initial structural mass ratio.
+        """
+        initial_total_mass = self.dry_mass + self.propellant_initial_mass
+        return self.dry_mass / initial_total_mass
+
     @funcify_method("Time (s)", "Motor center of mass (m)")
     def center_of_mass(self):
         """Position of the center of mass as a function of time. The position
diff --git a/rocketpy/prints/hybrid_motor_prints.py b/rocketpy/prints/hybrid_motor_prints.py
index 4dcd7b113..986f43806 100644
--- a/rocketpy/prints/hybrid_motor_prints.py
+++ b/rocketpy/prints/hybrid_motor_prints.py
@@ -77,6 +77,7 @@ def motor_details(self):
         print(
             f"Total Propellant Mass: {self.hybrid_motor.propellant_initial_mass:.3f} kg"
         )
+        print(f"Structural to total mass ratio: {self.hybrid_motor.structural_mass_ratio:.3f}")
         avg = self.hybrid_motor.exhaust_velocity.average(*self.hybrid_motor.burn_time)
         print(f"Average Propellant Exhaust Velocity: {avg:.3f} m/s")
         print(f"Average Thrust: {self.hybrid_motor.average_thrust:.3f} N")
diff --git a/rocketpy/prints/liquid_motor_prints.py b/rocketpy/prints/liquid_motor_prints.py
index fb493ed0a..752ba3247 100644
--- a/rocketpy/prints/liquid_motor_prints.py
+++ b/rocketpy/prints/liquid_motor_prints.py
@@ -47,6 +47,7 @@ def motor_details(self):
         print(
             f"Total Propellant Mass: {self.liquid_motor.propellant_initial_mass:.3f} kg"
         )
+        print(f"Structural to total mass ratio: {self.liquid_motor.structural_mass_ratio:.3f}")
         avg = self.liquid_motor.exhaust_velocity.average(*self.liquid_motor.burn_time)
         print(f"Average Propellant Exhaust Velocity: {avg:.3f} m/s")
         print(f"Average Thrust: {self.liquid_motor.average_thrust:.3f} N")
diff --git a/rocketpy/prints/motor_prints.py b/rocketpy/prints/motor_prints.py
index d9b7fbc98..15b9e42f8 100644
--- a/rocketpy/prints/motor_prints.py
+++ b/rocketpy/prints/motor_prints.py
@@ -35,6 +35,7 @@ def motor_details(self):
         print("Motor Details")
         print("Total Burning Time: " + str(self.motor.burn_out_time) + " s")
         print(f"Total Propellant Mass: {self.motor.propellant_initial_mass:.3f} kg")
+        print(f"Structural to total mass ratio: {self.motor.structural_mass_ratio:.3f}")
         print(
             "Average Propellant Exhaust Velocity: "
             f"{self.motor.exhaust_velocity.average(*self.motor.burn_time):.3f} m/s"
diff --git a/rocketpy/prints/solid_motor_prints.py b/rocketpy/prints/solid_motor_prints.py
index 31c50e6e8..859eb02bd 100644
--- a/rocketpy/prints/solid_motor_prints.py
+++ b/rocketpy/prints/solid_motor_prints.py
@@ -65,8 +65,7 @@ def motor_details(self):
         print(
             f"Total Propellant Mass: {self.solid_motor.propellant_initial_mass:.3f} kg"
         )
-        mass_ratio = self.solid_motor.dry_mass / self.solid_motor.total_mass(0)
-        print(f"Structural to total mass ratio: {mass_ratio:.3f}")
+        print(f"Structural to total mass ratio: {self.solid_motor.structural_mass_ratio:.3f}")
         average = self.solid_motor.exhaust_velocity.average(*self.solid_motor.burn_time)
         print(f"Average Propellant Exhaust Velocity: {average:.3f} m/s")
         print(f"Average Thrust: {self.solid_motor.average_thrust:.3f} N")

From 7c151601486d1e40899c4bd9b032da98d5fa5bb5 Mon Sep 17 00:00:00 2001
From: Lucas de Oliveira Prates <lucasdelprates@gmail.com>
Date: Wed, 30 Oct 2024 10:11:44 -0300
Subject: [PATCH 03/10] ENH: add structural mass ratio to rocket

---
 rocketpy/motors/motor.py         |  3 +++
 rocketpy/prints/rocket_prints.py |  3 +--
 rocketpy/rocket/rocket.py        | 22 ++++++++++++++++++++++
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/rocketpy/motors/motor.py b/rocketpy/motors/motor.py
index ea495e524..54b9cb751 100644
--- a/rocketpy/motors/motor.py
+++ b/rocketpy/motors/motor.py
@@ -510,6 +510,8 @@ def structural_mass_ratio(self):
             Initial structural mass ratio.
         """
         initial_total_mass = self.dry_mass + self.propellant_initial_mass
+        if initial_total_mass == 0:
+            raise ValueError("Motor total mass is zero!")
         return self.dry_mass / initial_total_mass
 
     @funcify_method("Time (s)", "Motor center of mass (m)")
@@ -1517,6 +1519,7 @@ def __init__(self):
         self.nozzle_radius = 0
         self.thrust = Function(0, "Time (s)", "Thrust (N)")
         self.propellant_mass = Function(0, "Time (s)", "Propellant Mass (kg)")
+        self.propellant_initial_mass = 0
         self.total_mass = Function(0, "Time (s)", "Total Mass (kg)")
         self.total_mass_flow_rate = Function(
             0, "Time (s)", "Mass Depletion Rate (kg/s)"
diff --git a/rocketpy/prints/rocket_prints.py b/rocketpy/prints/rocket_prints.py
index ef5e850c0..7b768ea2f 100644
--- a/rocketpy/prints/rocket_prints.py
+++ b/rocketpy/prints/rocket_prints.py
@@ -36,8 +36,7 @@ def inertia_details(self):
         print(f"Rocket Mass: {self.rocket.mass:.3f} kg (without motor)")
         print(f"Rocket Dry Mass: {self.rocket.dry_mass:.3f} kg (with unloaded motor)")
         print(f"Rocket Loaded Mass: {self.rocket.total_mass(0):.3f} kg")
-        mass_ratio = self.rocket.dry_mass / self.rocket.total_mass(0)
-        print(f"Rocket Structural to total mass ratio: {mass_ratio:.3f}")
+        print(f"Rocket Structural Mass Ratio: {self.rocket.structural_mass_ratio:.3f}")
         print(
             f"Rocket Inertia (with unloaded motor) 11: {self.rocket.dry_I_11:.3f} kg*m2"
         )
diff --git a/rocketpy/rocket/rocket.py b/rocketpy/rocket/rocket.py
index 758447fde..5a0b1f669 100644
--- a/rocketpy/rocket/rocket.py
+++ b/rocketpy/rocket/rocket.py
@@ -361,6 +361,7 @@ def __init__(  # pylint: disable=too-many-statements
 
         # calculate dynamic inertial quantities
         self.evaluate_dry_mass()
+        self.evaluate_structural_mass_ratio()
         self.evaluate_total_mass()
         self.evaluate_center_of_dry_mass()
         self.evaluate_center_of_mass()
@@ -433,6 +434,26 @@ def evaluate_dry_mass(self):
 
         return self.dry_mass
 
+    def evaluate_structural_mass_ratio(self):
+        """Calculates and returns the rocket's structural mass ratio.
+        It is defined as the ratio between of the dry mass
+        (Motor + Rocket) and the initial total mass
+        (Motor + Propellant + Rocket).
+
+        Returns
+        -------
+        self.structural_mass_ratio: float
+            Initial structural mass ratio dry mass (Rocket + Motor) (kg)
+            divided by total mass (Rocket + Motor + Propellant) (kg).
+        """
+        # Make sure there is a motor associated with the rocket
+
+        self.structural_mass_ratio = self.dry_mass / (
+            self.dry_mass + self.motor.propellant_initial_mass
+        )
+
+        return self.structural_mass_ratio
+
     def evaluate_center_of_mass(self):
         """Evaluates rocket center of mass position relative to user defined
         rocket reference system.
@@ -951,6 +972,7 @@ def add_motor(self, motor, position):  # pylint: disable=too-many-statements
         self.nozzle_position = self.motor.nozzle_position * _ + self.motor_position
         self.total_mass_flow_rate = self.motor.total_mass_flow_rate
         self.evaluate_dry_mass()
+        self.evaluate_structural_mass_ratio()
         self.evaluate_total_mass()
         self.evaluate_center_of_dry_mass()
         self.evaluate_nozzle_to_cdm()

From 01b2fff8392a340c288ed3d1e402152436f6009e Mon Sep 17 00:00:00 2001
From: Lucas de Oliveira Prates <lucasdelprates@gmail.com>
Date: Wed, 30 Oct 2024 10:12:13 -0300
Subject: [PATCH 04/10] ENH: capitalize words on prints

---
 rocketpy/prints/hybrid_motor_prints.py | 2 +-
 rocketpy/prints/liquid_motor_prints.py | 2 +-
 rocketpy/prints/motor_prints.py        | 2 +-
 rocketpy/prints/solid_motor_prints.py  | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/rocketpy/prints/hybrid_motor_prints.py b/rocketpy/prints/hybrid_motor_prints.py
index 986f43806..e69d291f5 100644
--- a/rocketpy/prints/hybrid_motor_prints.py
+++ b/rocketpy/prints/hybrid_motor_prints.py
@@ -77,7 +77,7 @@ def motor_details(self):
         print(
             f"Total Propellant Mass: {self.hybrid_motor.propellant_initial_mass:.3f} kg"
         )
-        print(f"Structural to total mass ratio: {self.hybrid_motor.structural_mass_ratio:.3f}")
+        print(f"Structural Mass Ratio: {self.hybrid_motor.structural_mass_ratio:.3f}")
         avg = self.hybrid_motor.exhaust_velocity.average(*self.hybrid_motor.burn_time)
         print(f"Average Propellant Exhaust Velocity: {avg:.3f} m/s")
         print(f"Average Thrust: {self.hybrid_motor.average_thrust:.3f} N")
diff --git a/rocketpy/prints/liquid_motor_prints.py b/rocketpy/prints/liquid_motor_prints.py
index 752ba3247..4c80326ab 100644
--- a/rocketpy/prints/liquid_motor_prints.py
+++ b/rocketpy/prints/liquid_motor_prints.py
@@ -47,7 +47,7 @@ def motor_details(self):
         print(
             f"Total Propellant Mass: {self.liquid_motor.propellant_initial_mass:.3f} kg"
         )
-        print(f"Structural to total mass ratio: {self.liquid_motor.structural_mass_ratio:.3f}")
+        print(f"Structural Mass Ratio: {self.liquid_motor.structural_mass_ratio:.3f}")
         avg = self.liquid_motor.exhaust_velocity.average(*self.liquid_motor.burn_time)
         print(f"Average Propellant Exhaust Velocity: {avg:.3f} m/s")
         print(f"Average Thrust: {self.liquid_motor.average_thrust:.3f} N")
diff --git a/rocketpy/prints/motor_prints.py b/rocketpy/prints/motor_prints.py
index 15b9e42f8..f5efff8e0 100644
--- a/rocketpy/prints/motor_prints.py
+++ b/rocketpy/prints/motor_prints.py
@@ -35,7 +35,7 @@ def motor_details(self):
         print("Motor Details")
         print("Total Burning Time: " + str(self.motor.burn_out_time) + " s")
         print(f"Total Propellant Mass: {self.motor.propellant_initial_mass:.3f} kg")
-        print(f"Structural to total mass ratio: {self.motor.structural_mass_ratio:.3f}")
+        print(f"Structural Mass Ratio: {self.motor.structural_mass_ratio:.3f}")
         print(
             "Average Propellant Exhaust Velocity: "
             f"{self.motor.exhaust_velocity.average(*self.motor.burn_time):.3f} m/s"
diff --git a/rocketpy/prints/solid_motor_prints.py b/rocketpy/prints/solid_motor_prints.py
index 859eb02bd..6f4c28d5b 100644
--- a/rocketpy/prints/solid_motor_prints.py
+++ b/rocketpy/prints/solid_motor_prints.py
@@ -65,7 +65,7 @@ def motor_details(self):
         print(
             f"Total Propellant Mass: {self.solid_motor.propellant_initial_mass:.3f} kg"
         )
-        print(f"Structural to total mass ratio: {self.solid_motor.structural_mass_ratio:.3f}")
+        print(f"Structural Mass Ratio: {self.solid_motor.structural_mass_ratio:.3f}")
         average = self.solid_motor.exhaust_velocity.average(*self.solid_motor.burn_time)
         print(f"Average Propellant Exhaust Velocity: {average:.3f} m/s")
         print(f"Average Thrust: {self.solid_motor.average_thrust:.3f} N")

From 3051605abc083b4df972c6d92289864f14531491 Mon Sep 17 00:00:00 2001
From: Lucas de Oliveira Prates <lucasdelprates@gmail.com>
Date: Wed, 30 Oct 2024 10:22:41 -0300
Subject: [PATCH 05/10] DOC: adding structural mass ratio attribute to
 docstrings

---
 rocketpy/motors/hybrid_motor.py | 2 ++
 rocketpy/motors/liquid_motor.py | 2 ++
 rocketpy/motors/solid_motor.py  | 2 ++
 rocketpy/rocket/rocket.py       | 2 ++
 4 files changed, 8 insertions(+)

diff --git a/rocketpy/motors/hybrid_motor.py b/rocketpy/motors/hybrid_motor.py
index 1a1bbb3db..dbaa6ee26 100644
--- a/rocketpy/motors/hybrid_motor.py
+++ b/rocketpy/motors/hybrid_motor.py
@@ -72,6 +72,8 @@ class HybridMotor(Motor):
     HybridMotor.propellant_mass : Function
         Total propellant mass in kg as a function of time, this includes the
         mass of fluids in each tank and the mass of the solid grains.
+    Motor.structural_mass_ratio: float
+        Initial ratio between the dry mass and the total mass.
     HybridMotor.total_mass_flow_rate : Function
         Time derivative of propellant total mass in kg/s as a function
         of time as obtained by the thrust source.
diff --git a/rocketpy/motors/liquid_motor.py b/rocketpy/motors/liquid_motor.py
index 9ec3d1130..6839e2395 100644
--- a/rocketpy/motors/liquid_motor.py
+++ b/rocketpy/motors/liquid_motor.py
@@ -47,6 +47,8 @@ class LiquidMotor(Motor):
     LiquidMotor.propellant_mass : Function
         Total propellant mass in kg as a function of time, includes fuel
         and oxidizer.
+    Motor.structural_mass_ratio: float
+        Initial ratio between the dry mass and the total mass.
     LiquidMotor.total_mass_flow_rate : Function
         Time derivative of propellant total mass in kg/s as a function
         of time as obtained by the tanks mass flow.
diff --git a/rocketpy/motors/solid_motor.py b/rocketpy/motors/solid_motor.py
index 81faf453f..09f22a59f 100644
--- a/rocketpy/motors/solid_motor.py
+++ b/rocketpy/motors/solid_motor.py
@@ -70,6 +70,8 @@ class SolidMotor(Motor):
         of propellant and dry mass.
     SolidMotor.propellant_mass : Function
         Total propellant mass in kg as a function of time.
+    Motor.structural_mass_ratio: float
+        Initial ratio between the dry mass and the total mass.
     SolidMotor.total_mass_flow_rate : Function
         Time derivative of propellant total mass in kg/s as a function
         of time as obtained by the thrust source.
diff --git a/rocketpy/rocket/rocket.py b/rocketpy/rocket/rocket.py
index 5a0b1f669..9ceba3894 100644
--- a/rocketpy/rocket/rocket.py
+++ b/rocketpy/rocket/rocket.py
@@ -89,6 +89,8 @@ class Rocket:
         Function of time expressing the total mass of the rocket,
         defined as the sum of the propellant mass and the rocket
         mass without propellant.
+    Rocket.structural_mass_ratio: float
+        Initial ratio between the dry mass and the total mass.
     Rocket.total_mass_flow_rate : Function
         Time derivative of rocket's total mass in kg/s as a function
         of time as obtained by the thrust source of the added motor.

From 2143ed396fe7264a3838cf9f8d4142423d99512e Mon Sep 17 00:00:00 2001
From: Lucas de Oliveira Prates <lucasdelprates@gmail.com>
Date: Wed, 30 Oct 2024 10:28:59 -0300
Subject: [PATCH 06/10] DOC: fix incorrect documentation names of attributes

---
 rocketpy/motors/hybrid_motor.py | 2 +-
 rocketpy/motors/liquid_motor.py | 2 +-
 rocketpy/motors/solid_motor.py  | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/rocketpy/motors/hybrid_motor.py b/rocketpy/motors/hybrid_motor.py
index dbaa6ee26..2916486d0 100644
--- a/rocketpy/motors/hybrid_motor.py
+++ b/rocketpy/motors/hybrid_motor.py
@@ -72,7 +72,7 @@ class HybridMotor(Motor):
     HybridMotor.propellant_mass : Function
         Total propellant mass in kg as a function of time, this includes the
         mass of fluids in each tank and the mass of the solid grains.
-    Motor.structural_mass_ratio: float
+    HybridMotor.structural_mass_ratio: float
         Initial ratio between the dry mass and the total mass.
     HybridMotor.total_mass_flow_rate : Function
         Time derivative of propellant total mass in kg/s as a function
diff --git a/rocketpy/motors/liquid_motor.py b/rocketpy/motors/liquid_motor.py
index 6839e2395..cde0e9d03 100644
--- a/rocketpy/motors/liquid_motor.py
+++ b/rocketpy/motors/liquid_motor.py
@@ -47,7 +47,7 @@ class LiquidMotor(Motor):
     LiquidMotor.propellant_mass : Function
         Total propellant mass in kg as a function of time, includes fuel
         and oxidizer.
-    Motor.structural_mass_ratio: float
+    LiquidMotor.structural_mass_ratio: float
         Initial ratio between the dry mass and the total mass.
     LiquidMotor.total_mass_flow_rate : Function
         Time derivative of propellant total mass in kg/s as a function
diff --git a/rocketpy/motors/solid_motor.py b/rocketpy/motors/solid_motor.py
index 09f22a59f..f6f09967e 100644
--- a/rocketpy/motors/solid_motor.py
+++ b/rocketpy/motors/solid_motor.py
@@ -70,7 +70,7 @@ class SolidMotor(Motor):
         of propellant and dry mass.
     SolidMotor.propellant_mass : Function
         Total propellant mass in kg as a function of time.
-    Motor.structural_mass_ratio: float
+    SolidMotor.structural_mass_ratio: float
         Initial ratio between the dry mass and the total mass.
     SolidMotor.total_mass_flow_rate : Function
         Time derivative of propellant total mass in kg/s as a function

From 234e10d7861cd399030b2fbbc9616a0a56e9db5c Mon Sep 17 00:00:00 2001
From: Lucas Prates <57069366+Lucas-Prates@users.noreply.github.com>
Date: Fri, 1 Nov 2024 11:44:29 -0300
Subject: [PATCH 07/10] Remove erroneous comment

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

diff --git a/rocketpy/rocket/rocket.py b/rocketpy/rocket/rocket.py
index 9ceba3894..fd7ef8a2a 100644
--- a/rocketpy/rocket/rocket.py
+++ b/rocketpy/rocket/rocket.py
@@ -448,7 +448,6 @@ def evaluate_structural_mass_ratio(self):
             Initial structural mass ratio dry mass (Rocket + Motor) (kg)
             divided by total mass (Rocket + Motor + Propellant) (kg).
         """
-        # Make sure there is a motor associated with the rocket
 
         self.structural_mass_ratio = self.dry_mass / (
             self.dry_mass + self.motor.propellant_initial_mass

From 0f4503dbde751f15390d27c9b86df4888f8f5ff3 Mon Sep 17 00:00:00 2001
From: Lucas de Oliveira Prates <lucasdelprates@gmail.com>
Date: Fri, 1 Nov 2024 21:17:45 -0300
Subject: [PATCH 08/10] DOC: modify changelog

---
 CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f68f10b8c..bc4f552b1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -32,7 +32,7 @@ Attention: The newest changes should be on top -->
 
 ### Added
 
-
+- ENH: add structural to total mass ratio for motor and rocket [#713](https://github.com/RocketPy-Team/RocketPy/pull/713)
 
 ### Changed
 

From ed2ae39327575781dfea459e6f05edab15329e5d Mon Sep 17 00:00:00 2001
From: Lucas de Oliveira Prates <lucasdelprates@gmail.com>
Date: Tue, 5 Nov 2024 11:17:09 -0300
Subject: [PATCH 09/10] ENH: properly testing division by zero when computing
 the structural mass ratio

---
 rocketpy/motors/motor.py  |  7 ++++---
 rocketpy/rocket/rocket.py | 11 ++++++-----
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/rocketpy/motors/motor.py b/rocketpy/motors/motor.py
index 54b9cb751..027a3c104 100644
--- a/rocketpy/motors/motor.py
+++ b/rocketpy/motors/motor.py
@@ -510,9 +510,10 @@ def structural_mass_ratio(self):
             Initial structural mass ratio.
         """
         initial_total_mass = self.dry_mass + self.propellant_initial_mass
-        if initial_total_mass == 0:
-            raise ValueError("Motor total mass is zero!")
-        return self.dry_mass / initial_total_mass
+        try:
+            return self.dry_mass / initial_total_mass
+        except ZeroDivisionError as e:
+            raise ValueError("Total motor mass (dry + propellant) cannot be zero") from e
 
     @funcify_method("Time (s)", "Motor center of mass (m)")
     def center_of_mass(self):
diff --git a/rocketpy/rocket/rocket.py b/rocketpy/rocket/rocket.py
index fd7ef8a2a..06c556810 100644
--- a/rocketpy/rocket/rocket.py
+++ b/rocketpy/rocket/rocket.py
@@ -448,11 +448,12 @@ def evaluate_structural_mass_ratio(self):
             Initial structural mass ratio dry mass (Rocket + Motor) (kg)
             divided by total mass (Rocket + Motor + Propellant) (kg).
         """
-
-        self.structural_mass_ratio = self.dry_mass / (
-            self.dry_mass + self.motor.propellant_initial_mass
-        )
-
+        try:
+            self.structural_mass_ratio = self.dry_mass / (
+                self.dry_mass + self.motor.propellant_initial_mass
+            )
+        except ZeroDivisionError as e:
+            raise ValueError("Total rocket mass (dry + propellant) cannot be zero") from e
         return self.structural_mass_ratio
 
     def evaluate_center_of_mass(self):

From e532489b5fd2e17b9f1d1c618ab83cb7df88d396 Mon Sep 17 00:00:00 2001
From: Lucas de Oliveira Prates <lucasdelprates@gmail.com>
Date: Tue, 5 Nov 2024 11:25:00 -0300
Subject: [PATCH 10/10] MNT: make black

---
 rocketpy/motors/motor.py  | 4 +++-
 rocketpy/rocket/rocket.py | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/rocketpy/motors/motor.py b/rocketpy/motors/motor.py
index 027a3c104..e0e6dfc9a 100644
--- a/rocketpy/motors/motor.py
+++ b/rocketpy/motors/motor.py
@@ -513,7 +513,9 @@ def structural_mass_ratio(self):
         try:
             return self.dry_mass / initial_total_mass
         except ZeroDivisionError as e:
-            raise ValueError("Total motor mass (dry + propellant) cannot be zero") from e
+            raise ValueError(
+                "Total motor mass (dry + propellant) cannot be zero"
+            ) from e
 
     @funcify_method("Time (s)", "Motor center of mass (m)")
     def center_of_mass(self):
diff --git a/rocketpy/rocket/rocket.py b/rocketpy/rocket/rocket.py
index 06c556810..ed376f582 100644
--- a/rocketpy/rocket/rocket.py
+++ b/rocketpy/rocket/rocket.py
@@ -453,7 +453,9 @@ def evaluate_structural_mass_ratio(self):
                 self.dry_mass + self.motor.propellant_initial_mass
             )
         except ZeroDivisionError as e:
-            raise ValueError("Total rocket mass (dry + propellant) cannot be zero") from e
+            raise ValueError(
+                "Total rocket mass (dry + propellant) cannot be zero"
+            ) from e
         return self.structural_mass_ratio
 
     def evaluate_center_of_mass(self):