def create_hodographic_shaping_object(trajectory_parameters: list,
bodies: tudatpy.kernel.simulation.environment_setup.SystemOfBodies) \
-> tudatpy.kernel.simulation.shape_based_thrust.HodographicShaping:
"""
It creates and returns the hodographic shaping object, based on the trajectory parameters.
Parameters
----------
trajectory_parameters : list
List of trajectory parameters to be optimized.
bodies : tudatpy.kernel.simulation.environment_setup.SystemOfBodies
System of bodies present in the simulation.
Returns
-------
hodographic_shaping_object : tudatpy.kernel.simulation.shape_based_thrust.HodographicShaping
Hodographic shaping object.
"""
# Time settings
initial_time = get_trajectory_initial_time(trajectory_parameters)
time_of_flight = get_trajectory_time_of_flight(trajectory_parameters)
final_time = get_trajectory_final_time(trajectory_parameters)
# Number of revolutions
number_of_revolutions = int(trajectory_parameters[2])
# Compute relevant frequency and scale factor for shaping functions
frequency = 2.0 * np.pi / time_of_flight
scale_factor = 1.0 / time_of_flight
# Retrieve shaping functions and free parameters
radial_velocity_shaping_functions, radial_free_coefficients = get_radial_velocity_shaping_functions(
trajectory_parameters, frequency, scale_factor, time_of_flight,
number_of_revolutions)
normal_velocity_shaping_functions, normal_free_coefficients = get_normal_velocity_shaping_functions(
trajectory_parameters, frequency, scale_factor, time_of_flight,
number_of_revolutions)
axial_velocity_shaping_functions, axial_free_coefficients = get_axial_velocity_shaping_functions(
trajectory_parameters, frequency, scale_factor, time_of_flight,
number_of_revolutions)
# Retrieve boundary conditions and central body gravitational parameter
initial_state = bodies.get_body(
'Earth').get_state_in_based_frame_from_ephemeris(initial_time)
final_state = bodies.get_body(
'Mars').get_state_in_based_frame_from_ephemeris(final_time)
gravitational_parameter = bodies.get_body('Sun').gravitational_parameter
# Create and return shape-based method
hodographic_shaping_object = shape_based_thrust.HodographicShaping(
initial_state, final_state, time_of_flight, gravitational_parameter,
number_of_revolutions, radial_velocity_shaping_functions,
normal_velocity_shaping_functions, axial_velocity_shaping_functions,
radial_free_coefficients, normal_free_coefficients,
axial_free_coefficients)
return hodographic_shaping_object
def set_capsule_shape_parameters(
shape_parameters: list,
bodies: tudatpy.kernel.simulation.environment_setup.SystemOfBodies,
capsule_density: float):
"""
It computes and creates the properties of the capsule (shape, mass, aerodynamic coefficient interface...).
Parameters
----------
shape_parameters : list of floats
List of shape parameters to be optimized.
bodies : tudatpy.kernel.simulation.environment_setup.SystemOfBodies
System of bodies present in the simulation.
capsule_density : float
Constant density of the vehicle.
Returns
-------
none
"""
# Compute shape constraint
length_limit = shape_parameters[1] - shape_parameters[4] * (
1 - np.cos(shape_parameters[3]))
length_limit /= np.tan(-shape_parameters[3])
# Add safety factor
length_limit -= 0.01
# Apply constraint
if shape_parameters[2] >= length_limit:
shape_parameters[2] = length_limit
# Create capsule
new_capsule = geometry.Capsule(*shape_parameters[0:5])
# Compute new body mass
new_capsule_mass = capsule_density * new_capsule.volume
# Set capsule mass
bodies.get_body('Capsule').set_constant_mass(new_capsule_mass)
# Create aerodynamic interface from shape parameters (this calls the local inclination analysis)
new_aerodynamic_coefficient_interface = get_capsule_coefficient_interface(
new_capsule)
# Update the Capsule's aerodynamic coefficient interface
bodies.get_body('Capsule').set_aerodynamic_coefficient_interface(
new_aerodynamic_coefficient_interface)
def get_initial_state(simulation_start_epoch: float,
bodies: tudatpy.kernel.simulation.environment_setup.SystemOfBodies) -> np.ndarray:
"""
Converts the initial state to inertial coordinates.
The initial state is expressed in Earth-centered spherical coordinates.
These are first converted into Earth-centered cartesian coordinates,
then they are finally converted in the global (inertial) coordinate
system.
Parameters
----------
simulation_start_epoch : float
Start of the simulation [s] with t=0 at J2000.
bodies : tudatpy.kernel.simulation.environment_setup.SystemOfBodies
System of bodies present in the simulation.
Returns
-------
initial_state_inertial_coordinates : np.ndarray
The initial state of the vehicle expressed in inertial coordinates.
"""
# Set initial spherical elements
# position vector (m)
radial_distance = spice_interface.get_average_radius('Earth') + 120.0E3
# latitude (rad)
latitude = np.deg2rad(0.0)
# longitude (rad)
longitude = np.deg2rad(68.75)
# velocity (m/s)
speed = 7.83E3
# flight path angle (rad)
flight_path_angle = np.deg2rad(-1.5)
# heading angle (rad)
heading_angle = np.deg2rad(34.37)
# Convert spherical elements to body-fixed cartesian coordinates
initial_cartesian_state_body_fixed = conversion.spherical_to_cartesian(radial_distance,
latitude,
longitude,
speed,
flight_path_angle,
heading_angle)
# Get rotational ephemerides of the Earth
earth_rotational_model = bodies.get_body('Earth').rotation_model
# Transform the state to the global (inertial) frame
initial_cartesian_state_inertial = conversion.transform_to_inertial_orientation(initial_cartesian_state_body_fixed,
simulation_start_epoch,
earth_rotational_model)
return initial_cartesian_state_inertial
def add_capsule_to_body_system(
bodies: tudatpy.kernel.simulation.environment_setup.SystemOfBodies,
shape_parameters: list, capsule_density: float):
"""
It creates the capsule body object and adds it to the body system, setting its shape based on the shape parameters
provided.
Parameters
----------
bodies : tudatpy.kernel.simulation.environment_setup.SystemOfBodies
System of bodies present in the simulation.
shape_parameters : list of floats
List of shape parameters to be optimized.
capsule_density : float
Constant density of the vehicle.
Returns
-------
none
"""
# Create new vehicle object and add it to the existing system of bodies
bodies.create_empty_body('Capsule')
# Update the capsule shape parameters
set_capsule_shape_parameters(shape_parameters, bodies, capsule_density)
def get_thrust_acceleration_model_from_parameters(thrust_parameters: list,
bodies: tudatpy.kernel.simulation.environment_setup.SystemOfBodies,
initial_time: float,
specific_impulse: float) -> \
tudatpy.kernel.simulation.propagation_setup.acceleration.ThrustAccelerationSettings:
"""
Creates the thrust acceleration models from the LunarAscentThrustGuidance class and sets it in the propagator.
Parameters
----------
thrust_parameters : list of floats
List of thrust parameters.
bodies : tudatpy.kernel.simulation.environment_setup.SystemOfBodies
System of bodies present in the simulation.
initial_time : float
The start time of the simulation in seconds.
specific_impulse : float
Specific impulse of the vehicle.
Returns
-------
tudatpy.kernel.simulation.propagation_setup.acceleration.ThrustAccelerationSettings
Thrust acceleration settings object.
"""
# Create Thrust Guidance object
thrust_guidance = LunarAscentThrustGuidance(bodies.get_body('Vehicle'),
initial_time,
thrust_parameters)
# Retrieves thrust functions
thrust_direction_function = thrust_guidance.get_current_thrust_direction
thrust_magnitude_function = thrust_guidance.get_current_thrust_magnitude
# Set thrust functions in the acceleration model
thrust_direction_settings = propagation_setup.acceleration.custom_thrust_direction(
thrust_direction_function)
thrust_magnitude_settings = propagation_setup.acceleration.custom_thrust_magnitude(
thrust_magnitude_function, lambda time: specific_impulse)
# Create and return thrust acceleration settings
return propagation_setup.acceleration.ThrustAccelerationSettings(
thrust_direction_settings, thrust_magnitude_settings)