def create_section_accelerations(section_name, thrust_acceleration):
# Duplicate the environmental accelerations (use copy to avoiding keeping the same dict linked to both sections)
accelerations_on_rocket = accelerations_environment.copy()
# Add the thrust acceleration to the given section
accelerations_on_rocket[section_name] = [thrust_acceleration]
# Create acceleration models for the given section
return propagation_setup.create_acceleration_models(
bodies, {section_name: accelerations_on_rocket}, bodies_to_propagate,
central_bodies)
def get_acceleration_models(bodies_to_propagate, central_bodies, bodies):
# Define accelerations acting on Spacecraft
accelerations_settings_spacecraft = dict(
Sun = [ propagation_setup.acceleration.cannonball_radiation_pressure(),
propagation_setup.acceleration.point_mass_gravity() ],
Itokawa = [ propagation_setup.acceleration.spherical_harmonic_gravity(4, 4) ],
Jupiter = [ propagation_setup.acceleration.point_mass_gravity() ],
Saturn = [ propagation_setup.acceleration.point_mass_gravity() ],
Mars = [ propagation_setup.acceleration.point_mass_gravity() ],
Earth = [ propagation_setup.acceleration.point_mass_gravity() ]
)
# Create global accelerations settings dictionary
acceleration_settings = {"Spacecraft": accelerations_settings_spacecraft}
# Create acceleration models
return propagation_setup.create_acceleration_models(
bodies,
acceleration_settings,
bodies_to_propagate,
central_bodies)
First off, the acceleration settings that act on `Delfi-C3` are to be defined.
In this case, these simply consist in the Earth gravitational effect modelled as a point mass.
The acceleration settings defined are then applied to `Delfi-C3` in a dictionary.
This dictionary is finally input to the propagation setup to create the acceleration models.
"""
# Define accelerations acting on Delfi-C3
acceleration_settings_delfi_c3 = dict(
Earth=[propagation_setup.acceleration.point_mass_gravity()])
acceleration_settings = {"Delfi-C3": acceleration_settings_delfi_c3}
# Create acceleration models
acceleration_models = propagation_setup.create_acceleration_models(
bodies, acceleration_settings, bodies_to_propagate, central_bodies)
### Define the initial state
"""
The initial state of the vehicle that will be propagated is now defined.
This initial state always has to be provided as a cartesian state, in the form of a list with the first three elements reprensenting the initial position, and the three remaining elements representing the initial velocity.
In this case, let's make use of the `keplerian_to_cartesian_elementwise()` function that is included in the `element_conversion` module, so that the initial state can be input as Keplerian elements, and then converted in Cartesian elements.
"""
# Set initial conditions for the satellite that will be
# propagated in this simulation. The initial conditions are given in
# Keplerian elements and later on converted to Cartesian elements
earth_gravitational_parameter = bodies.get("Earth").gravitational_parameter
initial_state = element_conversion.keplerian_to_cartesian_elementwise(
thrust_direction_settings=thrust_direction_settings,
thrust_magnitude_settings=thrust_magnitude_settings,
)
],
# Define the acceleration due to the Earth, Moon, and Sun as Point Mass
Earth=[propagation_setup.acceleration.point_mass_gravity()],
Moon=[propagation_setup.acceleration.point_mass_gravity()],
Sun=[propagation_setup.acceleration.point_mass_gravity()])
# Compile the accelerations acting on the vehicle
acceleration_dict = dict(Vehicle=acceleration_on_vehicle)
# Create the acceleration models from the acceleration mapping dictionary
acceleration_models = propagation_setup.create_acceleration_models(
body_system=system_of_bodies,
selected_acceleration_per_body=acceleration_dict,
bodies_to_propagate=bodies_to_propagate,
central_bodies=central_bodies)
### Define the initial state
"""
The initial state of the vehicle that will be propagated is now defined.
In this example, this state is very straightforwardly set directly in cartesian coordinates.
The Vehicle will thus start 8000km from the center of the Earth, at a velocity of 7.5km/s.
"""
# Get system initial state (in cartesian coordinates)
system_initial_state = np.array([8.0e6, 0, 0, 0, 7.5e3, 0])