Dynamics Base

Basic dynamics model for BSK-RL.

class DynamicsModel(satellite: Satellite, dyn_rate: float, priority: int = 200, **kwargs)[source]

Bases: ABC

The abstract base dynamics model.

One DynamicsModel is instantiated for each satellite in the environment each time the environment is reset and new simulator is created.

Parameters:

  • satellite (Satellite) – Satellite represented by this model.

  • dyn_rate (float) – [s] Rate of dynamics simulation.

  • priority (int) – Model priority.

  • kwargs – Passed through to setup functions.

property simulator: Simulator

Reference to the episode simulator.

property world: WorldModel

Reference to the episode world model.

is_alive(log_failure=False) → bool[source]

Check if the dynamics model has failed any aliveness requirements.

Returns:

True if the satellite dynamics are still alive.

Return type:

bool

reset_for_action() → None[source]

Reset whenever a flight software action is called.

Return type:

None

class BasicDynamicsModel(*args, **kwargs)[source]

Bases: DynamicsModel

A dynamics model with a basic feature set.

Includes the following:

  • Spacecraft hub physical properties

  • Gravity

  • Constant disturbance torque (defaults to none)

  • Aerodynamic drag

  • Eclipse checking for power generation

  • Reaction wheels

  • Momentum desaturation thrusters

  • Solar panels, battery, and power system

Parameters:

  • *args – Passed to superclass

  • **kwargs – Passed to superclass

property sigma_BN

Body attitude MRP relative to inertial frame.

property BN

Body relative to inertial frame rotation matrix.

property omega_BN_B

Body rate relative to inertial frame in body frame [rad/s].

property BP

Body relative to planet freame rotation matrix.

property HN

Hill frame relative to inertial frame rotation matrix.

property r_BN_N

Body position relative to inertial origin in inertial frame [m].

property r_BN_P

Body position relative to inertial origin in planet frame [m].

property v_BN_N

Body velocity relative to inertial origin in inertial frame [m/s].

property v_BN_P

Planet-frame derivative of r_BN.

property omega_BP_P

Body angular velocity relative to planet frame in plant frame [rad/s].

property omega_BH_H

Body angular velocity relative to Hill frame in Hill frame [rad/s].

property semi_major_axis

Semimajor axis of the satellite’s orbit [km].

property eccentricity

Eccentricity of the satellite’s orbit [-].

property inclination

Inclination of the satellite’s orbit [rad].

property ascending_node

Longitude of ascending node of the satellite’s orbit [rad].

property argument_of_periapsis

Argument of periapsis of the satellite’s orbit [rad].

property true_anomaly

True anomaly of the satellite’s orbit [rad].

property beta_angle

Beta angle of the satellite’s orbit, between 0 and 2pi [rad].

The angle between the angular momentum vector and the sun direction vector.

property battery_charge

Battery charge [W*s].

property battery_charge_fraction

Battery charge as a fraction of capacity.

property wheel_speeds

Wheel speeds [rad/s].

property wheel_speeds_fraction

Wheel speeds normalized by maximum allowable speed.

setup_spacecraft_hub(mass: float, width: float, depth: float, height: float, sigma_init: Iterable[float], omega_init: Iterable[float], oe: Iterable[float] | None, rN: Iterable[float] | None, vN: Iterable[float] | None, mu: float, priority: int = 2000, **kwargs) → None[source]

Set up the spacecraft hub physical properties and state.

The hub is assumed to be a uniform-density rectangular prism with the center of mass at the center.

Parameters:

  • mass (float) – [kg] Hub mass.

  • width (float) – [m] Hub width.

  • depth (float) – [m] Hub depth.

  • height (float) – [m] Hub height.

  • sigma_init (Iterable[float]) – Initial attitude MRP.

  • omega_init (Iterable[float]) – [rad/s] Initial body rate.

  • oe (Iterable[float] | None) – Orbital element tuple of (semimajor axis [km], eccentricity, inclination [rad], ascending node [rad], argument of periapsis [rad], initial true anomaly [rad]). Either oe and mu or rN and vN must be provided, but not both.

  • mu (float) – Gravitational parameter (used only with oe).

  • rN (Iterable[float] | None) – [m] Initial inertial position.

  • vN (Iterable[float] | None) – [m/s] Initial inertial velocity.

  • priority (int) – Model priority.

  • kwargs – Passed to other setup functions.

Return type:

None

setup_gravity_bodies() → None[source]

Set up gravitational bodies from the WorldModel to included in the simulation.

Return type:

None

setup_disturbance_torque(disturbance_vector: Iterable[float] | None = None, **kwargs) → None[source]

Set up a constant disturbance torque acting on the satellite.

Parameters:

  • disturbance_vector (Iterable[float] | None) – [N*m] Constant disturbance torque in the body frame.

  • kwargs – Passed to other setup functions.

Return type:

None

setup_density_model() → None[source]

Set up the atmospheric density model effector.

Return type:

None

setup_drag_effector(width: float, depth: float, height: float, panelArea: float, dragCoeff: float, priority: int = 999, **kwargs) → None[source]

Set up the satellite drag effector.

The drag effector causes aerodynamic forces and torques to act on the satellite. For purposes of this model, the satellite is assumed to be a rectangular prism with a solar panel on one end.

Parameters:

  • width (float) – [m] Hub width.

  • depth (float) – [m] Hub depth.

  • height (float) – [m] Hub height.

  • panelArea (float) – [m^2] Solar panel surface area.

  • dragCoeff (float) – Drag coefficient.

  • priority (int) – Model priority.

  • kwargs – Passed to other setup functions.

Return type:

None

setup_simple_nav_object(priority: int = 1400, **kwargs) → None[source]

Set up the navigation module.

Parameters:

  • priority (int) – Model priority.

  • kwargs – Passed to other setup functions.

Return type:

None

altitude_valid() → bool[source]

Decorated with aliveness_checker

Check that satellite has not deorbited.

Checks if altitude is greater than 200km above Earth’s surface.

Return type:

bool

setup_reaction_wheel_dyn_effector(wheelSpeeds: Iterable[float], maxWheelSpeed: float, u_max: float, priority: int = 997, **kwargs) → None[source]

Set the reaction wheel state effector parameters.

Three reaction wheels modeled on the HR16 wheel are used.

Parameters:

  • wheelSpeeds (Iterable[float]) – [rpm] Initial speeds of each wheel.

  • maxWheelSpeed (float) – [rpm] Failure speed for wheels.

  • u_max (float) – [N*m] Maximum torque producible by each wheel.

  • priority (int) – Model priority.

  • kwargs – Passed to other setup functions.

Return type:

None

rw_speeds_valid() → bool[source]

Decorated with aliveness_checker

Check if any wheel speed exceeds the maxWheelSpeed.

Return type:

bool

setup_thruster_dyn_effector(priority: int = 996) → None[source]

Set up the thruster state effector.

Parameters:

priority (int) – Model priority.

Return type:

None

setup_thruster_power(thrusterPowerDraw, priority: int = 899, **kwargs) → None[source]

Set up the thruster power draw.

When momentum desaturating using wheels, power is consumed at this rate.

Parameters:

  • thrusterPowerDraw – [W] Constant power draw desat mode is active.

  • priority (int) – Model priority.

  • kwargs – Passed to other setup functions.

Return type:

None

setup_eclipse_object() → None[source]

Add the spacecraft to the eclipse module.

Return type:

None

setup_solar_panel(panelArea: float, panelEfficiency: float, nHat_B: Iterable[float], priority: int = 898, **kwargs) → None[source]

Set the solar panel parameters for power generation.

Power generation takes into account panel size and efficiency, the eclipse state, and the angle of solar incidence.

Parameters:

  • panelArea (float) – [m^2] Solar panel area.

  • panelEfficiency (float) – Efficiency coefficient of solar to electrical power conversion.

  • nHat_B (Iterable[float]) – Body-fixed array normal vector.

  • priority (int) – Model priority.

  • kwargs – Passed to other setup functions.

Return type:

None

setup_battery(batteryStorageCapacity: float, storedCharge_Init: float, priority: int = 799, **kwargs) → None[source]

Set the battery model parameters.

Parameters:

  • batteryStorageCapacity (float) – [W*s] Maximum battery charge.

  • storedCharge_Init (float) – [W*s] Initial battery charge.

  • priority (int) – Model priority.

  • kwargs – Passed to other setup functions.

Return type:

None

battery_valid() → bool[source]

Decorated with aliveness_checker

Check if the battery has charge remaining.

Note that this check is instantaneous. If a satellite runs out of power during a environment step but then recharges to have positive power at the end of the step, the satellite will still be considered alive.

Return type:

bool

setup_power_sink(basePowerDraw: float, priority: int = 897, **kwargs) → None[source]

Set the instrument power sink parameters.

Parameters:

  • basePowerDraw (float) – [W] Baseline satellite power draw. Should be negative.

  • priority (int) – Model priority.

  • kwargs – Passed to other setup functions.

Return type:

None

setup_reaction_wheel_power(rwBasePower: float, rwMechToElecEfficiency: float, rwElecToMechEfficiency: float, priority: int = 987, **kwargs) → None[source]

Set the reaction wheel power draw.

Parameters:

  • rwBasePower (float) – [W] Constant power draw when operational.

  • rwMechToElecEfficiency (float) – Efficiency factor to convert mechanical power to electrical power.

  • rwElecToMechEfficiency (float) – Efficiency factor to convert electrical power to mechanical power.

  • priority (int) – Model priority.

  • kwargs – Passed to other setup functions.

Return type:

None