Class NBodyDynamics¶

Defined in File numerical_orbit_dynamics.h

Inheritance Relationships¶

Base Type¶

public lupnt::NumericalDynamics (Class NumericalDynamics)

Class Documentation¶

class NBodyDynamics : public lupnt::NumericalDynamics ¶

Numerical point-mass, gravity-field, SRP, drag, and relativity orbit dynamics.

The model propagates Cartesian position and velocity in the selected integration frame. Body ephemerides are obtained in SI units internally and scaled to the configured UnitSystem at the dynamics boundary, so the propagated state, body constants, and force-model parameters remain unit-consistent.

Public Functions

NBodyDynamics()¶

NBodyDynamics(Config &dynamics_config)¶

Construct an n-body dynamics model from a YAML configuration.

Supported configuration fields include the integration frame, force-model switches, SRP and drag ballistic coefficients, and the unit system.

virtual State Propagate(const State &x0, Real t0, Real tf, const State *u, MatXd *stm) override¶

Propagate a Cartesian state and optionally compute the STM.

Parameters:

x0 – Initial Cartesian state in the configured frame and unit system.
t0 – Initial TDB epoch in seconds.
tf – Final TDB epoch in seconds.
u – Optional control input.
stm – Optional state transition matrix output.

Returns:

Final Cartesian state in the configured frame and unit system.

virtual VecX ComputeRates(Real t, const State &x) const override¶

Compute Cartesian position and velocity rates.

Parameters:

t – TDB epoch in seconds.
x – Cartesian state in the configured frame and unit system.

Returns:

Time derivative of the state in the configured unit system.

void AddBody(const Body &body)¶

Add a perturbing or central body to the dynamics model.

Bodies should use the same UnitSystem as the dynamics model. SetUnits() updates already-added built-in bodies to the requested units.

void RemoveBody(const Body &body)¶: Remove a body from the dynamics model by matching its BodyId.

inline bool GetUseSrp()¶: Return true when solar radiation pressure is enabled.

inline bool GetUseDrag()¶: Return true when atmospheric drag is enabled.

inline bool GetUseRelativity() const¶: Return true when post-Newtonian relativistic corrections are enabled.

inline Real GetSrpCoeff() const¶: Return the SRP ballistic coefficient used by the force model.

inline Real GetDragCoeff() const¶: Return the drag ballistic coefficient used by the force model.

inline virtual StateType GetStateType() const override¶

Return the StateType tag of the state vector this dynamics model operates on (e.g. Cart6::TYPE, Attitude::TYPE, ClockState3::TYPE).

Used by state-converters and asset wiring code to verify that a dynamics object is paired with a compatible state representation.

inline Frame GetFrame()¶: Return the integration frame.

inline std::vector<Body> GetBodies()¶: Return the bodies currently included in the dynamics model.

inline UnitSystem GetUnits() const¶: Return the active distance, time, and mass unit system.

inline void SetAutodiff(bool use_ad)¶: Enable or disable automatic differentiation rates.

void SetSrpCoeff(Real bcoeff)¶: Set the SRP ballistic coefficient directly.

void SetDragCoeff(Real bcoeff)¶: Set the drag ballistic coefficient directly.

void SetSrpCoefficient(Real CR, Real area, Real mass)¶: Set SRP coefficient from reflectivity coefficient, area, and mass.

void SetDragCoefficient(Real CD, Real area, Real mass)¶: Set drag coefficient from drag coefficient, area, and mass.

inline void SetUseSrp(bool use_srp)¶: Enable or disable solar radiation pressure.

inline void SetUseDrag(bool use_drag)¶: Enable or disable atmospheric drag.

inline void SetUseRelativity(bool use_relativity)¶: Enable or disable post-Newtonian relativistic corrections.

inline void SetFrame(Frame frame)¶: Set the frame used for numerical integration.

void SetUnits(const UnitSystem &units)¶

Set the active unit system for states, constants, and acceleration output.

Built-in bodies already registered with the model are recreated in the new unit system. Time epochs remain TDB seconds.

virtual State Propagate(const State &x0, Real t0, Real tf, const State *u = nullptr) override¶

Propagate the state from t0 to tf without computing a state transition matrix.

This is the core propagation entry point implemented by every concrete dynamics class (e.g. NumericalDynamics::Propagate, AnalyticalDynamics::Propagate, ClockDynamics::Propagate). It is called once per integration/measurement step by simulation drivers in applications/ and by agents/ to advance an object’s true or estimated state.

Parameters:

x0 – Initial state at time t0 (layout/units defined by the subclass).
t0 – Initial epoch [s, TDB since J2000 for orbit/attitude dynamics].
tf – Final epoch [s, TDB since J2000 for orbit/attitude dynamics].
u – Optional control/forcing input (e.g. thrust, RTN reference state); nullptr if unused.

Returns:

Propagated state at time tf.

virtual MatX Propagate(const State &x0, const VecX &tfs, const State *u = nullptr)¶

Propagate the state to a sequence of output epochs.

Repeatedly calls Propagate(x0, t0, tf, u) between consecutive entries of tfs, accumulating each result as a row of the returned matrix. Used by applications/ and analysis scripts to generate a full trajectory time history in one call, with optional progress-bar output (see SetPrintProgress).

Parameters:

x0 – Initial state at tfs(0).
tfs – Vector of output epochs [s, TDB since J2000], including the initial epoch as tfs(0).
u – Optional control/forcing input applied at every step; nullptr if unused.

Returns:

Matrix whose i-th row is the propagated state at tfs(i).