Crate astrodyn_dynamics 

Rigid-body dynamics: state, mass properties, forces, and integration.

This crate is the JEOD-faithful port of the dynamics half of models/dynamics/. It owns the per-vehicle state types (TranslationalState, RotationalState, SixDofState), the rigid- body mass model (MassProperties, MassBody, MassPoint, MassTree, point_mass_inertia), the force-collection pipeline (collect_forces, ForceContributions, TotalForce, GravityAcceleration, compute_translational_acceleration, compute_translational_derivatives, compute_frame_derivatives, compute_t_inertial_struct), and a battery of integrators (rk4_translational_step, rk4_sixdof_step, adaptive RKF4(5) in rkf45, multistep abm4/Adams–Bashforth–Moulton, and gauss_jackson).

Initial-condition machinery in body_init mirrors JEOD’s BodyAction subclasses: init_from_orbital_elements, init_from_mean_anomaly, init_from_time_periapsis, init_from_lvlh, init_from_ned, and compute_ned_rotation. Frame propagation lives in propagation: propagate_body_frames, propagate_forward, propagate_reverse. Holonomic constraints (HolonomicConstraint, PendulumConstraint, BaumgarteSolver, apply_constraint) port the constraint-stabilization layer used by tethers and articulated structures. Declaratively driven kinematic joints — single-axis frame-rotation drivers used by articulated sub-trees that consume a prescribed angular trajectory rather than integrating one — live in kinematic_joint (JointKinematicsSpec, evaluate_joint_kinematics). Root-to-leaf state propagation through kinematic-child chains lives in kinematic_propagation (compute_kinematic_child_state, compute_kinematic_child_state_typed, derive_kinematic_child_from_states, KinematicChildInputs, KinematicChildOutputs).

JEOD source: models/dynamics/dyn_body/, models/dynamics/mass/, models/dynamics/body_action/, and models/utils/integration/. Pure Rust, zero Bevy dependency — orchestration lives in astrodyn and ECS wiring lives in the astrodyn_bevy root crate.

Example

Compute the parallel-axis (Steiner) inertia contribution of a 10 kg point mass offset 2 m along +X from the reference point. The resulting matrix has 0 on the (0,0) diagonal (no inertia about the axis through the offset) and mass * r^2 = 40 on the perpendicular diagonal entries:

use astrodyn_dynamics::point_mass_inertia;
use glam::DVec3;

let i = point_mass_inertia(10.0, DVec3::new(2.0, 0.0, 0.0));
assert!(i.x_axis.x.abs() < 1e-12);
assert!((i.y_axis.y - 40.0).abs() < 1e-12);
assert!((i.z_axis.z - 40.0).abs() < 1e-12);

Re-exports

pub use abm4::abm4_translational_step;

pub use abm4::Abm4State;

pub use attach::combine_states_at_attach;

pub use attach::AttachCombineInputs;

pub use attach::AttachCombineOutputs;

pub use body_init::compute_ned_rotation;

pub use body_init::init_from_lvlh;

pub use body_init::init_from_mean_anomaly;

pub use body_init::init_from_ned;

pub use body_init::init_from_orbital_elements;

pub use body_init::init_from_time_periapsis;

pub use constraints::apply_constraint;

pub use constraints::BaumgarteSolver;

pub use constraints::HolonomicConstraint;

pub use constraints::PendulumConstraint;

pub use forces::collect_forces;

pub use forces::compute_frame_derivatives;

pub use forces::compute_t_inertial_struct;

pub use forces::compute_translational_acceleration;

pub use forces::compute_translational_derivatives;

pub use forces::DynamicsConfig;

pub use forces::ForceContributions;

pub use forces::FrameDerivatives;

pub use forces::GravityAcceleration;

pub use forces::TotalForce;

pub use frame_attach::derive_frame_attached_state;

pub use frame_attach::FrameAttachInputs;

pub use gauss_jackson::config::GaussJacksonConfig;

pub use gauss_jackson::GaussJacksonState;

pub use gauss_jackson::IntegratorResult;

pub use integration::rk4_sixdof_step;

pub use integration::rk4_translational_step;

pub use integration::IntegratorType;

pub use kinematic_joint::evaluate as evaluate_joint_kinematics;

pub use kinematic_joint::evaluate_closure as evaluate_closure_kinematics;

pub use kinematic_joint::evaluate_model as evaluate_joint_kinematics_model;

pub use kinematic_joint::evaluate_multi_dof as evaluate_multi_dof_kinematics;

pub use kinematic_joint::evaluate_sinusoidal as evaluate_sinusoidal_kinematics;

pub use kinematic_joint::ClosureJointKinematicsSpec;

pub use kinematic_joint::JointKinematicsModel;

pub use kinematic_joint::JointKinematicsSpec;

pub use kinematic_joint::MultiDofJointKinematicsSpec;

pub use kinematic_joint::SingleDofKinematics;

pub use kinematic_joint::SinusoidalJointKinematicsSpec;

pub use kinematic_joint::MAX_MULTI_DOF_AXES;

pub use kinematic_propagation::compute_kinematic_child_state;

pub use kinematic_propagation::compute_kinematic_child_state_dquat;

pub use kinematic_propagation::compute_kinematic_child_state_typed;

pub use kinematic_propagation::derive_kinematic_child_from_states;

pub use kinematic_propagation::KinematicChildInputs;

pub use kinematic_propagation::KinematicChildOutputs;

pub use mass::MassProperties;

pub use mass::MassPropertiesTyped;

pub use mass::INERTIA_CONSISTENCY_TOL;

pub use mass_body::point_mass_inertia;

pub use mass_body::MassBody;

pub use mass_body::MassBodyId;

pub use mass_body::MassPoint;

pub use mass_body::MassPointState;

pub use mass_body::MassTree;

pub use mass_storage::compute_node_composite;

pub use mass_storage::finalize_child_in_parent_frame;

pub use mass_storage::recompute_composites_via_storage;

pub use mass_storage::MassNodeOutputs;

pub use mass_storage::MassNodeView;

pub use mass_storage::MassStorage;

pub use propagation::propagate_body_frames;

pub use propagation::propagate_forward;

pub use propagation::propagate_reverse;

pub use rkf45::rkf45_adaptive_sixdof_step;

pub use rkf45::rkf45_adaptive_translational_step;

pub use rkf45::rkf45_sixdof_step;

pub use rkf45::rkf45_translational_step;

pub use rkf45::AdaptiveConfig;

pub use rkf45::AdaptiveResult;

pub use rotational::compute_left_quat_deriv;

pub use rotational::compute_rotational_acceleration;

pub use rotational::normalize_integ;

pub use rotational::RotationalState;

pub use rotational::RotationalStateTyped;

pub use rotational::SixDofState;

pub use rotational::SixDofStateTyped;

pub use state::TranslationalState;

pub use subtree::DetachedSubtreeState;

pub use wrench::shift_wrench_to_parent;

pub use wrench::shift_wrench_to_parent_typed;

pub use wrench::Wrench;

Modules

abm4

Adams-Bashforth-Moulton 4th-order (ABM4) integrator for second-order ODEs.

attach

Mass-tree attach: combine two free bodies’ kinematic states into a single rigid body via JEOD’s “magical” merge algorithm.

body_init

Body initialization functions for translational state.

constraints

Holonomic constraint dynamics with Baumgarte stabilization.

forces

Per-body force / torque accumulators consumed by the integrator.

frame_attach

Frame-attached body integration kernel.

gauss_jackson

Gauss-Jackson (Störmer-Cowell) integrator for second-order ODEs.

integration

Integration-method dispatch and the per-method translational / rotational step kernels.

kinematic_joint

Declaratively driven kinematic joints.

kinematic_propagation

Kinematic state derivation for a passive rigid attachment.

mass

MassProperties and the typed sibling MassPropertiesTyped — mass, inertia tensor, and CoM offset for a rigid body.

mass_body

Arena-based mass tree: a faithful port of JEOD’s MassBody hierarchy.

mass_storage

Storage-agnostic mass-tree composition.

propagation

State propagation: compute derived frame states from an integrated frame state and mass offsets.

rkf45

Runge-Kutta-Fehlberg 4(5) integrator.

rotational

Rotational state: attitude quaternion, angular velocity, and the integration kernels that propagate them under applied torque.

state

TranslationalState — position and velocity in the integration frame.

subtree

Composite-body kinematic state of a free-flying mass-tree subtree.

wrench

Composite-rigid-body wrench shift: parallel-axis transfer of a child’s (force, torque) pair to its parent’s structural frame.