astrodynamics

astrodynamics is a pure Rust numerical astrodynamics engine for orbit propagation, force models, and future flight-dynamics tooling.

The current crate focuses on a clean propagation foundation:

• Cartesian inertial state representation
• Two-body gravity
• J2 perturbation
• Fixed-step RK4
• Adaptive Dormand-Prince 5(4) (DP54)
• Oracle tests for Kepler invariants and J2 secular RAAN drift

This is a deliberately scoped 0.1.0. It is a propagation core, not yet a complete flight-dynamics platform. Dense output, event detection, richer contexts, estimation, maneuvers, and higher-fidelity force models are planned future work.

Units and conventions

• Position: kilometers
• Velocity: kilometers per second
• Time: seconds
• State frame: inertial Cartesian state

Example

use astrodynamics::forces::{CompositeForceModel, J2Gravity, TwoBodyGravity};
use astrodynamics::integrators::{DP54, Integrator};
use astrodynamics::propagator::{OrbitalDynamics, PropagationContext, api::IntegratorOptions};
use astrodynamics::CartesianState;

let initial = CartesianState::new(
    0.0,
    [7000.0, 0.0, 0.0],
    [0.0, 7.54605329, 0.0],
);

let mut forces = CompositeForceModel::new();
forces.add(Box::new(TwoBodyGravity::default()));
forces.add(Box::new(J2Gravity::default()));

let dynamics = OrbitalDynamics { force_model: &forces };
let integrator = DP54;
let ctx = PropagationContext::default();
let opts = IntegratorOptions {
    abs_tol: 1.0e-12,
    rel_tol: 1.0e-12,
    ..IntegratorOptions::default()
};

let result = integrator
    .propagate(initial, 3600.0, &dynamics, &ctx, &opts)
    .expect("propagation failed");

let final_state = result.final_state;
assert!(final_state.position_km.norm() > 6000.0);

Validation

The current test suite includes:

• circular-orbit full-period return checks
• elliptic-orbit energy and angular-momentum invariants
• analytical J2 secular RAAN drift comparison

Status

This crate is intended to become the standalone numerical core beneath higher level Elixir and application-facing satellite tooling. Today, it should be read as a solid propagation foundation with honest scope, not a finished mission-analysis suite.

License

MIT