Aetherion

ΑETHERION — Flight Dynamics Library

AETHERION is a high-precision, research-grade C++ library for
rocket and aerospace flight dynamics, built on:

The name ΑΙΘΕΡΙΟΝ (Aetherion) is inspired by the Greek word Αιθήρ,
referring to the upper atmosphere — the pristine realm of celestial motion.

Full 6-DOF rigid-body dynamics using Spatial Vector Algebra formalism
Inertial-frame (ECI) equations of motion with no pseudo-forces
Rotating atmosphere support via air-relative velocity only
AD-friendly equations for CppAD, dual numbers, and other libraries
US1976 Standard Atmosphere and clean gravity models
Lie structure preserving Runge-Kutta-Munthe-Kaas integrator (with a fully implicit RADAU-IIA solver implementation)
Discrete extended Kalman filter on a product manifold containing Lie groups for state estimation
Post-modern C++23 design

ΑETHERION implements all major constructs from Featherstone’s Rigid Body Dynamics Algorithms:

Equation of motion:

Equation of Motion

Control surfaces can be modeled as rigidly attached bodies.

ΑETHERION uses:

All transformations follow:

Transform equation

notation for transforms and spatial transforms.

This keeps the frame algebra clean, explicit, and AD-friendly.

ΑETHERION provides:

US1976 Standard Atmosphere
- temperature
- pressure
- density
- speed of sound
Gravity models
Branch-free formulations ideal for AD and Kalman filtering