Crate astrodyn_atmosphere

Expand description

Neutral-atmosphere density, temperature, pressure, and wind models.

Pure-Rust port of JEOD’s atmosphere models from models/environment/atmosphere/. All evaluations are framed by the AtmosphereState return type — density (kg/m^3), temperature (K), pressure (Pa), and inertial-frame wind velocity (m/s). The crate has zero Bevy dependency; orchestration lives in astrodyn.

§Models

exponential — rho = rho_0 * exp(-(h - h_0) / H). A simple, single-parameter scale-height model intended as a fallback and as a sanity-check baseline for tests. Not physically accurate above ~100 km where diffusive equilibrium takes over.
met — Marshall Engineering Thermosphere model. Faithful port of JEOD’s MET implementation, which is built on the Jacchia 1970/1971 thermosphere papers (SAO Special Reports No. 313 and 332). MET combines temperature-profile integration via Gauss quadrature with seasonal- latitude density corrections and is the production model for LEO drag.

§Co-rotation wind

compute_corotation_wind (and its typed sibling compute_corotation_wind_typed) implement JEOD’s WindVelocity::update_wind() for a planet whose angular velocity points along the inertial Z axis: wind = omega × r. Aerodynamic drag computes its relative velocity against this co-rotating wind, not against the bare inertial frame.

§Typed quantities

AtmosphereState is parameterized over the atmosphere planet P so the wind vector carries Velocity<PlanetInertial> directly. AtmosphereState<Earth> and AtmosphereState<Mars> are distinct types and the compiler refuses to feed Mars’s wind to an Earth drag kernel. Producers that determine the planet at runtime (evaluate_atmosphere, the runner’s per-body atmospheric_state) return AtmosphereState<SelfPlanet>; mission code that knows the planet at compile time uses the typed sibling evaluate_atmosphere_typed::() and consumes AtmosphereState. The boundary between the two is the AtmosphereState::<SelfPlanet>::relabel method, restricted to the planet-erased variant so a planet-pinned AtmosphereState<Earth> cannot accidentally be retagged as AtmosphereState<Mars>. JEOD source paths used: models/environment/atmosphere/MET/ and the broader models/environment/atmosphere/ model directory; the wind-frame convention is documented in models/environment/atmosphere/base_atmos/include/wind_velocity.hh (“the inertial frame of the planet causing the wind velocity”).

§Example

Default exponential atmosphere with Earth sea-level reference values:

use astrodyn_atmosphere::exponential::ExponentialAtmosphere;

let atmos = ExponentialAtmosphere::default();
let sea_level = atmos.density(0.0);
assert!((sea_level.density - 1.225).abs() < 1e-9);

// Density falls off exponentially with altitude.
let one_scale_height = atmos.density(8_500.0);
assert!(one_scale_height.density < sea_level.density);

Modules§

exponential: Exponential atmosphere model.
met: MET (Marshall Engineering Thermosphere) atmosphere model.

Structs§

AtmosphereState: Atmospheric state at a given position.
BodyAttitude: RootInertial → body attitude of vehicle V, witnessed unit-norm and scalar-first / left-transformation (JEOD canonical).
BodyFrame: Body (CoM-centered) frame of vehicle V. Rotates with the vehicle.
Earth: Planet marker for Earth.
Ecef: Earth-centered Earth-fixed frame (ITRF-like). Rotates with Earth.
FrameTransform: Proper rotation taking vectors expressed in From to the same vectors expressed in To.
GMST: Greenwich Mean Sidereal Time (angle, but seconds-ized by convention).
GPS: GPS Time (TAI − 19 s).
GravParam: Gravitational parameter μ = GM tagged with the source planet P.
HarmonicDegree: Spherical-harmonic degree or order index. Unitless ordinal.
InertiaTensor: Mass moment of inertia tensor (kg·m²) expressed in frame F.
IntegOrigin: The integration-frame origin: position and velocity of the integration-frame origin expressed in root-inertial coordinates.
IntegrationFrame: A body’s integration frame — a non-rotating quasi-inertial frame whose origin generally differs from the root inertial origin.
LeftTransform: r' = q r q⁻¹ — the JEOD convention.
Lvlh: Local Vertical / Local Horizontal frame relative to chief vehicle Chief. Z axis points planet-ward; Y opposes orbital angular momentum; X completes the right-handed triad (approximately along-track in near-circular orbits).
Mars: Planet marker for Mars.
MassNode: Mass-tree wildcard inertial-flavor frame for kinematic-propagation scratch state.
Moon: Planet marker for Moon.
Ned: North-East-Down topocentric frame relative to chief vehicle Chief.
NormalizedQuat: A quaternion witnessed to have unit norm at construction time.
PlanetFixed: Planet-fixed frame for any planet P. Rotates with that planet.
PlanetInertial: A particular planet’s inertial (non-rotating, J2000-aligned) frame, centered at the planet’s CoM.
Qty3: Componentwise 3-vector: each of x, y, z carries the dimension D, and the whole vector carries the frame tag F.
Quat: Quaternion tagged with its storage layout and transformation convention.
RightTransform: r' = q⁻¹ r q — the opposite of JEOD; common in many textbooks.
RootInertial: The simulation’s root inertial frame — the unique inertial node at the top of the frame tree.
ScalarFirst: Storage layout [q0, q1, q2, q3] where q0 is the scalar part (JEOD).
ScalarLast: Storage layout [x, y, z, w] where w is the scalar part (glam).
SecondsSince: Seconds elapsed in the named time scale, measured from that scale’s epoch.
SelfPlanet: Phantom marker for “this entity’s own planet” — used by ECS adapters whose per-entity components carry PlanetFixed phantoms but whose planet identity is determined at runtime by the entity itself.
SelfRef: Phantom marker for “this entity’s own vehicle frame” — used by ECS adapters whose per-entity components carry frame phantoms but whose vehicle identity is determined at runtime by the entity itself.
StructuralFrame: Structural (geometric-origin) frame of vehicle V. Rotates with vehicle.
Sun: Planet marker for Sun.
TAI: International Atomic Time.
TDB: Barycentric Dynamical Time (relativistic correction to TT).
TT: Terrestrial Time (TAI + 32.184 s).
TimeConverter: Explicit converter between two time scales.
UT1: Universal Time 1 (Earth-rotation based).
UTC: Coordinated Universal Time (leap-second stepped).

Traits§

Array3Ext: Extension trait on [f64; 3] (raw component arrays from CSVs or JEOD initial conditions) producing frame-tagged 3-vectors.
F64Ext: Unit-construction extension on f64.
Frame: Compile-time reference frame tag.
Layout: Compile-time quaternion storage layout marker.
Planet: Compile-time planet tag used to parameterize planet-fixed frames.
TimeScale: Compile-time time-scale tag.
Transform: Compile-time quaternion transformation convention marker.
Vec3Ext: Extension trait on glam::DVec3 producing frame-tagged 3-vectors.
Vehicle: Compile-time vehicle tag used to parameterize vehicle-relative frames.

Functions§

compute_corotation_wind: Compute atmospheric co-rotation wind velocity in the inertial frame.
compute_corotation_wind_typed: Typed variant of compute_corotation_wind.

Type Aliases§

Acceleration: Acceleration in frame F. Base SI unit: m/s².
AngularAcceleration: Angular acceleration in frame F. Base SI unit: rad/s².
AngularMomentum: Angular momentum in frame F. Base SI unit: kg·m²/s.
AngularVelocity: Angular velocity in frame F. Base SI unit: rad/s.
Force: Force in frame F. Base SI unit: newtons.
JeodQuat: The JEOD canonical quaternion type: scalar-first, left-transformation.
Jerk: Jerk (time derivative of acceleration) in frame F. Base SI unit: m/s³.
MassFlowRate: Scalar mass-flow rate.
Position: Position in frame F (default: RootInertial). Base SI unit: meters.
SpecificAngMom: Scalar specific angular momentum.
SpecificEnergy: Scalar specific energy.
Torque: Torque in frame F. Base SI unit: N·m.
Velocity: Velocity in frame F. Base SI unit: m/s.