Crate keplerian_sim

Keplerian Orbital Mechanics

This library crate contains logic for Keplerian orbits, similar to the ones you’d find in a game like Kerbal Space Program.

Keplerian orbits are special in that they are more stable and predictable than Newtonian orbits. In fact, unlike Newtonian orbits, Keplerian orbits don’t use time steps to calculate the next position of an object. Keplerian orbits use state vectors to determine the object’s full trajectory at any given time.
This way, you don’t need to worry about lag destabilizing Keplerian orbits.

However, Keplerian orbits are significantly more complex to calculate than just using Newtonian physics. It’s also a two-body simulation, meaning that it doesn’t account for external forces like gravity from other bodies or the engines of a spacecraft.

The way Kerbal Space Program handles this is to have an “on-rails” physics system utilizing Keplerian orbits, and an “active” physics system utilizing Newtonian two-body physics.

Getting started

This crate provides four main structs:

• Orbit: A struct representing an orbit around a celestial body. Each instance of this struct has some cached data to speed up certain calculations, and has a larger memory footprint.
• CompactOrbit: A struct representing an orbit around a celestial body. This struct has a smaller memory footprint than the regular Orbit struct, but some calculations may take 2~10x slower because it doesn’t save any cached calculations.
• Body: A struct representing a celestial body. This struct contains information about the body’s mass, radius, and orbit.
• Universe: A struct representing the entire simulation. This struct contains a list of all the bodies in the simulation, and can calculate the absolute position of any body at any given time. To do this, it stores parent-child relationships between bodies.

We also provide a body_presets module, which contains some preset celestial bodies to use in your simulation. It contains many celestial bodies, like the Sun, the Moon, and all the planets in the Solar System.

Example

use glam::DVec3;

use keplerian_sim::{Orbit, OrbitTrait};

// Create a perfectly circular orbit with a radius of 1 meter
let orbit = Orbit::default();
assert_eq!(orbit.get_position_at_time(0.0), DVec3::new(1.0, 0.0, 0.0));

Modules

body_presets

This module contains presets for common celestial bodies.

Structs

Body

A struct representing a celestial body.

CompactOrbit

A minimal struct representing a Keplerian orbit.

Matrix3x2

A struct representing a 3x2 matrix.

Orbit

A struct representing a Keplerian orbit with some cached values.

Universe

Struct that represents the simulation of the universe.

Enums

ApoapsisSetterError

An error to describe why setting the periapsis of an orbit failed.

MuSetterMode

A mode to describe how the gravitational parameter setter should behave.

Traits

OrbitTrait

A trait that defines the methods that a Keplerian orbit must implement.