add nature::orbital_velocity

src/nature.rs

@@ -11,6 +11,7 @@
 // This module manages the messy, impure parts of our universe.
 
 use crate::prelude::*;
+use bevy::prelude::Vec3;
 
 pub const OXYGEN_USE_KG_PER_S: f32 = 1e-5;
 pub const OXY_S: f32 = OXYGEN_USE_KG_PER_S;
@@ -168,6 +169,17 @@ pub fn simple_orbital_period(mass: f64, distance: f64) -> f64 {
     return 2.0 * PI * (distance.powf(3.0) / (G * mass)).sqrt();
 }
 
+/// Calculates the orbital velocity with given parameters, assuming prograde circular orbit.
+pub fn orbital_velocity(coords: Vec3, mass: f64) -> Vec3 {
+    let r = coords.length() as f64;
+    let speed = (G * mass / r).sqrt() as f32;
+
+    // This generates a perpendicular orbital vector in the prograde direction
+    let perpendicular = Vec3::new(-coords.z, 0.0, -coords.x).normalize();
+
+    return perpendicular * speed;
+}
+
 pub fn phase_dist_to_coords(phase_radians: f64, distance: f64) -> DVec3 {
     return DVec3::new(
         distance * phase_radians.cos(),