Added moon support; turn back on barycenter calculation

seanpile · Dec 10, 2016 · 3ed042c · 3ed042c
1 parent fba9323
commit 3ed042c
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Showing 3 changed files with 56 additions and 16 deletions.
diff --git a/scripts/CanvasDisplay.js b/scripts/CanvasDisplay.js
@@ -2,7 +2,7 @@ const MIN_BODY_RADIUS = 5;
 const MAX_BODY_RADIUS = 25;
 const BASE_TIME_SCALE = 86400;
 let timeScale = 5;
-let numToRun = 1000;
+let numToRun = 10000;
 
 define(function () {
 
@@ -53,6 +53,10 @@ define(function () {
       radius = 3;
       color = "purple";
       break;
+    case "mars":
+      radius = 5;
+      color = "red";
+      break;
     default:
       radius = 5;
       color = "black";
@@ -91,14 +95,15 @@ define(function () {
       }, this);
 
       ctx.strokeStyle = "red";
+      ctx.lineWidth = 0.5;
       ctx.beginPath();
-      ctx.moveTo(25, 0);
-      ctx.lineTo(-25, 0);
+      ctx.moveTo(50, 0);
+      ctx.lineTo(-50, 0);
       ctx.stroke();
       ctx.closePath();
       ctx.beginPath();
-      ctx.moveTo(0, 25);
-      ctx.lineTo(0, -25);
+      ctx.moveTo(0, 50);
+      ctx.lineTo(0, -50);
       ctx.stroke();
 
       last += step;

diff --git a/scripts/SolarSystem.js b/scripts/SolarSystem.js
@@ -8,9 +8,10 @@ define(["Vector"], function (Vector) {
   // Calculate a new 'CoM' given all of the current bodies and update the
   // coordinates of all current bodies.
   SolarSystem.prototype.update = function (t, dt) {
-
-    //this.updateBarycenter();
+    this.updateBarycenter();
     this.updateEphemeris(t, dt);
+
+    //console.log(this.bodies[2].velocity);
   };
 
   // Calcluate the barycenter of the system and adjust the coordinate
@@ -28,7 +29,6 @@ define(["Vector"], function (Vector) {
 
     this.bodies.forEach(function (body) {
       body.position = body.position.plus(newCenterOfMass);
-      body.velocity = body.velocity.plus(newCenterOfMass);
     });
   };
 

diff --git a/scripts/main.js b/scripts/main.js
@@ -4,21 +4,56 @@ requirejs(["SolarSystem", "CanvasDisplay", "Vector", "verlet-integrator"],
 
     const AU = 149597870700.0; // m
     const SUN_MASS = 1.989e30 / AU; // kg
-    const EARTH_MASS = 5.97e24 / AU; // kg
-    const MOON_MASS = 7.3476e22 / AU; // kg
-    const JUPITER_MASS = 1.898e27 / AU; // kg
-    const EARTH_TO_SUN = 149.6e9 / AU; // m
-    const MOON_TO_EARTH = 0.3633e9 / AU; // m
     const UNIVERSAL_GRAVITY = 6.674e-11 / Math.pow(AU, 2); // N⋅m^2/kg^2
 
+    const EARTH = {
+      name: "earth",
+      mass: 5.97e24 / AU, // kg
+      distanceToSun: 149.6e9 / AU, // m
+      moons: [{
+        name: "moon",
+        mass: 7.3476e22 / AU, // kg
+        distanceToPrimary: 0.3633e9 / AU // m
+      }]
+    };
+
+    const MARS = {
+      name: "mars",
+      mass: 0.642e24 / AU, // kg
+      distanceToSun: 227.9e9 / AU
+    };
+
     let integrator = new VerletIntegrator(UNIVERSAL_GRAVITY);
     let solarSystem = new SolarSystem(integrator);
 
     let sun = solarSystem.addBody("sun", SUN_MASS);
-    let earth = solarSystem.addBody("earth", EARTH_MASS);
 
-    earth.position = new Vector(0, EARTH_TO_SUN, 0);
-    earth.velocity = new Vector(-Math.sqrt(UNIVERSAL_GRAVITY * (SUN_MASS + EARTH_MASS) / EARTH_TO_SUN), 0, 0).times(1);
+    [EARTH, MARS].forEach(function (properties) {
+      let body = solarSystem.addBody(properties.name, properties.mass);
+      let random = Math.random();
+
+      //randomized locations on a unit circle
+
+      if (random <= 0.25) {
+        body.position = new Vector(0, properties.distanceToSun, 0);
+        body.velocity = new Vector(-Math.sqrt(UNIVERSAL_GRAVITY * (SUN_MASS + properties.mass) / properties.distanceToSun), 0, 0);
+      } else if (random <= 0.5) {
+        body.position = new Vector(-properties.distanceToSun, 0, 0);
+        body.velocity = new Vector(0, -Math.sqrt(UNIVERSAL_GRAVITY * (SUN_MASS + properties.mass) / properties.distanceToSun), 0);
+      } else {
+        body.position = new Vector(0, -properties.distanceToSun, 0);
+        body.velocity = new Vector(Math.sqrt(UNIVERSAL_GRAVITY * (SUN_MASS + properties.mass) / properties.distanceToSun), 0, 0);
+      }
+
+      if (properties.moons) {
+        properties.moons.forEach(function (props) {
+          let moon = solarSystem.addBody(props.name, props.mass);
+          moon.position = body.position.plus(body.position.times(1 / body.position.magnitude()).times(props.distanceToPrimary));
+          moon.velocity = body.velocity.plus(
+            body.velocity.times(1 / body.velocity.magnitude()).times(-Math.sqrt(UNIVERSAL_GRAVITY * (props.mass + body.mass) / props.distanceToPrimary)));
+        });
+      }
+    });
 
     let canvas = document.getElementById("expanse-simulation");
     let simulation = new Display(canvas, solarSystem);