ootk
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Orbital Object Toolkit including Multiple Propagators, Initial Orbit Determination, and Maneuver Calculations.
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JavaScript
/**
* @author @thkruz Theodore Kruczek
* @license AGPL-3.0-or-later
* @copyright (c) 2025 Kruczek Labs LLC
*
* Orbital Object ToolKit is free software: you can redistribute it and/or modify it under the
* terms of the GNU Affero General Public License as published by the Free Software
* Foundation, either version 3 of the License, or (at your option) any later version.
*
* Orbital Object ToolKit is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License along with
* Orbital Object ToolKit. If not, see <http://www.gnu.org/licenses/>.
*/
import { Moon, Sun, Vector3D } from '../main.js';
// / Third-body gravity model.
export class ThirdBodyGravity {
moon;
sun;
// / Create a new [ThirdBodyGravity] object with the selected bodies enabled.
constructor(moon = false, sun = false) {
this.moon = moon;
this.sun = sun;
// Nothing to do here.
}
static _moonGravity(state) {
const rMoon = Moon.eci(state.epoch);
const aNum = rMoon.subtract(state.position);
const aDen = aNum.magnitude() ** 3;
const bNum = rMoon;
const bDen = rMoon.magnitude() ** 3;
const gravity = aNum.scale(1 / aDen).add(bNum.scale(-1 / bDen));
return gravity.scale(Moon.mu);
}
static _sunGravity(state) {
const rSun = Sun.positionApparent(state.epoch);
const aNum = rSun.subtract(state.position);
const aDen = aNum.magnitude() ** 3;
const bNum = rSun;
const bDen = rSun.magnitude() ** 3;
const gravity = aNum.scale(1 / aDen).add(bNum.scale(-1 / bDen));
return gravity.scale(Sun.mu);
}
acceleration(state) {
let accVec = Vector3D.origin;
if (this.moon) {
accVec = accVec.add(ThirdBodyGravity._moonGravity(state));
}
if (this.sun) {
accVec = accVec.add(ThirdBodyGravity._sunGravity(state));
}
return accVec;
}
}
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