/**
 * @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 { J2000, Vector3D } from '../main.js';
import { Force } from './Force.js';
export declare class Gravity implements Force {
    mu: number;
    /**
     * Create a new [Gravity] object with optional gravitational
     * @param mu Gravitational parameter _(km²/s³)_.
     */
    constructor(mu?: number);
    /**
     * Calculates the gravitational force in spherical coordinates.
     * @param state The J2000 state containing the position and velocity vectors.
     * @returns The gravitational force vector in spherical coordinates.
     */
    private _spherical;
    /**
     * Calculates the acceleration due to gravity at a given state.
     * @param state The J2000 state at which to calculate the acceleration.
     * @returns The acceleration vector.
     */
    acceleration(state: J2000): Vector3D;
}