/SolarSystem/SolarSystemBodyFactory.cs

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using MathNet.Numerics.LinearAlgebra.Double;



namespace SolarSystem

{

    public class SolarSystemBodyFactory

    {

        private static readonly Double MassOfSun = 1.9891 * Math.Pow(10, 30);



        public static Body CreateSun()

        {

            return new Body()

            {

                Name = "Sun",

                Radius = 6.96342 * Math.Pow(10, 5),

                Mass = 1.9891 * Math.Pow(10, 30),

                Position = new DenseVector(new[] { 0d, 0d }),

                Velocity = new DenseVector(new[] { 0d, 0d }),                

                Rotation = 0,

                RotationVelocity = 0

            };

        }



        public static Body CreateBody(String name, Double radius, Double mass, Double semiMajorAxis, Double eccentricity, Double rotationVelocity)

        {

            var position = new DenseVector(new[] { GetDistanceAtAphelion(semiMajorAxis, eccentricity), 0 });

            var velocity = new DenseVector(new[] { 0, GetVelocityAtAphelion(semiMajorAxis, eccentricity) });



            return new Body() { Name = name, Radius = radius, Position = position, Velocity = velocity, Rotation = 0, RotationVelocity = rotationVelocity };

        }



        private static Double GetDistanceAtAphelion(Double semiMajorAxis, Double eccentricity)

        {

            return (1 + eccentricity) * semiMajorAxis;

        }



        private static Double GetVelocityAtAphelion(Double semiMajorAxis, Double eccentricity)

        {

            var distance = GetDistanceAtAphelion(semiMajorAxis, eccentricity);

            return Math.Sqrt(Constants.GravitationalConstant * MassOfSun * (2 / distance - 1 / semiMajorAxis));

        }

    }

}