public void ResolveAtmopsherics(IMassiveBody body)
{
DVector2 difference = body.Position - Position;
double distance = difference.Length() - Height * 0.5;
difference.Normalize();
Altitude = distance - body.SurfaceRadius;
// The object is in the atmosphere of body B
if (Altitude < body.AtmosphereHeight)
{
var surfaceNormal = new DVector2(-difference.Y, difference.X);
double altitudeFromCenter = Altitude + body.SurfaceRadius;
// Distance of circumference at this altitude ( c= 2r * pi )
double pathCirumference = 2 * Math.PI * altitudeFromCenter;
double rotationalSpeed = pathCirumference / body.RotationPeriod;
// Simple collision detection
if (Altitude <= 0)
{
var normal = new DVector2(-difference.X, -difference.Y);
Position = body.Position + normal * (body.SurfaceRadius);
Pitch = normal.Angle();
AccelerationN.X = -AccelerationG.X;
AccelerationN.Y = -AccelerationG.Y;
OnGround = true;
}
else
{
OnGround = false;
}
double atmosphericDensity = body.GetAtmosphericDensity(Altitude);
RelativeVelocity = (body.Velocity + surfaceNormal * rotationalSpeed) - Velocity;
double velocityMagnitude = RelativeVelocity.LengthSquared();
if (velocityMagnitude > 0)
{
DVector2 normalizedRelativeVelocity = RelativeVelocity.Clone();
normalizedRelativeVelocity.Normalize();
double formDragTerm = FormDragCoefficient * FrontalArea;
double skinFrictionTerm = SkinFrictionCoefficient * ExposedSurfaceArea;
double dragTerm = formDragTerm + skinFrictionTerm;
// Drag ( Fd = 0.5pv^2dA )
DVector2 dragForce = normalizedRelativeVelocity * (0.5 * atmosphericDensity * velocityMagnitude * dragTerm);
// Reject insane forces
if (dragForce.Length() < 50000000)
{
AccelerationD = dragForce / Mass;
}
}
}
}
