public double GetAtmosphericViscosity(double altitude)
{
return(_proxy.GetAtmosphericViscosity(altitude));
}
public void ResolveAtmopsherics(IMassiveBody body)
{
// Don't resolve drag for children
if (Parent != null)
{
return;
}
DVector2 difference = body.Position - Position;
double distance = difference.Length();
difference.Normalize();
double altitude = distance - body.SurfaceRadius;
// The spacecraft is in the bodies atmopshere
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);
Velocity = (body.Velocity + surfaceNormal * rotationalSpeed);
Rotation = normal.Angle();
AccelerationN.X = -AccelerationG.X;
AccelerationN.Y = -AccelerationG.Y;
}
double atmosphericDensity = body.GetAtmosphericDensity(altitude);
DVector2 relativeVelocity = (body.Velocity + surfaceNormal * rotationalSpeed) - Velocity;
double velocity = relativeVelocity.Length();
double velocitySquared = relativeVelocity.LengthSquared();
if (velocitySquared > 0)
{
double speed = relativeVelocity.Length();
// Heating
HeatingRate = 1.83e-4 * Math.Pow(speed, 3) * Math.Sqrt(atmosphericDensity / (Width * 0.5));
relativeVelocity.Normalize();
double dragTerm = TotalDragCoefficient() * TotalDragArea();
// Drag ( Fd = 0.5pv^2dA )
DVector2 dragForce = relativeVelocity * (0.5 * atmosphericDensity * velocitySquared * dragTerm);
AccelerationD += dragForce / Mass;
double reynoldsNumber = (velocity * Height) / body.GetAtmosphericViscosity(altitude);
double frictionCoefficient = 0.455 / Math.Pow(Math.Log10(reynoldsNumber), 2.58);
double frictionTerm = frictionCoefficient * TotalSurfaceArea();
// Skin friction ( Fs = 0.5CfpV^2S )
DVector2 skinFriction = relativeVelocity * (0.5 * atmosphericDensity * velocitySquared * frictionTerm);
AccelerationD += skinFriction / Mass;
}
}
else
{
HeatingRate = 0;
}
}
