public static double SuicideBurnCountdown(Orbit orbit, VesselState vesselState, Vessel vessel)
{
if (vesselState.mainBody == null)
{
return(0);
}
if (orbit.PeA > 0)
{
return(Double.PositiveInfinity);
}
double angleFromHorizontal = 90 - Vector3d.Angle(-vessel.srf_velocity, vesselState.up);
angleFromHorizontal = MuUtils.Clamp(angleFromHorizontal, 0, 90);
double sine = Math.Sin(angleFromHorizontal * Math.PI / 180);
double g = vesselState.localg;
double T = vesselState.limitedMaxThrustAccel;
double effectiveDecel = 0.5 * (-2 * g * sine + Math.Sqrt((2 * g * sine) * (2 * g * sine) + 4 * (T * T - g * g)));
double decelTime = vesselState.speedSurface / effectiveDecel;
Vector3d estimatedLandingSite = vesselState.CoM + 0.5 * decelTime * vessel.srf_velocity;
double terrainRadius = vesselState.mainBody.Radius + vesselState.mainBody.TerrainAltitude(estimatedLandingSite);
double impactTime = 0;
try
{
impactTime = orbit.NextTimeOfRadius(vesselState.time, terrainRadius);
}
catch (ArgumentException)
{
return(0);
}
return(impactTime - decelTime / 2 - vesselState.time);
}
//Time during a's next orbit at which object a comes nearest to object b.
//If a is hyperbolic, the examined interval is the next 100 units of mean anomaly.
//This is quite a large segment of the hyperbolic arc. However, for extremely high
//hyperbolic eccentricity it may not find the actual closest approach.
public static double NextClosestApproachTime(this Orbit a, Orbit b, double UT)
{
double closestApproachTime = UT;
double closestApproachDistance = Double.MaxValue;
double minTime = UT;
double interval = a.period;
if (a.eccentricity > 1)
{
interval = 100 / a.MeanMotion(); //this should be an interval of time that covers a large chunk of the hyperbolic arc
}
double maxTime = UT + interval;
const int numDivisions = 20;
for (int iter = 0; iter < 8; iter++)
{
double dt = (maxTime - minTime) / numDivisions;
for (int i = 0; i < numDivisions; i++)
{
double t = minTime + i * dt;
double distance = a.Separation(b, t);
if (distance < closestApproachDistance)
{
closestApproachDistance = distance;
closestApproachTime = t;
}
}
minTime = MuUtils.Clamp(closestApproachTime - dt, UT, UT + interval);
maxTime = MuUtils.Clamp(closestApproachTime + dt, UT, UT + interval);
}
return(closestApproachTime);
}