private void CalculateExtendedParameters()
{
if (IsStationary)
{
return;
}
// Calculate extended parameters.
// http://en.wikipedia.org/wiki/Standard_gravitational_parameter#Two_bodies_orbiting_each_other
GravitationalParameter_Km3S2 = GMath.GravitationalParameter_Km3s2(_parentMass + _myMass); // Normalize GravitationalParameter from m^3/s^2 to km^3/s^2
GravitationalParameterAU = GMath.GrabitiationalParameter_Au3s2(_parentMass + _myMass); // (149597870700 * 149597870700 * 149597870700);
GravitationalParameter_m3S2 = GMath.StandardGravitationalParameter(_parentMass + _myMass);
double orbitalPeriod = 2 * Math.PI * Math.Sqrt(Math.Pow(Distance.AuToKm(SemiMajorAxis_AU), 3) / (GravitationalParameter_Km3S2));
if (orbitalPeriod * 10000000 > long.MaxValue)
{
OrbitalPeriod = TimeSpan.MaxValue;
}
else
{
OrbitalPeriod = TimeSpan.FromSeconds(orbitalPeriod);
}
// http://en.wikipedia.org/wiki/Mean_motion
MeanMotion_DegreesSec = Math.Sqrt(GravitationalParameter_Km3S2 / Math.Pow(Distance.AuToKm(SemiMajorAxis_AU), 3)); // Calculated in radians.
MeanMotion_DegreesSec = Angle.ToDegrees(MeanMotion_DegreesSec); // Stored in degrees.
Apoapsis_AU = (1 + Eccentricity) * SemiMajorAxis_AU;
Periapsis_AU = (1 - Eccentricity) * SemiMajorAxis_AU;
SOI_m = OrbitMath.GetSOI(SemiMajorAxis, _myMass, _parentMass);
}
/// <summary>
/// Creates on Orbit at current location from a given velocity
/// </summary>
/// <returns>The Orbit Does not attach the OrbitDB to the entity!</returns>
/// <param name="parent">Parent. must have massdb</param>
/// <param name="entity">Entity. must have massdb</param>
/// <param name="velocity_m">Velocity in meters.</param>
public static OrbitDB FromVelocity_m(Entity parent, Entity entity, Vector3 velocity_m, DateTime atDateTime)
{
var parentMass = parent.GetDataBlob <MassVolumeDB>().Mass;
var myMass = entity.GetDataBlob <MassVolumeDB>().Mass;
//var epoch1 = parent.Manager.ManagerSubpulses.StarSysDateTime; //getting epoch from here is incorrect as the local datetime doesn't change till after the subpulse.
//var parentPos = OrbitProcessor.GetAbsolutePosition_AU(parent.GetDataBlob<OrbitDB>(), atDateTime); //need to use the parent position at the epoch
var posdb = entity.GetDataBlob <PositionDB>();
posdb.SetParent(parent);
var ralitivePos = posdb.RelativePosition_m;//entity.GetDataBlob<PositionDB>().AbsolutePosition_AU - parentPos;
if (ralitivePos.Length() > OrbitProcessor.GetSOI_m(parent))
{
throw new Exception("Entity not in target SOI");
}
//var sgp = GameConstants.Science.GravitationalConstant * (myMass + parentMass) / 3.347928976e33;
var sgp_m = GMath.StandardGravitationalParameter(myMass + parentMass);
var ke_m = OrbitMath.KeplerFromPositionAndVelocity(sgp_m, ralitivePos, velocity_m, atDateTime);
OrbitDB orbit = new OrbitDB(parent)
{
SemiMajorAxis = ke_m.SemiMajorAxis,
Eccentricity = ke_m.Eccentricity,
Inclination = ke_m.Inclination,
LongitudeOfAscendingNode = ke_m.LoAN,
ArgumentOfPeriapsis = ke_m.AoP,
MeanAnomalyAtEpoch = ke_m.MeanAnomalyAtEpoch,
Epoch = atDateTime,
_parentMass = parentMass,
_myMass = myMass
};
orbit.CalculateExtendedParameters();
var pos = OrbitProcessor.GetPosition_m(orbit, atDateTime);
var d = (pos - ralitivePos).Length();
if (d > 1)
{
var e = new Event(atDateTime, "Positional difference of " + Stringify.Distance(d) + " when creating orbit from velocity");
e.Entity = entity;
e.SystemGuid = entity.Manager.ManagerGuid;
e.EventType = EventType.Opps;
//e.Faction = entity.FactionOwner;
StaticRefLib.EventLog.AddEvent(e);
//other info:
var keta = Angle.ToDegrees(ke_m.TrueAnomalyAtEpoch);
var obta = Angle.ToDegrees(OrbitProcessor.GetTrueAnomaly(orbit, atDateTime));
var tadif = Angle.ToDegrees(Angle.DifferenceBetweenRadians(keta, obta));
var pos1 = OrbitProcessor.GetPosition_m(orbit, atDateTime);
var pos2 = OrbitProcessor.GetPosition_m(orbit, ke_m.TrueAnomalyAtEpoch);
var d2 = (pos1 - pos2).Length();
}
return(orbit);
}
/// <summary>
/// This was designed so that fast moving objects will get interpolated a lot more than slow moving objects
/// so fast moving objects shouldn't loose positional acuracy when close to a planet,
/// and slow moving objects won't have processor time wasted on them by calulcating too often.
/// However this seems to be unstable and looses energy, unsure why. currently set it to just itterate/interpolate every second.
/// so currently will be using more time to get through this than neccisary.
/// </summary>
/// <param name="entity">Entity.</param>
/// <param name="deltaSeconds">Delta seconds.</param>
public static void NewtonMove(Entity entity, int deltaSeconds)
{
NewtonMoveDB newtonMoveDB = entity.GetDataBlob <NewtonMoveDB>();
NewtonThrustAbilityDB newtonThrust = entity.GetDataBlob <NewtonThrustAbilityDB>();
PositionDB positionDB = entity.GetDataBlob <PositionDB>();
double mass_Kg = entity.GetDataBlob <MassVolumeDB>().Mass;
double parentMass_kg = newtonMoveDB.ParentMass;
var manager = entity.Manager;
DateTime dateTimeFrom = newtonMoveDB.LastProcessDateTime;
DateTime dateTimeNow = manager.ManagerSubpulses.StarSysDateTime;
DateTime dateTimeFuture = dateTimeNow + TimeSpan.FromSeconds(deltaSeconds);
double deltaT = (dateTimeFuture - dateTimeFrom).TotalSeconds;
double secondsToItterate = deltaT;
while (secondsToItterate > 0)
{
//double timeStep = Math.Max(secondsToItterate / speed_kms, 1);
//timeStep = Math.Min(timeStep, secondsToItterate);
double timeStepInSeconds = 1;//because the above seems unstable and looses energy.
double distanceToParent_m = positionDB.GetDistanceTo_m(newtonMoveDB.SOIParent.GetDataBlob <PositionDB>());
distanceToParent_m = Math.Max(distanceToParent_m, 0.1); //don't let the distance be 0 (once collision is in this will likely never happen anyway)
double gravForce = GameConstants.Science.GravitationalConstant * (mass_Kg * parentMass_kg / Math.Pow(distanceToParent_m, 2));
Vector3 gravForceVector = gravForce * -Vector3.Normalise(positionDB.RelativePosition_m);
Vector3 totalDVFromGrav = (gravForceVector / mass_Kg) * timeStepInSeconds;
double maxAccelFromThrust1 = newtonThrust.ExhaustVelocity * Math.Log(mass_Kg / (mass_Kg - newtonThrust.FuelBurnRate)); //per second
double maxAccelFromThrust = newtonThrust.ThrustInNewtons / mass_Kg; //per second
Vector3 manuverDV = newtonMoveDB.DeltaVForManuver_m; //how much dv needed to complete the manuver.
double dryMass = mass_Kg - newtonThrust.FuelBurnRate * timeStepInSeconds; //how much our ship weighs after a timestep of fuel is used.
//how much dv can we get in this timestep.
double deltaVThisStep = OrbitMath.TsiolkovskyRocketEquation(mass_Kg, dryMass, newtonThrust.ExhaustVelocity);
deltaVThisStep = Math.Min(manuverDV.Length(), deltaVThisStep); //don't use more Dv than what is called for.
deltaVThisStep = Math.Min(newtonThrust.DeltaV, deltaVThisStep); //check we've got the deltaV to spend.
Vector3 totalDVFromThrust = Vector3.Normalise(manuverDV) * deltaVThisStep;
//remove the deltaV we're expending from the max (TODO: Remove fuel from cargo, change mass of ship)
newtonThrust.DeltaV -= deltaVThisStep;
//remove the vectorDV from the amount needed to fully complete the manuver.
newtonMoveDB.DeltaVForManuver_m -= totalDVFromThrust;
Vector3 totalDV = totalDVFromGrav + totalDVFromThrust;
Vector3 newVelocity = totalDV + newtonMoveDB.CurrentVector_ms;
newtonMoveDB.CurrentVector_ms = newVelocity;
Vector3 deltaPos = (newtonMoveDB.CurrentVector_ms + newVelocity) / 2 * timeStepInSeconds;
positionDB.RelativePosition_m += deltaPos;
double sOIRadius = OrbitProcessor.GetSOI_m(newtonMoveDB.SOIParent);
if (positionDB.RelativePosition_m.Length() >= sOIRadius)
{
Entity newParent;
Vector3 parentRalitiveVector;
//if our parent is a regular kepler object (normaly this is the case)
if (newtonMoveDB.SOIParent.HasDataBlob <OrbitDB>())
{
var orbitDB = newtonMoveDB.SOIParent.GetDataBlob <OrbitDB>();
newParent = orbitDB.Parent;
var parentVelocity = OrbitProcessor.InstantaneousOrbitalVelocityVector_m(orbitDB, entity.StarSysDateTime);
parentRalitiveVector = newtonMoveDB.CurrentVector_ms + parentVelocity;
}
else //if (newtonMoveDB.SOIParent.HasDataBlob<NewtonMoveDB>())
{ //this will pretty much never happen.
newParent = newtonMoveDB.SOIParent.GetDataBlob <NewtonMoveDB>().SOIParent;
var parentVelocity = newtonMoveDB.SOIParent.GetDataBlob <NewtonMoveDB>().CurrentVector_ms;
parentRalitiveVector = newtonMoveDB.CurrentVector_ms + parentVelocity;
}
parentMass_kg = newParent.GetDataBlob <MassVolumeDB>().Mass;
Vector3 posRalitiveToNewParent = positionDB.AbsolutePosition_m - newParent.GetDataBlob <PositionDB>().AbsolutePosition_m;
var dateTime = dateTimeNow + TimeSpan.FromSeconds(deltaSeconds - secondsToItterate);
double sgp = GMath.StandardGravitationalParameter(parentMass_kg + mass_Kg);
var kE = OrbitMath.KeplerFromPositionAndVelocity(sgp, posRalitiveToNewParent, parentRalitiveVector, dateTime);
positionDB.SetParent(newParent);
newtonMoveDB.ParentMass = parentMass_kg;
newtonMoveDB.SOIParent = newParent;
newtonMoveDB.CurrentVector_ms = parentRalitiveVector;
}
if (newtonMoveDB.DeltaVForManuver_m.Length() <= 0) //if we've completed the manuver.
{
var dateTime = dateTimeNow + TimeSpan.FromSeconds(deltaSeconds - secondsToItterate);
double sgp = GMath.StandardGravitationalParameter(parentMass_kg + mass_Kg);
KeplerElements kE = OrbitMath.KeplerFromPositionAndVelocity(sgp, positionDB.RelativePosition_m, newtonMoveDB.CurrentVector_ms, dateTime);
var parentEntity = Entity.GetSOIParentEntity(entity, positionDB);
if (kE.Eccentricity < 1) //if we're going to end up in a regular orbit around our new parent
{
var newOrbit = OrbitDB.FromKeplerElements(
parentEntity,
mass_Kg,
kE,
dateTime);
entity.RemoveDataBlob <NewtonMoveDB>();
entity.SetDataBlob(newOrbit);
positionDB.SetParent(parentEntity);
var newPos = OrbitProcessor.GetPosition_m(newOrbit, dateTime);
positionDB.RelativePosition_m = newPos;
}
break;
}
secondsToItterate -= timeStepInSeconds;
}
newtonMoveDB.LastProcessDateTime = dateTimeFuture;
}