//Computes the delta-V of the burn required to change an orbit's inclination to a given value
//at a given UT. If the latitude at that time is too high, so that the desired inclination
//cannot be attained, the burn returned will achieve as low an inclination as possible (namely, inclination = latitude).
//The input inclination is in degrees.
//Note that there are two orbits through each point with a given inclination. The convention used is:
// - first, clamp newInclination to the range -180, 180
// - if newInclination > 0, do the cheaper burn to set that inclination
// - if newInclination < 0, do the more expensive burn to set that inclination
public static Vector3d DeltaVToChangeInclination(Orbit o, double UT, double newInclination)
{
double latitude = o.referenceBody.GetLatitude(o.SwappedAbsolutePositionAtUT(UT));
double desiredHeading = HeadingForInclination(newInclination, latitude);
Vector3d actualHorizontalVelocity = Vector3d.Exclude(o.Up(UT), o.SwappedOrbitalVelocityAtUT(UT));
Vector3d eastComponent = actualHorizontalVelocity.magnitude * Math.Sin(Math.PI / 180 * desiredHeading) * o.East(UT);
Vector3d northComponent = actualHorizontalVelocity.magnitude * Math.Cos(Math.PI / 180 * desiredHeading) * o.North(UT);
if (Vector3d.Dot(actualHorizontalVelocity, northComponent) < 0) northComponent *= -1;
if (MuUtils.ClampDegrees180(newInclination) < 0) northComponent *= -1;
Vector3d desiredHorizontalVelocity = eastComponent + northComponent;
return desiredHorizontalVelocity - actualHorizontalVelocity;
}
//Computes the deltaV of the burn needed to set a given LAN at a given UT.
public static Vector3d DeltaVToShiftLAN(Orbit o, double UT, double newLAN)
{
Vector3d pos = o.SwappedAbsolutePositionAtUT(UT);
// Burn position in the same reference frame as LAN
double burn_latitude = o.referenceBody.GetLatitude(pos);
double burn_longitude = o.referenceBody.GetLongitude(pos) + o.referenceBody.rotationAngle;
const double target_latitude = 0; // Equator
double target_longitude = 0; // Prime Meridian
// Select the location of either the descending or ascending node.
// If the descending node is closer than the ascending node, or there is no ascending node, target the reverse of the newLAN
// Otherwise target the newLAN
if (o.AscendingNodeEquatorialExists() && o.DescendingNodeEquatorialExists())
{
if (o.TimeOfDescendingNodeEquatorial(UT) < o.TimeOfAscendingNodeEquatorial(UT))
{
// DN is closer than AN
// Burning for the AN would entail flipping the orbit around, and would be very expensive
// therefore, burn for the corresponding Longitude of the Descending Node
target_longitude = MuUtils.ClampDegrees360(newLAN + 180.0);
}
else
{
// DN is closer than AN
target_longitude = MuUtils.ClampDegrees360(newLAN);
}
}
else if (o.AscendingNodeEquatorialExists() && !o.DescendingNodeEquatorialExists())
{
// No DN
target_longitude = MuUtils.ClampDegrees360(newLAN);
}
else if (!o.AscendingNodeEquatorialExists() && o.DescendingNodeEquatorialExists())
{
// No AN
target_longitude = MuUtils.ClampDegrees360(newLAN + 180.0);
}
else
{
throw new ArgumentException("OrbitalManeuverCalculator.DeltaVToShiftLAN: No Equatorial Nodes");
}
double desiredHeading = MuUtils.ClampDegrees360(Heading(burn_latitude, burn_longitude, target_latitude, target_longitude));
Vector3d actualHorizontalVelocity = Vector3d.Exclude(o.Up(UT), o.SwappedOrbitalVelocityAtUT(UT));
Vector3d eastComponent = actualHorizontalVelocity.magnitude * Math.Sin(Math.PI / 180 * desiredHeading) * o.East(UT);
Vector3d northComponent = actualHorizontalVelocity.magnitude * Math.Cos(Math.PI / 180 * desiredHeading) * o.North(UT);
Vector3d desiredHorizontalVelocity = eastComponent + northComponent;
return desiredHorizontalVelocity - actualHorizontalVelocity;
}
//Computes the delta-V of the burn required to change an orbit's inclination to a given value
//at a given UT. If the latitude at that time is too high, so that the desired inclination
//cannot be attained, the burn returned will achieve as low an inclination as possible (namely, inclination = latitude).
//The input inclination is in degrees.
//Note that there are two orbits through each point with a given inclination. The convention used is:
// - first, clamp newInclination to the range -180, 180
// - if newInclination > 0, do the cheaper burn to set that inclination
// - if newInclination < 0, do the more expensive burn to set that inclination
public static Vector3d DeltaVToChangeInclination(Orbit o, double UT, double newInclination)
{
double latitude = o.referenceBody.GetLatitude(o.SwappedAbsolutePositionAtUT(UT));
double desiredHeading = HeadingForInclination(newInclination, latitude);
Vector3d actualHorizontalVelocity = Vector3d.Exclude(o.Up(UT), o.SwappedOrbitalVelocityAtUT(UT));
Vector3d eastComponent = actualHorizontalVelocity.magnitude * Math.Sin(Math.PI / 180 * desiredHeading) * o.East(UT);
Vector3d northComponent = actualHorizontalVelocity.magnitude * Math.Cos(Math.PI / 180 * desiredHeading) * o.North(UT);
if (Vector3d.Dot(actualHorizontalVelocity, northComponent) < 0)
{
northComponent *= -1;
}
if (MuUtils.ClampDegrees180(newInclination) < 0)
{
northComponent *= -1;
}
Vector3d desiredHorizontalVelocity = eastComponent + northComponent;
return(desiredHorizontalVelocity - actualHorizontalVelocity);
}
//Computes the deltaV of the burn needed to set a given LAN at a given UT.
public static Vector3d DeltaVToShiftLAN(Orbit o, double UT, double newLAN)
{
Vector3d pos = o.SwappedAbsolutePositionAtUT(UT);
// Burn position in the same reference frame as LAN
double burn_latitude = o.referenceBody.GetLatitude(pos);
double burn_longitude = o.referenceBody.GetLongitude(pos) + o.referenceBody.rotationAngle;
const double target_latitude = 0; // Equator
double target_longitude = 0; // Prime Meridian
// Select the location of either the descending or ascending node.
// If the descending node is closer than the ascending node, or there is no ascending node, target the reverse of the newLAN
// Otherwise target the newLAN
if (o.AscendingNodeEquatorialExists() && o.DescendingNodeEquatorialExists())
{
if (o.TimeOfDescendingNodeEquatorial(UT) < o.TimeOfAscendingNodeEquatorial(UT))
{
// DN is closer than AN
// Burning for the AN would entail flipping the orbit around, and would be very expensive
// therefore, burn for the corresponding Longitude of the Descending Node
target_longitude = MuUtils.ClampDegrees360(newLAN + 180.0);
}
else
{
// DN is closer than AN
target_longitude = MuUtils.ClampDegrees360(newLAN);
}
}
else if (o.AscendingNodeEquatorialExists() && !o.DescendingNodeEquatorialExists())
{
// No DN
target_longitude = MuUtils.ClampDegrees360(newLAN);
}
else if (!o.AscendingNodeEquatorialExists() && o.DescendingNodeEquatorialExists())
{
// No AN
target_longitude = MuUtils.ClampDegrees360(newLAN + 180.0);
}
else
{
throw new ArgumentException("OrbitalManeuverCalculator.DeltaVToShiftLAN: No Equatorial Nodes");
}
double desiredHeading = MuUtils.ClampDegrees360(Heading(burn_latitude, burn_longitude, target_latitude, target_longitude));
Vector3d actualHorizontalVelocity = Vector3d.Exclude(o.Up(UT), o.SwappedOrbitalVelocityAtUT(UT));
Vector3d eastComponent = actualHorizontalVelocity.magnitude * Math.Sin(Math.PI / 180 * desiredHeading) * o.East(UT);
Vector3d northComponent = actualHorizontalVelocity.magnitude * Math.Cos(Math.PI / 180 * desiredHeading) * o.North(UT);
Vector3d desiredHorizontalVelocity = eastComponent + northComponent;
return(desiredHorizontalVelocity - actualHorizontalVelocity);
}
