OrbitUtils Class Reference

Classes
class	OrbitElements
	A "struct-like" class that holds all the orbital elements determined by RVtoCOE and used by COEtoRV. There are some specific cases that need to be considered: More...

Static Public Member Functions
static float	HillRadius (GameObject primary, GameObject secondary)
	Calculates the Hill Radius (radius at which the secondary's gravity becomes dominant, when the secondary is in orbit around the primary).
static NBody	GetCenterNbody (Transform objectInOrbit, GameObject centerObject)
	Get the center.
static Vector3d	CenterOfMass (NBody body1, NBody body2)
static double	CalcAForPeriod (double period, double centerMass)
	Calculate the semi-major axis for the required period.
static int	CalcKeplerDepth (IFixedOrbit fixedBody)
	Determine how many parents/grandparents etc. have Kepler mode. GE uses this to ensure evolution starts at the most central body in a heirarchy and works out to the leaves.
static float	SoiRadius (NBody planet, NBody moon)
	Determine the SOI radius in internal physics units.
static bool	IsOnRails (NBody nbody)
static void	FindC2C3 (double znew, out double c2new, out double c3new)
static double	TimeOfFlight (Vector3d r0, Vector3d r1, double p, double mu, Vector3d normal)
	Determine the time of flight in physics time units (GE internal time) that it takes for the body in orbit to go from position r0 to position r1 in an orbit with parameter p.
static double	TimeOfFlightEllipse (Vector3d r0, Vector3d r1, Vector3d axis, double eccentricity, double orbit_period)
	Simpler approach from Curtis for the case of an ellipse. This handles very large values of r (>1E10) without some of the precision issues that the OrbitUtils.TimeOfFlight has at values near 0, 180 degrees with large r.
static OrbitElements	RVtoCOE (Vector3 r_in, Vector3 v_in, NBody centerBody, float mu, bool relativePos, double ecc_threshold=small, double incl_threshold=small)
static OrbitElements	RVtoCOE (Vector3 r_in, Vector3 v_in, NBody centerBody, bool relativePos, double ecc_threshold=small, double incl_threshold=small)
static OrbitElements	RVtoCOE (Vector3d r_in, Vector3d v_in, NBody centerBody, bool relativePos, double ecc_threshold=small, double incl_threshold=small)
	Pre-4.0 method signature without explicit use of mu.
static OrbitElements	RVtoCOE (Vector3d r_in, Vector3d v_in, NBody centerBody, double mu, bool relativePos, double ecc_threshold=small, double incl_threshold=small)
static void	COEtoRV (OrbitElements oe, NBody centerBody, ref Vector3d r, ref Vector3d v, bool relativePos)
static void	COEtoRVRelative (OrbitElements oe, double mu, ref Vector3d r, ref Vector3d v)
static void	COEtoRV (OrbitElements oe, NBody centerBody, double mu, ref Vector3d r, ref Vector3d v, bool relativePos, double ecc_threshold=small, double incl_threshold=small)
static Vector3d	TransformToOrbitFrame (Vector3d v, OrbitElements oe)
	Transform the vector v by the rotation matrix due to the COE.
static double	PhaseAngleRadiansForDirection (Vector3d pos, OrbitElements oe)
static void	COEtoRVMirror (OrbitElements oe, NBody centerBody, ref Vector3d r, ref Vector3d v, bool relativePos)
static double	GetPhaseFromOE (OrbitUtils.OrbitElements oe, double ecc_threshold=small, double incl_threshold=small)
	Returns the current phase in radian.
static double	FlightPathAngle (double sin_nu, double cos_nu, double ecc)
	Determine the flight path angle. This is the angle from (h x r) to the velocity vector.
static bool	CheckHitPlanet (double planetRadius, double planetMass, Vector3d r1c, Vector3d v1tc, Vector3d r2c, Vector3d v2tc, int nrev)
static double	ConvertEtoTrueAnomoly (double eValue, double ecc)
	Convert the eccentric anomaly (angle from center of ellipse wrt x-axis) to the true anomoly (angle from focus wrt periapsis/x-axis if e=0).
static double	ConvertEtoMeanAnomoly (double eValue, double ecc)
static double	ConvertTrueAnomolytoE (double nu, double ecc)
static double	ConvertMeanAnomolyToE (double M, double ecc)
static double	GsTime (double jdut1)
static void	LsTime (double lon, double jdut1, out double lst, out double gst)
static Vector3	FindNodes (OrbitPredictor ship, OrbitPredictor target)

Static Public Attributes
const double	small = 1E-3
const double	verySmall = 1E-9
const double	ecc_circular = 1E-3
static	Vector3

Member Function Documentation

CalcAForPeriod()

static double OrbitUtils.CalcAForPeriod ( double  period, double  centerMass  )

static

Calculate the semi-major axis for the required period.

Parameters

period
centerMass

Returns

ConvertEtoTrueAnomoly()

static double OrbitUtils.ConvertEtoTrueAnomoly ( double  eValue, double  ecc  )

static

Convert the eccentric anomaly (angle from center of ellipse wrt x-axis) to the true anomoly (angle from focus wrt periapsis/x-axis if e=0).

Equations from front cover of Vallado.

Parameters

eValue
ecc

Returns

FlightPathAngle()

static double OrbitUtils.FlightPathAngle ( double  sin_nu, double  cos_nu, double  ecc  )

static

Determine the flight path angle. This is the angle from (h x r) to the velocity vector.

Formulae from the front pages in Vallado.

Parameters

sin_nu	Sine of the true anaomoly
cos_nu	Cosine of the true anomoly
ecc	Eccentricity

Returns

Flight Path Angle in Radians

GetCenterNbody()

static NBody OrbitUtils.GetCenterNbody ( Transform  objectInOrbit, GameObject  centerObject  )

static

Get the center.

Parameters

objectInOrbit

Returns

GetPhaseFromOE()

static double OrbitUtils.GetPhaseFromOE ( OrbitUtils::OrbitElements  oe, double  ecc_threshold = small, double  incl_threshold = small  )

static

Returns the current phase in radian.

Parameters

oe

Returns

HillRadius()

static float OrbitUtils.HillRadius ( GameObject  primary, GameObject  secondary  )

static

Calculates the Hill Radius (radius at which the secondary's gravity becomes dominant, when the secondary is in orbit around the primary).

Returns

The radius.

Parameters

primary	Primary.
secondary	Secondary. In orbit around primary

RVtoCOE()

static OrbitElements OrbitUtils.RVtoCOE ( Vector3d  r_in, Vector3d  v_in, NBody  centerBody, bool  relativePos, double  ecc_threshold = small, double  incl_threshold = small  )

static

Pre-4.0 method signature without explicit use of mu.

Parameters

r_in
v_in
centerBody
relativePos

Returns

SoiRadius()

static float OrbitUtils.SoiRadius ( NBody  planet, NBody  moon  )

static

Determine the SOI radius in internal physics units.

Parameters

planet
moon

Returns

TimeOfFlight()

static double OrbitUtils.TimeOfFlight ( Vector3d  r0, Vector3d  r1, double  p, double  mu, Vector3d  normal  )

static

Determine the time of flight in physics time units (GE internal time) that it takes for the body in orbit to go from position r0 to position r1 in an orbit with parameter p.

The angle between two 3D vectors cannot be greater than 180 degrees unless the orientation of the plane they define is also specified. The normal parameter is used for this. If an angle less than 180 is desired then the cross product of r0 and v0 can be used as the normal. Calling TOF via the OrbitUniversal wrapper will handle all that automatically.

Parameters

r0	from point (with respect to center)
r1	to point (with respect to center)
p	orbit semi-parameter
mu	centerbody mass
normal	normal to orital plane

Returns

time to travel from r0 to r1 in GE time

TimeOfFlightEllipse()

static double OrbitUtils.TimeOfFlightEllipse ( Vector3d  r0, Vector3d  r1, Vector3d  axis, double  eccentricity, double  orbit_period  )

static

Simpler approach from Curtis for the case of an ellipse. This handles very large values of r (>1E10) without some of the precision issues that the OrbitUtils.TimeOfFlight has at values near 0, 180 degrees with large r.

Parameters

r0
r1

Returns

TransformToOrbitFrame()

static Vector3d OrbitUtils.TransformToOrbitFrame ( Vector3d  v, OrbitElements  oe  )

static

Transform the vector v by the rotation matrix due to the COE.

Parameters

v
oe

Returns

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The documentation for this class was generated from the following file:

• C:/Users/musgr/Documents/Unity/gravityengine/Assets/GravityEngine/Scripts/Orbits/OrbitUtils.cs