GravityEngine2.Lambert Class Reference

Classes
struct	LambertOutput

Public Types
enum	EnergyType { LOW , HIGH }
enum	MotionDirection { SHORT , LONG }
enum	Status { OK , G_NOT_CONVERGED , HIT_PLANET , ERROR_OUT }

Static Public Member Functions
static LambertOutput	Battin (double mu, double3 r1, double3 r2, double3 v1, MotionDirection dm, EnergyType de, int nrev, double t_xfer, double radius)
static bool	CheckHitPlanet (double mu, double radius, double3 r1, double3 v1t, double3 r2, double3 v2t, int nrev)
static double	ComputeTransferTime (double mu, double3 r1, double3 r2, ref LambertOutput lambertOutput)
static double double double tminenergy	MinTimes (double mu, double3 r1, double3 r2, MotionDirection dm, int nrev)
static double double double tminenergy	MinTimesPrograde (double mu, double3 r1, double3 r2, double3 v1, bool prograde=true)
static LambertOutput	TransferProgradeToPoint (double mu, double3 r1, double3 r2, double3 v1, double timeXfer, double radius=0.0, bool prograde=true)
	Solve the Lambert problem for a prograde transfer and given timeXfer to a specific fixed destination point.
static LambertOutput	TransferProgradeToPointWithFPA (double mu, double3 r1, double3 r2, double3 v1, double fpa, double radius=0)
	Determine the velocity change to transfer from r1 to r2 with a given flight path angle.
static LambertOutput	TransferProgradeToTarget (double mu, double3 r1, double3 r2, double3 v1, double3 v2, double timeXfer, double radius=0.0, bool prograde=true)
	Solve the Lambert problem for a prograde transfer and given timeXfer to a target in motion. The position and velocity vectors of the target are computed at the time of arrival.
static LambertOutput	Universal (double mu, double3 r1, double3 r2, double3 v1, MotionDirection motionDir, EnergyType energyType, int nrev, double t_xfer, double kbi=0, double radius=0.0)

Static Public Attributes
static double	tmin
	Calculate the reference time of flight for a Lambert transfer.
static double double	tminp

Member Function Documentation

TransferProgradeToPoint()

static LambertOutput GravityEngine2.Lambert.TransferProgradeToPoint ( double mu, double3 r1, double3 r2, double3 v1, double timeXfer, double radius = 0::0, bool prograde = true )

static

Solve the Lambert problem for a prograde transfer and given timeXfer to a specific fixed destination point.

The default is prograde but this can be optionally over-ridden to force a retrograde transfer direction.

Parameters

mu	gravitational parameter of central body
r1	position vector at departure
r2	position vector at arrival
v1	velocity vector at departure
timeXfer	time of flight
radius	radius of central body
prograde	if false, force retrograde transfer

Returns

TransferProgradeToPointWithFPA()

static LambertOutput GravityEngine2.Lambert.TransferProgradeToPointWithFPA ( double mu, double3 r1, double3 r2, double3 v1, double fpa, double radius = 0 )

static

Determine the velocity change to transfer from r1 to r2 with a given flight path angle.

This algorithm is very efficient (no inner iteration to root find) BUT it does not compute the transfer time. This can be done explicitly with ComputeXferTime.

If a radius is specified then a hit check will require that the orbit velocity at r2 is computed and this will result in additional computation.

Parameters

mu	GM of the central body
r1	Initial position
r2	Final position
v1	Initial velocity
fpa	Flight path angle
radius	Radius of the central body

Returns

TransferProgradeToTarget()

static LambertOutput GravityEngine2.Lambert.TransferProgradeToTarget ( double mu, double3 r1, double3 r2, double3 v1, double3 v2, double timeXfer, double radius = 0::0, bool prograde = true )

static

Solve the Lambert problem for a prograde transfer and given timeXfer to a target in motion. The position and velocity vectors of the target are computed at the time of arrival.

Parameters

mu	gravitational parameter of central body
r1	position vector of interceptor at departure
r2	position vector of target at departure
v1	velocity vector of interceptor at departure
v2	velocity vector of target at departure
timeXfer	time of flight
radius	radius of central body
prograde	if false, force retrograde transfer

Returns

Member Data Documentation

tmin

static double GravityEngine2.Lambert.tmin

static

Calculate the reference time of flight for a Lambert transfer.

Calculate the minimum time of flight for a Lambert transfer.

By default, this is a prograde transfer but can be optionally over-ridden to force a retrograde transfer.

Parameters

mu	gravitational parameter of central body
r1	position vector at departure
r2	position vector at arrival
prograde	if false, force retrograde transfer

Returns

tuple of minimum time of flight, minimum parabolic time of flight, and minimum energy time of flight

The purpose of tmin is not clear to me. Current code ignores this.

Parameters

mu	gravitational parameter of central body
r1	position vector at departure
r2	position vector at arrival
dm	direction of motion
nrev	number of revolutions

Returns

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

• ge2/GE2/Assets/GravityEngine2/Runtime/Core/Transfers/Lambert.cs