Booster External Acceleration. More...

Classes
class	Stage
	Utility class to bundle together the attributes for a rocket stage. More...

Public Types
enum	Guidance { LINEAR_TANGENT_EC , MANUAL_VEC , MANUAL_PITCH , PITCH_TABLE , GRAVITY_TURN , PEG_2D , PEG2D_GT , UNUSED }

enum	PEG2DMode { GRAVITY_TURN_S0 , SLEW_TO_PEG , PEG , PEG_FROM_START }

Static Public Member Functions
static int	ActiveStageReadback (double3[] data)

static double3[]	Allocate (Guidance guidance, int numStages, GEBodyState bodyStateSI, double dtSec, double mu_SI, double tStartSec, int pitchTableSize=0)

static void	AutoStageSet (double3[] data, bool enabled)
	Set the auto-stage control bit in the booster data block to indicated the value of the enabled parameter.

static double	BurnTimeForStage (double3[] data, int stage)

static void	EnabledSet (double3[] data, bool enabled)
	Set the ENABLED flag in the data block.

static int double3 double3 v	EvolveSelfIntegrated (ref ExternalAccel.EAStateData eaState, int extAccelId, double tGE, double dt, ref GEPhysicsCore.GEPhysicsJob gePhysJob)

static double	FuelReadout (double3[] data, int stageReq=-1)
	Get fuel for the designated stage. If the stage is -1, this is a request for the active stage.

static double3[]	GravityTurnSetup (double3[] data, double vStart, double pitchKickDeg, double pitchRateDegPerSec)

static void	LinearTangentECSetup (double3[] data, double linTan_a, double linTan_b, double tStartSec, double tEndSec)
	Create data[] array for a linear tangent steering law of the form tan(theta) = (1-t/t_f) tan(theta0) as found in (6.59) of "Design of Rockets and Launch Vehicles", Edberg & Cpsta, AIAA Press.

static void	ManualPitchSetup (double pitchRad, double3[] data)
	Allocate a data block with numStages that will use a manual pitch value for ascent guidance.

static void	ManualVecSetThrustDir (double3[] data, double3 thrustDir)
	Full manual control with acceleration explicitly specified.

static double	MassAtTime (double3[] data, double t)

static void	PayloadCompute (double3[] data)
	Compute and configure the per stage payload values for each stage in a multi-stage booster. e.g. 3 stages: 0, 1, 2 Stage 2 has a payload mass of payloadMassKg. Stage 1 has a payload mass of playloadMassKg + stage2 (fuel + dry mass) Stage 0 has a payload mass of stage 1 payload mass + stage1 (fuel + dry mass)

static double	PayloadReadout (double3[] data, int stageNum)

static void	Peg2DSetup (double3[] data, PEG2DMode pegMode, double gt_at_vel, double gt_pitch_kick, double pitch_rate, double target_altitude, double target_vz, double burnTimeSec)
	Setup PEG2D params. Call after Booster.Allocate() and Booster.StageSetup().

static double	PitchFromTable (NativeArray< double3 > data, double t, int guid_base)
	Look up the entry in the pitch table. Assume the pitch table might not be regular and that since we're integrating time will advance forward monotonically. Just walk the table to find an entry but keep track of where we were.

static double	PitchReadback (double3[] data)

static void	PitchTableSetup (double3[] data, double tStartSec, double tEndSec, double3[] pitchTable)

static bool bool stopSelfIntegrating	SelfIntegratingStatusActions (int status)

static int double fuel_used	StageNumFuelAtTime (double3[] data, double t)

static void	StageSetup (double3[] data, int stageNum, Stage stage)
	Add a stage to the Booster. This assumes data[] has been created with the correct number of total stages, prior to using this method to fill in the details.

static string	StatusString (int status)

static void	SteeringPlaneSet (double3[] data, double3 orbitCenter, double3 orbitNormal)

static void	ThrottleSet (double3[] data, double throttle)

static double	ThrustAtTime (double3[] data, double t)

static double	TotalBurnTime (double3[] data)
	Total burn time for the booster extracted from a copy of the data[] block with 0 offset.

Static Public Attributes
const int	AUTO_STAGE = 1 << 1

const int	COPY_FROM_BODY = 1 << 3

const int	ENABLED = 1 << 0

const int	FUEL_OUT = 1 << 0

static int double3	r

static bool	remove

const int	SEND_EVENTS = 1 << 2

static int	stage

const int	STAGED = 1 << 1

static int	status
	Dedicated history-dependent evolution of the booster. This is called by RunStep() in GEPhysicsCore. Typically the timescale of NBody evolution is much larger than the typical timescale of a rocket launch or powered descent. This routine does simple integration using a guidance model with updates typically on the order of 0.1 seconds. This is an appropriate timestep for e.g. a gravity turn.

const int	STATUS_CUTOFF = 3

const int	STATUS_FUEL_OUT = 1

const int	STATUS_STAGED = 2

Detailed Description

Booster External Acceleration.

This class provides the external acceleration of a multi-stage booster. It will be called for each timestep in the numerical integration. Booster also provides a set of methods to assist in determining the launch trajewctory and end state without being used as part of GEPhysicsCore. This allows tuning of booster parameters ahead of launch.

This implementation supports:

multiple stages that (may) reduce the mass of the booster as time goes on (i.e. rocket equation stuff)
a choice of guidance laws for the direction of the thrust: LINEAR_TANGENT_EC: linear tangent to the steering plane MANUAL_VEC: manual vector thrust direction MANUAL_PITCH: manual pitch in a target plane PITCH_TABLE: pitch from a table of pitch angle vs time GRAVITY_TURN: gravity turn to a target altitude PEG_2D: 2D PEG guidance PEG2D_GT: 2D PEG guidance with gravity turn at start

Booster setup allocates a block of double3[] to hold the state information required for the stages and guidance. This ensures it can be run within the Job system and can be Burst compiled.

Member Function Documentation

◆ AutoStageSet()

static void GravityEngine2.Booster.AutoStageSet	(	double3[]	data,
		bool	enabled )

static

Set the auto-stage control bit in the booster data block to indicated the value of the enabled parameter.

Parameters

data
enabled

◆ EnabledSet()

static void GravityEngine2.Booster.EnabledSet	(	double3[]	data,
		bool	enabled )

static

Set the ENABLED flag in the data block.

Parameters

data
enabled

◆ FuelReadout()

static double GravityEngine2.Booster.FuelReadout	(	double3[]	data,
		int	stageReq = -1 )

static

Get fuel for the designated stage. If the stage is -1, this is a request for the active stage.

Parameters

data
stage	0 based stage number

Returns

◆ LinearTangentECSetup()

static void GravityEngine2.Booster.LinearTangentECSetup	(	double3[]	data,
		double	linTan_a,
		double	linTan_b,
		double	tStartSec,
		double	tEndSec )

static

Create data[] array for a linear tangent steering law of the form tan(theta) = (1-t/t_f) tan(theta0) as found in (6.59) of "Design of Rockets and Launch Vehicles", Edberg & Cpsta, AIAA Press.

This uses a standard rocket equation data block but note that if the engine is throttled down the algorithm will still assume the same t_burn and compute the guidance accordingly.

SB = Steering Base [SB0] (law, t_start, t_end) start/end are for overall flight path for steering laws that use this [SB1] center [SB2] plane [SB3] (linTan_a, linTan_b, 0)

Parameters

theta0Deg
t_final

Returns

◆ ManualPitchSetup()

static void GravityEngine2.Booster.ManualPitchSetup	(	double	pitchRad,
		double3[]	data )

static

Allocate a data block with numStages that will use a manual pitch value for ascent guidance.

This adds a single double3 to the standard header + stages that contains: (SE = end of stage block + 1) data[SE+0].x = manual pitch value

Parameters

pitchRad
numStages

Returns

◆ ManualVecSetThrustDir()

static void GravityEngine2.Booster.ManualVecSetThrustDir	(	double3[]	data,
		double3	thrustDir )

static

Full manual control with acceleration explicitly specified.

Atypical since does not have any stages or standard steering plane info. [SB0] (law, 0, 0) [SB1] thrustDir

Parameters

thrustDir thrust direction vector (normalized)

Returns

◆ PayloadCompute()

static void GravityEngine2.Booster.PayloadCompute ( double3[] data )

static

Compute and configure the per stage payload values for each stage in a multi-stage booster. e.g. 3 stages: 0, 1, 2 Stage 2 has a payload mass of payloadMassKg. Stage 1 has a payload mass of playloadMassKg + stage2 (fuel + dry mass) Stage 0 has a payload mass of stage 1 payload mass + stage1 (fuel + dry mass)

Parameters

data
payloadMassKg

◆ Peg2DSetup()

static void GravityEngine2.Booster.Peg2DSetup	(	double3[]	data,
		PEG2DMode	pegMode,
		double	gt_at_vel,
		double	gt_pitch_kick,
		double	pitch_rate,
		double	target_altitude,
		double	target_vz,
		double	burnTimeSec )

static

Setup PEG2D params. Call after Booster.Allocate() and Booster.StageSetup().

data[guid_base] = new double3((int)Guidance.PEG_2D, 0, 0);
data[guid_base + PEG2D_MODE_OFFSET] = new double3((int)pegMode, gt_at_vel, gt_pitch_kick);
data[guid_base + PEG2D_TARGET_ALTITUDE_OFFSET] = new double3(pitch_rate, target_altitude, target_vz);
data[guid_base + PEG2D_PEG_A_OFFSET] = double3.zero;
data[guid_base + PEG2D_PEG_T_OFFSET] = double3.zero;
data[guid_base + PEG2D_PITCH_LOCK_OFFSET] = new double3(0, 0, math.radians(90.0));

Parameters

data
pegMode
gt_at_vel
gt_pitch_kick
pitch_rate
target_altitude
target_vz

◆ PitchFromTable()

static double GravityEngine2.Booster.PitchFromTable	(	NativeArray< double3 >	data,
		double	t,
		int	guid_base )

static

Look up the entry in the pitch table. Assume the pitch table might not be regular and that since we're integrating time will advance forward monotonically. Just walk the table to find an entry but keep track of where we were.

Angles in the pitch table are angles from the horizontal in radians. Need to convert to angle from the vertical in radians.

(Public so Unit tests can find it)

Parameters

data
t
b

Returns

◆ StageSetup()

static void GravityEngine2.Booster.StageSetup	(	double3[]	data,
		int	stageNum,
		Stage	stage )

static

Add a stage to the Booster. This assumes data[] has been created with the correct number of total stages, prior to using this method to fill in the details.

The shadow_ea_desc_index is used to indicate that this stage is shadowed by a GSBody that will track its motion once it has burned out. When staging occurs the current R, V, t values are copied to the shadow GSBody. Otherwise these values are updated at the end of the self-integrating evolution.

Parameters

data
stageNum
stage
shadow_ea_desc_index

◆ TotalBurnTime()

static double GravityEngine2.Booster.TotalBurnTime ( double3[] data )

static

Total burn time for the booster extracted from a copy of the data[] block with 0 offset.

Parameters

data

Returns: burn time (sec.)

Member Data Documentation

◆ status

int GravityEngine2.Booster.status

static

Dedicated history-dependent evolution of the booster. This is called by RunStep() in GEPhysicsCore. Typically the timescale of NBody evolution is much larger than the typical timescale of a rocket launch or powered descent. This routine does simple integration using a guidance model with updates typically on the order of 0.1 seconds. This is an appropriate timestep for e.g. a gravity turn.

A copy of (r, v, t) state is maintained in the EAStateData block to reduce conversion inaccuracy.
Time is the time since launch start in seconds.

Parameters

eaState
eaDesc
t_until	time to integrate to
dt	GEPhysicsCore dt (in GE units)
data
scaleTtoSec
scaleLtoKm

Returns

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

ge2/GE2/Assets/GravityEngine2/Runtime/Core/ExternalAcceleration/SelfIntegrating/Booster.cs

Classes

Public Types

Static Public Member Functions

Static Public Attributes

Detailed Description

Member Function Documentation

◆ AutoStageSet()

◆ EnabledSet()

◆ FuelReadout()

◆ LinearTangentECSetup()

◆ ManualPitchSetup()

◆ ManualVecSetThrustDir()

◆ PayloadCompute()

◆ Peg2DSetup()

◆ PitchFromTable()

◆ StageSetup()

◆ TotalBurnTime()

Member Data Documentation

◆ status