Models a generic rocket engine. More...

#include <FGRocket.h>

Inheritance diagram for FGRocket:

Collaboration diagram for FGRocket:

Public Member Functions
	FGRocket (FGFDMExec exec, Element el, int engine_number, struct FGEngine::Inputs &input)
	Constructor. More...

	~FGRocket (void)
	Destructor.

double	CalcFuelNeed (void)
	The fuel need is calculated based on power levels and flow rate for that power level. More...

double	CalcOxidizerNeed (void)
	The oxidizer need is calculated based on power levels and flow rate for that power level. More...

void	Calculate (void)
	Determines the thrust. More...

std::string	GetEngineLabels (const std::string &delimiter)

std::string	GetEngineValues (const std::string &delimiter)

bool	GetFlameout (void)
	Gets the flame-out status. More...

double	GetIsp (void) const

double	GetMixtureRatio (void) const

double	GetOxiFlowRate (void) const

double	GetThrustVariation (void) const
	Returns the thrust variation, if any. More...

double	GetTotalImpulse (void) const
	Gets the total impulse of the rocket. More...

double	GetTotalIspVariation (void) const
	Returns the Total Isp variation, if any. More...

double	GetVacTotalImpulse (void) const
	Gets the total impulse of the rocket. More...

void	SetIsp (double isp)

void	SetMixtureRatio (double mix)

void	SetThrustVariation (double var)
	Sets the thrust variation for a solid rocket engine. More...

void	SetTotalIspVariation (double var)
	Sets the variation in total motor energy. More...

Public Member Functions inherited from FGEngine
	FGEngine (int engine_number, struct Inputs &input)

virtual const FGColumnVector3 &	GetBodyForces (void)

virtual bool	GetCranking (void) const

virtual double	getFuelFlow_gph () const

virtual double	getFuelFlow_pph () const

virtual double	GetFuelFlowRate (void) const

virtual double	GetFuelFlowRateGPH (void) const

virtual double	GetFuelUsedLbs (void) const

virtual const FGColumnVector3 &	GetMoments (void)

virtual const std::string &	GetName (void) const

size_t	GetNumSourceTanks () const

virtual double	GetPowerAvailable (void)

virtual bool	GetRunning (void) const

unsigned int	GetSourceTank (unsigned int i) const

virtual bool	GetStarter (void) const

virtual bool	GetStarved (void) const

virtual double	GetThrottleMax (void) const

virtual double	GetThrottleMin (void) const

virtual double	GetThrust (void) const

FGThruster *	GetThruster (void) const

EngineType	GetType (void) const

virtual int	InitRunning (void)

void	LoadThruster (FGFDMExec exec, Element el)

void	LoadThrusterInputs ()

virtual void	ResetToIC (void)
	Resets the Engine parameters to the initial conditions.

virtual void	SetFuelDensity (double d)

virtual void	SetFuelFreeze (bool f)

virtual void	SetName (const std::string &name)

virtual void	SetPlacement (const FGColumnVector3 &location, const FGColumnVector3 &orientation)
	Sets engine placement information.

virtual void	SetRunning (bool bb)

virtual void	SetStarter (bool s)

virtual void	SetStarved (bool tt)

virtual void	SetStarved (void)

Public Member Functions inherited from FGModelFunctions
std::string	GetFunctionStrings (const std::string &delimeter) const
	Gets the strings for the current set of functions. More...

std::string	GetFunctionValues (const std::string &delimeter) const
	Gets the function values. More...

FGFunction *	GetPreFunction (const std::string &name)
	Get one of the "pre" function. More...

bool	Load (Element el, FGPropertyManager PropertyManager, std::string prefix="")

void	PostLoad (Element el, FGPropertyManager PropertyManager, std::string prefix="")

void	PreLoad (Element el, FGPropertyManager PropertyManager, std::string prefix="")

void	RunPostFunctions (void)

void	RunPreFunctions (void)

Public Member Functions inherited from FGJSBBase
	FGJSBBase ()
	Constructor for FGJSBBase.

virtual	~FGJSBBase ()
	Destructor for FGJSBBase.

void	disableHighLighting (void)
	Disables highlighting in the console output.

std::string	GetVersion (void)
	Returns the version number of JSBSim. More...

void	PutMessage (const Message &msg)
	Places a Message structure on the Message queue. More...

void	PutMessage (const std::string &text)
	Creates a message with the given text and places it on the queue. More...

void	PutMessage (const std::string &text, bool bVal)
	Creates a message with the given text and boolean value and places it on the queue. More...

void	PutMessage (const std::string &text, int iVal)
	Creates a message with the given text and integer value and places it on the queue. More...

void	PutMessage (const std::string &text, double dVal)
	Creates a message with the given text and double value and places it on the queue. More...

int	SomeMessages (void)
	Reads the message on the queue (but does not delete it). More...

void	ProcessMessage (void)
	Reads the message on the queue and removes it from the queue. More...

Message *	ProcessNextMessage (void)
	Reads the next message on the queue and removes it from the queue. More...

Additional Inherited Members
Public Types inherited from FGEngine
enum	EngineType { etUnknown, etRocket, etPiston, etTurbine, etTurboprop, etElectric }

Public Types inherited from FGJSBBase
enum	{ eL = 1, eM, eN }
	Moments L, M, N.

enum	{ eP = 1, eQ, eR }
	Rates P, Q, R.

enum	{ eU = 1, eV, eW }
	Velocities U, V, W.

enum	{ eX = 1, eY, eZ }
	Positions X, Y, Z.

enum	{ ePhi = 1, eTht, ePsi }
	Euler angles Phi, Theta, Psi.

enum	{ eDrag = 1, eSide, eLift }
	Stability axis forces, Drag, Side force, Lift.

enum	{ eRoll = 1, ePitch, eYaw }
	Local frame orientation Roll, Pitch, Yaw.

enum	{ eNorth = 1, eEast, eDown }
	Local frame position North, East, Down.

enum	{ eLat = 1, eLong, eRad }
	Locations Radius, Latitude, Longitude.

enum	{ inNone = 0, inDegrees, inRadians, inMeters, inFeet }
	Conversion specifiers.

Static Public Member Functions inherited from FGJSBBase
static double	CelsiusToFahrenheit (double celsius)
	Converts from degrees Celsius to degrees Fahrenheit. More...

static double	CelsiusToKelvin (double celsius)
	Converts from degrees Celsius to degrees Kelvin. More...

static double	CelsiusToRankine (double celsius)
	Converts from degrees Celsius to degrees Rankine. More...

static double	Constrain (double min, double value, double max)
	Constrain a value between a minimum and a maximum value.

static bool	EqualToRoundoff (double a, double b)
	Finite precision comparison. More...

static bool	EqualToRoundoff (float a, float b)
	Finite precision comparison. More...

static bool	EqualToRoundoff (float a, double b)
	Finite precision comparison. More...

static bool	EqualToRoundoff (double a, float b)
	Finite precision comparison. More...

static double	FahrenheitToCelsius (double fahrenheit)
	Converts from degrees Fahrenheit to degrees Celsius. More...

static double	FeetToMeters (double measure)
	Converts from feet to meters. More...

static double	GaussianRandomNumber (void)

static double	KelvinToCelsius (double kelvin)
	Converts from degrees Kelvin to degrees Celsius. More...

static double	KelvinToFahrenheit (double kelvin)
	Converts from degrees Kelvin to degrees Fahrenheit. More...

static double	KelvinToRankine (double kelvin)
	Converts from degrees Kelvin to degrees Rankine. More...

static double	MachFromVcalibrated (double vcas, double p, double psl, double rhosl)
	Calculate the Mach number from the calibrated airspeed. More...

static double	PitotTotalPressure (double mach, double p)
	Compute the total pressure in front of the Pitot tube. More...

static double	RankineToCelsius (double rankine)
	Converts from degrees Rankine to degrees Celsius. More...

static double	RankineToKelvin (double rankine)
	Converts from degrees Rankine to degrees Kelvin. More...

static double	sign (double num)

static double	VcalibratedFromMach (double mach, double p, double psl, double rhosl)
	Calculate the calibrated airspeed from the Mach number. More...

Public Attributes inherited from FGEngine
struct Inputs &	in

Static Public Attributes inherited from FGJSBBase
static short	debug_lvl = 1

static char	highint [5] = {27, '[', '1', 'm', '\0' }
	highlights text

static char	halfint [5] = {27, '[', '2', 'm', '\0' }
	low intensity text

static char	normint [6] = {27, '[', '2', '2', 'm', '\0' }
	normal intensity text

static char	reset [5] = {27, '[', '0', 'm', '\0' }
	resets text properties

static char	underon [5] = {27, '[', '4', 'm', '\0' }
	underlines text

static char	underoff [6] = {27, '[', '2', '4', 'm', '\0' }
	underline off

static char	fgblue [6] = {27, '[', '3', '4', 'm', '\0' }
	blue text

static char	fgcyan [6] = {27, '[', '3', '6', 'm', '\0' }
	cyan text

static char	fgred [6] = {27, '[', '3', '1', 'm', '\0' }
	red text

static char	fggreen [6] = {27, '[', '3', '2', 'm', '\0' }
	green text

static char	fgdef [6] = {27, '[', '3', '9', 'm', '\0' }
	default text

Protected Member Functions inherited from FGEngine
void	Debug (int from)

virtual bool	Load (FGFDMExec exec, Element el)

Protected Member Functions inherited from FGModelFunctions
virtual bool	InitModel (void)

Protected Member Functions inherited from FGJSBBase
void	Debug (int)

Static Protected Member Functions inherited from FGJSBBase
static std::string	CreateIndexedPropertyName (const std::string &Property, int index)

Protected Attributes inherited from FGEngine
bool	Cranking

const int	EngineNumber

double	EnginePitch

double	EngineYaw

double	FuelDensity

double	FuelExpended

double	FuelFlow_gph

double	FuelFlow_pph

double	FuelFlowRate

bool	FuelFreeze

double	FuelUsedLbs

double	MaxThrottle

double	MinThrottle

std::string	Name

double	PctPower

bool	Running

double	SLFuelFlowMax

std::vector< int >	SourceTanks

bool	Starter

bool	Starved

FGThruster *	Thruster

EngineType	Type

double	X

double	Y

double	Z

Protected Attributes inherited from FGModelFunctions
FGPropertyReader	LocalProperties

std::vector< FGFunction * >	PostFunctions

std::vector< FGFunction * >	PreFunctions

Static Protected Attributes inherited from FGJSBBase
static const double	degtorad = 0.017453292519943295769236907684886

static const double	fpstokts = 1.0/ktstofps

static const double	fttom = 0.3048

static int	gaussian_random_number_phase = 0

static const double	hptoftlbssec = 550.0

static const double	in3tom3 = 1.638706E-5

static const double	inchtoft = 0.08333333

static const double	inhgtopa = 3386.38

static const std::string	JSBSim_version = "1.0 " __DATE__ " " __TIME__

static const double	kgtolb = 2.20462

static const double	kgtoslug = 0.06852168

static const double	ktstofps = 1.68781

static const double	lbtoslug = 1.0/slugtolb

static Message	localMsg

static const double	m3toft3 = 1.0/(fttomfttomfttom)

static double	Mair = 28.9645

static unsigned int	messageId = 0

static std::queue< Message >	Messages

static const std::string	needed_cfg_version = "2.0"

static const double	psftoinhg = 0.014138

static const double	psftopa = 47.88

static const double	radtodeg = 57.295779513082320876798154814105

static double	Reng = 1716.56

static double	Rstar = 1545.348

static const double	SHRatio = 1.40

static const double	slugtolb = 32.174049

Detailed Description

Models a generic rocket engine.

The rocket engine is modeled given the following parameters:

Specific Impulse (in sec)

Additionally, the following control inputs, operating characteristics, and location are required, as with all other engine types:

Throttle setting (in percent, from 0 to 1.0)
Maximum allowable throttle setting
Minimum working throttle setting
Sea level fuel flow at maximum thrust
Sea level oxidizer flow at maximum thrust
X, Y, Z location in structural coordinate frame
Pitch and Yaw

The nozzle exit pressure (p2) is returned via a call to FGNozzle::GetPowerRequired(). This exit pressure is used to get the at-altitude thrust level.

One can model the thrust of a solid rocket by providing a normalized thrust table as a function of time. For instance, the space shuttle solid rocket booster normalized thrust value looks roughly like this:

    
 <thrust_table name="propulsion/thrust_time" type="internal">
   <tableData>
      0.0   0.00
      0.2   0.91
      8.0   0.97
     16.0   0.99
     20.0   1.00
     21.0   1.00
     24.0   0.95
     32.0   0.85
     40.0   0.78
     48.0   0.72
     50.0   0.71
     52.0   0.71
     56.0   0.73
     64.0   0.78
     72.0   0.82
     80.0   0.81
     88.0   0.73
     96.0   0.69
    104.0   0.59
    112.0   0.46
    120.0   0.09
    132.0   0.00
   </tableData>
 </thrust_table>

The left column is time, the right column is normalized thrust. Inside the FGRocket class code, the maximum thrust is calculated, and multiplied by this table. The Rocket class also tracks burn time. All that needs to be done is for the rocket engine to be throttle up to 1. At that time, the solid rocket fuel begins burning and thrust is provided.

@author Jon S. Berndt
$Id: FGRocket.h,v 1.22 2015/09/27 09:54:21 bcoconni Exp $
@see FGNozzle,
FGThruster,
FGForce,
FGEngine,

Definition at line 132 of file FGRocket.h.

Constructor & Destructor Documentation

◆ FGRocket()

FGRocket	(	FGFDMExec *	exec,
		Element *	el,
		int	engine_number,
		struct FGEngine::Inputs &	input
	)

Constructor.

Parameters

exec	pointer to JSBSim parent object, the FDM Executive.
el	a pointer to the XML Element instance representing the engine.
engine_number	engine number

Definition at line 59 of file FGRocket.cpp.

   : FGEngine(engine_number, input), isp_function(0L), FDMExec(exec)
 {
   Load(exec, el);
 
   Type = etRocket;
   Element* thrust_table_element = 0;
   ThrustTable = 0L;
   BurnTime = 0.0;
   previousFuelNeedPerTank = 0.0;
   previousOxiNeedPerTank = 0.0;
   PropellantFlowRate = 0.0;
   TotalPropellantExpended = 0.0;
   FuelFlowRate = FuelExpended = 0.0;
   OxidizerFlowRate = OxidizerExpended = 0.0;
   SLOxiFlowMax = SLFuelFlowMax = PropFlowMax = 0.0;
   MxR = 0.0;
   BuildupTime = 0.0;
   It = ItVac = 0.0;
   ThrustVariation = 0.0;
   TotalIspVariation = 0.0;
   VacThrust = 0.0;
   Flameout = false;
 
   // Defaults
    MinThrottle = 0.0;
    MaxThrottle = 1.0;
 
   std::stringstream strEngineNumber;
   strEngineNumber << EngineNumber;
 
   FGPropertyManager* PropertyManager = exec->GetPropertyManager();
   bindmodel(PropertyManager); // Bind model properties first, since they might be needed in functions.
 
   Element* isp_el = el->FindElement("isp");
 
   // Specific impulse may be specified as a constant value or as a function - perhaps as a function of mixture ratio.
   if (isp_el) {
     Element* isp_func_el = isp_el->FindElement("function");
     if (isp_func_el) {
       isp_function = new FGFunction(exec->GetPropertyManager(),isp_func_el, strEngineNumber.str());
     } else {
     Isp = el->FindElementValueAsNumber("isp");
     }
   } else {
     throw("Specific Impulse <isp> must be specified for a rocket engine");
   }
   
   if (el->FindElement("builduptime"))
     BuildupTime = el->FindElementValueAsNumber("builduptime");
   if (el->FindElement("maxthrottle"))
     MaxThrottle = el->FindElementValueAsNumber("maxthrottle");
   if (el->FindElement("minthrottle"))
     MinThrottle = el->FindElementValueAsNumber("minthrottle");
 
   if (el->FindElement("slfuelflowmax")) {
     SLFuelFlowMax = el->FindElementValueAsNumberConvertTo("slfuelflowmax", "LBS/SEC");
     if (el->FindElement("sloxiflowmax")) {
     SLOxiFlowMax = el->FindElementValueAsNumberConvertTo("sloxiflowmax", "LBS/SEC");
     }
     PropFlowMax = SLOxiFlowMax + SLFuelFlowMax;
     MxR = SLOxiFlowMax/SLFuelFlowMax;
   } else if (el->FindElement("propflowmax")) {
     PropFlowMax = el->FindElementValueAsNumberConvertTo("propflowmax", "LBS/SEC");
     // Mixture ratio may be specified here, but it can also be specified as a function or via property
     if (el->FindElement("mixtureratio")) {
       MxR = el->FindElementValueAsNumber("mixtureratio");
     }
   }
 
   if (isp_function) Isp = isp_function->GetValue(); // cause Isp function to be executed if present.
   // If there is a thrust table element, this is a solid propellant engine.
   thrust_table_element = el->FindElement("thrust_table");
   if (thrust_table_element) {
     ThrustTable = new FGTable(PropertyManager, thrust_table_element);
     Element* variation_element = el->FindElement("variation");
     if (variation_element) {
       if (variation_element->FindElement("thrust")) {
         ThrustVariation = variation_element->FindElementValueAsNumber("thrust");
       }
       if (variation_element->FindElement("total_isp")) {
         TotalIspVariation = variation_element->FindElementValueAsNumber("total_isp");
       }
     }
   }
 
 
   Debug(0);
 }

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Member Function Documentation

◆ CalcFuelNeed()

double CalcFuelNeed ( void )

virtual

The fuel need is calculated based on power levels and flow rate for that power level.

It is also turned from a rate into an actual amount (pounds) by multiplying it by the delta T and the rate.

Returns: Total fuel requirement for this engine in pounds.

Reimplemented from FGEngine.

Definition at line 225 of file FGRocket.cpp.

 {
   if (ThrustTable != 0L) {          // Thrust table given - infers solid fuel
     FuelFlowRate = VacThrust/Isp;   // This calculates wdot (weight flow rate in lbs/sec)
     FuelFlowRate /= (1 + TotalIspVariation);
   } else {
     SLFuelFlowMax = PropFlowMax / (1 + MxR);
     FuelFlowRate = SLFuelFlowMax * PctPower;
   }
 
   FuelExpended = FuelFlowRate * in.TotalDeltaT; // For this time step ...
   return FuelExpended;
 }

◆ CalcOxidizerNeed()

double CalcOxidizerNeed ( void )

virtual

The oxidizer need is calculated based on power levels and flow rate for that power level.

It is also turned from a rate into an actual amount (pounds) by multiplying it by the delta T and the rate.

Returns: Total oxidizer requirement for this engine in pounds.

Reimplemented from FGEngine.

Definition at line 241 of file FGRocket.cpp.

 {
   SLOxiFlowMax = PropFlowMax * MxR / (1 + MxR);
   OxidizerFlowRate = SLOxiFlowMax * PctPower;
   OxidizerExpended = OxidizerFlowRate * in.TotalDeltaT;
   return OxidizerExpended;
 }

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◆ Calculate()

void Calculate ( void )

virtual

Determines the thrust.

Implements FGEngine.

Definition at line 159 of file FGRocket.cpp.

 {
   if (FDMExec->IntegrationSuspended()) return;
 
   RunPreFunctions();
 
   PropellantFlowRate = (FuelExpended + OxidizerExpended)/in.TotalDeltaT;
   TotalPropellantExpended += FuelExpended + OxidizerExpended;
   // If Isp has been specified as a function, override the value of Isp to that, otherwise
   // assume a constant value is given.
   if (isp_function) Isp = isp_function->GetValue();
 
   // If there is a thrust table, it is a function of propellant burned. The
   // engine is started when the throttle is advanced to 1.0. After that, it
   // burns without regard to throttle setting.
 
   if (ThrustTable != 0L) { // Thrust table given -> Solid fuel used
 
     if ((in.ThrottlePos[EngineNumber] == 1 || BurnTime > 0.0 ) && !Starved) {
 
       VacThrust = ThrustTable->GetValue(TotalPropellantExpended)
                 * (ThrustVariation + 1)
                 * (TotalIspVariation + 1);
       if (BurnTime <= BuildupTime && BuildupTime > 0.0) {
         VacThrust *= sin((BurnTime/BuildupTime)*M_PI/2.0);
         // VacThrust *= (1-cos((BurnTime/BuildupTime)*M_PI))/2.0; // 1 - cos approach
       }
       BurnTime += in.TotalDeltaT; // Increment burn time
     } else {
       VacThrust = 0.0;
     }
 
   } else { // liquid fueled rocket assumed
 
     if (in.ThrottlePos[EngineNumber] < MinThrottle || Starved) { // Combustion not supported
 
       PctPower = 0.0; // desired thrust
       Flameout = true;
       VacThrust = 0.0;
 
     } else { // Calculate thrust
 
       // PctPower = Throttle / MaxThrottle; // Min and MaxThrottle range from 0.0 to 1.0, normally.
       
       PctPower = in.ThrottlePos[EngineNumber];
       Flameout = false;
       VacThrust = Isp * PropellantFlowRate;
 
     }
 
   } // End thrust calculations
 
   LoadThrusterInputs();
   It += Thruster->Calculate(VacThrust) * in.TotalDeltaT;
   ItVac += VacThrust * in.TotalDeltaT;
 
   RunPostFunctions();
 }

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◆ GetFlameout()

bool GetFlameout ( void )

inline

Gets the flame-out status.

The engine will "flame out" if the throttle is set below the minimum sustainable-thrust setting.

Returns: true if engine has flamed out.

Definition at line 171 of file FGRocket.h.

171 {return Flameout;}

◆ GetThrustVariation()

double GetThrustVariation ( void ) const

inline

Returns the thrust variation, if any.

Definition at line 207 of file FGRocket.h.

207 {return ThrustVariation;}

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◆ GetTotalImpulse()

double GetTotalImpulse ( void ) const

inline

Gets the total impulse of the rocket.

Returns: The cumulative actual total impulse of the rocket up to this time.

Definition at line 161 of file FGRocket.h.

161 {return It;}

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◆ GetTotalIspVariation()

double GetTotalIspVariation ( void ) const

inline

Returns the Total Isp variation, if any.

Definition at line 210 of file FGRocket.h.

210 {return TotalIspVariation;}

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◆ GetVacTotalImpulse()

double GetVacTotalImpulse ( void ) const

inline

Gets the total impulse of the rocket.

Returns: The cumulative vacuum total impulse of the rocket up to this time.

Definition at line 165 of file FGRocket.h.

165 {return ItVac;}

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◆ SetThrustVariation()

void SetThrustVariation ( double var )

inline

Sets the thrust variation for a solid rocket engine.

Solid propellant rocket motor thrust characteristics are typically defined at 70 degrees F temperature. At any other temperature, performance will be different. Warmer propellant grain will burn quicker and at higher thrust. Total motor impulse is not changed for change in thrust.

Parameters

var	the variation in percent. That is, a 2 percent variation would be specified as 0.02. A positive 2% variation in thrust would increase the thrust by 2%, and shorten the burn time.

Definition at line 195 of file FGRocket.h.

195 {ThrustVariation = var;}

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◆ SetTotalIspVariation()

void SetTotalIspVariation ( double var )

inline

Sets the variation in total motor energy.

The total energy present in a solid rocket motor can be modified (such as might happen with manufacturing variations) by setting the total Isp variation.

Parameters

var	the variation in percent. That is, a 2 percent variation would be specified as 0.02. This variation will affect the total thrust, but not the burn time.

Definition at line 204 of file FGRocket.h.

204 {TotalIspVariation = var;}

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

Public Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ FGRocket()

Member Function Documentation

◆ CalcFuelNeed()

◆ CalcOxidizerNeed()

◆ Calculate()

◆ GetFlameout()

◆ GetThrustVariation()

◆ GetTotalImpulse()

◆ GetTotalIspVariation()

◆ GetVacTotalImpulse()

◆ SetThrustVariation()

◆ SetTotalIspVariation()