#include <iostream>
#include <sstream>
#include "FGRocket.h"
-#include "FGState.h"
-#include "models/FGPropulsion.h"
#include "FGThruster.h"
-#include "FGTank.h"
using namespace std;
namespace JSBSim {
-static const char *IdSrc = "$Id$";
+static const char *IdSrc = "$Id: FGRocket.cpp,v 1.27 2012/04/08 15:19:08 jberndt Exp $";
static const char *IdHdr = ID_ROCKET;
/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
CLASS IMPLEMENTATION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
-FGRocket::FGRocket(FGFDMExec* exec, Element *el, int engine_number)
- : FGEngine(exec, el, engine_number)
+FGRocket::FGRocket(FGFDMExec* exec, Element *el, int engine_number, struct Inputs& input)
+ : FGEngine(exec, el, engine_number, input), isp_function(0L)
{
+ Type = etRocket;
Element* thrust_table_element = 0;
ThrustTable = 0L;
BurnTime = 0.0;
previousFuelNeedPerTank = 0.0;
previousOxiNeedPerTank = 0.0;
PropellantFlowRate = 0.0;
- FuelFlowRate = 0.0;
- OxidizerFlowRate = 0.0;
- SLOxiFlowMax = 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 = 0.0;
+ ThrustVariation = 0.0;
+ TotalIspVariation = 0.0;
+ Flameout = false;
// Defaults
MinThrottle = 0.0;
MaxThrottle = 1.0;
- if (el->FindElement("isp"))
+ string base_property_name = CreateIndexedPropertyName("propulsion/engine", EngineNumber);
+
+ std::stringstream strEngineNumber;
+ strEngineNumber << EngineNumber;
+
+ Element* isp_el = el->FindElement("isp");
+ Element* isp_func_el=0;
+
+ bindmodel(); // Bind model properties first, since they might be needed in functions.
+
+ // Specific impulse may be specified as a constant value or as a function - perhaps as a function of mixture ratio.
+ if (isp_el) {
+ 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"))
+
+ if (el->FindElement("slfuelflowmax")) {
SLFuelFlowMax = el->FindElementValueAsNumberConvertTo("slfuelflowmax", "LBS/SEC");
- if (el->FindElement("sloxiflowmax"))
+ 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");
+ }
+ }
}
- bindmodel();
Debug(0);
-
- Type = etRocket;
- Flameout = false;
-
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-double FGRocket::Calculate(void)
+void FGRocket::Calculate(void)
{
- double dT = State->Getdt()*Propulsion->GetRate();
- double thrust;
+ if (FDMExec->IntegrationSuspended()) return;
- if (!Flameout && !Starved) ConsumeFuel();
+ RunPreFunctions();
- PropellantFlowRate = (FuelExpended + OxidizerExpended)/dT;
- Throttle = FCS->GetThrottlePos(EngineNumber);
+ 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
if (ThrustTable != 0L) { // Thrust table given -> Solid fuel used
- if ((Throttle == 1 || BurnTime > 0.0 ) && !Starved) {
- double TotalEngineFuelBurned=0.0;
- for (int i=0; i<(int)SourceTanks.size(); i++) {
- FGTank* tank = Propulsion->GetTank(i);
- if (SourceTanks[i] == 1) {
- TotalEngineFuelBurned += tank->GetCapacity() - tank->GetContents();
- }
- }
+ if ((in.ThrottlePos[EngineNumber] == 1 || BurnTime > 0.0 ) && !Starved) {
- VacThrust = ThrustTable->GetValue(TotalEngineFuelBurned);
+ 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 += State->Getdt(); // Increment burn time
+ BurnTime += in.TotalDeltaT; // Increment burn time
} else {
VacThrust = 0.0;
}
} else { // liquid fueled rocket assumed
- if (Throttle < MinThrottle || Starved) { // Combustion not supported
+ if (in.ThrottlePos[EngineNumber] < MinThrottle || Starved) { // Combustion not supported
PctPower = 0.0; // desired thrust
Flameout = true;
} else { // Calculate thrust
- // This is nonsensical. Max throttle should be assumed to be 1.0. One might
- // conceivably have a throttle setting > 1.0 for some rocket engines. But, 1.0
- // should always be the default.
// PctPower = Throttle / MaxThrottle; // Min and MaxThrottle range from 0.0 to 1.0, normally.
- PctPower = Throttle;
+ PctPower = in.ThrottlePos[EngineNumber];
Flameout = false;
VacThrust = Isp * PropellantFlowRate;
} // End thrust calculations
- thrust = Thruster->Calculate(VacThrust);
- It += thrust * dT;
+ LoadThrusterInputs();
+ It += Thruster->Calculate(VacThrust) * in.TotalDeltaT;
- return thrust;
-}
-
-//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-// This overrides the base class ConsumeFuel() function, for special rocket
-// engine processing.
-
-void FGRocket::ConsumeFuel(void)
-{
- unsigned int i;
- FGTank* Tank;
- bool haveOxTanks = false;
- double Fshortage=0, Oshortage=0, TanksWithFuel=0, TanksWithOxidizer=0;
-
- if (FuelFreeze) return;
- if (TrimMode) return;
-
- // Count how many assigned tanks have fuel for this engine at this time.
- // If there is/are fuel tanks but no oxidizer tanks, this indicates
- // a solid rocket is being modeled.
-
- for (i=0; i<SourceTanks.size(); i++) {
- Tank = Propulsion->GetTank(SourceTanks[i]);
- switch(Tank->GetType()) {
- case FGTank::ttFUEL:
- if (Tank->GetContents() > 0.0 && Tank->GetSelected()) ++TanksWithFuel;
- break;
- case FGTank::ttOXIDIZER:
- haveOxTanks = true;
- if (Tank->GetContents() > 0.0 && Tank->GetSelected()) ++TanksWithOxidizer;
- break;
- }
- }
-
- // If this engine has burned out, it is starved.
-
- if (TanksWithFuel==0 || (haveOxTanks && TanksWithOxidizer==0)) {
- Starved = true;
- return;
- }
-
- // Expend fuel from the engine's tanks if the tank is selected as a source
- // for this engine.
-
- double fuelNeedPerTank = CalcFuelNeed()/TanksWithFuel;
- double oxiNeedPerTank = CalcOxidizerNeed()/TanksWithOxidizer;
-
- for (i=0; i<SourceTanks.size(); i++) {
- Tank = Propulsion->GetTank(SourceTanks[i]);
- if ( ! Tank->GetSelected()) continue; // If this tank is not selected as a source, skip it.
- switch(Tank->GetType()) {
- case FGTank::ttFUEL:
- Fshortage += Tank->Drain(2.0*fuelNeedPerTank - previousFuelNeedPerTank);
- previousFuelNeedPerTank = fuelNeedPerTank;
- break;
- case FGTank::ttOXIDIZER:
- Oshortage += Tank->Drain(2.0*oxiNeedPerTank - previousOxiNeedPerTank);
- previousOxiNeedPerTank = oxiNeedPerTank;
- break;
- }
- }
-
- if (Fshortage < 0.00 || (haveOxTanks && Oshortage < 0.00)) Starved = true;
- else Starved = false;
+ RunPostFunctions();
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+//
+// The FuelFlowRate can be affected by the TotalIspVariation value (settable
+// in a config file or via properties). The TotalIspVariation parameter affects
+// thrust, but the thrust determines fuel flow rate, so it must be adjusted
+// for Total Isp Variation.
double FGRocket::CalcFuelNeed(void)
{
- double dT = State->Getdt()*Propulsion->GetRate();
-
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 {
- FuelFlowRate = SLFuelFlowMax*PctPower;
+ SLFuelFlowMax = PropFlowMax / (1 + MxR);
+ FuelFlowRate = SLFuelFlowMax * PctPower;
}
- FuelExpended = FuelFlowRate*dT; // For this time step ...
+ FuelExpended = FuelFlowRate * in.TotalDeltaT; // For this time step ...
return FuelExpended;
}
double FGRocket::CalcOxidizerNeed(void)
{
- double dT = State->Getdt()*Propulsion->GetRate();
- OxidizerFlowRate = SLOxiFlowMax*PctPower;
- OxidizerExpended = OxidizerFlowRate*dT;
+ SLOxiFlowMax = PropFlowMax * MxR / (1 + MxR);
+ OxidizerFlowRate = SLOxiFlowMax * PctPower;
+ OxidizerExpended = OxidizerFlowRate * in.TotalDeltaT;
return OxidizerExpended;
}
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-// This funciton should tie properties to rocket engine specific properties
+// This function should tie properties to rocket engine specific properties
// that are not bound in the base class (FGEngine) code.
//
void FGRocket::bindmodel()
property_name = base_property_name + "/total-impulse";
PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetTotalImpulse);
- property_name = base_property_name + "/oxi-flow-rate-pps";
- PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetOxiFlowRate);
property_name = base_property_name + "/vacuum-thrust_lbs";
PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetVacThrust);
+
+ if (ThrustTable) { // Solid rocket motor
+ property_name = base_property_name + "/thrust-variation_pct";
+ PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetThrustVariation,
+ &FGRocket::SetThrustVariation);
+ property_name = base_property_name + "/total-isp-variation_pct";
+ PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetTotalIspVariation,
+ &FGRocket::SetTotalIspVariation);
+ } else { // Liquid rocket motor
+ property_name = base_property_name + "/oxi-flow-rate-pps";
+ PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetOxiFlowRate);
+ property_name = base_property_name + "/mixture-ratio";
+ PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetMixtureRatio,
+ &FGRocket::SetMixtureRatio);
+ property_name = base_property_name + "/isp";
+ PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetIsp,
+ &FGRocket::SetIsp);
+ }
}
//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
cout << " Minimum Throttle = " << MinThrottle << endl;
cout << " Fuel Flow (max) = " << SLFuelFlowMax << endl;
cout << " Oxidizer Flow (max) = " << SLOxiFlowMax << endl;
- cout << " Mixture ratio = " << SLOxiFlowMax/SLFuelFlowMax << endl;
+ if (SLFuelFlowMax > 0)
+ cout << " Mixture ratio = " << SLOxiFlowMax/SLFuelFlowMax << endl;
}
}
if (debug_lvl & 2 ) { // Instantiation/Destruction notification
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