1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
5 Date started: 09/12/2000
6 Purpose: This module models a rocket engine
8 ------------- Copyright (C) 2000 Jon S. Berndt (jon@jsbsim.org) --------------
10 This program is free software; you can redistribute it and/or modify it under
11 the terms of the GNU Lesser General Public License as published by the Free Software
12 Foundation; either version 2 of the License, or (at your option) any later
15 This program is distributed in the hope that it will be useful, but WITHOUT
16 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
17 FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
20 You should have received a copy of the GNU Lesser General Public License along with
21 this program; if not, write to the Free Software Foundation, Inc., 59 Temple
22 Place - Suite 330, Boston, MA 02111-1307, USA.
24 Further information about the GNU Lesser General Public License can also be found on
25 the world wide web at http://www.gnu.org.
27 FUNCTIONAL DESCRIPTION
28 --------------------------------------------------------------------------------
30 This class descends from the FGEngine class and models a rocket engine based on
31 parameters given in the engine config file for this class
34 --------------------------------------------------------------------------------
35 09/12/2000 JSB Created
37 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
39 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
44 #include "models/FGPropulsion.h"
45 #include "FGThruster.h"
52 static const char *IdSrc = "$Id: FGRocket.cpp,v 1.19 2010/02/25 05:21:36 jberndt Exp $";
53 static const char *IdHdr = ID_ROCKET;
55 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
57 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
59 FGRocket::FGRocket(FGFDMExec* exec, Element *el, int engine_number)
60 : FGEngine(exec, el, engine_number)
62 Element* thrust_table_element = 0;
65 previousFuelNeedPerTank = 0.0;
66 previousOxiNeedPerTank = 0.0;
67 PropellantFlowRate = 0.0;
68 FuelFlowRate = FuelExpended = 0.0;
69 OxidizerFlowRate = OxidizerExpended = 0.0;
70 SLOxiFlowMax = SLFuelFlowMax = 0.0;
73 ThrustVariation = 0.0;
74 TotalIspVariation = 0.0;
80 if (el->FindElement("isp"))
81 Isp = el->FindElementValueAsNumber("isp");
82 if (el->FindElement("builduptime"))
83 BuildupTime = el->FindElementValueAsNumber("builduptime");
84 if (el->FindElement("maxthrottle"))
85 MaxThrottle = el->FindElementValueAsNumber("maxthrottle");
86 if (el->FindElement("minthrottle"))
87 MinThrottle = el->FindElementValueAsNumber("minthrottle");
88 if (el->FindElement("slfuelflowmax"))
89 SLFuelFlowMax = el->FindElementValueAsNumberConvertTo("slfuelflowmax", "LBS/SEC");
90 if (el->FindElement("sloxiflowmax"))
91 SLOxiFlowMax = el->FindElementValueAsNumberConvertTo("sloxiflowmax", "LBS/SEC");
93 // If there is a thrust table element, this is a solid propellant engine.
94 thrust_table_element = el->FindElement("thrust_table");
95 if (thrust_table_element) {
96 ThrustTable = new FGTable(PropertyManager, thrust_table_element);
97 Element* variation_element = el->FindElement("variation");
98 if (variation_element) {
99 if (variation_element->FindElement("thrust")) {
100 ThrustVariation = variation_element->FindElementValueAsNumber("thrust");
102 if (variation_element->FindElement("total_isp")) {
103 TotalIspVariation = variation_element->FindElementValueAsNumber("total_isp");
117 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
119 FGRocket::~FGRocket(void)
125 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
127 double FGRocket::Calculate(void)
129 double dT = FDMExec->GetDeltaT()*Propulsion->GetRate();
132 if (!Flameout && !Starved) ConsumeFuel();
134 PropellantFlowRate = (FuelExpended + OxidizerExpended)/dT;
135 Throttle = FCS->GetThrottlePos(EngineNumber);
137 // If there is a thrust table, it is a function of propellant burned. The
138 // engine is started when the throttle is advanced to 1.0. After that, it
139 // burns without regard to throttle setting.
141 if (ThrustTable != 0L) { // Thrust table given -> Solid fuel used
143 if ((Throttle == 1 || BurnTime > 0.0 ) && !Starved) {
144 double TotalEngineFuelBurned=0.0;
145 for (int i=0; i<(int)SourceTanks.size(); i++) {
146 FGTank* tank = Propulsion->GetTank(i);
147 if (SourceTanks[i] == 1) {
148 TotalEngineFuelBurned += tank->GetCapacity() - tank->GetContents();
152 VacThrust = ThrustTable->GetValue(TotalEngineFuelBurned)
153 * (ThrustVariation + 1)
154 * (TotalIspVariation + 1);
155 if (BurnTime <= BuildupTime && BuildupTime > 0.0) {
156 VacThrust *= sin((BurnTime/BuildupTime)*M_PI/2.0);
157 // VacThrust *= (1-cos((BurnTime/BuildupTime)*M_PI))/2.0; // 1 - cos approach
159 BurnTime += FDMExec->GetDeltaT(); // Increment burn time
164 } else { // liquid fueled rocket assumed
166 if (Throttle < MinThrottle || Starved) { // Combustion not supported
168 PctPower = 0.0; // desired thrust
172 } else { // Calculate thrust
174 // This is nonsensical. Max throttle should be assumed to be 1.0. One might
175 // conceivably have a throttle setting > 1.0 for some rocket engines. But, 1.0
176 // should always be the default.
177 // PctPower = Throttle / MaxThrottle; // Min and MaxThrottle range from 0.0 to 1.0, normally.
181 VacThrust = Isp * PropellantFlowRate;
185 } // End thrust calculations
187 thrust = Thruster->Calculate(VacThrust);
193 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
194 // This overrides the base class ConsumeFuel() function, for special rocket
195 // engine processing.
197 void FGRocket::ConsumeFuel(void)
201 bool haveOxTanks = false;
202 double Fshortage=0, Oshortage=0, TanksWithFuel=0, TanksWithOxidizer=0;
204 if (FuelFreeze) return;
205 if (TrimMode) return;
207 // Count how many assigned tanks have fuel for this engine at this time.
208 // If there is/are fuel tanks but no oxidizer tanks, this indicates
209 // a solid rocket is being modeled.
211 for (i=0; i<SourceTanks.size(); i++) {
212 Tank = Propulsion->GetTank(i);
213 switch(Tank->GetType()) {
215 if (Tank->GetContents() > 0.0 && Tank->GetSelected() && SourceTanks[i] > 0) ++TanksWithFuel;
217 case FGTank::ttOXIDIZER:
218 if (Tank->GetContents() > 0.0 && Tank->GetSelected() && SourceTanks[i] > 0) {
226 // If this engine has burned out, it is starved.
228 if (TanksWithFuel==0 || (haveOxTanks && TanksWithOxidizer==0)) {
233 // Expend fuel from the engine's tanks if the tank is selected as a source
236 double fuelNeedPerTank = 0;
237 double oxiNeedPerTank = 0;
239 if (TanksWithFuel > 0) fuelNeedPerTank = CalcFuelNeed()/TanksWithFuel;
240 if (TanksWithOxidizer > 0) oxiNeedPerTank = CalcOxidizerNeed()/TanksWithOxidizer;
242 for (i=0; i<SourceTanks.size(); i++) {
243 Tank = Propulsion->GetTank(i);
244 if ( ! Tank->GetSelected() || SourceTanks[i] == 0) continue; // If this tank is not selected as a source, skip it.
245 switch(Tank->GetType()) {
247 Fshortage += Tank->Drain(2.0*fuelNeedPerTank - previousFuelNeedPerTank);
248 previousFuelNeedPerTank = fuelNeedPerTank;
250 case FGTank::ttOXIDIZER:
251 Oshortage += Tank->Drain(2.0*oxiNeedPerTank - previousOxiNeedPerTank);
252 previousOxiNeedPerTank = oxiNeedPerTank;
257 if (Fshortage < 0.00 || (haveOxTanks && Oshortage < 0.00)) Starved = true;
258 else Starved = false;
261 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
263 // The FuelFlowRate can be affected by the TotalIspVariation value (settable
264 // in a config file or via properties). The TotalIspVariation parameter affects
265 // thrust, but the thrust determines fuel flow rate, so it must be adjusted
266 // for Total Isp Variation.
268 double FGRocket::CalcFuelNeed(void)
270 double dT = FDMExec->GetDeltaT()*Propulsion->GetRate();
272 if (ThrustTable != 0L) { // Thrust table given - infers solid fuel
273 FuelFlowRate = VacThrust/Isp; // This calculates wdot (weight flow rate in lbs/sec)
274 FuelFlowRate /= (1 + TotalIspVariation);
276 FuelFlowRate = SLFuelFlowMax*PctPower;
279 FuelExpended = FuelFlowRate*dT; // For this time step ...
283 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
285 double FGRocket::CalcOxidizerNeed(void)
287 double dT = FDMExec->GetDeltaT()*Propulsion->GetRate();
288 OxidizerFlowRate = SLOxiFlowMax*PctPower;
289 OxidizerExpended = OxidizerFlowRate*dT;
290 return OxidizerExpended;
293 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
295 string FGRocket::GetEngineLabels(const string& delimiter)
297 std::ostringstream buf;
299 buf << Name << " Total Impulse (engine " << EngineNumber << " in psf)" << delimiter
300 << Thruster->GetThrusterLabels(EngineNumber, delimiter);
305 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
307 string FGRocket::GetEngineValues(const string& delimiter)
309 std::ostringstream buf;
311 buf << It << delimiter << Thruster->GetThrusterValues(EngineNumber, delimiter);
316 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
317 // This function should tie properties to rocket engine specific properties
318 // that are not bound in the base class (FGEngine) code.
320 void FGRocket::bindmodel()
322 string property_name, base_property_name;
323 base_property_name = CreateIndexedPropertyName("propulsion/engine", EngineNumber);
325 property_name = base_property_name + "/total-impulse";
326 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetTotalImpulse);
327 property_name = base_property_name + "/vacuum-thrust_lbs";
328 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetVacThrust);
330 if (ThrustTable) { // Solid rocket motor
331 property_name = base_property_name + "/thrust-variation_pct";
332 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetThrustVariation,
333 &FGRocket::SetThrustVariation);
334 property_name = base_property_name + "/total-isp-variation_pct";
335 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetTotalIspVariation,
336 &FGRocket::SetTotalIspVariation);
337 } else { // Liquid rocket motor
338 property_name = base_property_name + "/oxi-flow-rate-pps";
339 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetOxiFlowRate);
343 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
344 // The bitmasked value choices are as follows:
345 // unset: In this case (the default) JSBSim would only print
346 // out the normally expected messages, essentially echoing
347 // the config files as they are read. If the environment
348 // variable is not set, debug_lvl is set to 1 internally
349 // 0: This requests JSBSim not to output any messages
351 // 1: This value explicity requests the normal JSBSim
353 // 2: This value asks for a message to be printed out when
354 // a class is instantiated
355 // 4: When this value is set, a message is displayed when a
356 // FGModel object executes its Run() method
357 // 8: When this value is set, various runtime state variables
358 // are printed out periodically
359 // 16: When set various parameters are sanity checked and
360 // a message is printed out when they go out of bounds
362 void FGRocket::Debug(int from)
364 if (debug_lvl <= 0) return;
366 if (debug_lvl & 1) { // Standard console startup message output
367 if (from == 0) { // Constructor
368 cout << " Engine Name: " << Name << endl;
369 cout << " Vacuum Isp = " << Isp << endl;
370 cout << " Maximum Throttle = " << MaxThrottle << endl;
371 cout << " Minimum Throttle = " << MinThrottle << endl;
372 cout << " Fuel Flow (max) = " << SLFuelFlowMax << endl;
373 cout << " Oxidizer Flow (max) = " << SLOxiFlowMax << endl;
374 if (SLFuelFlowMax > 0)
375 cout << " Mixture ratio = " << SLOxiFlowMax/SLFuelFlowMax << endl;
378 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
379 if (from == 0) cout << "Instantiated: FGRocket" << endl;
380 if (from == 1) cout << "Destroyed: FGRocket" << endl;
382 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
384 if (debug_lvl & 8 ) { // Runtime state variables
386 if (debug_lvl & 16) { // Sanity checking
388 if (debug_lvl & 64) {
389 if (from == 0) { // Constructor
390 cout << IdSrc << endl;
391 cout << IdHdr << endl;