1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
5 Date started: 09/12/2000
6 Purpose: This module models a rocket engine
8 ------------- Copyright (C) 2000 Jon S. Berndt (jsb@hal-pc.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 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
47 static const char *IdSrc = "$Id$";
48 static const char *IdHdr = ID_ROCKET;
50 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
52 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
54 FGRocket::FGRocket(FGFDMExec* exec, Element *el, int engine_number)
55 : FGEngine(exec, el, engine_number)
57 Element* thrust_table_element = 0;
60 previousFuelNeedPerTank = 0.0;
61 previousOxiNeedPerTank = 0.0;
62 PropellantFlowRate = 0.0;
64 OxidizerFlowRate = 0.0;
72 if (el->FindElement("isp"))
73 Isp = el->FindElementValueAsNumber("isp");
74 if (el->FindElement("maxthrottle"))
75 MaxThrottle = el->FindElementValueAsNumber("maxthrottle");
76 if (el->FindElement("minthrottle"))
77 MinThrottle = el->FindElementValueAsNumber("minthrottle");
78 if (el->FindElement("slfuelflowmax"))
79 SLFuelFlowMax = el->FindElementValueAsNumberConvertTo("slfuelflowmax", "LBS/SEC");
80 if (el->FindElement("sloxiflowmax"))
81 SLOxiFlowMax = el->FindElementValueAsNumberConvertTo("sloxiflowmax", "LBS/SEC");
83 thrust_table_element = el->FindElement("thrust_table");
84 if (thrust_table_element) {
85 ThrustTable = new FGTable(PropertyManager, thrust_table_element);
97 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
99 FGRocket::~FGRocket(void)
104 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
106 double FGRocket::Calculate(void)
108 double dT = State->Getdt()*Propulsion->GetRate();
110 if (!Flameout && !Starved) ConsumeFuel();
112 PropellantFlowRate = (FuelExpended + OxidizerExpended)/dT;
113 Throttle = FCS->GetThrottlePos(EngineNumber);
115 // If there is a thrust table, it is a function of propellant remaining. The
116 // engine is started when the throttle is advanced to 1.0. After that, it
117 // burns without regard to throttle setting. The table returns a value between
118 // zero and one, representing the percentage of maximum vacuum thrust being
121 if (ThrustTable != 0L) { // Thrust table given -> Solid fuel used
123 if ((Throttle == 1 || BurnTime > 0.0 ) && !Starved) {
124 BurnTime += State->Getdt();
125 double TotalEngineFuelAvailable=0.0;
126 for (int i=0; i<(int)SourceTanks.size(); i++)
127 TotalEngineFuelAvailable += Propulsion->GetTank(SourceTanks[i])->GetContents();
129 VacThrust = ThrustTable->GetValue(TotalEngineFuelAvailable);
134 } else { // liquid fueled rocket assumed
136 if (Throttle < MinThrottle || Starved) { // Combustion not supported
138 PctPower = Thrust = 0.0; // desired thrust
142 } else { // Calculate thrust
144 PctPower = Throttle / MaxThrottle; // Min and MaxThrottle range from 0.0 to 1.0, normally.
146 VacThrust = Isp * PropellantFlowRate;
150 } // End thrust calculations
152 Thrust = Thruster->Calculate(VacThrust);
158 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
159 // This overrides the base class ConsumeFuel() function, for special rocket
160 // engine processing.
162 void FGRocket::ConsumeFuel(void)
166 bool haveOxTanks = false;
167 double Fshortage=0, Oshortage=0, TanksWithFuel=0, TanksWithOxidizer=0;
169 if (FuelFreeze) return;
170 if (TrimMode) return;
172 // Count how many assigned tanks have fuel for this engine at this time.
173 // If there is/are fuel tanks but no oxidizer tanks, this indicates
174 // a solid rocket is being modeled.
176 for (i=0; i<SourceTanks.size(); i++) {
177 Tank = Propulsion->GetTank(SourceTanks[i]);
178 switch(Tank->GetType()) {
180 if (Tank->GetContents() > 0.0 && Tank->GetSelected()) ++TanksWithFuel;
182 case FGTank::ttOXIDIZER:
184 if (Tank->GetContents() > 0.0 && Tank->GetSelected()) ++TanksWithOxidizer;
189 // If this engine has burned out, it is starved.
191 if (TanksWithFuel==0 || (haveOxTanks && TanksWithOxidizer==0)) {
196 // Expend fuel from the engine's tanks if the tank is selected as a source
199 double fuelNeedPerTank = CalcFuelNeed()/TanksWithFuel;
200 double oxiNeedPerTank = CalcOxidizerNeed()/TanksWithOxidizer;
202 for (i=0; i<SourceTanks.size(); i++) {
203 Tank = Propulsion->GetTank(SourceTanks[i]);
204 if ( ! Tank->GetSelected()) continue; // If this tank is not selected as a source, skip it.
205 switch(Tank->GetType()) {
207 Fshortage += Tank->Drain(2.0*fuelNeedPerTank - previousFuelNeedPerTank);
208 previousFuelNeedPerTank = fuelNeedPerTank;
210 case FGTank::ttOXIDIZER:
211 Oshortage += Tank->Drain(2.0*oxiNeedPerTank - previousOxiNeedPerTank);
212 previousOxiNeedPerTank = oxiNeedPerTank;
217 if (Fshortage < 0.00 || (haveOxTanks && Oshortage < 0.00)) Starved = true;
218 else Starved = false;
221 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
223 double FGRocket::CalcFuelNeed(void)
225 double dT = State->Getdt()*Propulsion->GetRate();
227 if (ThrustTable != 0L) { // Thrust table given - infers solid fuel
228 FuelFlowRate = VacThrust/Isp; // This calculates wdot (weight flow rate in lbs/sec)
230 FuelFlowRate = SLFuelFlowMax*PctPower;
233 FuelExpended = FuelFlowRate*dT; // For this time step ...
237 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
239 double FGRocket::CalcOxidizerNeed(void)
241 double dT = State->Getdt()*Propulsion->GetRate();
242 OxidizerFlowRate = SLOxiFlowMax*PctPower;
243 OxidizerExpended = OxidizerFlowRate*dT;
244 return OxidizerExpended;
247 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
249 string FGRocket::GetEngineLabels(string delimeter)
251 std::ostringstream buf;
253 buf << Name << " Total Impulse (engine " << EngineNumber << " in psf)" << delimeter
254 << Thruster->GetThrusterLabels(EngineNumber, delimeter);
259 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
261 string FGRocket::GetEngineValues(string delimeter)
263 std::ostringstream buf;
265 buf << It << delimeter << Thruster->GetThrusterValues(EngineNumber, delimeter);
270 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
271 // This funciton should tie properties to rocket engine specific properties
272 // that are not bound in the base class (FGEngine) code.
274 void FGRocket::bindmodel()
276 char property_name[80];
278 snprintf(property_name, 80, "propulsion/engine[%u]/total-impulse", EngineNumber);
279 PropertyManager->Tie( property_name, this, &FGRocket::GetTotalImpulse);
280 snprintf(property_name, 80, "propulsion/engine[%u]/oxi-flow-rate-pps", EngineNumber);
281 PropertyManager->Tie( property_name, this, &FGRocket::GetOxiFlowRate);
282 snprintf(property_name, 80, "propulsion/engine[%u]/vacuum-thrust_lbs", EngineNumber);
283 PropertyManager->Tie( property_name, this, &FGRocket::GetVacThrust);
286 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
287 // The bitmasked value choices are as follows:
288 // unset: In this case (the default) JSBSim would only print
289 // out the normally expected messages, essentially echoing
290 // the config files as they are read. If the environment
291 // variable is not set, debug_lvl is set to 1 internally
292 // 0: This requests JSBSim not to output any messages
294 // 1: This value explicity requests the normal JSBSim
296 // 2: This value asks for a message to be printed out when
297 // a class is instantiated
298 // 4: When this value is set, a message is displayed when a
299 // FGModel object executes its Run() method
300 // 8: When this value is set, various runtime state variables
301 // are printed out periodically
302 // 16: When set various parameters are sanity checked and
303 // a message is printed out when they go out of bounds
305 void FGRocket::Debug(int from)
307 if (debug_lvl <= 0) return;
309 if (debug_lvl & 1) { // Standard console startup message output
310 if (from == 0) { // Constructor
311 cout << " Engine Name: " << Name << endl;
312 cout << " Vacuum Isp = " << Isp << endl;
313 cout << " Maximum Throttle = " << MaxThrottle << endl;
314 cout << " Minimum Throttle = " << MinThrottle << endl;
315 cout << " Fuel Flow (max) = " << SLFuelFlowMax << endl;
316 cout << " Oxidizer Flow (max) = " << SLOxiFlowMax << endl;
317 cout << " Mixture ratio = " << SLOxiFlowMax/SLFuelFlowMax << endl;
320 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
321 if (from == 0) cout << "Instantiated: FGRocket" << endl;
322 if (from == 1) cout << "Destroyed: FGRocket" << endl;
324 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
326 if (debug_lvl & 8 ) { // Runtime state variables
328 if (debug_lvl & 16) { // Sanity checking
330 if (debug_lvl & 64) {
331 if (from == 0) { // Constructor
332 cout << IdSrc << endl;
333 cout << IdHdr << endl;