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 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
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)
105 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
107 double FGRocket::Calculate(void)
109 double dT = State->Getdt()*Propulsion->GetRate();
112 if (!Flameout && !Starved) ConsumeFuel();
114 PropellantFlowRate = (FuelExpended + OxidizerExpended)/dT;
115 Throttle = FCS->GetThrottlePos(EngineNumber);
117 // If there is a thrust table, it is a function of propellant remaining. The
118 // engine is started when the throttle is advanced to 1.0. After that, it
119 // burns without regard to throttle setting. The table returns a value between
120 // zero and one, representing the percentage of maximum vacuum thrust being
123 if (ThrustTable != 0L) { // Thrust table given -> Solid fuel used
125 if ((Throttle == 1 || BurnTime > 0.0 ) && !Starved) {
126 BurnTime += State->Getdt();
127 double TotalEngineFuelAvailable=0.0;
128 for (int i=0; i<(int)SourceTanks.size(); i++)
129 TotalEngineFuelAvailable += Propulsion->GetTank(SourceTanks[i])->GetContents();
131 VacThrust = ThrustTable->GetValue(TotalEngineFuelAvailable);
136 } else { // liquid fueled rocket assumed
138 if (Throttle < MinThrottle || Starved) { // Combustion not supported
140 PctPower = 0.0; // desired thrust
144 } else { // Calculate thrust
146 PctPower = Throttle / MaxThrottle; // Min and MaxThrottle range from 0.0 to 1.0, normally.
148 VacThrust = Isp * PropellantFlowRate;
152 } // End thrust calculations
154 thrust = Thruster->Calculate(VacThrust);
160 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
161 // This overrides the base class ConsumeFuel() function, for special rocket
162 // engine processing.
164 void FGRocket::ConsumeFuel(void)
168 bool haveOxTanks = false;
169 double Fshortage=0, Oshortage=0, TanksWithFuel=0, TanksWithOxidizer=0;
171 if (FuelFreeze) return;
172 if (TrimMode) return;
174 // Count how many assigned tanks have fuel for this engine at this time.
175 // If there is/are fuel tanks but no oxidizer tanks, this indicates
176 // a solid rocket is being modeled.
178 for (i=0; i<SourceTanks.size(); i++) {
179 Tank = Propulsion->GetTank(SourceTanks[i]);
180 switch(Tank->GetType()) {
182 if (Tank->GetContents() > 0.0 && Tank->GetSelected()) ++TanksWithFuel;
184 case FGTank::ttOXIDIZER:
186 if (Tank->GetContents() > 0.0 && Tank->GetSelected()) ++TanksWithOxidizer;
191 // If this engine has burned out, it is starved.
193 if (TanksWithFuel==0 || (haveOxTanks && TanksWithOxidizer==0)) {
198 // Expend fuel from the engine's tanks if the tank is selected as a source
201 double fuelNeedPerTank = CalcFuelNeed()/TanksWithFuel;
202 double oxiNeedPerTank = CalcOxidizerNeed()/TanksWithOxidizer;
204 for (i=0; i<SourceTanks.size(); i++) {
205 Tank = Propulsion->GetTank(SourceTanks[i]);
206 if ( ! Tank->GetSelected()) continue; // If this tank is not selected as a source, skip it.
207 switch(Tank->GetType()) {
209 Fshortage += Tank->Drain(2.0*fuelNeedPerTank - previousFuelNeedPerTank);
210 previousFuelNeedPerTank = fuelNeedPerTank;
212 case FGTank::ttOXIDIZER:
213 Oshortage += Tank->Drain(2.0*oxiNeedPerTank - previousOxiNeedPerTank);
214 previousOxiNeedPerTank = oxiNeedPerTank;
219 if (Fshortage < 0.00 || (haveOxTanks && Oshortage < 0.00)) Starved = true;
220 else Starved = false;
223 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
225 double FGRocket::CalcFuelNeed(void)
227 double dT = State->Getdt()*Propulsion->GetRate();
229 if (ThrustTable != 0L) { // Thrust table given - infers solid fuel
230 FuelFlowRate = VacThrust/Isp; // This calculates wdot (weight flow rate in lbs/sec)
232 FuelFlowRate = SLFuelFlowMax*PctPower;
235 FuelExpended = FuelFlowRate*dT; // For this time step ...
239 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
241 double FGRocket::CalcOxidizerNeed(void)
243 double dT = State->Getdt()*Propulsion->GetRate();
244 OxidizerFlowRate = SLOxiFlowMax*PctPower;
245 OxidizerExpended = OxidizerFlowRate*dT;
246 return OxidizerExpended;
249 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
251 string FGRocket::GetEngineLabels(string delimeter)
253 std::ostringstream buf;
255 buf << Name << " Total Impulse (engine " << EngineNumber << " in psf)" << delimeter
256 << Thruster->GetThrusterLabels(EngineNumber, delimeter);
261 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
263 string FGRocket::GetEngineValues(string delimeter)
265 std::ostringstream buf;
267 buf << It << delimeter << Thruster->GetThrusterValues(EngineNumber, delimeter);
272 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
273 // This funciton should tie properties to rocket engine specific properties
274 // that are not bound in the base class (FGEngine) code.
276 void FGRocket::bindmodel()
278 string property_name, base_property_name;
279 base_property_name = CreateIndexedPropertyName("propulsion/engine", EngineNumber);
281 property_name = base_property_name + "/total-impulse";
282 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetTotalImpulse);
283 property_name = base_property_name + "/oxi-flow-rate-pps";
284 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetOxiFlowRate);
285 property_name = base_property_name + "/vacuum-thrust_lbs";
286 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetVacThrust);
289 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
290 // The bitmasked value choices are as follows:
291 // unset: In this case (the default) JSBSim would only print
292 // out the normally expected messages, essentially echoing
293 // the config files as they are read. If the environment
294 // variable is not set, debug_lvl is set to 1 internally
295 // 0: This requests JSBSim not to output any messages
297 // 1: This value explicity requests the normal JSBSim
299 // 2: This value asks for a message to be printed out when
300 // a class is instantiated
301 // 4: When this value is set, a message is displayed when a
302 // FGModel object executes its Run() method
303 // 8: When this value is set, various runtime state variables
304 // are printed out periodically
305 // 16: When set various parameters are sanity checked and
306 // a message is printed out when they go out of bounds
308 void FGRocket::Debug(int from)
310 if (debug_lvl <= 0) return;
312 if (debug_lvl & 1) { // Standard console startup message output
313 if (from == 0) { // Constructor
314 cout << " Engine Name: " << Name << endl;
315 cout << " Vacuum Isp = " << Isp << endl;
316 cout << " Maximum Throttle = " << MaxThrottle << endl;
317 cout << " Minimum Throttle = " << MinThrottle << endl;
318 cout << " Fuel Flow (max) = " << SLFuelFlowMax << endl;
319 cout << " Oxidizer Flow (max) = " << SLOxiFlowMax << endl;
320 cout << " Mixture ratio = " << SLOxiFlowMax/SLFuelFlowMax << endl;
323 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
324 if (from == 0) cout << "Instantiated: FGRocket" << endl;
325 if (from == 1) cout << "Destroyed: FGRocket" << endl;
327 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
329 if (debug_lvl & 8 ) { // Runtime state variables
331 if (debug_lvl & 16) { // Sanity checking
333 if (debug_lvl & 64) {
334 if (from == 0) { // Constructor
335 cout << IdSrc << endl;
336 cout << IdHdr << endl;