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 FGTank* tank = Propulsion->GetTank(i);
130 if (SourceTanks[i] == 1) {
131 TotalEngineFuelAvailable += tank->GetContents();
135 VacThrust = ThrustTable->GetValue(TotalEngineFuelAvailable);
140 } else { // liquid fueled rocket assumed
142 if (Throttle < MinThrottle || Starved) { // Combustion not supported
144 PctPower = 0.0; // desired thrust
148 } else { // Calculate thrust
150 PctPower = Throttle / MaxThrottle; // Min and MaxThrottle range from 0.0 to 1.0, normally.
152 VacThrust = Isp * PropellantFlowRate;
156 } // End thrust calculations
158 thrust = Thruster->Calculate(VacThrust);
164 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
165 // This overrides the base class ConsumeFuel() function, for special rocket
166 // engine processing.
168 void FGRocket::ConsumeFuel(void)
172 bool haveOxTanks = false;
173 double Fshortage=0, Oshortage=0, TanksWithFuel=0, TanksWithOxidizer=0;
175 if (FuelFreeze) return;
176 if (TrimMode) return;
178 // Count how many assigned tanks have fuel for this engine at this time.
179 // If there is/are fuel tanks but no oxidizer tanks, this indicates
180 // a solid rocket is being modeled.
182 for (i=0; i<SourceTanks.size(); i++) {
183 Tank = Propulsion->GetTank(SourceTanks[i]);
184 switch(Tank->GetType()) {
186 if (Tank->GetContents() > 0.0 && Tank->GetSelected()) ++TanksWithFuel;
188 case FGTank::ttOXIDIZER:
190 if (Tank->GetContents() > 0.0 && Tank->GetSelected()) ++TanksWithOxidizer;
195 // If this engine has burned out, it is starved.
197 if (TanksWithFuel==0 || (haveOxTanks && TanksWithOxidizer==0)) {
202 // Expend fuel from the engine's tanks if the tank is selected as a source
205 double fuelNeedPerTank = CalcFuelNeed()/TanksWithFuel;
206 double oxiNeedPerTank = CalcOxidizerNeed()/TanksWithOxidizer;
208 for (i=0; i<SourceTanks.size(); i++) {
209 Tank = Propulsion->GetTank(SourceTanks[i]);
210 if ( ! Tank->GetSelected()) continue; // If this tank is not selected as a source, skip it.
211 switch(Tank->GetType()) {
213 Fshortage += Tank->Drain(2.0*fuelNeedPerTank - previousFuelNeedPerTank);
214 previousFuelNeedPerTank = fuelNeedPerTank;
216 case FGTank::ttOXIDIZER:
217 Oshortage += Tank->Drain(2.0*oxiNeedPerTank - previousOxiNeedPerTank);
218 previousOxiNeedPerTank = oxiNeedPerTank;
223 if (Fshortage < 0.00 || (haveOxTanks && Oshortage < 0.00)) Starved = true;
224 else Starved = false;
227 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
229 double FGRocket::CalcFuelNeed(void)
231 double dT = State->Getdt()*Propulsion->GetRate();
233 if (ThrustTable != 0L) { // Thrust table given - infers solid fuel
234 FuelFlowRate = VacThrust/Isp; // This calculates wdot (weight flow rate in lbs/sec)
236 FuelFlowRate = SLFuelFlowMax*PctPower;
239 FuelExpended = FuelFlowRate*dT; // For this time step ...
243 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
245 double FGRocket::CalcOxidizerNeed(void)
247 double dT = State->Getdt()*Propulsion->GetRate();
248 OxidizerFlowRate = SLOxiFlowMax*PctPower;
249 OxidizerExpended = OxidizerFlowRate*dT;
250 return OxidizerExpended;
253 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
255 string FGRocket::GetEngineLabels(string delimeter)
257 std::ostringstream buf;
259 buf << Name << " Total Impulse (engine " << EngineNumber << " in psf)" << delimeter
260 << Thruster->GetThrusterLabels(EngineNumber, delimeter);
265 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
267 string FGRocket::GetEngineValues(string delimeter)
269 std::ostringstream buf;
271 buf << It << delimeter << Thruster->GetThrusterValues(EngineNumber, delimeter);
276 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
277 // This funciton should tie properties to rocket engine specific properties
278 // that are not bound in the base class (FGEngine) code.
280 void FGRocket::bindmodel()
282 string property_name, base_property_name;
283 base_property_name = CreateIndexedPropertyName("propulsion/engine", EngineNumber);
285 property_name = base_property_name + "/total-impulse";
286 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetTotalImpulse);
287 property_name = base_property_name + "/oxi-flow-rate-pps";
288 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetOxiFlowRate);
289 property_name = base_property_name + "/vacuum-thrust_lbs";
290 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetVacThrust);
293 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
294 // The bitmasked value choices are as follows:
295 // unset: In this case (the default) JSBSim would only print
296 // out the normally expected messages, essentially echoing
297 // the config files as they are read. If the environment
298 // variable is not set, debug_lvl is set to 1 internally
299 // 0: This requests JSBSim not to output any messages
301 // 1: This value explicity requests the normal JSBSim
303 // 2: This value asks for a message to be printed out when
304 // a class is instantiated
305 // 4: When this value is set, a message is displayed when a
306 // FGModel object executes its Run() method
307 // 8: When this value is set, various runtime state variables
308 // are printed out periodically
309 // 16: When set various parameters are sanity checked and
310 // a message is printed out when they go out of bounds
312 void FGRocket::Debug(int from)
314 if (debug_lvl <= 0) return;
316 if (debug_lvl & 1) { // Standard console startup message output
317 if (from == 0) { // Constructor
318 cout << " Engine Name: " << Name << endl;
319 cout << " Vacuum Isp = " << Isp << endl;
320 cout << " Maximum Throttle = " << MaxThrottle << endl;
321 cout << " Minimum Throttle = " << MinThrottle << endl;
322 cout << " Fuel Flow (max) = " << SLFuelFlowMax << endl;
323 cout << " Oxidizer Flow (max) = " << SLOxiFlowMax << endl;
324 cout << " Mixture ratio = " << SLOxiFlowMax/SLFuelFlowMax << endl;
327 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
328 if (from == 0) cout << "Instantiated: FGRocket" << endl;
329 if (from == 1) cout << "Destroyed: FGRocket" << endl;
331 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
333 if (debug_lvl & 8 ) { // Runtime state variables
335 if (debug_lvl & 16) { // Sanity checking
337 if (debug_lvl & 64) {
338 if (from == 0) { // Constructor
339 cout << IdSrc << endl;
340 cout << IdHdr << endl;