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 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
45 #include "models/FGPropulsion.h"
46 #include "FGThruster.h"
53 static const char *IdSrc = "$Id$";
54 static const char *IdHdr = ID_ROCKET;
56 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
58 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
60 FGRocket::FGRocket(FGFDMExec* exec, Element *el, int engine_number)
61 : FGEngine(exec, el, engine_number)
63 Element* thrust_table_element = 0;
66 previousFuelNeedPerTank = 0.0;
67 previousOxiNeedPerTank = 0.0;
68 PropellantFlowRate = 0.0;
70 OxidizerFlowRate = 0.0;
74 ThrustVariation = 0.0;
75 TotalIspVariation = 0.0;
81 if (el->FindElement("isp"))
82 Isp = el->FindElementValueAsNumber("isp");
83 if (el->FindElement("builduptime"))
84 BuildupTime = el->FindElementValueAsNumber("builduptime");
85 if (el->FindElement("maxthrottle"))
86 MaxThrottle = el->FindElementValueAsNumber("maxthrottle");
87 if (el->FindElement("minthrottle"))
88 MinThrottle = el->FindElementValueAsNumber("minthrottle");
89 if (el->FindElement("slfuelflowmax"))
90 SLFuelFlowMax = el->FindElementValueAsNumberConvertTo("slfuelflowmax", "LBS/SEC");
91 if (el->FindElement("sloxiflowmax"))
92 SLOxiFlowMax = el->FindElementValueAsNumberConvertTo("sloxiflowmax", "LBS/SEC");
94 // If there is a thrust table element, this is a solid propellant engine.
95 thrust_table_element = el->FindElement("thrust_table");
96 if (thrust_table_element) {
97 ThrustTable = new FGTable(PropertyManager, thrust_table_element);
98 Element* variation_element = el->FindElement("variation");
99 if (variation_element) {
100 if (variation_element->FindElement("thrust")) {
101 ThrustVariation = variation_element->FindElementValueAsNumber("thrust");
103 if (variation_element->FindElement("total_isp")) {
104 TotalIspVariation = variation_element->FindElementValueAsNumber("total_isp");
118 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
120 FGRocket::~FGRocket(void)
126 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
128 double FGRocket::Calculate(void)
130 double dT = State->Getdt()*Propulsion->GetRate();
133 if (!Flameout && !Starved) ConsumeFuel();
135 PropellantFlowRate = (FuelExpended + OxidizerExpended)/dT;
136 Throttle = FCS->GetThrottlePos(EngineNumber);
138 // If there is a thrust table, it is a function of propellant burned. The
139 // engine is started when the throttle is advanced to 1.0. After that, it
140 // burns without regard to throttle setting.
142 if (ThrustTable != 0L) { // Thrust table given -> Solid fuel used
144 if ((Throttle == 1 || BurnTime > 0.0 ) && !Starved) {
145 double TotalEngineFuelBurned=0.0;
146 for (int i=0; i<(int)SourceTanks.size(); i++) {
147 FGTank* tank = Propulsion->GetTank(i);
148 if (SourceTanks[i] == 1) {
149 TotalEngineFuelBurned += tank->GetCapacity() - tank->GetContents();
153 VacThrust = ThrustTable->GetValue(TotalEngineFuelBurned)
154 * (ThrustVariation + 1)
155 * (TotalIspVariation + 1);
156 if (BurnTime <= BuildupTime && BuildupTime > 0.0) {
157 VacThrust *= sin((BurnTime/BuildupTime)*M_PI/2.0);
158 // VacThrust *= (1-cos((BurnTime/BuildupTime)*M_PI))/2.0; // 1 - cos approach
160 BurnTime += State->Getdt(); // Increment burn time
165 } else { // liquid fueled rocket assumed
167 if (Throttle < MinThrottle || Starved) { // Combustion not supported
169 PctPower = 0.0; // desired thrust
173 } else { // Calculate thrust
175 // This is nonsensical. Max throttle should be assumed to be 1.0. One might
176 // conceivably have a throttle setting > 1.0 for some rocket engines. But, 1.0
177 // should always be the default.
178 // PctPower = Throttle / MaxThrottle; // Min and MaxThrottle range from 0.0 to 1.0, normally.
182 VacThrust = Isp * PropellantFlowRate;
186 } // End thrust calculations
188 thrust = Thruster->Calculate(VacThrust);
194 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
195 // This overrides the base class ConsumeFuel() function, for special rocket
196 // engine processing.
198 void FGRocket::ConsumeFuel(void)
202 bool haveOxTanks = false;
203 double Fshortage=0, Oshortage=0, TanksWithFuel=0, TanksWithOxidizer=0;
205 if (FuelFreeze) return;
206 if (TrimMode) return;
208 // Count how many assigned tanks have fuel for this engine at this time.
209 // If there is/are fuel tanks but no oxidizer tanks, this indicates
210 // a solid rocket is being modeled.
212 for (i=0; i<SourceTanks.size(); i++) {
213 Tank = Propulsion->GetTank(SourceTanks[i]);
214 switch(Tank->GetType()) {
216 if (Tank->GetContents() > 0.0 && Tank->GetSelected()) ++TanksWithFuel;
218 case FGTank::ttOXIDIZER:
220 if (Tank->GetContents() > 0.0 && Tank->GetSelected()) ++TanksWithOxidizer;
225 // If this engine has burned out, it is starved.
227 if (TanksWithFuel==0 || (haveOxTanks && TanksWithOxidizer==0)) {
232 // Expend fuel from the engine's tanks if the tank is selected as a source
235 double fuelNeedPerTank = CalcFuelNeed()/TanksWithFuel;
236 double oxiNeedPerTank = CalcOxidizerNeed()/TanksWithOxidizer;
238 for (i=0; i<SourceTanks.size(); i++) {
239 Tank = Propulsion->GetTank(SourceTanks[i]);
240 if ( ! Tank->GetSelected()) continue; // If this tank is not selected as a source, skip it.
241 switch(Tank->GetType()) {
243 Fshortage += Tank->Drain(2.0*fuelNeedPerTank - previousFuelNeedPerTank);
244 previousFuelNeedPerTank = fuelNeedPerTank;
246 case FGTank::ttOXIDIZER:
247 Oshortage += Tank->Drain(2.0*oxiNeedPerTank - previousOxiNeedPerTank);
248 previousOxiNeedPerTank = oxiNeedPerTank;
253 if (Fshortage < 0.00 || (haveOxTanks && Oshortage < 0.00)) Starved = true;
254 else Starved = false;
257 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
259 // The FuelFlowRate can be affected by the TotalIspVariation value (settable
260 // in a config file or via properties). The TotalIspVariation parameter affects
261 // thrust, but the thrust determines fuel flow rate, so it must be adjusted
262 // for Total Isp Variation.
264 double FGRocket::CalcFuelNeed(void)
266 double dT = State->Getdt()*Propulsion->GetRate();
268 if (ThrustTable != 0L) { // Thrust table given - infers solid fuel
269 FuelFlowRate = VacThrust/Isp; // This calculates wdot (weight flow rate in lbs/sec)
270 FuelFlowRate /= (1 + TotalIspVariation);
272 FuelFlowRate = SLFuelFlowMax*PctPower;
275 FuelExpended = FuelFlowRate*dT; // For this time step ...
279 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
281 double FGRocket::CalcOxidizerNeed(void)
283 double dT = State->Getdt()*Propulsion->GetRate();
284 OxidizerFlowRate = SLOxiFlowMax*PctPower;
285 OxidizerExpended = OxidizerFlowRate*dT;
286 return OxidizerExpended;
289 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
291 string FGRocket::GetEngineLabels(const string& delimiter)
293 std::ostringstream buf;
295 buf << Name << " Total Impulse (engine " << EngineNumber << " in psf)" << delimiter
296 << Thruster->GetThrusterLabels(EngineNumber, delimiter);
301 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
303 string FGRocket::GetEngineValues(const string& delimiter)
305 std::ostringstream buf;
307 buf << It << delimiter << Thruster->GetThrusterValues(EngineNumber, delimiter);
312 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
313 // This function should tie properties to rocket engine specific properties
314 // that are not bound in the base class (FGEngine) code.
316 void FGRocket::bindmodel()
318 string property_name, base_property_name;
319 base_property_name = CreateIndexedPropertyName("propulsion/engine", EngineNumber);
321 property_name = base_property_name + "/total-impulse";
322 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetTotalImpulse);
323 property_name = base_property_name + "/vacuum-thrust_lbs";
324 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetVacThrust);
326 if (ThrustTable) { // Solid rocket motor
327 property_name = base_property_name + "/thrust-variation_pct";
328 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetThrustVariation,
329 &FGRocket::SetThrustVariation);
330 property_name = base_property_name + "/total-isp-variation_pct";
331 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetTotalIspVariation,
332 &FGRocket::SetTotalIspVariation);
333 } else { // Liquid rocket motor
334 property_name = base_property_name + "/oxi-flow-rate-pps";
335 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetOxiFlowRate);
339 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
340 // The bitmasked value choices are as follows:
341 // unset: In this case (the default) JSBSim would only print
342 // out the normally expected messages, essentially echoing
343 // the config files as they are read. If the environment
344 // variable is not set, debug_lvl is set to 1 internally
345 // 0: This requests JSBSim not to output any messages
347 // 1: This value explicity requests the normal JSBSim
349 // 2: This value asks for a message to be printed out when
350 // a class is instantiated
351 // 4: When this value is set, a message is displayed when a
352 // FGModel object executes its Run() method
353 // 8: When this value is set, various runtime state variables
354 // are printed out periodically
355 // 16: When set various parameters are sanity checked and
356 // a message is printed out when they go out of bounds
358 void FGRocket::Debug(int from)
360 if (debug_lvl <= 0) return;
362 if (debug_lvl & 1) { // Standard console startup message output
363 if (from == 0) { // Constructor
364 cout << " Engine Name: " << Name << endl;
365 cout << " Vacuum Isp = " << Isp << endl;
366 cout << " Maximum Throttle = " << MaxThrottle << endl;
367 cout << " Minimum Throttle = " << MinThrottle << endl;
368 cout << " Fuel Flow (max) = " << SLFuelFlowMax << endl;
369 cout << " Oxidizer Flow (max) = " << SLOxiFlowMax << endl;
370 cout << " Mixture ratio = " << SLOxiFlowMax/SLFuelFlowMax << endl;
373 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
374 if (from == 0) cout << "Instantiated: FGRocket" << endl;
375 if (from == 1) cout << "Destroyed: FGRocket" << endl;
377 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
379 if (debug_lvl & 8 ) { // Runtime state variables
381 if (debug_lvl & 16) { // Sanity checking
383 if (debug_lvl & 64) {
384 if (from == 0) { // Constructor
385 cout << IdSrc << endl;
386 cout << IdHdr << endl;