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;
79 if (el->FindElement("isp"))
80 Isp = el->FindElementValueAsNumber("isp");
81 if (el->FindElement("builduptime"))
82 BuildupTime = el->FindElementValueAsNumber("builduptime");
83 if (el->FindElement("maxthrottle"))
84 MaxThrottle = el->FindElementValueAsNumber("maxthrottle");
85 if (el->FindElement("minthrottle"))
86 MinThrottle = el->FindElementValueAsNumber("minthrottle");
87 if (el->FindElement("slfuelflowmax"))
88 SLFuelFlowMax = el->FindElementValueAsNumberConvertTo("slfuelflowmax", "LBS/SEC");
89 if (el->FindElement("sloxiflowmax"))
90 SLOxiFlowMax = el->FindElementValueAsNumberConvertTo("sloxiflowmax", "LBS/SEC");
92 thrust_table_element = el->FindElement("thrust_table");
93 if (thrust_table_element) {
94 ThrustTable = new FGTable(PropertyManager, thrust_table_element);
106 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
108 FGRocket::~FGRocket(void)
114 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
116 double FGRocket::Calculate(void)
118 double dT = State->Getdt()*Propulsion->GetRate();
121 if (!Flameout && !Starved) ConsumeFuel();
123 PropellantFlowRate = (FuelExpended + OxidizerExpended)/dT;
124 Throttle = FCS->GetThrottlePos(EngineNumber);
126 // If there is a thrust table, it is a function of propellant burned. The
127 // engine is started when the throttle is advanced to 1.0. After that, it
128 // burns without regard to throttle setting.
130 if (ThrustTable != 0L) { // Thrust table given -> Solid fuel used
132 if ((Throttle == 1 || BurnTime > 0.0 ) && !Starved) {
133 double TotalEngineFuelBurned=0.0;
134 for (int i=0; i<(int)SourceTanks.size(); i++) {
135 FGTank* tank = Propulsion->GetTank(i);
136 if (SourceTanks[i] == 1) {
137 TotalEngineFuelBurned += tank->GetCapacity() - tank->GetContents();
141 VacThrust = ThrustTable->GetValue(TotalEngineFuelBurned);
142 if (BurnTime <= BuildupTime && BuildupTime > 0.0) {
143 VacThrust *= sin((BurnTime/BuildupTime)*M_PI/2.0);
144 // VacThrust *= (1-cos((BurnTime/BuildupTime)*M_PI))/2.0; // 1 - cos approach
146 BurnTime += State->Getdt(); // Increment burn time
151 } else { // liquid fueled rocket assumed
153 if (Throttle < MinThrottle || Starved) { // Combustion not supported
155 PctPower = 0.0; // desired thrust
159 } else { // Calculate thrust
161 // This is nonsensical. Max throttle should be assumed to be 1.0. One might
162 // conceivably have a throttle setting > 1.0 for some rocket engines. But, 1.0
163 // should always be the default.
164 // PctPower = Throttle / MaxThrottle; // Min and MaxThrottle range from 0.0 to 1.0, normally.
168 VacThrust = Isp * PropellantFlowRate;
172 } // End thrust calculations
174 thrust = Thruster->Calculate(VacThrust);
180 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
181 // This overrides the base class ConsumeFuel() function, for special rocket
182 // engine processing.
184 void FGRocket::ConsumeFuel(void)
188 bool haveOxTanks = false;
189 double Fshortage=0, Oshortage=0, TanksWithFuel=0, TanksWithOxidizer=0;
191 if (FuelFreeze) return;
192 if (TrimMode) return;
194 // Count how many assigned tanks have fuel for this engine at this time.
195 // If there is/are fuel tanks but no oxidizer tanks, this indicates
196 // a solid rocket is being modeled.
198 for (i=0; i<SourceTanks.size(); i++) {
199 Tank = Propulsion->GetTank(SourceTanks[i]);
200 switch(Tank->GetType()) {
202 if (Tank->GetContents() > 0.0 && Tank->GetSelected()) ++TanksWithFuel;
204 case FGTank::ttOXIDIZER:
206 if (Tank->GetContents() > 0.0 && Tank->GetSelected()) ++TanksWithOxidizer;
211 // If this engine has burned out, it is starved.
213 if (TanksWithFuel==0 || (haveOxTanks && TanksWithOxidizer==0)) {
218 // Expend fuel from the engine's tanks if the tank is selected as a source
221 double fuelNeedPerTank = CalcFuelNeed()/TanksWithFuel;
222 double oxiNeedPerTank = CalcOxidizerNeed()/TanksWithOxidizer;
224 for (i=0; i<SourceTanks.size(); i++) {
225 Tank = Propulsion->GetTank(SourceTanks[i]);
226 if ( ! Tank->GetSelected()) continue; // If this tank is not selected as a source, skip it.
227 switch(Tank->GetType()) {
229 Fshortage += Tank->Drain(2.0*fuelNeedPerTank - previousFuelNeedPerTank);
230 previousFuelNeedPerTank = fuelNeedPerTank;
232 case FGTank::ttOXIDIZER:
233 Oshortage += Tank->Drain(2.0*oxiNeedPerTank - previousOxiNeedPerTank);
234 previousOxiNeedPerTank = oxiNeedPerTank;
239 if (Fshortage < 0.00 || (haveOxTanks && Oshortage < 0.00)) Starved = true;
240 else Starved = false;
243 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
245 double FGRocket::CalcFuelNeed(void)
247 double dT = State->Getdt()*Propulsion->GetRate();
249 if (ThrustTable != 0L) { // Thrust table given - infers solid fuel
250 FuelFlowRate = VacThrust/Isp; // This calculates wdot (weight flow rate in lbs/sec)
252 FuelFlowRate = SLFuelFlowMax*PctPower;
255 FuelExpended = FuelFlowRate*dT; // For this time step ...
259 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
261 double FGRocket::CalcOxidizerNeed(void)
263 double dT = State->Getdt()*Propulsion->GetRate();
264 OxidizerFlowRate = SLOxiFlowMax*PctPower;
265 OxidizerExpended = OxidizerFlowRate*dT;
266 return OxidizerExpended;
269 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
271 string FGRocket::GetEngineLabels(const string& delimiter)
273 std::ostringstream buf;
275 buf << Name << " Total Impulse (engine " << EngineNumber << " in psf)" << delimiter
276 << Thruster->GetThrusterLabels(EngineNumber, delimiter);
281 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
283 string FGRocket::GetEngineValues(const string& delimiter)
285 std::ostringstream buf;
287 buf << It << delimiter << Thruster->GetThrusterValues(EngineNumber, delimiter);
292 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
293 // This funciton should tie properties to rocket engine specific properties
294 // that are not bound in the base class (FGEngine) code.
296 void FGRocket::bindmodel()
298 string property_name, base_property_name;
299 base_property_name = CreateIndexedPropertyName("propulsion/engine", EngineNumber);
301 property_name = base_property_name + "/total-impulse";
302 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetTotalImpulse);
303 property_name = base_property_name + "/oxi-flow-rate-pps";
304 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetOxiFlowRate);
305 property_name = base_property_name + "/vacuum-thrust_lbs";
306 PropertyManager->Tie( property_name.c_str(), this, &FGRocket::GetVacThrust);
309 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
310 // The bitmasked value choices are as follows:
311 // unset: In this case (the default) JSBSim would only print
312 // out the normally expected messages, essentially echoing
313 // the config files as they are read. If the environment
314 // variable is not set, debug_lvl is set to 1 internally
315 // 0: This requests JSBSim not to output any messages
317 // 1: This value explicity requests the normal JSBSim
319 // 2: This value asks for a message to be printed out when
320 // a class is instantiated
321 // 4: When this value is set, a message is displayed when a
322 // FGModel object executes its Run() method
323 // 8: When this value is set, various runtime state variables
324 // are printed out periodically
325 // 16: When set various parameters are sanity checked and
326 // a message is printed out when they go out of bounds
328 void FGRocket::Debug(int from)
330 if (debug_lvl <= 0) return;
332 if (debug_lvl & 1) { // Standard console startup message output
333 if (from == 0) { // Constructor
334 cout << " Engine Name: " << Name << endl;
335 cout << " Vacuum Isp = " << Isp << endl;
336 cout << " Maximum Throttle = " << MaxThrottle << endl;
337 cout << " Minimum Throttle = " << MinThrottle << endl;
338 cout << " Fuel Flow (max) = " << SLFuelFlowMax << endl;
339 cout << " Oxidizer Flow (max) = " << SLOxiFlowMax << endl;
340 cout << " Mixture ratio = " << SLOxiFlowMax/SLFuelFlowMax << endl;
343 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
344 if (from == 0) cout << "Instantiated: FGRocket" << endl;
345 if (from == 1) cout << "Destroyed: FGRocket" << endl;
347 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
349 if (debug_lvl & 8 ) { // Runtime state variables
351 if (debug_lvl & 16) { // Sanity checking
353 if (debug_lvl & 64) {
354 if (from == 0) { // Constructor
355 cout << IdSrc << endl;
356 cout << IdHdr << endl;