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 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 General Public License for more
20 You should have received a copy of the GNU 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 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 if (el->FindElement("shr"))
58 SHR = el->FindElementValueAsNumber("shr");
59 if (el->FindElement("max_pc"))
60 maxPC = el->FindElementValueAsNumberConvertTo("max_pc", "PSF");
61 if (el->FindElement("prop_eff"))
62 propEff = el->FindElementValueAsNumber("prop_eff");
63 if (el->FindElement("maxthrottle"))
64 MaxThrottle = el->FindElementValueAsNumber("maxthrottle");
65 if (el->FindElement("minthrottle"))
66 MinThrottle = el->FindElementValueAsNumber("minthrottle");
67 if (el->FindElement("slfuelflowmax"))
68 SLFuelFlowMax = el->FindElementValueAsNumberConvertTo("slfuelflowmax", "LBS/SEC");
69 if (el->FindElement("sloxiflowmax"))
70 SLOxiFlowMax = el->FindElementValueAsNumberConvertTo("sloxiflowmax", "LBS/SEC");
71 if (el->FindElement("variance"))
72 Variance = el->FindElementValueAsNumber("variance");
80 kFactor = (2.0*SHR*SHR/(SHR-1.0))*pow(2.0/(SHR+1), (SHR+1)/(SHR-1));
83 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
85 FGRocket::~FGRocket(void)
90 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
92 double FGRocket::Calculate(void)
96 if (!Flameout && !Starved) ConsumeFuel();
98 Throttle = FCS->GetThrottlePos(EngineNumber);
100 if (Throttle < MinThrottle || Starved) {
101 PctPower = Thrust = 0.0; // desired thrust
105 PctPower = Throttle / MaxThrottle;
106 //todo: remove Variance?
107 PC = maxPC*PctPower * (1.0 + Variance * ((double)rand()/(double)RAND_MAX - 0.5));
108 // The Cf (below) is CF from Eqn. 3-30, "Rocket Propulsion Elements", Fifth Edition,
109 // George P. Sutton. Note that the thruster function GetPowerRequired() might
110 // be better called GetResistance() or something; this function returns the
111 // nozzle exit pressure.
112 Cf = sqrt(kFactor*(1 - pow(Thruster->GetPowerRequired()/(PC), (SHR-1)/SHR)));
116 return Thruster->Calculate(Cf*maxPC*PctPower*propEff);
119 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
121 string FGRocket::GetEngineLabels(string delimeter)
123 std::ostringstream buf;
125 buf << Name << "_ChamberPress[" << EngineNumber << "]" << delimeter
126 << Thruster->GetThrusterLabels(EngineNumber, delimeter);
131 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
133 string FGRocket::GetEngineValues(string delimeter)
135 std::ostringstream buf;
137 buf << PC << delimeter << Thruster->GetThrusterValues(EngineNumber, delimeter);
142 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
143 // The bitmasked value choices are as follows:
144 // unset: In this case (the default) JSBSim would only print
145 // out the normally expected messages, essentially echoing
146 // the config files as they are read. If the environment
147 // variable is not set, debug_lvl is set to 1 internally
148 // 0: This requests JSBSim not to output any messages
150 // 1: This value explicity requests the normal JSBSim
152 // 2: This value asks for a message to be printed out when
153 // a class is instantiated
154 // 4: When this value is set, a message is displayed when a
155 // FGModel object executes its Run() method
156 // 8: When this value is set, various runtime state variables
157 // are printed out periodically
158 // 16: When set various parameters are sanity checked and
159 // a message is printed out when they go out of bounds
161 void FGRocket::Debug(int from)
163 if (debug_lvl <= 0) return;
165 if (debug_lvl & 1) { // Standard console startup message output
166 if (from == 0) { // Constructor
167 cout << " Engine Name: " << Name << endl;
168 cout << " Specific Heat Ratio = " << SHR << endl;
169 cout << " Maximum Chamber Pressure = " << maxPC << endl;
170 cout << " Propulsive Efficiency = " << propEff << endl;
171 cout << " MaxThrottle = " << MaxThrottle << endl;
172 cout << " MinThrottle = " << MinThrottle << endl;
173 cout << " FuelFlowMax = " << SLFuelFlowMax << endl;
174 cout << " OxiFlowMax = " << SLOxiFlowMax << endl;
175 cout << " Variance = " << Variance << endl;
178 if (debug_lvl & 2 ) { // Instantiation/Destruction notification
179 if (from == 0) cout << "Instantiated: FGRocket" << endl;
180 if (from == 1) cout << "Destroyed: FGRocket" << endl;
182 if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
184 if (debug_lvl & 8 ) { // Runtime state variables
186 if (debug_lvl & 16) { // Sanity checking
188 if (debug_lvl & 64) {
189 if (from == 0) { // Constructor
190 cout << IdSrc << endl;
191 cout << IdHdr << endl;