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 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
43 static const char *IdSrc = "$Id$";
44 static const char *IdHdr = ID_ROCKET;
46 extern short debug_lvl;
48 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
50 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
52 FGRocket::FGRocket(FGFDMExec* exec, FGConfigFile* Eng_cfg) : FGEngine(exec)
56 Name = Eng_cfg->GetValue("NAME");
57 cout << " Engine Name: " << Name << endl;
58 Eng_cfg->GetNextConfigLine();
59 while (Eng_cfg->GetValue() != "/FG_ROCKET") {
63 cout << " Specific Heat Ratio = " << SHR << endl;
64 } else if (token == "MAX_PC") {
66 cout << " Maximum Chamber Pressure = " << maxPC << endl;
67 } else if (token == "PROP_EFF") {
69 cout << " Propulsive Efficiency = " << propEff << endl;
70 } else if (token == "MAXTHROTTLE") {
71 *Eng_cfg >> MaxThrottle;
72 cout << " MaxThrottle = " << MaxThrottle << endl;
73 } else if (token == "MINTHROTTLE") {
74 *Eng_cfg >> MinThrottle;
75 cout << " MinThrottle = " << MinThrottle << endl;
76 } else if (token == "SLFUELFLOWMAX") {
77 *Eng_cfg >> SLFuelFlowMax;
78 cout << " FuelFlowMax = " << SLFuelFlowMax << endl;
79 } else if (token == "SLOXIFLOWMAX") {
80 *Eng_cfg >> SLOxiFlowMax;
81 cout << " OxiFlowMax = " << SLOxiFlowMax << endl;
82 } else if (token == "VARIANCE") {
84 cout << " Variance = " << Variance << endl;
86 cout << "Unhandled token in Engine config file: " << token << endl;
92 kFactor = (2.0*SHR*SHR/(SHR-1.0))*pow(2.0/(SHR+1), (SHR+1)/(SHR-1));
94 if (debug_lvl & 2) cout << "Instantiated: FGRocket" << endl;
97 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
101 if (debug_lvl & 2) cout << "Destroyed: FGRocket" << endl;
104 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
106 float FGRocket::Calculate(float pe)
114 Throttle = FCS->GetThrottlePos(EngineNumber);
115 lastThrust = Thrust; // last actual thrust
117 if (Throttle < MinThrottle || Starved) {
118 PctPower = Thrust = 0.0; // desired thrust
121 PctPower = Throttle / MaxThrottle;
122 chamberPress = maxPC*PctPower * (1.0 + Variance * ((float)rand()/(float)RAND_MAX - 0.5));
123 Cf = sqrt(kFactor*(1 - pow(pe/(chamberPress), (SHR-1)/SHR)));
127 if (State->Getdt() > 0.0) { // actual thrust - if not in freeze
128 Thrust -= 0.8*(Thrust - lastThrust);
131 return Cf*maxPC*PctPower;
134 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
136 void FGRocket::Debug(void)
138 //TODO: Add your source code here