src/FDM/JSBSim/FGRocket.cpp

   1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   2
   3  Module:       FGRocket.cpp
   4  Author:       Jon S. Berndt
   5  Date started: 09/12/2000
   6  Purpose:      This module models a rocket engine
   7
   8  ------------- Copyright (C) 2000  Jon S. Berndt (jsb@hal-pc.org) --------------
   9
  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
  13  version.
  14
  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
  18  details.
  19
  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.
  23
  24  Further information about the GNU General Public License can also be found on
  25  the world wide web at http://www.gnu.org.
  26
  27 FUNCTIONAL DESCRIPTION
  28 --------------------------------------------------------------------------------
  29
  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
  32
  33 HISTORY
  34 --------------------------------------------------------------------------------
  35 09/12/2000  JSB  Created
  36
  37 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  38 INCLUDES
  39 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  40
  41 #include "FGDefs.h"
  42 #include "FGRocket.h"
  43
  44 static const char *IdSrc = "$Id$";
  45 static const char *IdHdr = ID_ROCKET;
  46
  47 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  48 CLASS IMPLEMENTATION
  49 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  50
  51 FGRocket::FGRocket(FGFDMExec* exec, FGConfigFile* Eng_cfg) : FGEngine(exec)
  52 {
  53   string token;
  54
  55   Name = Eng_cfg->GetValue("NAME");
  56   Eng_cfg->GetNextConfigLine();
  57
  58   while (Eng_cfg->GetValue() != "/FG_ROCKET") {
  59     *Eng_cfg >> token;
  60     if      (token == "SHR")           *Eng_cfg >> SHR;
  61     else if (token == "MAX_PC")        *Eng_cfg >> maxPC;
  62     else if (token == "PROP_EFF")      *Eng_cfg >> propEff;
  63     else if (token == "MAXTHROTTLE")   *Eng_cfg >> MaxThrottle;
  64     else if (token == "MINTHROTTLE")   *Eng_cfg >> MinThrottle;
  65     else if (token == "SLFUELFLOWMAX") *Eng_cfg >> SLFuelFlowMax;
  66     else if (token == "SLOXIFLOWMAX")  *Eng_cfg >> SLOxiFlowMax;
  67     else if (token == "VARIANCE")      *Eng_cfg >> Variance;
  68     else cerr << "Unhandled token in Engine config file: " << token << endl;
  69   }
  70
  71   if (debug_lvl > 0) {
  72     cout << "      Engine Name: " << Name << endl;
  73     cout << "      Specific Heat Ratio = " << SHR << endl;
  74     cout << "      Maximum Chamber Pressure = " << maxPC << endl;
  75     cout << "      Propulsive Efficiency = " << propEff << endl;
  76     cout << "      MaxThrottle = " << MaxThrottle << endl;
  77     cout << "      MinThrottle = " << MinThrottle << endl;
  78     cout << "      FuelFlowMax = " << SLFuelFlowMax << endl;
  79     cout << "      OxiFlowMax = " << SLOxiFlowMax << endl;
  80     cout << "      Variance = " << Variance << endl;
  81   }
  82
  83   EngineNumber = 0;
  84   Type = etRocket;
  85
  86   PC = 0.0;
  87   kFactor = (2.0*SHR*SHR/(SHR-1.0))*pow(2.0/(SHR+1), (SHR+1)/(SHR-1));
  88
  89   if (debug_lvl & 2) cout << "Instantiated: FGRocket" << endl;
  90 }
  91
  92 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  93
  94 FGRocket::~FGRocket()
  95 {
  96   if (debug_lvl & 2) cout << "Destroyed:    FGRocket" << endl;
  97 }
  98
  99 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 100
 101 float FGRocket::Calculate(float pe)
 102 {
 103   float Cf;
 104
 105   ConsumeFuel();
 106
 107   Throttle = FCS->GetThrottlePos(EngineNumber);
 108
 109   if (Throttle < MinThrottle || Starved) {
 110     PctPower = Thrust = 0.0; // desired thrust
 111     Flameout = true;
 112     PC = 0.0;
 113   } else {
 114     PctPower = Throttle / MaxThrottle;
 115     PC = maxPC*PctPower * (1.0 + Variance * ((float)rand()/(float)RAND_MAX - 0.5));
 116     Cf = sqrt(kFactor*(1 - pow(pe/(PC), (SHR-1)/SHR)));
 117     Flameout = false;
 118   }
 119
 120   return Cf*maxPC*PctPower*propEff;
 121 }
 122
 123 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 124
 125 void FGRocket::Debug(void)
 126 {
 127     //TODO: Add your source code here
 128 }
 129