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 "FGRocket.h"
  42
  43 static const char *IdSrc = "$Id$";
  44 static const char *IdHdr = ID_ROCKET;
  45
  46 extern short debug_lvl;
  47
  48 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  49 CLASS IMPLEMENTATION
  50 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  51
  52 FGRocket::FGRocket(FGFDMExec* exec, FGConfigFile* Eng_cfg) : FGEngine(exec)
  53 {
  54   string token;
  55
  56   Name = Eng_cfg->GetValue("NAME");
  57   Eng_cfg->GetNextConfigLine();
  58
  59   while (Eng_cfg->GetValue() != "/FG_ROCKET") {
  60     *Eng_cfg >> token;
  61     if      (token == "SHR")           *Eng_cfg >> SHR;
  62     else if (token == "MAX_PC")        *Eng_cfg >> maxPC;
  63     else if (token == "PROP_EFF")      *Eng_cfg >> propEff;
  64     else if (token == "MAXTHROTTLE")   *Eng_cfg >> MaxThrottle;
  65     else if (token == "MINTHROTTLE")   *Eng_cfg >> MinThrottle;
  66     else if (token == "SLFUELFLOWMAX") *Eng_cfg >> SLFuelFlowMax;
  67     else if (token == "SLOXIFLOWMAX")  *Eng_cfg >> SLOxiFlowMax;
  68     else if (token == "VARIANCE")      *Eng_cfg >> Variance;
  69     else cerr << "Unhandled token in Engine config file: " << token << endl;
  70   }
  71
  72   if (debug_lvl > 0) {
  73     cout << "      Engine Name: " << Name << endl;
  74     cout << "      Specific Heat Ratio = " << SHR << endl;
  75     cout << "      Maximum Chamber Pressure = " << maxPC << endl;
  76     cout << "      Propulsive Efficiency = " << propEff << endl;
  77     cout << "      MaxThrottle = " << MaxThrottle << endl;
  78     cout << "      MinThrottle = " << MinThrottle << endl;
  79     cout << "      FuelFlowMax = " << SLFuelFlowMax << endl;
  80     cout << "      OxiFlowMax = " << SLOxiFlowMax << endl;
  81     cout << "      Variance = " << Variance << endl;
  82   }
  83
  84   EngineNumber = 0;
  85   Type = etRocket;
  86
  87   PC = 0.0;
  88   kFactor = (2.0*SHR*SHR/(SHR-1.0))*pow(2.0/(SHR+1), (SHR+1)/(SHR-1));
  89
  90   if (debug_lvl & 2) cout << "Instantiated: FGRocket" << endl;
  91 }
  92
  93 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  94
  95 FGRocket::~FGRocket()
  96 {
  97   if (debug_lvl & 2) cout << "Destroyed:    FGRocket" << endl;
  98 }
  99
 100 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 101
 102 float FGRocket::Calculate(float pe)
 103 {
 104   float Cf;
 105
 106   ConsumeFuel();
 107
 108   Throttle = FCS->GetThrottlePos(EngineNumber);
 109
 110   if (Throttle < MinThrottle || Starved) {
 111     PctPower = Thrust = 0.0; // desired thrust
 112     Flameout = true;
 113     PC = 0.0;
 114   } else {
 115     PctPower = Throttle / MaxThrottle;
 116     PC = maxPC*PctPower * (1.0 + Variance * ((float)rand()/(float)RAND_MAX - 0.5));
 117     Cf = sqrt(kFactor*(1 - pow(pe/(PC), (SHR-1)/SHR)));
 118     Flameout = false;
 119   }
 120
 121   return Cf*maxPC*PctPower*propEff;
 122 }
 123
 124 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 125
 126 void FGRocket::Debug(void)
 127 {
 128     //TODO: Add your source code here
 129 }
 130