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 extern short debug_lvl;
  48
  49 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  50 CLASS IMPLEMENTATION
  51 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  52
  53 FGRocket::FGRocket(FGFDMExec* exec, FGConfigFile* Eng_cfg) : FGEngine(exec)
  54 {
  55   string token;
  56
  57   Name = Eng_cfg->GetValue("NAME");
  58   Eng_cfg->GetNextConfigLine();
  59
  60   while (Eng_cfg->GetValue() != "/FG_ROCKET") {
  61     *Eng_cfg >> token;
  62     if      (token == "SHR")           *Eng_cfg >> SHR;
  63     else if (token == "MAX_PC")        *Eng_cfg >> maxPC;
  64     else if (token == "PROP_EFF")      *Eng_cfg >> propEff;
  65     else if (token == "MAXTHROTTLE")   *Eng_cfg >> MaxThrottle;
  66     else if (token == "MINTHROTTLE")   *Eng_cfg >> MinThrottle;
  67     else if (token == "SLFUELFLOWMAX") *Eng_cfg >> SLFuelFlowMax;
  68     else if (token == "SLOXIFLOWMAX")  *Eng_cfg >> SLOxiFlowMax;
  69     else if (token == "VARIANCE")      *Eng_cfg >> Variance;
  70     else cerr << "Unhandled token in Engine config file: " << token << endl;
  71   }
  72
  73   if (debug_lvl > 0) {
  74     cout << "      Engine Name: " << Name << endl;
  75     cout << "      Specific Heat Ratio = " << SHR << endl;
  76     cout << "      Maximum Chamber Pressure = " << maxPC << endl;
  77     cout << "      Propulsive Efficiency = " << propEff << endl;
  78     cout << "      MaxThrottle = " << MaxThrottle << endl;
  79     cout << "      MinThrottle = " << MinThrottle << endl;
  80     cout << "      FuelFlowMax = " << SLFuelFlowMax << endl;
  81     cout << "      OxiFlowMax = " << SLOxiFlowMax << endl;
  82     cout << "      Variance = " << Variance << endl;
  83   }
  84
  85   EngineNumber = 0;
  86   Type = etRocket;
  87
  88   PC = 0.0;
  89   kFactor = (2.0*SHR*SHR/(SHR-1.0))*pow(2.0/(SHR+1), (SHR+1)/(SHR-1));
  90
  91   if (debug_lvl & 2) cout << "Instantiated: FGRocket" << endl;
  92 }
  93
  94 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  95
  96 FGRocket::~FGRocket()
  97 {
  98   if (debug_lvl & 2) cout << "Destroyed:    FGRocket" << endl;
  99 }
 100
 101 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 102
 103 float FGRocket::Calculate(float pe)
 104 {
 105   float Cf;
 106
 107   ConsumeFuel();
 108
 109   Throttle = FCS->GetThrottlePos(EngineNumber);
 110
 111   if (Throttle < MinThrottle || Starved) {
 112     PctPower = Thrust = 0.0; // desired thrust
 113     Flameout = true;
 114     PC = 0.0;
 115   } else {
 116     PctPower = Throttle / MaxThrottle;
 117     PC = maxPC*PctPower * (1.0 + Variance * ((float)rand()/(float)RAND_MAX - 0.5));
 118     Cf = sqrt(kFactor*(1 - pow(pe/(PC), (SHR-1)/SHR)));
 119     Flameout = false;
 120   }
 121
 122   return Cf*maxPC*PctPower*propEff;
 123 }
 124
 125 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 126
 127 void FGRocket::Debug(void)
 128 {
 129     //TODO: Add your source code here
 130 }
 131