Vivian Meazza:

The calculation of submodel mass from weight has been moved from AIBallistic
to Submodel so that it is calculated only once, rather than on every
iteration as a present. The parameter <contents> has been added, primarily
so that droptanks will have the proper mass. It is the path to an
appropriate property containing a weight in lbs.

Care has to be taken with the use of <contents> because after a reset there
appears to be a delay in submodel instantiation (dt not properly reset???)
and the weight property is not always picked up before it is set to zero in
the key bindings. Slightly hard to explain. It works fine if FGFS has not
been reset though. There is a partial solution which involves the rejigging
of the fuel and gui nasal scripts, but there is still the visible delay in
instantiation to be resolved. I've nearly done the nasal fixes, which will
form part of an update to the Hunter only. I'll probably complete those
later today.

src/AIModel/AIBallistic.cxx

@@ -116,8 +116,8 @@ void FGAIBallistic::setCd(double c) {
    Cd = c;
 }
 
-void FGAIBallistic::setWeight(double w) {
-   weight = w;
+void FGAIBallistic::setMass(double m) {
+   mass = m;
 }
 
 void FGAIBallistic::Run(double dt) {
@@ -129,14 +129,10 @@ void FGAIBallistic::Run(double dt) {
    double speed_east_deg_sec;
    double wind_speed_from_north_deg_sec;
    double wind_speed_from_east_deg_sec;
-   double mass;
-   
-   // the drag calculations below assume sea-level density,
-   // rho = 0.023780  slugs/ft3
-   // calculate mass
-   mass = weight * lbs_to_slugs;
    
    // drag = Cd * 0.5 * rho * speed * speed * drag_area;
+   // rho is adjusted for altitude in void FGAIBase::update,
+   // using Standard Atmosphere (sealevel temperature 15C)
    // acceleration = drag/mass;
    // adjust speed by drag
    speed -= (Cd * 0.5 * rho * speed * speed * drag_area/mass) * dt; 
@@ -189,3 +185,4 @@ double FGAIBallistic::_getTime() const {
 }
 
 // end AIBallistic
+

src/AIModel/AIBallistic.hxx

@@ -1,4 +1,4 @@
-// FGAIBallistic - AIBase derived class creates an AI ballistic object
+// FGAIBallistic.hxx - AIBase derived class creates an AI ballistic object
 //
 // Written by David Culp, started November 2003.
 // - davidculp2@comcast.net
@@ -47,7 +47,7 @@ public:
     void setWind_from_north( double fps );
     void setWind( bool val );
     void setCd( double c );
-    void setWeight( double w );
+    void setMass( double m );
 
     double _getTime() const;
 
@@ -66,9 +66,10 @@ private:
     double wind_from_north; // fps
     bool wind;              // if true, local wind will be applied to object
     double Cd;              // drag coefficient
-    double weight;          // lbs
+    double mass;            // slugs
 
     void Run(double dt);
 };
 
 #endif  // _FG_AIBALLISTIC_HXX
+

src/AIModel/AIBase.hxx

@@ -64,7 +64,7 @@ typedef struct {
    double wind_from_north;    // in feet per second
    double cd;                 // coefficient of drag
    bool wind;                 // if true, model reacts to parent wind
-   double weight;             // in lbs
+   double mass;               // in slugs
 } FGAIModelEntity;
 
 

src/AIModel/AIManager.cxx

@@ -206,7 +206,7 @@ FGAIManager::createBallistic( FGAIModelEntity *entity ) {
         ai_ballistic->setWind(entity->wind);
         ai_ballistic->setRoll(entity->roll);
         ai_ballistic->setCd(entity->cd);
-        ai_ballistic->setWeight(entity->weight);
+        ai_ballistic->setMass(entity->mass);
         ai_ballistic->init();
         ai_ballistic->bind();
         return ai_ballistic;

src/AIModel/AIScenario.cxx

@@ -81,7 +81,8 @@ FGAIScenario::FGAIScenario(string &filename)
      en->wind_from_north = entry_node->getDoubleValue("wind_from_north", 0);
      en->wind            = entry_node->getBoolValue("wind", false);
      en->cd              = entry_node->getDoubleValue  ("cd", 0.029); 
-     en->weight          = entry_node->getDoubleValue  ("weight", 0.030); 
+     en->mass            = entry_node->getDoubleValue  ("mass", 0.007); 
+
 
      en->fp             = NULL;
      if (en->flightplan != ""){
@@ -118,3 +119,4 @@ int FGAIScenario::nEntries( void )
 }
 
 // end scenario.cxx
+

src/Systems/submodel.cxx

@@ -25,6 +25,7 @@ SubmodelSystem::SubmodelSystem ()
   
   out[0] = out[1] = out[2] = 0;
   in[3] = out[3] = 1;
+  string contents_node;
 }
 
 SubmodelSystem::~SubmodelSystem ()
@@ -127,7 +128,7 @@ SubmodelSystem::release (submodel* sm, double dt)
   entity.wind_from_north = IC.wind_from_north;
   entity.wind = sm->wind;
   entity.cd = sm->cd;
-  entity.weight = sm->weight;
+  entity.mass = IC.mass;
   ai->createBallistic( &entity );
  
   if (sm->count > 0) (sm->count)--; 
@@ -138,6 +139,7 @@ SubmodelSystem::release (submodel* sm, double dt)
 void
 SubmodelSystem::load ()
 {
+
     int i;
     SGPropertyNode *path = fgGetNode("/sim/systems/submodels/path");
     SGPropertyNode root;
@@ -182,13 +184,18 @@ SubmodelSystem::load ()
      sm->first_time     = false;
      sm->cd             = entry_node->getDoubleValue("cd", 0.295);
      sm->weight         = entry_node->getDoubleValue("weight", 0.25);
+     sm->contents_node    = fgGetNode(entry_node->getStringValue("contents", "none"), true);
 
      sm->trigger->setBoolValue(false);
      sm->timer = sm->delay;
-
+ 
+     sm->contents = sm->contents_node->getDoubleValue();
+ 
      sm->prop = fgGetNode("/systems/submodels/submodel", i, true);
      sm->prop->tie("count", SGRawValuePointer<int>(&(sm->count)));
 
+//   sm->prop->tie("contents", SGRawValuePointer<double>(&(sm->contents)));
+//   sm->prop->tie("contents path", SGRawValuePointer<const char *>(&(sm->contents_node)));
      submodels.push_back( sm );
    }
 
@@ -201,7 +208,16 @@ void
 SubmodelSystem::transform( submodel* sm) 
 {
 
- // get initial conditions 
+// get initial conditions 
+ 
+// get the weight of the contents (lbs) and convert to mass (slugs)
+  sm->contents = sm->contents_node->getDoubleValue();
+  
+  IC.mass = (sm->weight + sm->contents) * lbs_to_slugs;;
+//  cout << IC.mass << endl;
+    
+// set contents to 0 in the parent
+   sm->contents_node->setDoubleValue(0); 
     
   IC.lat =        _user_lat_node->getDoubleValue();    
   IC.lon =        _user_lon_node->getDoubleValue();   
@@ -222,9 +238,8 @@ SubmodelSystem::transform( submodel* sm)
   in[0] = sm->x_offset;
   in[1] = sm->y_offset;
   in[2] = sm->z_offset; 
+ 
   
-  IC.mass = sm->weight * lbs_to_slugs;
-   
 // pre-process the trig functions
 
     cosRx = cos(-IC.roll * SG_DEGREES_TO_RADIANS);
@@ -331,3 +346,4 @@ SubmodelSystem::updatelat(double lat)
 
 
 
+

src/Systems/submodel.hxx

@@ -29,6 +29,7 @@ public:
  typedef struct {
   SGPropertyNode* trigger;
   SGPropertyNode* prop;
+  SGPropertyNode* contents_node;
   
   string             name;
   string             model;
@@ -50,7 +51,7 @@ public:
   bool               first_time;
   double             cd;
   double             weight;
-//  double             mass;
+  double             contents;
  } submodel; 
 
  typedef struct {
@@ -136,3 +137,4 @@ private:
 #endif // __SYSTEMS_SUBMODEL_HXX
 
 
+