- life_timer += dt;
- if (life_timer > life) setDie(true);
-
- double speed_north_deg_sec;
- 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;
- // acceleration = drag/mass;
- // adjust speed by drag
- speed -= (Cd * 0.5 * rho * speed * speed * drag_area/mass) * dt;
-
- // don't let speed become negative
- if ( speed < 0.0 ) speed = 0.0;
-
- // calculate vertical and horizontal speed components
- vs = sin( pitch * SG_DEGREES_TO_RADIANS ) * speed;
- hs = cos( pitch * SG_DEGREES_TO_RADIANS ) * speed;
-
- // convert horizontal speed (fps) to degrees per second
- speed_north_deg_sec = cos(hdg / SG_RADIANS_TO_DEGREES) * hs / ft_per_deg_lat;
- speed_east_deg_sec = sin(hdg / SG_RADIANS_TO_DEGREES) * hs / ft_per_deg_lon;
-
- // if wind not required, set to zero
- if (!wind){
- wind_from_north = 0;
- wind_from_east = 0;
- }
-
- // convert wind speed (fps) to degrees per second
- wind_speed_from_north_deg_sec = wind_from_north / ft_per_deg_lat;
- wind_speed_from_east_deg_sec = wind_from_east / ft_per_deg_lon;
-
- // set new position
- pos.setlat( pos.lat() + (speed_north_deg_sec - wind_speed_from_north_deg_sec) * dt );
- pos.setlon( pos.lon() + (speed_east_deg_sec - wind_speed_from_east_deg_sec) * dt );
-
- // adjust vertical speed for acceleration of gravity and buoyancy
- vs -= (gravity - buoyancy) * dt;
-
- // adjust altitude (feet)
- altitude += vs * dt;
- pos.setelev(altitude * SG_FEET_TO_METER);
-
- // recalculate pitch (velocity vector) if aerostabilized
- if (aero_stabilized) pitch = atan2( vs, hs ) * SG_RADIANS_TO_DEGREES;
-
- // recalculate total speed
- speed = sqrt( vs * vs + hs * hs);
-
- // set destruction flag if altitude less than sea level -1000
- if (altitude < -1000.0) setDie(true);
+ _life_timer += dt;
+
+ // if life = -1 the object does not die
+ if (_life_timer > life && life != -1)
+ setDie(true);
+
+ //set the contents in the appropriate tank or other property in the parent to zero
+ setContents(0);
+
+ //randomise Cd by +- 5%
+ if (_random)
+ _Cd = _Cd * 0.95 + (0.05 * sg_random());
+
+ // Adjust Cd by Mach number. The equations are based on curves
+ // for a conventional shell/bullet (no boat-tail).
+ double Cdm;
+
+ if (Mach < 0.7)
+ Cdm = 0.0125 * Mach + _Cd;
+ else if (Mach < 1.2 )
+ Cdm = 0.3742 * pow(Mach, 2) - 0.252 * Mach + 0.0021 + _Cd;
+ else
+ Cdm = 0.2965 * pow(Mach, -1.1506) + _Cd;
+
+ //cout << "Mach " << Mach << " Cdm " << Cdm << "// ballistic speed kts "<< speed << endl;
+
+ // 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 -= (Cdm * 0.5 * rho * speed * speed * _drag_area/_mass) * dt;
+
+ // don't let speed become negative
+ if ( speed < 0.0 )
+ speed = 0.0;
+
+ double speed_fps = speed * SG_KT_TO_FPS;
+ //double hs;
+
+ // calculate vertical and horizontal speed components
+ if (speed == 0.0) {
+ hs = vs = 0.0;
+ } else {
+ vs = sin( _elevation * SG_DEGREES_TO_RADIANS ) * speed_fps;
+ hs = cos( _elevation * SG_DEGREES_TO_RADIANS ) * speed_fps;
+ }
+
+ //resolve horizontal speed into north and east components:
+ double speed_north_fps = cos(_azimuth / SG_RADIANS_TO_DEGREES) * hs;
+ double speed_east_fps = sin(_azimuth / SG_RADIANS_TO_DEGREES) * hs;
+
+ // convert horizontal speed (fps) to degrees per second
+ double speed_north_deg_sec = speed_north_fps / ft_per_deg_lat;
+ double speed_east_deg_sec = speed_east_fps / ft_per_deg_lon;
+
+ // if wind not required, set to zero
+ if (!_wind) {
+ _wind_from_north = 0;
+ _wind_from_east = 0;
+ } else {
+ _wind_from_north = manager->get_wind_from_north();
+ _wind_from_east = manager->get_wind_from_east();
+ }
+
+ //calculate velocity due to external force
+ double force_speed_north_deg_sec = 0;
+ double force_speed_east_deg_sec = 0;
+// double vs_force_fps = 0;
+ double hs_force_fps = 0;
+ double v_force_acc_fpss = 0;
+ double force_speed_north_fps = 0;
+ double force_speed_east_fps = 0;
+ double h_force_lbs = 0;
+ double normal_force_lbs = 0;
+ double normal_force_fpss = 0;
+ double static_friction_force_lbs = 0;
+ double dynamic_friction_force_lbs = 0;
+ double friction_force_speed_north_fps = 0;
+ double friction_force_speed_east_fps = 0;
+ double friction_force_speed_north_deg_sec = 0;
+ double friction_force_speed_east_deg_sec = 0;
+ double force_elevation_deg = 0;
+
+ if (_external_force) {
+ SGPropertyNode *n = fgGetNode(_force_path.c_str(), true);
+ double force_lbs = n->getChild("force-lb", 0, true)->getDoubleValue();
+ force_elevation_deg = n->getChild("force-elevation-deg", 0, true)->getDoubleValue();
+ double force_azimuth_deg = n->getChild("force-azimuth-deg", 0, true)->getDoubleValue();
+
+ //resolve force into vertical and horizontal components:
+ double v_force_lbs = force_lbs * sin( force_elevation_deg * SG_DEGREES_TO_RADIANS );
+ h_force_lbs = force_lbs * cos( force_elevation_deg * SG_DEGREES_TO_RADIANS );
+
+ //ground interaction
+
+ if (getHtAGL()){
+ double deadzone = 0.1;
+
+ if (_ht_agl_ft <= (0 + _ground_offset + deadzone) && _solid){
+ normal_force_lbs = (_mass * slugs_to_lbs) - v_force_lbs;
+
+ if ( normal_force_lbs < 0 )
+ normal_force_lbs = 0;
+
+ pos.setElevationFt(0 + _ground_offset);
+ if (vs < 0)
+ vs = -vs * 0.5;
+
+ // calculate friction
+ // we assume a static Coefficient of Friction (mu) of 0.62 (wood on concrete)
+ double mu = 0.62;
+
+ static_friction_force_lbs = mu * normal_force_lbs * _frictionFactor;
+
+ //adjust horizontal force. We assume that a speed of <= 5 fps is static
+ if (h_force_lbs <= static_friction_force_lbs && hs <= 5){
+ h_force_lbs = hs = 0;
+ speed_north_fps = speed_east_fps = 0;
+ } else
+ dynamic_friction_force_lbs = (static_friction_force_lbs * 0.95);
+
+ //ignore wind when on the ground for now
+ //TODO fix this
+ _wind_from_north = 0;
+ _wind_from_east = 0;
+
+ }
+
+ }
+
+ //acceleration = (force(lbsf)/mass(slugs))
+ v_force_acc_fpss = v_force_lbs/_mass;
+ normal_force_fpss = normal_force_lbs/_mass;
+ double h_force_acc_fpss = h_force_lbs/_mass;
+ double dynamic_friction_acc_fpss = dynamic_friction_force_lbs/_mass;
+
+ // velocity = acceleration * dt
+ hs_force_fps = h_force_acc_fpss * dt;
+ double friction_force_fps = dynamic_friction_acc_fpss * dt;
+
+ //resolve horizontal speeds into north and east components:
+ force_speed_north_fps = cos(force_azimuth_deg * SG_DEGREES_TO_RADIANS) * hs_force_fps;
+ force_speed_east_fps = sin(force_azimuth_deg * SG_DEGREES_TO_RADIANS) * hs_force_fps;
+
+ friction_force_speed_north_fps = cos(getRecip(hdg) * SG_DEGREES_TO_RADIANS) * friction_force_fps;
+ friction_force_speed_east_fps = sin(getRecip(hdg) * SG_DEGREES_TO_RADIANS) * friction_force_fps;
+
+ // convert horizontal speed (fps) to degrees per second
+ force_speed_north_deg_sec = force_speed_north_fps / ft_per_deg_lat;
+ force_speed_east_deg_sec = force_speed_east_fps / ft_per_deg_lon;
+
+ friction_force_speed_north_deg_sec = friction_force_speed_north_fps / ft_per_deg_lat;
+ friction_force_speed_east_deg_sec = friction_force_speed_east_fps / ft_per_deg_lon;
+ }
+
+ // convert wind speed (fps) to degrees lat/lon per second
+ double wind_speed_from_north_deg_sec = _wind_from_north / ft_per_deg_lat;
+ double wind_speed_from_east_deg_sec = _wind_from_east / ft_per_deg_lon;
+
+ //recombine the horizontal velocity components
+ hs = sqrt(((speed_north_fps + force_speed_north_fps + friction_force_speed_north_fps)
+ * (speed_north_fps + force_speed_north_fps + friction_force_speed_north_fps))
+ + ((speed_east_fps + force_speed_east_fps + friction_force_speed_east_fps)
+ * (speed_east_fps + force_speed_east_fps + friction_force_speed_east_fps)));
+
+ if (hs <= 0.00001)
+ hs = 0;
+
+ // adjust vertical speed for acceleration of gravity, buoyancy, and vertical force
+ vs -= (_gravity - _buoyancy - v_force_acc_fpss - normal_force_fpss) * dt;
+
+ if (vs <= 0.00001 && vs >= -0.00001)
+ vs = 0;
+
+ // set new position
+ if(_slave_load_to_ac) {
+ setHitchPos();
+ pos.setLatitudeDeg(hitchpos.getLatitudeDeg());
+ pos.setLongitudeDeg(hitchpos.getLongitudeDeg());
+ pos.setElevationFt(hitchpos.getElevationFt());
+
+ if (getHtAGL()){
+ double deadzone = 0.1;
+
+ if (_ht_agl_ft <= (0 + _ground_offset + deadzone) && _solid){
+ pos.setElevationFt(0 + _ground_offset);
+ } else {
+ pos.setElevationFt(hitchpos.getElevationFt() + _load_offset);
+ }
+
+ }
+ } else {
+ pos.setLatitudeDeg( pos.getLatitudeDeg()
+ + (speed_north_deg_sec - wind_speed_from_north_deg_sec
+ + force_speed_north_deg_sec + friction_force_speed_north_deg_sec) * dt );
+ pos.setLongitudeDeg( pos.getLongitudeDeg()
+ + (speed_east_deg_sec - wind_speed_from_east_deg_sec
+ + force_speed_east_deg_sec + friction_force_speed_east_deg_sec) * dt );
+ pos.setElevationFt(pos.getElevationFt() + vs * dt);
+ }
+
+ // recalculate total speed
+ if ( vs == 0 && hs == 0)
+ speed = 0;
+ else
+ speed = sqrt( vs * vs + hs * hs) / SG_KT_TO_FPS;
+
+ // recalculate elevation and azimuth (velocity vectors)
+ _elevation = atan2( vs, hs ) * SG_RADIANS_TO_DEGREES;
+ _azimuth = atan2((speed_east_fps + force_speed_east_fps + friction_force_speed_east_fps),
+ (speed_north_fps + force_speed_north_fps + friction_force_speed_north_fps))
+ * SG_RADIANS_TO_DEGREES;
+
+ // rationalise azimuth
+ if (_azimuth < 0)
+ _azimuth += 360;
+
+ if (_aero_stabilised) { // we simulate rotational moment of inertia by using a filter
+ const double coeff = 0.9;
+
+ // we assume a symetrical MI about the pitch and yaw axis
+ setPch(_elevation, dt, coeff);
+ setHdg(_azimuth, dt, coeff);
+ } else if (_force_stabilised) { // we simulate rotational moment of inertia by using a filter
+ const double coeff = 0.9;
+ double ratio = h_force_lbs/(_mass * slugs_to_lbs);
+
+ if (ratio > 1) ratio = 1;
+ if (ratio < -1) ratio = -1;
+
+ double force_pitch = acos(ratio) * SG_RADIANS_TO_DEGREES;
+
+ if (force_pitch <= force_elevation_deg)
+ force_pitch = force_elevation_deg;
+
+ // we assume a symetrical MI about the pitch and yaw axis
+ setPch(force_pitch,dt, coeff);
+ setHdg(_azimuth, dt, coeff);
+ }
+
+ //do impacts and collisions
+ if (_report_impact && !_impact_reported)
+ handle_impact();
+
+ if (_report_collision && !_collision_reported)
+ handle_collision();
+
+ // set destruction flag if altitude less than sea level -1000
+ if (altitude_ft < -1000.0 && life != -1)
+ setDie(true);