1 // FGAIBallistic - FGAIBase-derived class creates a ballistic object
3 // Written by David Culp, started November 2003.
4 // - davidculp2@comcast.net
6 // This program is free software; you can redistribute it and/or
7 // modify it under the terms of the GNU General Public License as
8 // published by the Free Software Foundation; either version 2 of the
9 // License, or (at your option) any later version.
11 // This program is distributed in the hope that it will be useful, but
12 // WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 // General Public License for more details.
16 // You should have received a copy of the GNU General Public License
17 // along with this program; if not, write to the Free Software
18 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 #include <simgear/math/point3d.hxx>
27 #include "AIBallistic.hxx"
30 FGAIBallistic::FGAIBallistic(FGAIManager* mgr) {
32 _type_str = "ballistic";
42 FGAIBallistic::~FGAIBallistic() {
46 bool FGAIBallistic::init() {
48 aero_stabilized = true;
56 void FGAIBallistic::bind() {
58 props->tie("sim/time/elapsed-sec",
59 SGRawValueMethods<FGAIBallistic,double>(*this,
60 &FGAIBallistic::_getTime));
63 void FGAIBallistic::unbind() {
64 // FGAIBase::unbind();
65 props->untie("sim/time/elapsed-sec");
68 void FGAIBallistic::update(double dt) {
75 void FGAIBallistic::setAzimuth(double az) {
80 void FGAIBallistic::setElevation(double el) {
81 pitch = elevation = el;
84 void FGAIBallistic::setRoll(double rl) {
88 void FGAIBallistic::setStabilization(bool val) {
89 aero_stabilized = val;
92 void FGAIBallistic::setDragArea(double a) {
96 void FGAIBallistic::setLife(double seconds) {
100 void FGAIBallistic::setBuoyancy(double fpss) {
104 void FGAIBallistic::setWind_from_east(double fps) {
105 wind_from_east = fps;
108 void FGAIBallistic::setWind_from_north(double fps) {
109 wind_from_north = fps;
112 void FGAIBallistic::setWind(bool val) {
116 void FGAIBallistic::setCd(double c) {
120 void FGAIBallistic::setMass(double m) {
124 void FGAIBallistic::Run(double dt) {
127 // cout << "life timer 1" << life_timer << dt << endl;
128 if (life_timer > life) setDie(true);
130 double speed_north_deg_sec;
131 double speed_east_deg_sec;
132 double wind_speed_from_north_deg_sec;
133 double wind_speed_from_east_deg_sec;
134 double Cdm; // Cd adjusted by Mach Number
136 // Adjust Cd by Mach number. The equations are based on curves
137 // for a conventional shell/bullet (no boat-tail).
138 if ( Mach < 0.7 ) { Cdm = 0.0125 * Mach + Cd; }
139 else if ( 0.7 < Mach && Mach < 1.2 ) {
140 Cdm = 0.3742 * pow ( Mach, 2) - 0.252 * Mach + 0.0021 + Cd; }
141 else { Cdm = 0.2965 * pow ( Mach, -1.1506 ) + Cd; }
143 // cout << " Mach , " << Mach << " , Cdm , " << Cdm << endl;
145 // drag = Cd * 0.5 * rho * speed * speed * drag_area;
146 // rho is adjusted for altitude in void FGAIBase::update,
147 // using Standard Atmosphere (sealevel temperature 15C)
148 // acceleration = drag/mass;
149 // adjust speed by drag
150 speed -= (Cdm * 0.5 * rho * speed * speed * drag_area/mass) * dt;
152 // don't let speed become negative
153 if ( speed < 0.0 ) speed = 0.0;
155 // calculate vertical and horizontal speed components
156 vs = sin( pitch * SG_DEGREES_TO_RADIANS ) * speed;
157 hs = cos( pitch * SG_DEGREES_TO_RADIANS ) * speed;
159 // convert horizontal speed (fps) to degrees per second
160 speed_north_deg_sec = cos(hdg / SG_RADIANS_TO_DEGREES) * hs / ft_per_deg_lat;
161 speed_east_deg_sec = sin(hdg / SG_RADIANS_TO_DEGREES) * hs / ft_per_deg_lon;
163 // if wind not required, set to zero
169 // convert wind speed (fps) to degrees per second
170 wind_speed_from_north_deg_sec = wind_from_north / ft_per_deg_lat;
171 wind_speed_from_east_deg_sec = wind_from_east / ft_per_deg_lon;
174 pos.setlat( pos.lat() + (speed_north_deg_sec - wind_speed_from_north_deg_sec) * dt );
175 pos.setlon( pos.lon() + (speed_east_deg_sec - wind_speed_from_east_deg_sec) * dt );
177 // adjust vertical speed for acceleration of gravity and buoyancy
178 vs -= (gravity - buoyancy) * dt;
180 // adjust altitude (feet)
182 pos.setelev(altitude * SG_FEET_TO_METER);
184 // recalculate pitch (velocity vector) if aerostabilized
185 if (aero_stabilized) pitch = atan2( vs, hs ) * SG_RADIANS_TO_DEGREES;
187 // recalculate total speed
188 speed = sqrt( vs * vs + hs * hs);
190 // set destruction flag if altitude less than sea level -1000
191 if (altitude < -1000.0) setDie(true);
195 double FGAIBallistic::_getTime() const {
196 // cout << "life timer 2" << life_timer << endl;