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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
24 #include <simgear/math/point3d.hxx>
27 #include "AIBallistic.hxx"
30 FGAIBallistic::FGAIBallistic() : FGAIBase(otBallistic) {
36 aero_stabilised = false;
39 FGAIBallistic::~FGAIBallistic() {
42 void FGAIBallistic::readFromScenario(SGPropertyNode* scFileNode) {
46 FGAIBase::readFromScenario(scFileNode);
48 setAzimuth(scFileNode->getDoubleValue("azimuth", 0.0));
49 setElevation(scFileNode->getDoubleValue("elevation", 0.0));
50 setDragArea(scFileNode->getDoubleValue("eda", 0.007));
51 setLife(scFileNode->getDoubleValue("life", 900.0));
52 setBuoyancy(scFileNode->getDoubleValue("buoyancy", 0));
53 setWind_from_east(scFileNode->getDoubleValue("wind_from_east", 0));
54 setWind_from_north(scFileNode->getDoubleValue("wind_from_north", 0));
55 setWind(scFileNode->getBoolValue("wind", false));
56 setRoll(scFileNode->getDoubleValue("roll", 0.0));
57 setCd(scFileNode->getDoubleValue("cd", 0.029));
58 setMass(scFileNode->getDoubleValue("mass", 0.007));
59 setStabilisation(scFileNode->getBoolValue("aero_stabilized", false));
62 bool FGAIBallistic::init() {
71 void FGAIBallistic::bind() {
73 props->tie("sim/time/elapsed-sec",
74 SGRawValueMethods<FGAIBallistic,double>(*this,
75 &FGAIBallistic::_getTime));
78 void FGAIBallistic::unbind() {
79 // FGAIBase::unbind();
80 props->untie("sim/time/elapsed-sec");
83 void FGAIBallistic::update(double dt) {
90 void FGAIBallistic::setAzimuth(double az) {
95 void FGAIBallistic::setElevation(double el) {
96 pitch = elevation = el;
99 void FGAIBallistic::setRoll(double rl) {
103 void FGAIBallistic::setStabilisation(bool val) {
104 aero_stabilised = val;
107 void FGAIBallistic::setDragArea(double a) {
111 void FGAIBallistic::setLife(double seconds) {
115 void FGAIBallistic::setBuoyancy(double fpss) {
119 void FGAIBallistic::setWind_from_east(double fps) {
120 wind_from_east = fps;
123 void FGAIBallistic::setWind_from_north(double fps) {
124 wind_from_north = fps;
127 void FGAIBallistic::setWind(bool val) {
131 void FGAIBallistic::setCd(double c) {
135 void FGAIBallistic::setMass(double m) {
139 void FGAIBallistic::Run(double dt) {
142 // cout << "life timer 1" << life_timer << dt << endl;
143 if (life_timer > life) setDie(true);
145 double speed_north_deg_sec;
146 double speed_east_deg_sec;
147 double wind_speed_from_north_deg_sec;
148 double wind_speed_from_east_deg_sec;
149 double Cdm; // Cd adjusted by Mach Number
151 // Adjust Cd by Mach number. The equations are based on curves
152 // for a conventional shell/bullet (no boat-tail).
153 if ( Mach < 0.7 ) { Cdm = 0.0125 * Mach + Cd; }
154 else if ( 0.7 < Mach && Mach < 1.2 ) {
155 Cdm = 0.3742 * pow ( Mach, 2) - 0.252 * Mach + 0.0021 + Cd; }
156 else { Cdm = 0.2965 * pow ( Mach, -1.1506 ) + Cd; }
158 // cout << " Mach , " << Mach << " , Cdm , " << Cdm << endl;
160 // drag = Cd * 0.5 * rho * speed * speed * drag_area;
161 // rho is adjusted for altitude in void FGAIBase::update,
162 // using Standard Atmosphere (sealevel temperature 15C)
163 // acceleration = drag/mass;
164 // adjust speed by drag
165 speed -= (Cdm * 0.5 * rho * speed * speed * drag_area/mass) * dt;
167 // don't let speed become negative
168 if ( speed < 0.0 ) speed = 0.0;
170 // calculate vertical and horizontal speed components
171 vs = sin( pitch * SG_DEGREES_TO_RADIANS ) * speed;
172 hs = cos( pitch * SG_DEGREES_TO_RADIANS ) * speed;
174 // convert horizontal speed (fps) to degrees per second
175 speed_north_deg_sec = cos(hdg / SG_RADIANS_TO_DEGREES) * hs / ft_per_deg_lat;
176 speed_east_deg_sec = sin(hdg / SG_RADIANS_TO_DEGREES) * hs / ft_per_deg_lon;
178 // if wind not required, set to zero
184 // convert wind speed (fps) to degrees per second
185 wind_speed_from_north_deg_sec = wind_from_north / ft_per_deg_lat;
186 wind_speed_from_east_deg_sec = wind_from_east / ft_per_deg_lon;
189 pos.setlat( pos.lat() + (speed_north_deg_sec - wind_speed_from_north_deg_sec) * dt );
190 pos.setlon( pos.lon() + (speed_east_deg_sec - wind_speed_from_east_deg_sec) * dt );
192 // adjust vertical speed for acceleration of gravity and buoyancy
193 vs -= (gravity - buoyancy) * dt;
195 // adjust altitude (feet)
197 pos.setelev(altitude * SG_FEET_TO_METER);
199 // recalculate pitch (velocity vector) if aerostabilized
200 // cout << "aero_stabilised " << aero_stabilised << endl ;
201 if (aero_stabilised) pitch = atan2( vs, hs ) * SG_RADIANS_TO_DEGREES;
203 // recalculate total speed
204 speed = sqrt( vs * vs + hs * hs);
206 // set destruction flag if altitude less than sea level -1000
207 if (altitude < -1000.0) setDie(true);
211 double FGAIBallistic::_getTime() const {
212 // cout << "life timer 2" << life_timer << endl;