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() {
33 FGAIBallistic::~FGAIBallistic() {
37 bool FGAIBallistic::init() {
39 vs = sin( elevation * 0.017453293 ) * speed;
40 hs = cos( elevation * 0.017453293 ) * speed;
41 aero_stabilized = true;
47 void FGAIBallistic::bind() {
51 void FGAIBallistic::unbind() {
55 void FGAIBallistic::update(double dt) {
63 void FGAIBallistic::setAzimuth(double az) {
68 void FGAIBallistic::setElevation(double el) {
73 void FGAIBallistic::setStabilization(bool val) {
74 aero_stabilized = val;
78 void FGAIBallistic::Run(double dt) {
80 double speed_north_deg_sec;
81 double speed_east_deg_sec;
82 double ft_per_deg_lon;
83 double ft_per_deg_lat;
85 // get size of a degree at this latitude
86 ft_per_deg_lat = 366468.96 - 3717.12 * cos(pos.lat()/SG_RADIANS_TO_DEGREES);
87 ft_per_deg_lon = 365228.16 * cos(pos.lat() / SG_RADIANS_TO_DEGREES);
89 // the two drag calculations below assume sea-level density,
90 // mass of 0.03 slugs, drag coeff of 0.295, frontal area of 0.007 ft2
91 // adjust horizontal speed due to drag
92 hs -= 0.000082 * hs * hs * dt;
93 if ( hs < 0.0 ) hs = 0.0;
95 // adjust vertical speed due to drag
97 vs -= 0.000082 * vs * vs * dt;
99 vs += 0.000082 * vs * vs * dt;
102 // convert horizontal speed (fps) to degrees per second
103 speed_north_deg_sec = cos(hdg / SG_RADIANS_TO_DEGREES) * hs / ft_per_deg_lat;
104 speed_east_deg_sec = sin(hdg / SG_RADIANS_TO_DEGREES) * hs / ft_per_deg_lon;
107 pos.setlat( pos.lat() + speed_north_deg_sec * dt);
108 pos.setlon( pos.lon() + speed_east_deg_sec * dt);
110 // adjust vertical speed for acceleration of gravity
113 // adjust altitude (meters)
114 altitude += vs * dt * SG_FEET_TO_METER;
115 pos.setelev(altitude);
117 // adjust pitch if aerostabilized
118 if (aero_stabilized) pitch = atan2( vs, hs ) * SG_RADIANS_TO_DEGREES;
120 // set destruction flag if altitude less than sea level -1000
121 if (altitude < -1000.0) setDie(true);