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ksp: c: initial drag and parachute support

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still doesn't work quite right
This commit is contained in:
Vince Weaver 2016-05-31 00:46:16 -04:00
parent 0dd398cf15
commit d751608ca9
1 changed files with 38 additions and 1 deletions
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39
ksp/c/ksp_launch.c
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@ -91,6 +91,14 @@ int main(int argc, char **argv) {
double deltat=1.0;
/* atmospheric pressure */
double pressure=101325; /* Pascals */
double pressure0=101325;
double density=0; /* kg/m^3 */
double temperature=273; /* K */
double drag=0.0,drag_a=0.0;
int parachutes_deployed=0;
int parachutes=3;
int stage=2;
@ -184,6 +192,26 @@ int main(int argc, char **argv) {
rocket_acceleration_y+=gravity_y;
rocket_acceleration_x+=gravity_x;
/* Adjust pressure */
pressure=pressure0*exp(-(rocket_altitude-KERBIN_RADIUS)/5600);
density=pressure/(287*temperature);
/* 0.5*rho*v^2*d*A */
/* d=coefficient of drag, A=surface area */
/* d=1.05 for cube (wikipedia) */
/* d=0.8 for long cylinder */
/* d=0.5 for long cone */
if (parachutes_deployed) {
drag=0.5*density*rocket_velocity*rocket_velocity*1.5*1000.0*parachutes;
}
else {
drag=0.5*density*rocket_velocity*rocket_velocity*0.5*1.0;
}
drag_a=drag/(total_mass[stage]*1000);
if (rocket_velocity_y>0) drag_a=-drag_a;
rocket_acceleration_y+=drag_a;
/* v=v0+at */
v0_x=rocket_velocity_x;
@ -218,6 +246,7 @@ int main(int argc, char **argv) {
((rocket_altitude)/KERBIN_RADIUS)*
((rocket_altitude)/KERBIN_RADIUS));
home();
htabvtab(1,21);
@ -241,6 +270,10 @@ int main(int argc, char **argv) {
else if (rocket_acceleration_y<0) printf("FROWN");
else printf("NEUTRAL");
htabvtab(20,14);
printf("pressure=%lf density=%lf drag=%lf drag_a=%lf\n",
pressure,density,drag,drag_a);
htabvtab(20,13);
printf("grav angle=%lf\n",gravity_angle*180.0/PI);
@ -268,6 +301,7 @@ int main(int argc, char **argv) {
scanf("%c",&input);
if (input==' ') {
if (stage>0) stage--;
else parachutes_deployed=1;
}
if (input=='d') {
angle+=45.0;
@ -304,7 +338,10 @@ int main(int argc, char **argv) {
fprintf(logfile,"%lf %lf\n",rocket_x/1000.0,rocket_y/1000.0);
}
if (vlogfile) {
fprintf(vlogfile,"%lf %lf %lf\n",time,rocket_altitude,rocket_velocity);
fprintf(vlogfile,
"t=%lf h=%lf v=%lf g=%lf d=%lf ray=%lf\n",
time,rocket_altitude-KERBIN_RADIUS,rocket_velocity,
gravity_y,drag_a,rocket_acceleration_y);
}
}
log_step++;