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/*
* Copyright © 2014 Keith Packard <keithp@keithp.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*/
#include "ao-fakeflight.h"
/* Mass (kg) of the airframe */
double
rocket_mass(struct flight *f, struct rocket *r)
{
double time = f->time;
double m = r->empty_mass;
int n;
for (n = 0; n < MAX_MOTORS; n++) {
struct motor *motor = &r->motors[n];
if (motor->burn_time) {
double fuel_time_remain = fmin (motor->burn_time, fmax(motor->burn_time - (time - motor->delay), 0.0));
double fuel_fraction = fuel_time_remain / motor->burn_time;
m += fuel_fraction * motor->fuel_mass;
}
}
return m;
}
/* Force (N) due to thrust */
double
rocket_thrust(struct flight *f, struct rocket *r)
{
double time = f->time;
double thrust = 0.0;
int n;
for (n = 0; n < MAX_MOTORS; n++) {
struct motor *motor = &r->motors[n];
if (motor->burn_time) {
if (motor->delay <= time && time < motor->delay + motor->burn_time)
thrust += motor->average_thrust;
}
}
return thrust;
}
/* Drag (N) due to air resistance */
double
rocket_drag(struct flight *f, struct rocket *r)
{
double pressure = cc_altitude_to_pressure(f->altitude);
double temperature = cc_altitude_to_temperature(f->altitude);
double drag = force_drag(f->speed, density_air(pressure, temperature),
r->models[f->state].cd,
area_circle(r->models[f->state].diameter));
/* drag operates in opposition to motion through air */
if (f->speed >= 0)
drag = -drag;
return drag;
}
/* Force (N) due to gravity */
double
rocket_gravity(struct flight *f, struct rocket *r)
{
double gravity = force_gravity(rocket_mass (f, r), f->altitude);
}
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