UKHAS Wiki

#include <stdlib.h>
#include <stdio.h>
#include <math.h>
 
float air_density(float alt)					//model from NASA
{    
     float temp,pres;
     if (alt < 11000.0)
     {    // below 11Km - Troposphere
          temp = 15.04 - (0.00649 * alt);
          pres = 101.29 * pow((temp + 273.1) / 288.08, 5.256); 
     }
     else
     {
         if (alt < 25000.0)
         { // between 11Km and 25Km - lower Stratosphere
              temp = -56.46;
              pres = 22.65 * exp(1.73 - ( 0.000157 * alt));
         }
         else
         { // above 25Km - upper Stratosphere
               temp = -131.21 + (0.00299 * alt);
               pres = 2.488 * pow((temp + 273.1) / 216.6, -11.388);
         }
     }
     return(pres / (0.2869 * (temp + 273.1)));
}
 
int main()
{
	int n;
	float a;
	FILE * output;
	output=fopen("sqrt_density.h","w");
	fprintf(output,"u08 sqrt_density[256]={");
	a=air_density(0);	
	for(n=0;n<256;n++)
	{
		fprintf(output,"%d,",(int)(255.0*sqrt(air_density(n*100)/a)));
	}
	fprintf(output,"};");
	fclose(output);
}

u08 sqrt_density[256]={255,253,252,251,250,248,247,246,245,244,242,241,240,239,238,237,235,234,233,232,231,230,228,227,226,225,224,223,221,220,219,218,217,216,215,214,213,211,210,209,208,207,206,205,204,203,202,200,199,198,197,196,195,194,193,192,191,190,189,188,187,186,185,184,183,182,181,180,179,178,176,175,174,173,172,172,171,170,169,168,167,166,165,164,163,162,161,160,159,158,157,156,155,154,153,152,151,150,149,149,148,147,146,145,144,143,142,141,140,140,139,138,137,135,134,133,132,131,130,129,128,127,126,125,124,123,122,121,120,119,118,118,117,116,115,114,113,112,111,110,109,109,108,107,106,105,104,104,103,102,101,100,100,99,98,97,97,96,95,94,94,93,92,91,91,90,89,88,88,87,86,86,85,84,84,83,82,82,81,80,80,79,79,78,77,77,76,76,75,74,74,73,73,72,71,71,70,70,69,69,68,68,67,67,66,66,65,65,64,63,63,62,62,62,61,61,60,60,59,59,58,58,57,57,56,56,55,55,55,54,54,53,53,53,52,52,51,51,50,50,50,49,49,49,48,48,47,47,47,46,46,45,45,44,44,44,};