NO. 2 



.MKIIIOD OF REACHING EXTRE^JE ALTITUDES 



39 



The quantity, p. — The above expression (8), for the resistance, 

 holds only at atmospheric pressure. At high altitudes the pressure, 

 of course, decreases greatly. If we call p the mean density through- 

 out any interval of altitude, and p^ the density at sea-level, the right 



member of (8), on being multiplied bv S and-'' , will give the air 



resistance, R, experienced by the rocket. 



A curve representing the relation between density and altitude 

 up to 120,000 ft. is shown in figure 6. This curve is derived from 





05 



«o 



^. 



10 



H 



-to 



Sir* 



CVJ 





10 20 30 40 50 60 70 80 90 100 110 IZO 130 140 

 Altitude in Thousands oj Feet. 



Fig. 6. 



a table of pressures and temperatures in Arrhenius' " Lehrbuch der 

 Kosmischen Physik." The ordinates of the curve are the num- 

 bers -^ . 

 Po 



Beyond 120,000 ft. the density is calculated by the empirical rule 

 which assumes the density to become halved at every increase in 

 altitude of 3.5 miles. A comparison was made between the values 

 obtained in this way and those obtained from the very probable pres- 

 sures deduced by Wegener, in the following way : The mean density 

 between two levels for which Wegener gives pressures was obtained 

 by multiplying the difiference in pressure by 13.6, and dividing by the 



