48 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 7I 



The enormous difference between the total initial masses required 

 for low-efficiency rockets, compared with those for high, may at 

 first appear surprising ; but they should be expected from the 

 exponential nature of equations (6) and (7). Thus if the " effective 

 velocity " is reduced from 7,000 ft./sec. to half this value, the mini- 



FiG. 7, 



mum masses for each interval, neglecting air resistance, will be those 

 for 7,000 ft./sec. squared; and including air resistance, still greater. 

 Similarly for an effective velocity of 960 ft./sec. which is that for 

 reloading rockets having the same velocity of ejection as Coston ship 

 rockets, the minimum masses will be those for 7,000 ft./sec. raised 



