UPPER ATMOSPHERE — MASSEY 



183 



which their velocity is increased, and thus return to earth at a distant 

 point. The phenomenon is essentially similar to long-range radio 

 propagation (see fig. 3) . The distance from the source to the point 

 where the reflected rays, returning from different directions, are re- 

 ceived gives the height of the reflecting high-temperature layer. Re- 

 cently a more precise sound-ranging method has been introduced for 

 use with rockets. At suitable heights grenades Avere ejected from a 



200 300 400 



Temperature (° absolute) 



500 



Figure 2. — Pressure and temperature in the atmosphere as a function of height. The full 

 line is obtained directly from the mean rocket observations made at White Sands, N. Mex. 

 Above 100 km. there is uncertainty in deriving the temperature from the pressure and 

 density, owing to changes in composition. The dotted lines indicate two results obtained 

 on two extreme assumptions. 



rocket in flight and exploded. The explosions were photogi-aphed and 

 the arrival of the sound pulses at each of five ground stations was ac- 

 curately timed. From these observations the location of the explosion, 

 the velocity of sound at different levels, and the distribution of atmos- 

 pheric winds could be determined. An alternative method for measur- 

 ing the speed of sound by rocket is from determination of the ratio of 

 the pressures measured by two gages located on the side of the rocket at 



326511—55^—13 



