NO. 2 METHOD OF REACHING EXTREME ALTITUDES IJ 



an extremely short time — far too short to affect the photographic 

 plate; and that it is only when the velocity has been considerably 

 reduced that the " flash " is photographed. 



In experiment ii, a suggestion of this high-velocity portion of the 

 flash is seen, which, it will be noticed, is less in diameter than the end 

 of the nozzle. It should be remarked that it was only by accident that 

 the nozzle was illuminated by the flashes in experiments 9 and 11 irk 

 such a way as to be seen in the photograph. 



An interesting phenomenon connected with firing the chamber in' 

 air is the loudness of the sound produced by a comparatively small 

 amount of powder. This is, however, to be expected, inasmuch as, 

 the energy is entirely spent in producing motion of the air, whereas in, 

 the ordinary rifle, a large fraction of the energy of the powder- 

 becomes kinetic energy of the bullet. 



EXPERIMENTS WITH LARGE CHAMBER 



Inasmuch as all the steel chambers employed in the preceding ex- 

 periments were of the same internal diameter (1.26 cm.), it was con- 

 sidered desirable that at least a few experiments should be performed 

 with a larger chamber, first, in order to be certain that a large cham- 

 ber is operative ; and secondly, to see if such a chamber is not even 

 more efficient than a small chamber. This latter is to be expected 

 for the reason that heat and frictional losses should increase as the 

 square of the linear dimensions of the chamber ; and hence increase 

 in a less proportion than the mass of powder that can be used with 

 safety, which will vary as the cube of the linear dimensions. Evidence 

 in support of this expectation has already been given. Thus, for 

 ordinary rockets, the larger rocket has the higher efficiency, as evident 

 from table I. 



The large chamber was of nickel-alloy steel (Samson No. 3A), of 

 •115,000 lbs. tensil strength, for which the writer takes opportunity 

 of thanking the Carpenter Steel Company. This chamber had inside 

 diameter, and diameter of throat, both twice as large as those of the 

 chambers previously used ; but the thickness of wall of the chamber 

 and the taper of the nozzle were, however, the same. The inside of 

 the nozzle was well polished. Figure 3 shows a section of the 

 chamber ; the outer boundary being indicated by dotted lines, P being 

 the powder, and W the wadding. It will be noticed that the wadding 

 is just twice the size of that previously used. 



The mounting of the chamber, for the experiments, is shown in 

 plate 6, figure i. The chamber was held in the lower end of a 



