440 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1947 



Figure 8 shows the vohime of power plant plus fuel corresponding to 

 the weights shown in figure 7. Power-plant volumes are the volumes 

 occupied by the units if wrapped with cloth. In other words, power 

 plants having an odd shape will result in still more space unusable 

 for other airplane components. Power-plant volumes in cubic feet are 

 estimated as follows, representing the minimum space not available 

 for other airplane components: 



Power-^lant volumes 



Figure 8. — Power plant plus fuel volume. 



In comparing the engine volumes, the power plants in order of 

 preference are the rocket, propeller, turbojet, and ram- jet. Fortu- 

 nately, although the last-named has a considerable volume, its weight 

 and installation considerations are such that it is practical to convert 

 the aft fuselage, which always is relatively vacant because of balance 

 considerations, into the power plant proper. Tending to offset this 

 effect is the fact that the large mass airflows consumed dictate large 

 duct inlet scoops. The simplicity of mechanisms alleviates installa- 

 tion problems considerably. 



