456 ANNUAL REPORT SMITHSONIAN INSTITUTION, 194 7 



(/) Maximum rate of climb occurs at sea level. 



{g) Further improvements, adaptations, and variations will be 

 widely developed in terms of compound and gas-turbine engines and 

 various combinations of them. 



2. Turbojet aivplane. — {a) High maximum speeds where relatively 

 short range is required make this airplane mandatory for military 

 application. Maximum speed occurs at sea level. 



(&) Again, for short-range premium operation in commercial fields 

 this power plant is attractive. Eange improves markedly with alti- 

 tude, and economical cruising speeds are relatively high. 



(c) Eelatively high operating altitudes, at least up to 50,000 feet, 

 are feasible. At high altitudes respectable range is obtained. 



{d) Maximum speed of the order of 550 to 600 miles per hour and 

 above at sea level is ideally suited for air-to-ground military operation. 



(e) Maximum rate of climb occurs at sea level. 



(/) Speeds for maximum rate of climb are reasonably high. 



3. Ram-jet airplane. — {a) Maximum speed, of the order of 650 miles 

 per hour, occurs at sea level. 



(&) Climbing speeds are exceptionally high, being within 5 to 10 

 percent of maximum level-flight speeds. 



(c) Range is extremely limited, representing some 50 percent of 

 that for the turbojet, and also increases considerably with altitude. 



{d) Maximum rate of climb at sea level is exceptionally high, but 

 falls off rapidly with increase in altitude, resulting in a rather low 

 ceiling, below 40,000 feet. 



(e) Auxiliary take-off means are required. 



(/) Performance characteristics indicate that the ideal application 

 would be in the field of low-altitude, flat trajectory missiles against 

 such targets as battleships and aircraft carriers in particular. Air 

 launching would probably be more practical than surface launching. 



4. Rocket air-plane. — (a) This is the only man-carrying airplane 

 capable of flight at supersonic speeds, which distinguishes this type of 

 propulsion from the others considered. 



(&) Range is extremely limited and increases slightly with altitude. 



(c) As in the case of maximum speed, so also does rate of climb 

 increase phenomenally with altitude. 



{d) Ceiling, speed, and climb performance are limited only by the 

 amount of fuel it is possible to carry. 



(e) Performance characteristics indicate ideal application to mis- 

 siles following a trajectory. Peak altitudes greatly exceeding the 

 capability of any other man-made mechanisms are possible. Missile 

 ranges can be vastly extended. 



(/) Highly specialized applications in terms of research airplanes 

 and interceptors are evident. A research airplane could be used to 

 conduct tests in level flight for application to high-speed and diving 



