2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 95 



The advantages of the liquid-propellant rocket are that the propellant 

 materials possess several times the energy of powders, per unit mass, 

 and that moderate pressures may be employed, thus avoiding the 

 weight of the strong combustion chambers that would be necessary 

 if propulsion took place by successive explosions. 



Experiments with liquid oxygen and various liquid hydrocarbons, 

 including gasoline and liquid propane, as well as ether, were made 

 during the writer's spare time from 1920 to 1922, under a grant by 

 Clark University. Although oxygen and hydrogen, as earlier sug- 

 gested,* possess the greatest heat energy per unit mass, it seems likely 

 that liquid oxygen and liquid methane would afford the greatest heat 

 value of the combinations which could be used without considerable 

 difficulty. The most practical combination, however, appears to be 

 liquid oxygen and gasoline. 



In these experiments it was shown that a rocket chamber and 

 nozzle, since termed a " rocket motor," could use liquid oxygen to- 

 gether with a liquid fuel, and could exert a lifting force without 

 danger of explosion and without damage to the chamber and nozzle. 

 These rockets were held by springs in a testing frame, and the liquids 

 were forced into the chamber by the pressure of a noninflammable gas. 



The experiments were continued from 1922 to 1930. chiefly under 

 grants from the Smithsonian Institution. Although this work will be 

 made the subject of a later report, it is. desirable in the present paper 

 to call attention to some of the results obtained. On November i, 

 1923, a rocket motor operated in the testing frame, using liquid 

 oxygen and gasoline, both supplied by pumps on the rocket. 



In December 1925 the simpler plan previously employed of having 

 the liquids fed to the chamber under the pressure of an inert gas in 

 a tank on the rocket was again employed, and the rocket developed 

 by means of these tests was constructed so that it could be operated 

 independently of the testing frame. 



The first flight of a liquid oxygen-gasoline rocket was obtained on 

 March 16, 1926, in Auburn, Mass., and was reported to the Smith- 

 sonian Institution May 5, 1926. This rocket is shown in the frame 

 from which it was fired, in plate i, figure i. Pressure was produced 

 initially by an outside pressure tank, and after launching by an alcohol 

 heater on the rocket. 



It will be seen from the photograph that the combustion chamber 

 and nozzle were located forward of the remainder of the rocket, to 

 which connection was made by two pipes. This plan was of advantage 



* Smithsonian Misc. Coll., vol. 71, no. 2, 1919. 



