PREFACE 



The theoretical work herein presented was developed while the 

 writer was at Princeton University in 1912-13, the basis of the calcu- 

 lations being the assumption that, if nitrocellulose smokeless powder 

 were employed as propellant in a rocket, under such conditions as 

 are here explained, an efficiency of 50 per cent might be expected. 



Actual experimental investigations were not undertaken until 

 191 5-1 6, at which time the tests concerning ordinary rockets, steel 

 chambers and nozzles, and trials in vacuo, were performed at Clark 

 University. The original calculations were then repeated, using the 

 data from these experiments, and both the theoretical and experi- 

 mental results were submitted, in manuscript, to the Smithsonian 

 Institution, in December, 1916. This manuscript is here presented in 

 the original form, save for the notes at the end which are now added. 



A grant of $5,000 from the Hodgkins Fund, Smithsonian Institu- 

 tion, under which work is being done at present, was advanced toward 

 the development of a reloading, or multiple-charge rocket, herein 

 explained in principle, and this work was begun at the Worcester 

 Polytechnic Institute in 191 7, and was later undertaken as a war 

 proposition. It was continued, from June, 1918, up to very nearly 

 the time of signing of the armistice, at the Mt. Wilson Observatory 

 of the Carnegie Institution of Washington, where most of the experi- 

 mental results were obtained. 



In connection with the present publication, I take pleasure in 

 thanking Dr. A. G. Webster for the facilities of the shop and labora- 

 tory at Clark University, used in the preliminary experiments herein 

 described. I also take this opportunity of expressing my gratitude to 

 the Smithsonian Institution, for its support and encouragement in 

 the later work. 



Robert H. Goddard. 

 Clark College, 



Worcester, Massachusetts, 

 May 26, 1919. 



