DOCTOR LANGLEY'S PARADOX : TWO LETTERS 

 SUGGESTING THE DEVELOPMENT OF ROCKETS 



By RUSSELL J. PARKINSON * 



Museum Aide, National Air Museum, Smithsonian Institution; and 



Instructor of History, Duke University 



(With Three Plates) 



Two previously unpublished letters written in 1902 by Samuel Pier- 

 pont Langley, third Secretary of the Smithsonian Institution, have 

 recently been uncovered in the "Langley Documents on Aero- 

 dromics" held by the National Air Museum, Washington, D. C. 

 These letters not only anticipated the development of powered flight, 

 which Langley considered a certainty, but also demonstrated that 

 Langley 's far-ranging mind had foreseen even the development of 

 the modern rocket. 



Plagued by many problems, including the need to obtain a gasoline 

 engine of sufficient horsepower in relation to its total weight, Langley 

 had suffered innumerable delays in constructing an "aerodrome" or 

 flying machine intended to carry a man. After several years of dis- 

 appointment, and with some hesitation, he permitted his young as- 

 sistant, Charles M. Manly, to undertake the rebuilding of an unsuc- 

 cessful Balzar engine.^ Using a revolutionary principle of placing 

 steel jackets around cast-iron cylinder walls, Manly soon built an 

 engine which produced over 52 horsepower, the net weight of the 

 engine proper being only 2.4 pounds per horsepower. The success 

 of the "aerodrome" seemed assured. 



Langley's spirits revived, and his correspondence during the spring 

 and summer of 1902 indicated a renewed interest in the construction 

 of his large flying machine. A whole new realm of aeronautical pos- 

 sibilities formed in his mind, and he discussed these ideas among the 

 small group of friends and associates in whom he could confide. 

 Fortunately for history, it was Langley's custom to record the 



* This article was completed with the cooperation of the staff of the National 

 Air Museum. 



1 Built by Stephen M. Balzar of New York, it failed to meet the specifications 

 of producing 12 horsepower while weighing less than 100 pounds. 



SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 140, NO. 3 



SMITHSONIAN ...p « q 493^ 



INSTITUTION 



