This was earliest practical treatise on the development of rocketry for space flight. Like the Russian Konstantin Tsiolkovsky (Tsiolkovskii; Russian: Константи́н Эдуа́рдович Циолко́вский);and the Romanian-German Hermann Oberth, Goddard worked out the theory of rocket propulsion independently. Having explored the mathematical practicality of rocketry since 1906 and the experimental workability of reaction engines in laboratory vacuum tests since 1912, Goddard began to accumulate ideas for probing beyond the Earth’s stratosphere. His first two patents in 1914, for a liquid-fuel gun rocket and a multistage step rocket, led to modest recognition and financial support from the Smithsonian Institution.
The publication in 1919 by the Smithsonian of A Method of Reaching Extreme Altitudes gave Goddard distorted publicity because he had suggested that rocket power or jet propulsion could be used to attain escape velocity and that this theory could be proved by crashing a flash-powder missile on the moon. Sensitive to criticism of his moon-rocket idea, he worked quietly and steadily toward the perfection of his rocket technology and techniques.
"Goddard began experimenting with liquid oxygen and liquid-fueled rockets in September 1921, and tested the first liquid-fueled engine in November 1923. It had a cylindrical combustion chamber, using impinging jets to mix and atomize liquid oxygen and gasoline.
"He launched the first liquid-fueled (gasoline and liquid oxygen) rocket on March 16, 1926, in Auburn, Massachusetts. His journal entry of the event was notable for its laconic understatement: 'The first flight with a rocket using liquid propellants was made yesterday at Aunt Effie's farm.' The rocket, which was dubbed "Nell", rose just 41 feet during a 2.5-second flight that ended 184 feet away in a cabbage field, but it was an important demonstration that liquid propellants were possible." (Wikipedia article on Robert H. Goddard, accessed 05-15-2010)
Among Goddard’s successful innovations were "fuel-injection systems, regenerative cooling of combustion chambers, gyroscopic stabilization and control, instrumented payloads and recovery systems, guidance vanes in the exhaust plume, gimbaled and clustered engines, and aluminum fuel and oxidizer pumps" (Dictionary of Scientific Biography).
On March 19, 1936 the Smithsonian published Goddard's Liquid Propellant Rocket Development. The remainder of his work was documented in patents.
"Goddard avoided sharing details of his work with other scientists, and preferred to work alone with his technicians. Frank Malina, who was then studying rocketry at the California Institute of Technology, visited Goddard [in Roswell, New Mexico] in August of 1936. Goddard refused to discuss any of his research, other than that which had already been published in Liquid-Propellant Rocket Development. Theodore von Kármán, Malina's mentor at the time, was unhappy with Goddard's attitude and later wrote, 'Naturally we at Caltech wanted as much information as we could get from Goddard for our mutual benefit. But Goddard believed in secrecy. . . . The trouble with secrecy is that one can easily go in the wrong direction and never know it.' Goddard's concerns about secrecy led to criticism for failure to cooperate with other scientists and engineers.
"By 1939, von Kármán's Guggenheim Aeronautical Laboratory at Caltech [GALCIT] had received Army Air Corps funding to develop rockets to assist in aircraft take-off. Goddard learned of this in 1940, and openly expressed his displeasure. Malina could not understand why the Army did not arrange for an exchange of information between Goddard and Caltech, since both were under government contract at the same time. Goddard did not think he could be of that much help to Caltech because they were designing rockets with solid fuel and Goddard was using liquid fuels" (Wikipedia article on Goddard).
Goddard’s booklet of 1919 was preceded by the theoretical writings of Tsiolkovsky published in Russian 1903-14 and the theoretical paper by Robert Esnault-Pelterie published in French in 1913.
Goddard & Pendray, The Papers of Robert H. Goddard, I, 233-38.