4.1 Introduction

Konastantin Eduardovich Tsiolkowski, a Russian mathematics professor, was the first to observe that rocket propulsion was a prerequisite for space exploration. As early as 1883, Tsiolkowski noted that gas expulsion could create thrust; thus, a rocket could operate in a vacuum. In 1903 he published a milestone paper describing how space flight could be accomplished with rockets. He advocated the use of liquid hydrogen and liquid oxygen as propellants. He described staged rockets and showed mathematically that space exploration would require staging. Every time you use Eq. (4.19), think of Tsiolkowski.

Robert H. Goddard, professor of physics at Clark University, also observed that space flight would require liquid rocket propulsion. With this goal he was the first to design, build, and fly a liquid rocket, a feat that required over 200 patented inventions and his entire life. He flew the first liquid rocket in 1926. Using liquid oxygen and gasoline, it flew for 2.5 s, reaching an altitude of 41 ft and a speed of 63 mph. He developed pump-fed engines, clustered stages, quick disconnects, pressurization systems, and gyro stabilization. By the time he died in 1945, he had developed every type of equipment that would be required for a vehicle like the Saturn V. His rockets had reached a size of 2200 N (500 lb) and had reached altitudes of 1.9 km (2 miles).

Goddard's work was largely forgotten in the United States. Germany however followed his work closely and vigorously developed propulsion systems as weapons. After...