Robert H. Goddard - Mid-to-late 1910s

Mid-to-late 1910s

In the fall of 1914, Goddard's health had improved, and he accepted a part-time position as an instructor and research fellow at Clark University.

His position at Clark allowed him to further his rocketry research. He ordered numerous supplies that could be used to build rocket prototypes for launch, and spent much of 1915 in preparation for his first tests.

Goddard's first test launch of a powder rocket came on an early evening in 1915 following his daytime classes at Clark. The launch was loud and bright enough to arouse the alarm of the campus janitor, and Goddard had to reassure him that his experiments, while being serious study, were also quite harmless. After this incident, Goddard took his experiments inside the physics lab, in order to limit any disturbance.

At the Clark physics lab, Goddard conducted static tests of powder rockets to measure their thrust efficiency. He found his earlier estimates to be verified; powder rockets were converting only about 2 percent of their fuel into thrust. At this point he applied de Laval nozzles, which were generally used with steam turbine engines, and these greatly improved thrust efficiency. By mid-summer of 1915, Goddard had obtained an average thrust efficiency of 40 percent with nozzle velocities of 2051 meters per second.

Later that year, Goddard designed an elaborate experiment at the Clark physics lab to prove that a rocket would perform in a vacuum such as that in space. He believed it would, but the other scientists were not convinced. His experiment demonstrated that a rocket's performance was actually decreased under atmospheric pressure.

From 1916 to 1917, Goddard built and tested experimental ion thrusters, which he thought might be used for propulsion in the near-vacuum conditions of outer space. The small glass engines he built were tested at atmospheric pressure, where they generated a stream of ionized air.