After earning her PhD, Simon was offered a position at DuPont’s Pioneer Research Lab in Buffalo, New York. Here, she worked to develop new catalysts to change the properties of synthetic polymers. This work led to the development of two polymers which would later be named Dacron and Orlon.
After completing her work with DuPont, Simon transferred to Oak Ridge National Laboratory, in Oak Ridge, Tennessee. Here, she made discoveries in the field of radiochemistry in studying the triple-fission of uranium. While at ORNL, Simon also became the first to discover a new isotope of calcium. For a short period of time after leaving ORNL, she continued with similar research regarding uranium at Argonne National Laboratory in Chicago, Illinois.
In 1949, Simon began work at Lewis Research Center in Cleveland, Ohio, a division of the National Advisory Committee for Aeronautics (NACA), the predecessor of NASA. Once here, she was assigned to the fuels and combustion division, where she conducted research regarding flame velocities and types of fuel for aerospace applications. She also conducted studies to determine the minimum diameter of tubing necessary to maintain an engine flame. This led to Simon being credited in numerous technical publications and research papers for her work, and led to improvements in engine designs for aeronautic and spaceflight purposes.
As a result of her work at NACA, Simon was given the Rockefeller Federal Service Award, which entailed a $10,000 (~$110,000 in 2022) grant from the Rockefeller Foundation. She used this award to travel to Europe to further her education at the University of Cambridge in Cambridge, England. Simon also toured around Europe where she met with scientists from Germany, England, France, and Italy to examine their research regarding physical chemistry and radiochemistry. Upon returning from her tour, she was promoted to assistant chief of NACA’s combustion branch, where she became a pioneer in female corporate management. Throughout the 1950’s she served as an advocate for women in science and education, appearing in several radio shows and magazines.
Once leaving NACA, Simon briefly held a position at Magnolia Petroleum in Texas, where she did work regarding oil sands.
In 1956, Simon took a position at AVCO corporation, an aviation conglomerate in New England. There, she applied her previous experience with polymer construction and physical chemistry to develop the technology for early aerospace heat shields, which were critical to NASA’s crewed spacecraft endeavors. This technology would go on to be used most notably during NASA’s Apollo program, and later was applied to ballistic missiles at the height of the Cold War. Simon remained at AVCO for 30 years, during which she held the titles of vice president and director of research at the company, becoming the company’s first female corporate officer.