Yvonne Madelaine Brill (née Claeys; December 30, 1924 – March 27, 2013) was a Canadian American rocket and jet propulsion engineer. She is responsible for inventing the Electrothermal Hydrazine Thruster (EHT/Resistojet), a fuel-efficient rocket thruster that keeps today’s satellites in orbit, and holds a patent for its invention. During her career she was involved in a broad range of national space programs in the United States, including NASA and the International Maritime Satellite Organization.

Born in Winnipeg, Manitoba, Canada, Yvonne Brill, is a first-generation Canadian, as her parents were immigrants from Belgium. She was inspired to attend school by Amelia Earhart, the first woman pilot to fly across the Atlantic Ocean. When she was young, her father encouraged her to open a shop in their hometown, while her high school science teacher told her that a woman wouldn't get anywhere in science. She ignored both. Yvonne was the first in her family to go to college, graduating from the University of Manitoba in 1945 at the top of her class with a bachelor’s degree in both chemistry and mathematics (Int. Engineering). She had originally applied to their engineering program at 18, but was denied by the school, as they claimed that their mandatory summer camp did not have the necessary facilities to host female students. Her denial to Manitoba’s school of engineering forever inspired her to encourage women in the sciences, and in her, forged an unwavering confidence against gender-based discrimination. She went on to study at the University of Southern California, where she took night classes and graduated in 1951 with a master's degree in chemistry.

Following her graduation from USC, Brill began working at Douglas Aircraft in 1945 after being recruited despite her lack of an engineering degree. Her main interest was in engineering, but she transferred to Douglas’ chemistry department to work with rocket propellants, rocket engines, and ramjets. She then began working on the Project RAND contract at Douglas where they focused on a new field of rockets, including the first American satellite. It is believed that Brill was the only female rocket scientist in the 1940s, which was partly what attracted her to this line of work.

After raising her children and returning to full-time work, she took a position at RCA’s rocket subsidiary, Astro Electronics. Here, she developed the concept for a new rocket engine, inventing the Electrothermal Hydrazine Thruster (EHT/Resistojet) for which she holds US Patent No. 3,807,657. Her innovation resulted in not only higher engine performance, but also increased the reliability of the propulsion system. She also proposed the use of a single propellant because of the value and simplicity that it would provide. The reduction in propellant weight requirements enabled either increased payload capability or extended mission life. The Resistojet proved to be more suitable for controlling satellites’ orbit and their communication.

Her invention became a standard in the industry and has translated into millions of dollars of increased revenue for commercial communications satellite owners. Large aeronautics and aviation companies including, but not limited to, RCA, GE, Lockheed Martin, and Orbital Sciences have used the EHT in their communication satellites.

Brill contributed to the propulsion systems of TIROS, the first weather satellite; Nova, a series of rocket designs that were used in American Moon missions; Explorer 32, the first upper-atmosphere satellite; and the Mars Observer, which in 1992 almost entered a Mars orbit before losing communication with Earth.

Between the years of 1981 and 1983, Brill also contributed to development of the rocket engines of NASA’s space shuttles. She finished her career at NASA, overseeing the Space Shuttle Solid Rocket Program and on the Aerospace Safety Advisory Panel.

In light of her brilliance in the field of rocket science and subsequent contributions, Brill was the recipient of many prestigious awards and founded scholarships and a lectureship.