An Interview with Ann and Manuel Varela: Who was Yvonne Brill—and what did she have to do with rocket science? 

Jun 4, 2021 by

And I just kept pushing. I didn’t care whose shins I kicked. And of course, once you get it in space and it works, then it’s fine.” 

—Yvonne Madelaine Brill  

Michael F. Shaughnessy 

1) A very famous female chemist/engineer and scientist was Yvonne Brill. Where was she born, and what do we know about her early education? 

Yvonne Claeys Brill was born in Winnipeg, Manitoba, Canada, on December 30, 1924, and grew up in a nearby suburb. Her parents were Belgian immigrants who encouraged each of their children to succeed academically. Observing university students on the streetcars in her hometown and commuting to and from classes also motivated and inspired her to pursue a higher education degree. She did not have the encouragement of her teachers, as was to be expected for females at that time due to the subjects she was most interested in, those being chemistry, mathematics, and physics. Acquiring a teaching certificate was thought to be more appropriate.  

She earned her B.S. in Mathematics in 1945 from the University of Manitoba, though she was initially interested in engineering, a field in which females were restricted.

Brill was involved in several extracurricular programs at the University of Manitoba, such as Secretary and Editor in Chief of the Question Mark, Science Students’ Council member, the Science Co-Ed Council member, and the University Speed Skating Team.   

Immediately following graduation, she got a job offer from Douglas Aircraft Company in Santa Monica, California, to work in their research department. Brill was then offered a one-year contract that involved a transfer to the Aerodynamics department. Douglas Aircraft then shifted to the new field of rockets with a contract to work on Project RAND “research and development.” This new undertaking hoped to launch an Earth-orbiting satellite without the physical presence of humans. 

Later, Project RAND became the renowned Rand Corporation, one of the first research organizations collaborating with the U.S. Air Force. With Brill’s new appointment, she participated in innovative studies that characterized rocket propellant operations. Specifically, Brill computed and charted high-performance propellant temperature combinations, which were included in the U.S. National Bureau of Standards tables for some time.   

Brill began working on her Master of Science in Chemistry at the University of Southern California before the RAND project had begun, so she chose to attend classes by night and work at Douglas by day. She completed her M.S. in 1951.  

Eventually, the RAND project became more theoretical in nature, so Brill began working for the Marquardt Corporation, where she was the sole female engineer. Her role as group leader for the igniters and fuels team was instrumental in designing ignition systems for a U.S. supersonic ramjet missile. See Figure 1. 

Figure 1. Cutaway of the intake section of the Marquardt RJ43-MA-9 Ramjet Engine for BOMARC missile located at the San Diego Air & Space Museum annex Gillespie Field.

Brill met a research chemist, William Franklin Brill, who attended a Linus Pauling lecture at UCLA through some mutual friends. He became her husband the following year, in 1951. The couple’s employment opportunities were bicoastal; however, Brill was quoted to say, “Good jobs are easier to find than good husbands,” so they moved to the East Coast for his job a year after the wedding. Her career path took her to a full-time job at Wright Aeronautical and part-time work at FMC Corporation during the early childhood years of her three children. Then, when her children were a bit older, in 1966, she took a full-time job at RCA’s rocket affiliate Astro Electronics where she patented her propulsion system for satellites. 

Brill worked on significant projects such as the propulsion systems for the first weather satellite, Tiros, and on a series of rockets designed for U.S. missions to the moon for Nova. From 1981 to 1983, she worked at NASA’s headquarters in Washington DC, assisting with developing the rocket motor for the space shuttle. Next, Brill returned to RCA for a few years. From 1986 to 1991, she was the propulsion manager for the International Maritime Satellite Organization in London until she retired. 

2) Back in her time, there was much discrimination against women. What obstacles did Brill have to overcome? 

In her lifetime, Brill encountered several obstacles of a serious nature. For example, her father had wanted her to run a business by opening up a shop in her hometown. Further, one of her high school teachers was reported to have discouraged her when the question of higher education was considered. Brill’s high school teacher said that women in the sciences don’t go anywhere. Remarkably, Brill had chosen to ignore the advice of both her father and her secondary education science teacher.  

Once Brill did graduate from high school, her desire to study engineering had been thwarted. At the University of Manitoba, women were not allowed to enroll in engineering courses.  The apparent reasoning for this policy was based on a curriculum requirement, which was a “summer engineering camp.” The university officials were reported to have reasoned that specialized accommodations for women to attend were not possible. Brill had been denied admission to the university’s school of engineering. Thus, with engineering out of her reach, Brill majored in mathematics and chemistry while enrolled at the university.  

In the late 1940s and early 1950s, Brill hoped to acquire a Ph.D. degree in chemistry. However, she encountered entrenched sex discrimination in the hiring practices of chemistry-related jobs. In rocket engineering, Brill found the area exciting and elected to make a career out of it. She had realized that there were so few women in the engineering arena that they could not possibly establish new rules to keep only her out of the running for jobs. Such overt sex discrimination policies would have been too obvious. She further learned that in engineering, applying new knowledge would be an actual test of her abilities.

She knew that as long as she was willing and capable of doing the application work, her colleagues would respect her. These proved to be astute observations on Brill’s part.  

Nevertheless, when Brill entered the workforce of aerospace engineering, known colloquially as rocket science, primarily men dominated it. She was paid a salary that was not even remotely equal to her male counterparts, whose qualifications were virtually identical to hers. Further, she had to move constantly to follow her husband wherever his career dictated. Part of her coping strategy was to take on part-time work while staying in her field of expertise. The part-time job permitted Brill to stay at home and care for their three children.  

Brill would never get a doctoral degree.  

In later years, she was reported to have held a healthy attitude about the challenges she had encountered throughout her life. She never became bitter about having to deal with these problematic barriers. She managed to persevere and overcome each of these obstacles and make outstanding contributions to the science of rocket propulsion. During an interview late in life, Brill was asked how she succeeded when the odds were stacked against her. Brill replied, “I just had the drive to do it!”

Brill would become not only a role model for young girls hoping to become rocket scientists, but she also became a mentor and an active advocate for aspiring female scientists. Brill would participate in the “Take your daughters to work” program. Brill also was an active member of the Society of Women Engineers. Brill worked tirelessly to increase the membership numbers of women in the National Academy of Engineering and the Aerospace Engineering Division.  

3) Rocket propellants, rocket engines, and “ramjets”—all “rocket science”—so to speak—what were Brill’s contributions?  

While she was a graduate student, studying at night, Brill took on employment at Marquardt Corporation Company, housed in Van Nuys, in California, where she perfected a rocket propellant system. Brill recalled that they had reluctantly hired her. However, they knew they needed someone on board who had working knowledge on propellants because the outfit had Navy contracts that required new fuel production for the ramjet, a new type of rocket engine. These ramjet devices were regarded as a kind of high-capacity air-breathing rocket engine. When she joined the little company, Brill was the only female engineer on their staff. At Marquardt, Brill was in charge of studying fuels and ignitors that were to be incorporated into the ramjets. She focused her attention on stabilizing the flame that entered the ramjets. Brill looked at a series of high-energy solid fuels for that flame-stabilization process that could be used for obtaining reliable ignition at high altitudes and fast rocket speeds. She oversaw incorporating the new solid fuels into the ramjet engines. When completed, Brill’s innovations would successfully conduct the first supersonic flights with the ramjets in 1950 at Point Mugu, in California.  

With Brill’s expertise in chemistry and experience with ramjets, she focused her attention on solid propellants for rockets for the next stage of her career. Brill’s rocket propellant studies led to one of her most influential inventions—a rocket engine called the hydrazine resistojet thruster.

In the mid-1960s, she began working for RCA Astro Electronics. She was their first engineer to be hired who had expertise in rocket propulsion technology. Brill’s first assignment involved determining the best way to enhance the efficiency of the rockets that would send new communication satellites into orbit around the Earth. Her responsibility was to focus on the right rocket fuel to generate the best propulsion necessary for the mission. Brill’s group had considered hydrogen peroxide, but the chemical proved to be challenging to work with while in the laboratory.  

At that time, she learned that a group based in Caltech at the Jet Propulsion Laboratory had similar difficulties with another chemical called hydrazine. See Figure 2. In a brilliant deduction, Brill considered the best way to find combinations of chemicals to enhance the propulsion efficiency. She reasoned that if the equations, which describe the relationships between chemical propellant combinations and propulsion performance, are examined closely, then the best rocket performance could be plotted as a function of the temperature in the propellant chamber. Brill had deduced that when the square root of the chamber temperature was considered over the molecular weights of the products made during combustion, a straight line could be generated when she plotted the propulsion performance!  

File:Hydroxyzine synthesis.png

Figure 2. A synthetic scheme for the production of hydroxyzine.

With her newfound deduction regarding chamber temperature and performance output, Brill thought about the combustion products generated from hydrazine, such as hydrogen, nitrogen, and ammonia. She knew that hydrazine liberated a tremendous amount of heat because of its exothermic properties. Brill then reasoned that if the combustion products, the waste hydrogen, ammonia, and nitrogen, were heated up somehow, then the exothermic process would be significantly enhanced. Brill figured that if one could heat the exhaust products generated from the initial combustion process with a simple electrical heater, then the square root of the temperature equation predicted an enhancement in propulsion performance of 30%! This level of performance produced a remarkable discovery in propellant efficiency enhancement. It proved to be an important contribution towards building a reliable and economically feasible rocket thruster. Brill’s new, highly efficient thruster device was called the electrothermal hydrazine thruster or the hydrazine resistojet. Many space programs would adopt Brill’s rocket engine thruster device to send hundreds of spacecraft into orbit around Earth.  

4) Brill spent five years in London. What did she do there (other than visit Big Ben)? 

Starting in 1986, Brill became propulsion manager for England’s satellite program at the International Maritime Satellite Organization, housed in London. The organization had been involved with the United Nations as a charter. It was interested in developing communications between satellites orbiting the Earth and ships and other mobile units on the ground. Brill worked on the rocket engine that sent one of these prototype communications satellites, called INMARSAT-2, into space orbit around the Earth in 1990. The program has since helped establish a widely used satellite communications (SATCOM) system for mobile phones, faxing, telex, and data communications systems. See Figure 3. 

Figure 3. An RCA SATCOM II communications spacecraft is launched on a Delta 3926 launch vehicle.

5) Great quote: “It took one woman to invent rocket thrusters and two men to invent Post-It Notes.”  Your thoughts? 

We think it is a testament to the brilliance displayed by Brill’s innovative achievements in aerospace engineering. As an inventor, Brill revolutionized the communications satellite industry. The quote seems to stem from the occasion in 2010 when Brill was inducted into the National Inventor’s Hall of Fame and the two inventors of the Post-It notes. The source of the quote is Monica Hesse, a reporter from the Washington Post, who in 2010 wrote about the induction ceremonies in March of that year. Hesse astutely pointed out that Yvonne Brill was the only woman out of the 16 inductees that year to be included in the Hall of Fame honor for inventors. Hesse further noted that Brill’s patent (no. 3,807,657) for the electrothermal hydrazine thruster invention was responsible for keeping Earth-orbiting satellites in their proper places in outer space. As an aside, Hesse noted that while it took two men to invent the Post-Its, it nevertheless took one woman to create the idea for a rocket thruster. The Washington Post quotation has since taken a viral life of its own on the Internet and has become the stuff of rocket science lore.  

6) Brill is credited with the electrothermal hydrazine thruster. For what is this used? 

In the late 1960s, Brill began work towards what is considered her most significant contribution to rocket science: the electrothermal hydrazine thruster, known as the resistojet engine. Rocket science historians have noted Brill’s spacecraft propulsion invention as a “game-changer” because it permitted the rocket builders to consider only one fuel type. The novel use of a single fuel, hydrazine, offered a new simplicity to the rocket engine design. Before Brill’s invention, using a single propellant was not a high-performance option compared to so-called bipropellants. Brill’s invention further meant that relatively heavier payloads could be sent into space and at higher velocities required to leave the Earth’s gravitational pull. The electrically-heated hydrazine in Brill’s resistojet thruster now made possible the insertion of spacecraft, satellites, and even stations into Earth orbit. Furthermore, with the added efficiency of propulsion provided by Brill’s electrothermal hydrazine thruster, stable orbits were possible. This secure orbital insertion of spacecraft now permitted longer mission times.  

For the first time in history, Brill’s innovative electrothermal resistojet thruster was applied to a satellite in 1965 with the launching of Vela-1, but the propellant had been nitrogen or ammonia chemicals. In 1967, Brill proposed using hydrazine in the electrically heated resistojets.  

Brill’s electrothermal hydrazine thruster invention was used commercially for the first time in the early 1980s, when TRW Systems, Inc., launched a communications satellite called Intelsat 502. The corporation was involved in establishing a North-South Station-Keeping (NSSK) communications program, and Brill’s propulsion invention made the commercial application possible. In 1981, the NSSK program placed the communications satellite into a geosynchronous orbit in which the spacecraft has the same rotational speed and direction as ground-based facilities on Earth. In April of 1983, Aerojet Rocketdyne used the Brill invention, called the MR-501 thruster, to bring the SatCom1R satellite into orbit. This triumphant entry of the communications satellite into a low-Earth geosynchronous orbit paved the way for the widespread use of Brill’s electrically heated ramjet propulsion invention. The space-faring hydrazine resistojet concept developed and invented by Brill became the industry standard for satellite placement into low Earth orbits. The Brill thruster also permitted stationary geosynchronous orbits.  

7) Prior to Brill’s work, hydrogen peroxide was used for rocket propulsion. Why was this inefficient and ineffective? 

Hydrogen peroxide was used initially as a rocket propellant starting in the mid-1930s. See Figure 4. Germany used hydrogen peroxide to run their military machine, such as powering up their Messerschmidt Komet rocket fighter plane and running their turbo-pump gas generator for the V-2 rocket. The Germans had also used hydrogen peroxide for the propulsion of their submarines and torpedoes.  

File:Hydrogen peroxide.png

Figure 4. Hydrogen peroxide structural diagram.

At the time, the chemical provided a relative display of thrust with a certain degree of instability that provided a catalytic decomposition into an oxygen-rich hot gas. It could be used as a monopropellant with particular altitude control system (ACS) thrusters. Another function of hydrogen peroxide was its use as an oxidizer for axial thrusters of rockets.  

However, hydrogen peroxide can be highly toxic to humans, and as such, it was not easy to use practically without the high maintenance costs of safety. It was also expensive to use operationally, not to mention the burden of its use from an environmental standpoint. However, one of the principal causes for the reduced enthusiasm of hydrogen peroxide for use as a rocket engine propellant came from the much-improved performance rates due to Brill’s monopropellant hydrazine heated electrically in the resistojet thrusters. Lastly, Brill’s electrothermal hydrazine-based thruster design was less complicated to operate than the complex nature of the hydrogen peroxide engines. Thus, the hydrogen peroxide chemical for rocketry engine design would be eventually phased out. 

8) Before Brill’s death, she was honored by President Barack Obama. What were some of her recognitions? 

Brill had received the Society of Women Engineers (SWE) award in 1986 and was elected the following year into the National Academy of Engineering to further spacecraft propulsion technology and propellant performance. Additional career honors included: the NASA Distinguished Public Service Medal in 2001, given to non-Government employees; the Wylde Propulsion award from the American Institute of Aeronautics and Astronautics (AIAA) in 2002; an Honorary Fellow of the AIAA awarded in 2008; the John Fritz Medal awarded from the American Association of Engineering Societies in 2009; and induction in the National Inventors Hall of Fame for inventing the Dual Thrust Level Monopropellant Spacecraft Propulsion System in 2010.  

In 2011, President Obama awarded Brill the National Medal of Technology and Innovation, the nation’s highest honor for engineers and innovators, at a White House ceremony. See Figure 5. When asked how she thrived and became a pioneer in her field, she replied, “I just had the drive to do it!” 

Figure 5. National Medal of Technology and Innovation.

Brill focused on advancing women’s careers in engineering and science during the last two decades of her life by putting forth their names for awards and prizes of which she thought they merited. 

9) What have I neglected to ask about this famous woman scientist? 

Brill’s history-making invention of an innovative rocket thruster system (the electrothermal hydrazine resistojet) was used widely throughout the spaceflight industry. The Brill rocket thruster made it possible to use electricity to heat hydrazine fuel, thus enhancing rocket performance efficiency. The invention was used to launch and maintain satellites in long-term orbits around the Earth. The Brill rocket thruster is the industry standard to this day. Brill made, however, other significant contributions to aerospace engineering.  

In 1946, while working for Douglas Aircraft, Brill served on the innovative Project RAND, which later became the RAND Corporation. At the time, Brill’s project at RAND dealt with the then top-secret mission to place unmanned Earth-orbiting satellites in space.  

Brill was also a key player in developing the rocket propulsion systems that powered up TIROS (Television Infrared Observation Satellite), which, in 1960, is the first weather satellite in the world. The TIROS program was a widely used weather satellite program for over 25 years. Several of the original TIROS satellites are still in orbit. See Figure 6. 

Figure 6. Television infrared observation satellite TIROS 1.

Brill’s innovative propulsion systems were used for a pioneering high-altitude satellite called Explorer-32, launched in 1966. The orbiting satellite was used to study the Earth’s upper atmospheric contents.  

Brill was also a lead manager for the NOVA spacecraft propulsion system in the 1980s. Using Brill’s propulsion device, which used electric propulsion for the first time, the Navy launched a NOVA satellite that facilitated submarine communications and provided so-called ephemerous data (short-lived) in real-time.  

Also, in the 1980s, Brill was a manager for the Solid Rocket Motor Program for NASA’s space shuttle, officially called the Space Transportation System (STS). Brill had been key to identifying the lack of adequate infrastructure needed to support the production of solid rockets and supply their fuel. Brill designed, planned, and helped to build propellant production facilities, unique railroad cars for transport and supply of propellants. Brill’s effort led to the proper manufacture and supply infrastructure was realized in time for the space shuttle flights. At NASA, Brill served on the Aerospace Safety Advisory Panel between 1994 and 2001 to enhance space shuttle flights’ safety. She had been the first woman to serve on that NASA panel. 

In the early 1990s, Brill had worked on the propulsion rocket that sent the Mars Observer spacecraft to Mars. Unfortunately, just before reaching the planet, the Mars Observer spacecraft lost all communication with Earth. Because the Observer failed to insert into Mars orbit, it flew by the fourth planet instead, and the mission was considered a failure. Brill had not been involved with the planetary insertion problem.  

For additional information about this remarkable aerospace engineer, visit the following:  

How Yvonne Brill’s rocket design works: 

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