We have been told since childhood never to play with fire. Although it is related to our daily lives, including home heating and water, cooking, electricity and more, fire is extremely dangerous. We were all more indoctrinated with how to put out fires instead of how to light them. We have all been told about its destructive properties if handled improperly, and this fire must be controlled. One of the advantages of adulthood, and especially of being a scientist, is that you get paid to play with fire. Despite the complexity of the fire, there are still many things we do not know about its behavior. As more and more of humanity travels to space and lives in microgravity, it is important to learn how fire behaves in this unique environment in order to better prepare for the worst-case scenarios. But what if we could control the fire so that it was less dangerous and less destructive to the environment here on Earth?
To gain a deeper understanding of combustion, a team of academic researchers, NASA’s Glenn Research Center and the agency’s biological and physical sciences department and other organizations recently completed a series of investigations by the International Space Station (ISS). In-orbit testing for the Advanced Combustion Project by Microgravity Experiments, or ACME, began in 2017 and included six successful studies of premixed gaseous fuel flames.
Premixed flames are those in which the fuel and oxidant remain separated before reaction or ignition, like a candle flame. Premixed flames occur in many of the daily use scenarios mentioned above, where the fuel and oxidant are mixed before the reaction.
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“The microgravity environment allows researchers to study the behavior of flame without the influence of gravity, so they can study the basic physics behind the structure and behavior of flame,” said Dennis Stocker, NASA’s Glenn ACME scientist. “This knowledge can help designers and engineers here on Earth to develop furnaces, power plants, boilers and other fuel systems that are more efficient, less polluting and safer.
The six ACME experiments were:
Burn Rate Emulator (BRE) – Demonstrated materials can burn for minutes in the absence of airflow in the crew’s atmosphere, which is being considered for future missions.
Coflow Laminar Diffusion Flame (CLD Flame) – provides comparative data on soot and highly diluted extreme values to improve computational models.
Cold Gas Flame Study (CFI-G) – resulted in pre-mixed cold flames from gaseous fuels without improvements, such as heated reagents, pulsed plasma or ozone addition, that were required in ground tests.
Effects of electric field on laminar diffusion flames (E-FIELD Flames) – demonstrates the potential use of electric fields to reduce emissions from premixed flames.
Flame design – demonstrates for the first time quasi-stable pre-mixed spherical flames and radiative heat loss leading to extinction for larger flames.
Structure and reaction of spherical diffusion flames (s-Flame) – provides data on the growth and disappearance of the flame to improve computational models.
The experiments were performed with a modular set of hardware in the space station’s integrated combustion stand (CIR). The tests were remotely commanded by NASA’s Glenn ISS payload operations center in Cleveland.
“More than 1,500 flames were set on fire, more than three times the originally planned number,” Stoker said. “Several” firsts “were also achieved, perhaps in the areas of cool and spherical flames.”
Stoker said about 50 employees from NASA’s Glenn, academia, and ZIN Technologies, Inc. have maintained ACME during four and a half years of in-orbit operations. In addition, more than 30 crew members from six countries played a significant role in tuning the hardware for each investigation and replacing gas cylinders, ignition nozzles and other experiment-specific hardware if necessary. The ACME hardware has been removed by the CIR to make room for solid fuel ignition or extinguishing or SoFIE hardware, which launched in February 2022, the next step in NASA’s in-orbit combustion study. ACME hardware is scheduled to return to Earth in the coming months with the intention of launching itself back into space with future experiments.
JAXA astronaut Norishige Kanai reconfigured the High-Depth Multispectral Camera (HiBMs) as part of the Integrated Combustion Stand (CIR) for the E-FIELD Flames Electric Field Effects Experiment experiment. (Credits: NASA)
Microgravity
Fire is not the only thing affected by microgravity, as weightlessness has long been known to cause many physiological biochemical changes in the human body, including bone loss, muscle atrophy, fluid displacement to the upper extremities and cardiovascular deconditioning ( changes in the structure of the heart and blood vessels). No one knows better than NASA astronaut Scott Kelly, who spent 340 days in space aboard the ISS in March 2015. While his twin brother Mark remained on Earth so the two could be studied separately, Scott sent routine samples of your blood, urine and feces back to Earth by returning astronauts. Scott’s samples show many genetic changes, including structural changes in his chromosomes. While 91 percent of Scott’s genes returned to normal after six months on Earth, nine percent remained in space, which included his high-immune immune system. His mental abilities have also decreased from pre-flight levels, with short-term and logical tests showing that he is slower and less accurate. This was both an important and historic study, as humanity hopes to send astronauts to Mars in the coming years and astronauts will have to spend more time in weightlessness than Scott did aboard the ISS. The more we can learn about working and living in microgravity, whether human or non-human, the better future astronauts will be in future missions.
What else will we learn about microgravity as humanity continues to move farther into space? Only time will tell and that’s why we science!
As always, keep doing science and keep looking up!
Sources: NASA, Advances in Space Research, Encyclopedia of Bioastronautics, Student Science News
Image presented: Combustion researchers designed space station experiments that analyzed the behavior of spherical flames in microgravity. (Credits: NASA)
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