Fire acts strangely in microgravity.  Astronauts have lit more than 1,500 fires on the space station to find out why

Fire acts strangely in microgravity. Astronauts have lit more than 1,500 fires on the space station to find out why

Ever since childhood, we have all been told never to play with fire. Although relevant to our daily lives, including heating our homes and water, cooking, producing electricity and more, fire is extremely dangerous. We all became more indoctrinated with how to put out fires instead of how to start one. We have all been told about its destructive properties if they are handled incorrectly, and that the fire must be controlled. One of the benefits of adulthood, and especially being a scientist, is that you get paid to play with fire. Despite the complexity of the fire, there is still much we do not know about its behavior. With more and more of humanity traveling to space and living in microgravity, it is important to learn about how fire behaves in this unique environment to better prepare us for worst-case scenarios. But what if we could also control the fire so that it is not as dangerous and less destructive to the environment here on earth?

To gain a deeper understanding of combustion phenomena, a team of researchers from academia, NASA’s Glenn Research Center and the agency’s Biological and Physical Sciences Division and other organizations have recently completed a series of studies at the International Space Station (ISS). The orbit test for the Advanced Combustion via Microgravity Experiments, or ACME, project began in 2017 and included six successful investigations of non-premixed flames of gaseous fuel.

Non-premixed flames are those where the fuel and oxidant remain separate before reaction, or ignition, as a light flame. Premixed flames occur in many of the everyday scenarios mentioned above, where the fuel and oxidant are mixed before the reaction.

“A microgravity environment enables researchers to explore flame behavior without the influence of gravity, so they can investigate the underlying physics behind flame structure and behavior,” said Dennis Stocker, ACME Project Scientist at NASA Glenn. “This knowledge can help designers and engineers here on earth develop furnaces, power plants, boilers and other combustion systems that are more efficient, less polluting and safer.”

The six ACME experiments were:

Burning Rate Emulator (BRE) – proven material can burn for minutes in the absence of airflow in the crew’s atmosphere considered for future missions.

Coflow Laminar Diffusion Flame (CLD Flame) – provided benchmark data on sooty and very dilute extremes to improve computational models.

Cool Flames Investigation with Gases (CFI-G) – resulted in unmixed cold flames of gaseous fuels without improvements, such as heated reactants, pulsed plasma or ozone addition, which have been required in ground testing.

Electric Field Effects on Laminar Diffusion Flames (E-FIELD Flames) – demonstrated the potential use of electric fields to reduce emissions from premixed flames.

Flame Design – demonstrated, for the first time, quasi-stable non-premixed spherical flames and radiant heat loss leading to extinction for larger flames.

Structure and response of spherical diffusion flames (s-Flame) – provided data on flame growth and extinction to improve calculation models.

The experiments were performed with a single modular set of hardware in the space station’s Combustion Integrated Rack (CIR). The tests were remotely controlled from NASA’s Glenn ISS Payload Operations Center in Cleveland.

“Over 1,500 flames were ignited, more than three times as many as originally planned,” Stocker said. “Several” first “were also achieved, perhaps most remarkably in the areas of cool and spherical flames.”

Stocker said that about 50 employees from NASA Glenn, the academy and ZIN Technologies, Inc. supported ACME for four and a half years in orbit. In addition, more than 30 crew members from six countries played an important role in setting up the hardware for each survey and replacing gas cylinders, spark plugs, and other experiment-specific hardware as needed. The ACME hardware has been removed from the CIR to make way for Solid Fuel Ignition and Extinction, or SoFIE, hardware launched in February 2022, which is the next step in NASA’s research into combustion combustion. The ACME hardware is scheduled to return to Earth in the coming months with the intention of re-launching to the space station with future experiments.

JAXA astronaut Norishige Kanai reconfigures the High Bit-depth Multispectral Camera (HiBMs) in the Combustion Integrated Rack (CIR) experiment for electric field effects on laminar diffusion flames (E-FIELD Flames). (Credit: NASA)

Microgravity

Fire is not the only thing affected by microgravity, as weightlessness has long been known to cause many physiological biochemical changes to the human body, including bone loss, muscle atrophy, displacement of fluids to the upper extremities, and cardiovascular deconditioning (ie changes in the structure of the heart and blood vessels). No one knows about this better than NASA astronaut Scott Kelly, who spent 340 days in space aboard the ISS starting in March 2015. While his twin brother Mark remained on Earth so that the two could be studied separately, Scott sent routine samples of his blood, urine and feces back to Earth via returning astronauts. Scott’s samples showed many genetic changes, including structural changes in his chromosomes. While 91 percent of Scott’s genes were back to normal after six months back on Earth, nine percent remained in space, which included his immune system being on high alert. His mental abilities had also declined from preflight levels, with short-term and logical tests showing that he was slower and less accurate. This was both an important and historical study because humanity hopes to be able to send astronauts to Mars in the coming years, and the astronauts will have to spend more time in weightlessness than Scott did on board the ISS. The more we can learn about working and living in microgravity, whether it is human or non-human research, the better future astronauts will have it on future missions.

What more will we learn about microgravity as humanity continues to venture further into the cosmos? Only time will tell, and that’s why we do research!

As always, keep up the good work and keep up the good work!

Sources: NASA, Advances in space research, Encyclopedia of Bioastronautics, Science news for students

Selected image: Combustion scientists designed experiments on the space station that analyzed the behavior of spherical flames in microgravity. (Credit: NASA)

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