New Delhi: Astronauts face numerous risks during space flight, including microgravity and radiation exposure. However, the most immediate and significant threat is fire, especially on long missions to Mars or beyond Low Earth Orbit where escape options are limited. Scientists are now focusing on understanding fire behavior in space to enhance astronaut safety.
Researchers from the Center of Applied Space Technology and Microgravity (ZARM) at the University of Bremen have published a new study titled “Effect of oxygen concentration, pressure, and opposed flow velocity on the flame spread along thin PMMA sheets” in the Proceedings of the Combustion Institute. Led by Hans-Christoph Ries, the study investigates fire risks on spacecraft.
“A fire on board a spacecraft is one of the most dangerous scenarios in space missions,” said Dr. Florian Meyer, head of the Combustion Technology research group at ZARM. “There are hardly any options for getting to a safe place or escaping from a spacecraft. It is therefore crucial to understand the behavior of fires under these special conditions.”
Since 2016, ZARM has been studying fire behavior in microgravity conditions, similar to those on the International Space Station (ISS). These conditions include Earth-like oxygen levels, forced air circulation, and ambient pressure. Previous NASA experiments have shown that fire behaves differently in microgravity, initially burning with a smaller flame and taking longer to spread. However, fire in microgravity burns hotter, potentially igniting materials that are non-combustible on Earth and releasing toxic chemicals into the spacecraft’s air.
Future spacecraft for Mars missions will have lower ambient air pressure to reduce weight and facilitate quicker preparation for external missions. This lower pressure necessitates higher oxygen levels to meet astronauts’ respiration needs, potentially up to 35%, significantly increasing the fire risk.
In their latest experiments, the ZARM team tested fire behavior under these revised conditions using polymethyl methacrylate (PMMA), a common material being considered for future spacecraft due to its light and shatterproof properties. They varied three environmental factors: ambient pressure, oxygen content, and flow velocity, using the Bremen Drop Tower to simulate microgravity.
The results showed that while lower ambient pressure dampens fire, higher oxygen content significantly increases fire risk, with flames spreading up to three times faster than on Earth. Increased airflow in a higher-oxygen environment exacerbates this risk by delivering more oxygen to the flame.
“Our results highlight critical factors that need to be considered when developing fire safety protocols for astronautic space missions,” said Dr. Meyer. “By understanding how flames spread under different atmospheric conditions, we can mitigate the risk of fire and improve the safety of the crew.”
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