As we advance deeper into space, what should we do if we encounter a fire?

Author: Qian Hang, aerospace science expert at the First Academy of China Aerospace Science and Technology Corporation

With the development of science and technology, "heading into space" is no longer just a slogan. Perhaps one day, we will be able to board the "Dream Boat" spacecraft and extend our exploration into the more distant universe.

Image source: movie "Interstellar"

However, before we imagine the joy of exploring the unknown universe, we first have to face a series of very serious and realistic problems: How to deal with emergencies in a closed spacecraft?

The first and foremost problem is fire.

Is fire in the universe more terrifying?

This is not an unfounded worry. As early as 1967, the US Apollo 1 crew encountered a fire during ground testing, and three astronauts died. In 1997, the Russian Mir space station also encountered a high-risk fire. Fortunately, the astronauts wore breathing masks, endured the high temperature and smoke to put out the open flames, overcame the lack of oxygen in the small space, and worked hard to contact the ground team. Finally, under the guidance of experts, they turned the danger into safety.

Image source: Science Popularization China

There are densely packed electronic equipment on the spacecraft, a high-pressure oxygen environment inside the cabin that can help the development of flames, and an unavoidable vacuum outside the cabin. If there is a fire in the universe, there will be no firefighters to help us solve the problem.

How is fire different in the universe?

Friends who like science fiction or aerospace probably know that one of the differences between life in the universe and life on Earth is weightlessness.

On Earth, under the influence of gravity, hot air rises due to the pressure of the surrounding air, and the flame appears to burn upwards. However, in the weightless environment of space, the flame has no tendency to rise upwards, so the shape of the flame is more inclined to be round. At the same time, in space, because the influence of gravity is small, the flame can be more stable because there is no gravity to distort it.

Image source: NASA

And precisely because there is no gravity, water cannot be used to put out fires in space, because water will not fall and flow in space like it does on Earth, but will float in the cabin and cause short circuits in the cabin's instruments and equipment, or even cause the spacecraft to malfunction, so new fire-fighting measures are needed.

If a small fire occurs, astronauts can use fire-fighting gloves to put out the flames. If the fire is serious, special fire extinguishing agents, temporary isolation of compartments and the discharge of carbon dioxide into them, emergency decompression of the cabin, etc. are all solutions to space fire-fighting.

If you want to prevent fire, start with fire

How to gain practical experience in extinguishing fires in space? Scientists say this requires "setting fires" in space first.

NASA conducted three spacecraft fire experiments to ignite the Cygnus spacecraft from 2016 to 2017; my country's Shijian-10 recoverable satellite completed 19 experiments in space, two of which were related to fire.

Image caption: Image of methane combustion on the space station (left) and image of methane combustion under the same conditions on the ground (right)

Image source: Institute of Engineering Thermophysics, Combustion Energy Center of Tsinghua University

Although the above article points out the horror of a lot of fires in the universe, being able to safely "set fires" in the universe is also a manifestation of technical capabilities. In 2023, Chinese astronauts successfully performed the first on-orbit ignition test in the Combustion Science Experiment Cabinet in the Dream Spacecraft. This experiment verified the completeness of the functions of the space station's combustion science experiment system and the accuracy and scientificity of the overall experimental process, and also laid a good foundation for subsequent space science combustion experiment projects.

Today, the pace of space exploration continues to move forward, and higher standards are also being put forward for the safe operation of space stations: for example, it is necessary to use materials with better high-temperature insulation properties to replace cheap but flammable aluminum alloys, objects cannot be stacked in a cluttered manner, fire safety passages must be retained, two independent fire extinguishing systems must be set up, and safety drills must be conducted regularly.

With the joint efforts of scientists and astronauts, in the near future we may be able to embark on a safer journey of space exploration and see the sea of ​​stars together!