Consider an astronaut exploring the vast reaches of space which is mistakenly flung out of the spacecraft’s airlock. What would happen to the body if he was not wearing a spacesuit and was exposed to the vacuum of space?
The first thing to observe is that many Hollywood renditions of this scenario are exaggerated. They depict individuals bursting or quickly freezing to death because they are not wearing helmets or spacesuits. In actuality, the consequences would be similar but less dramatic. An astronaut floating in space without a suit would perish, but it would take minutes, not seconds, and it would be a grueling exit, with boiling physiological fluids and a virtually frozen nose and mouth.
Space is a vacuum empty of air. Therefore there is no atmosphere and no pressure imposed by air molecules, as there is on Earth. The temperature at which liquids boil and become gaseous is determined by atmospheric pressure. It is more difficult for gas bubbles to develop, rise to the surface, and escape when the pressure imposed by the air outside a liquid is high, as it is at sea level on Earth. However, because there is almost no air pressure in space, the boiling point of liquids falls dramatically.
“As you might expect, considering that water makes up 60 percent of the human body, this is a severe concern,” said Dr. Kris Lehnhardt, a NASA operational space medicine physician. When there is no pressure, liquid water in our bodies will boil, instantly transforming from a liquid to a gas. He said that all of your body’s water-containing tissues would begin to expand.
Some people have survived near-vacuums. Jim LeBlanc, an aerospace engineer at NASA, was working in a vast vacuum chamber in 1966, testing the performance of spacesuit prototypes. The line that supplied pressurized air to his suit was severed at some point during the experiment.
“As I staggered backward, I could feel the saliva on my tongue starting to bubble right before he fell unconscious, and that’s kind of the last thing I remember,” he said in the episode “The Space Suit” of the 2008 documentary series “Moon Machines.”
The development of gas bubbles in body fluids, known as ebullism, also occurs among deep-water scuba divers who surface too rapidly because they are transitioning from a high-pressure underwater environment to a low-pressure environment at the water’s surface.
Because the circulatory system has its internal pressure, blood traveling through veins in suit-less astronauts boils slower than water in the tissues. Yet, enormous ebullism in the body’s tissues would occur soon. A 2013 study published in the journal Aerospace Medicine and Human Performance indicated that previous exposure to vacuums in animals and people lost consciousness within 10 seconds. Some of them subsequently lost control of their bladders and bowel systems, and the swelling in their muscles reduced blood supply to their hearts and brains by acting as a vapor lock.
This is impossible for a person to live; death is almost inevitable in less than two minutes. According to NASA’s data, the vacuum of space would also draw air out of lungs, causing anyone to suffocate within minutes. The vacuum would continue to remove gas and water vapor from your body through your airways after an initial burst of air rushed out. The constant boiling of water would also have a cooling effect. The evaporation of water molecules would take heat energy from your body, causing the areas around your nose and mouth to practically ice. The rest of your body would cool as well, but at a slower rate since there would be less evaporation.