What if you go into space without an astronaut suit?

Despite there being a lot of speculation about the reactions that the human body would have to such conditions, a lot of them coming from our imagination or from science fiction movies, the truth is that it would be a horrifyingly amazing spectacle. Let's break down the process of exposing the human body to the vacuum and some variations on the main event.

Temperature and radiation

First, let's consider two main scenarios. Scenario one is located at a distance close to the planet earth, on the side of the planet that is in shadow. At this distance, the temperature of space is about -156 °C. Despite the fact that space is empty and there is no medium for it to travel through, remember that heat can be transferred by means of radiation, specifically the electromagnetic radiation emitted by the human body. Losing heat at about 958 Joules per second, your body would take roughly 72 minutes to cool from 36ºC to 20ºC. On the illuminated side, in scenario two, where a star lights you up, the behavior of the temperature would change, since ultraviolet rays would damage your skin and your body would heat up: the lit half of your body would receive 1,368 Joules per second, while the half in shadow would lose only 479 Joules per second.

Internal fluids

Being exposed to vacuum implies a variation in the behavior of substances and their boiling temperature, so body fluids boil. Boiling does not necessarily mean heating up: the fluids reach thermal and pressure conditions at which they turn into gas. By turning our internal fluids into gas, our body would swell up to twice its size. This means that no, definitely your cause of death in space would not be bursting like a balloon, since this phase is not lethal; on the contrary, the effects of exposure to a vacuum of up to 90 seconds can be reversible.

Lungs

Within 15 seconds of exposure to space you would lose consciousness, since your lungs would run out of oxygen reserves. Death would follow after about 2 minutes, when your organs collapse or fail for lack of oxygen, and you would not be aware of everything else your body had yet to go through.

Has anyone suffered a death like that?

A death from full exposure, such as being stranded without a spacesuit, has not happened as such in the history of space travel. However, in 1971, the Soviet spacecraft of the Soyuz 11 mission depressurized when a ventilation valve opened as its modules separated, before entering the atmosphere, and its three crew members, who were not wearing pressure suits, died of asphyxiation. They are the only people to have died above the Kármán line.