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Survival in space without spacesuit

In scores of science fiction stories, hapless adventurers find themselves unwittingly introduced to the vacuum of space without proper protection. There is often an alarming cacophony of screams and gasps as the increasingly bloated humans writhe and spasm. Their exposed veins and eyeballs soon bulge in what is clearly a disagreeable manner. The ill-fated adventurers rapidly swell like over-inflated balloons, ultimately bursting in a gruesome spray of blood.

As is true with many subjects, this representation in popular culture does not reflect the reality of exposure to outer space. Ever since humanity first began to probe outside of our protective atmosphere, a number of live organisms have been exposed to vacuum, both deliberately and otherwise. By combining these experiences with our knowledge of outer space, scientists have a pretty clear idea of what would happen if an unprotected human slipped into the cold, airless void.

In the 1960s, as technology was bringing the prospect of manned spaceflight into reality, engineers recognized the importance of determining the amount of time astronauts would have to react to integrity breaches such as a damaged spacecraft or punctured space-suits. To that end, NASA constructed an assortment of large altitude chambers to mimic the hostile environments found at varying distances above the Earth, accounting for factors such as air pressure, temperature, and radiation. Adventurous volunteers were subjected to simulations of the conditions found several miles up, and a handful of animal tests were conducted with even lower pressures.

Using the data from these experiments and their knowledge of outer space, scientists were able to make some reasonable conclusions about how the human body would respond to sudden depressurization. A series of accidents over the years proved most of their extrapolations to be accurate. In 1965, in a space-suit test gone awry, a technician in an altitude chamber was exposed to a hard vacuum. The defective suit was unable to hold pressure, and the man collapsed after fourteen seconds. He regained consciousness shortly after the chamber was repressurized, and he was uninjured. In a later incident, another technician spent four minutes trapped at low pressure by a malfunctioning altitude chamber. He lost consciousness and began to turn blue, but escaped death when one of the managers kicked in one of the machine's glass gauges, allowing air to seep into the chamber.

Artist's rendering of a Soviet Soyuz spacecraftIn 1971, three Russian cosmonauts aboard an early Soyuz spacecraft tragically experienced the vacuum of space first-hand, as described in the Almanac of Soviet Manned Space Flight:

"…the orbital module was normally separated by 12 pyrotechnic devices which were supposed to fire sequentially, but they incorrectly fired simultaneously, and this caused a ball joint in the capsule's pressure equalization valve to unseat, allowing air to escape. The valve normally opens at low altitude to equalize cabin air pressure to the outside air pressure. This caused the cabin to lose all its atmosphere in about 30 seconds while still at a height of 168 km. In seconds, Patsayev realized the problem and unstrapped from his seat to try and cover the valve inlet and shut off the valve but there was little time left. It would take 60 seconds to shut off the valve manually and Patsayev managed to half close it before passing out. Dobrovolsky and Volkov were virtually powerless to help since they were strapped in their seats, with little room to move in the small capsule and no real way to assist Patsayev. The men died shortly after passing out. […] The rest of the descent was normal and the capsule landed at 2:17 AM. The recovery forces located the capsule and opened the hatch only to find the cosmonauts motionless in their seats. On first glance they appeared to be asleep, but closer examination showed why there was no normal communication from the capsule during descent."
When the human body is suddenly exposed to the vacuum of space, a number of injuries begin to occur immediately. Though they are relatively minor at first, they accumulate rapidly into a life-threatening combination. The first effect is the expansion of gases within the lungs and digestive tract due to the reduction of external pressure. A victim of explosive decompression greatly increases their chances of survival simply by exhaling within the first few seconds, otherwise death is likely to occur once the lungs rupture and spill bubbles of air into the circulatory system. Such a life-saving exhalation might be due to a shout of surprise, though it would naturally go unheard where there is no air to carry it.

In the absence of atmospheric pressure water will spontaneously convert into vapor, which would cause the moisture in a victim's mouth and eyes to quickly boil away. The same effect would cause water in the muscles and soft tissues of the body to evaporate, prompting some parts of the body to swell to twice their usual size after a few moments. This bloating may result in some superficial bruising due to broken capillaries, but it would not be sufficient to break the skin.

A NASA altitude chamberWithin seconds the reduced pressure would cause the nitrogen which is dissolved in the blood to form gaseous bubbles, a painful condition known to divers as "the bends." Direct exposure to the sun's ultraviolet radiation would also cause a severe sunburn to any unprotected skin. Heat does not transfer out of the body very rapidly in the absence of a medium such as air or water, so freezing to death is not an immediate risk in outer space despite the extreme cold.

For about ten full seconds– a long time to be loitering in space without protection– an average human would be rather uncomfortable, but they would still have their wits about them. Depending on the nature of the decompression, this may give a victim sufficient time to take measures to save their own life. But this period of "useful consciousness" would wane as the effects of brain asphyxiation begin to set in. In the absence of air pressure the gas exchange of the lungs works in reverse, dumping oxygen out of the blood and accelerating the oxygen-starved state known as hypoxia. After about ten seconds a victim will experience loss of vision and impaired judgement, and the cooling effect of evaporation will lower the temperature in the victim's mouth and nose to near-freezing. Unconsciousness and convulsions would follow several seconds later, and a blue discoloration of the skin called cyanosis would become evident.

At this point the victim would be floating in a blue, bloated, unresponsive stupor, but their brain would remain undamaged and their heart would continue to beat. If pressurized oxygen is administered within about one and a half minutes, a person in such a state is likely make a complete recovery with only minor injuries, though the hypoxia-induced blindness may not pass for some time. Without intervention in those first ninety seconds, the blood pressure would fall sufficiently that the blood itself would begin to boil, and the heart would stop beating. There are no recorded instances of successful resuscitation beyond that threshold.

Though an unprotected human would not long survive in the clutches of outer space, it is remarkable that survival times can be measured in minutes rather than seconds, and that one could endure such an inhospitable environment for almost two minutes without suffering any irreversible damage. The human body is indeed a resilient machine.

News Inside news:

Hypoxia (medical)
Hypoxia is a pathological condition in which the body as a whole (generalised hypoxia) or region of the body (tissue hypoxia) is deprived of adequate oxygen supply. Hypoxia in which there is complete deprivation of oxygen supply is referred to as anoxia.

Hypoxia is distinguished from apoxemia. Apoxemia is an abnormally low partial pressure of oxygen (PO2) in arterial blood [1]. A frequent error is to use the term hypoxemia to mean low oxygen content in arterial blood. It is possible to have a low oxygen content (eg due to anemia) but a high PO2 also incorrect use can lead to confusion.

Generalised hypoxia occurs in healthy people when they ascend to high altitude, where it causes altitude sickness, and the potentially fatal complications of altitude sickness, high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE). Hypoxia also occurs in healthy individuals when breathing mixtures of gases with a low oxygen content, for example while diving underwater, especially with closed-circuit rebreather systems that control the amount of oxygen in the air breathed in. Altitude training uses mild hypoxia to increase the concentration of red blood cells in the body for increased athletic performance.

Surviving Rapid/Explosive Decompression
Expected outcome of a space-equivalent decompression has improved dramatically in the past 40 years, from an a priori assumption of non-survivability to the possibility of survival and rehabilitation. This paper outlines the history of Man’s struggle with altitude, examines the known pathophysiology of Ebullism, explores the measures taken to improve survival in the Shuttle era, and investigates the state-of-the-art in treatment of rapid/explosive decompression.
see for details-
http://www.sff.net/people/Geoffrey.Landis/ebullism.html

Air embolism-
An air embolism, or more generally gas embolism, is a medical condition caused by gas bubbles in the bloodstream (embolism in a medical context refers to any large moving mass or defect in the blood stream). Small amounts of air often get into the blood circulation accidentally during surgery and other medical procedures, but most of these in veins are stopped at the lungs, and a venous air embolism that shows symptoms is very rare. Death may occur if a large bubble of gas becomes lodged in the heart, stopping blood from flowing from the right ventricle to the lungs (this is similar to vapor lock in engine fuel systems). However, the amount of gas necessary for this to happen is quite variable, and also depends on a number of other factors, such as body position.

Gas embolism into an artery, termed arterial gas embolism, or AGE, is a more serious matter than in a vein, since a gas bubble in an artery may directly cause stoppage of blood flow to an area fed by the artery. The symptoms of AGE depend on the area of blood flow, and may be those of stroke or heart attack if the brain or heart (respectively) are affected.

About The film Danny Boyle's Sunshine-
Some say the world will end in fire, some say in ice. Along with Robert Frost and Al Gore, most of us favor the fire hypothesis these days. But Sunshine (Fox Searchlight), the new sci-fi thriller directed by Danny Boyle (Trainspotting, 28 Days Later), asks us to give some serious consideration to the ice theory. What if, 50 years from now, the sun were burning out as the Earth descended into frozen darkness? What if a previous mission to reignite our solar system's star with a nuclear bomb the size of Manhattan had disappeared without a trace? And what if a second ship, ominously named Icarus II (because flying into the sun worked out so well for Icarus) embarked seven years later in an attempt to do the same thing?

Here's a hint: That would suck, especially if you were part of the eight-member international crew sworn to restart the sun, die trying, or both. As the film opens, Capt. Kaneda (Hiroyuki Sanada) is informing the crew that they're about to enter the "dead zone," a region close enough to the sun's surface that transmissions to and from Earth will soon become impossible. Capa (Cillian Murphy), the mission's physicist, is the last one able to record and send a message to his family, provoking a shoving match with Mace (Chris Evans), the hotheaded engineer. Meanwhile, medical officer Searle (Cliff Curtis) is developing a quasitheological (and thoroughly skin-damaging) obsession with staring at the sun. The two females on board are better at holding it together: Corazon (Michelle Yeoh) tends plants in the ship's self-sustaining oxygen garden, while Cassie (Rose Byrne) pursues a slow-burn flirtation with Capa (who, for a world-class nuclear scientist, is pretty emo).

Shortly thereafter, the ship picks up a signal from an unexpected place: It's a distress call from Icarus I. After a tense vote, the crew agrees to divert their mission and locate the other ship. But a crew member makes a fatal navigation mistake, and, bit by bit, the Icarus II, with its fragile self-contained ecosystem, and even more precarious social order, begins to fall apart.

Release link: http://www.slate.com