Exposure to Space


Temperature Of Outer Space

Outer space is really, really cold. -454.8 degrees Fahrenheit (-270 degrees Celsius) cold. Brr… Well, that’s not completely true. On Earth you lose heat by convecting it into the air around you. In space, though, there is no medium into which you convect heat. Aside from evaporative cooling, the only way to lose heat is to radiate it, which is a far slower process. Only matter can have a temperature, nothingness doesn’t. And space is mostly a big empty void of nothingness. However, most random objects floating deep in space will be that temperature or very close to it.

Outer space lacks air, so heat is only transferred via infrared radiation. This means that heat loss occurs very gradually. An object in deep space will eventually get to a few degrees Kelvin, but it’s not the instant blood-freeze that’s sometimes depicted in the movies. More like hours to freeze, and there’s plenty of things to kill you before that. Something that’s been floating in space for a long time will be really cold, too. Touching it would be horrible idea, as conduction would steal the heat out of you.

At the same time, solar winds can be really, really hot. The sun has a surface temperature of 9,980 °F (5,526 °C), and it radiates quite a bit of infrared. Likewise, interstellar gas clouds may be thousands of degrees.

The real nasty part here is the extremes of temperature, and the stresses they produce on objects outside of atmospheres and convection. At high earth orbit, the side of you that’s in the sun will eventually reach 248 °F (120 °C). At the same time, the parts of you in the shade could eventually get as cold as -148 °F (-100 °C). The hot part is above boiling (212 °F / 100 °C), the cold part is below the harshest antarctic record (-128 °F / -89 °C). The human body doesn’t take those temperatures very well, especially not at the same time.

The temperature of other items will depend upon a number of factors: how reflective they are, how close they are to the sun and whether or not they’re pointed at it, their shape and mass, how long they’ve been out there, etc. Polished aluminum pointed at the sun from roughly the same distance as the earth might heat up to 850°F. Something that’s got an opaque coat of high-quality white paint might not get up above -40°F even if aimed at the sun.

Will You Stay Conscious?

Medicine defines the “time of useful consciousness”, that is, how long after a decompression incident will someone be awake and be sufficiently aware to take active measures to save their lives. The expected result of vacuum exposure and time of useful consciousness is ~9 to 11 seconds. In rapid sequence thereafter, paralysis will be followed by generalized convulsions and paralysis once again. During this time, water vapor will form rapidly in the soft tissues and somewhat less rapidly in the venous blood. This evolution of water vapor will cause marked swelling of the body to perhaps twice its normal volume unless it is restrained by a pressure suit. (It has been demonstrated that a properly fitted elastic garment can entirely prevent ebullism.)

Would Your Blood Boil?

Your blood is at a higher pressure than the outside environment. A typical blood pressure might be 75/120. The “75” part of this means that between heartbeats, the blood is at a pressure of 75 Torr (equal to about 100 mbar) above the external pressure. If the external pressure drops to zero, at a blood pressure of 75 Torr the boiling point of water is 46 degrees Celsius (115 F). This is well above body temperature of 37 C (98.6 F). Blood won’t boil, because the elastic pressure of the blood vessels keeps it it a pressure high enough that the body temperature is below the boiling point— at least, until the heart stops beating (at which point you have other things to worry about!).

Would You Freeze?

Space isn’t “cold,” it isn’t “hot”, it really isn’t anything. What space is, though, is a very good insulator. (In fact, vacuum is the secret behind thermos bottles.) Astronauts tend to have more problem with overheating than keeping warm.

If you were exposed to space without a spacesuit, your skin would most feel slightly cool, due to water evaporating off your skin, leading to a small amount of evaporative cooling. But you wouldn’t freeze solid!

Explosive Decompression

Gastrointestinal Tract During Rapid Decompression
One of the potential dangers during a rapid decompression is the expansion of gases within body cavities. The abdominal distress during rapid decompression is usually no more severe than that which might occur during slower decompression. Nevertheless, abdominal distention, when it does occur, may have several important effects. The diaphragm is displaced upward by the expansion of trapped gas in the stomach, which can retard respiratory movements. Distention of these abdominal organs may also stimulate the abdominal branches of the vagus nerve, resulting in cardiovascular depression, and if severe enough, cause a reduction in blood pressure, unconsciousness, and shock. Usually, abdominal distress can be relieved after a rapid decompression by the passage of excess gas.

The Lungs During Rapid Decompression.
Because of the relatively large volume of air normally contained in the lungs, the delicate nature of the pulmonary tissue, and the intricate system of alveolar airways for ventilation, it is recognized that the lungs are potentially the most vulnerable part of the body during a rapid decompression. Whenever a rapid decompression is faster than the inherent capability of the lungs to decompress (vent), a transient positive pressure will temporarily build up in the lungs. If the escape of air from the lungs is blocked or seriously impeded during a sudden drop in the cabin pressure, it is possible for a dangerously high pressure to build up and to overdistend the lungs and thorax. No serious injuries have resulted from rapid decompressions with open airways, even while wearing an oxygen mask, but disastrous, or fatal, consequences can result if the pulmonary passages are blocked, such as forceful breath-holding with the lungs full of air. Under this condition, when none of the air in the lungs can escape during a decompression, the lungs and thorax becomes over-expanded by the excessively high intrapulmonic pressure, causing actual tearing and rupture of the lung tissues and capillaries. The trapped air is forced through the lungs into the thoracic cage, and air can be injected directly into the general circulation by way of the ruptured blood vessels, with massive air bubbles moving throughout the body and lodging in vital organs such as the heart and brain.
The movement of these air bubbles is similar to the air embolism that can occur in SCUBA diving and submarine escape when an individual ascends from underwater to the surface with breath-holding. Because of lung construction, momentary breath-holding, such as swallowing or yawning, will not cause sufficient pressure in the lungs to exceed their tensile strength.

Exposure to Space

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