Question

What would happen to you if you fell out of a spaceship, naked? Hollywood has given us many portrayals of this event, with the skin boiling or instantly freezing; but what actually happens, and what effect is most severe? The lack of oxygen is one: we know that humans can only survive a number of minutes without breathing. But there are a number of other factors to consider. (A) Assume a human is a 2 m tall cylinder of 75 kg of water. Estimate how long it would take for its temperature to drop by 10˚C. Is heat loss a significant factor? (B) In light of the answer to part (A), use the phase diagram for water to explain what would begin to happen to the blood in surface capillaries (and, eventually, the blood in major veins and arteries). (C) Should you hold your breath? Why/why not? What would happen to the air in your lungs? What ideal gas process is approximated? (D) Sun exposure is a serious concern. 2^nd-degree burns can occur if the skin absorbs more than about 5 J/cm². If you are floating in near-earth orbit, how long do you have before you burn? (E) Are there any other factors we should consider? Which do you think is the most life-threatening?

Answer 1