Las penas del Agente Smith

En uno de los libros que me estoy leyendo (lo que me recuerda que tengo aquí al lado un pequeño puñado pendiente de comentar) y cuyo título no desvelaré para ahorrar disgustos innecesarios, dos personajes protagonizan una pelea en una ciudad ubicada sobre un asteroide y protegida del espacio exterior mediante paredes semipermeables. En uno de los empujones de la lucha, los dos personajes son arrojados al vacío. Uno lleva un traje protector, pero el otro empieza a sufrir al instante los síntomas que el lector medio de ciencia ficción esperaría: ojos abultándose y luchando por salir de las órbitas, sangre escapando por cualquier orificio que encuentre libre y entrando en ebullición, etc…

Esa parte de la narración me ha recordado una página de ésas que encontré hace tiempo, guardé en mis marcadores sin darle mayor importancia y olvidé inmediatamente después. En realidad, nada de lo que está explicado en el libro ocurriría. El Dr. Geoffrey Landis, un escritor de ciencia ficción que no he tenido el placer (o el disgusto) de leer, y físico e ingeniero por el MIT para más señas, escribió sobre el asunto en Human Exposure to Vacuum, basándose en datos publicados por la NASA y por médicos al servicio de la fuerza aérea de los Estados Unidos.

Si están vagos, les doy la respuesta corta:

A frequently asked question is: how realistic is the scene in 2001: A Space Odyssey where astronaut Bowman makes a space-walk without a helmet? How long could a human survive if exposed to vacuum? Would you explode? Would you survive? How long would you remain conscious?

The quick answers to these questions are: Clarke got it about right in 2001. You would survive about a ninety seconds, you wouldn’t explode, you would remain conscious for about ten seconds.

Ahora, que si tienen un rato…

The best data I have comes from the chapter on the effects of Barometric pressure in Bioastronautics Data Book, Second edition, NASA SP-3006. This chapter discusses animal studies of decompression to vacuum. It does not mention any human studies. [On] page 5, (following a general discussion of low pressures and ebullism), the author gives an account of what is to be the expected result of vacuum exposure:

“Some degree of consciousness will probably be retained for 9 to 11 seconds (see chapter 2 under Hypoxia). 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 at pressures as low as 15 mm Hg absolute [Webb, 1969, 1970].) Heart rate may rise initially, but will fall rapidly thereafter. Arterial blood pressure will also fall over a period of 30 to 60 seconds, while venous pressure rises due to distention of the venous system by gas and vapor. Venous pressure will meet or exceed arterial pressure within one minute. There will be virtually no effective circulation of blood. After an initial rush of gas from the lungs during decompression, gas and water vapor will continue to flow outward through the airways. This continual evaporation of water will cool the mouth and nose to near-freezing temperatures; the remainder of the body will also become cooled, but more slowly.

“Cook and Bancroft (1966) reported occasional deaths of animals due to fibrillation of the heart during the first minute of exposure to near vacuum conditions. Ordinarily, however, survival was the rule if recompression occurred within about 90 seconds. … Once heart action ceased, death was inevitable, despite attempts at resuscitation….

[on recompression] “Breathing usually began spontaneously… Neurological problems, including blindness and other defects in vision, were common after exposures (see problems due to evolved gas), but usually disappeared fairly rapidly.

“It is very unlikely that a human suddenly exposed to a vacuum would have more than 5 to 10 seconds to help himself. If immediate help is at hand, although one’s appearance and condition will be grave, it is reasonable to assume that recompression to a tolerable pressure (200 mm Hg, 3.8 psia) within 60 to 90 seconds could result in survival, and possibly in rather rapid recovery.”

Note that this discussion covers the effect of vacuum exposure only. The decompression event itself can have disasterous effects if the person being decompressed makes the mistake of trying to hold his or her breath. This will result in rupturing of the lungs, with almost certainly fatal results. There is a good reason that it is called “explosive” decompression.

Eso no es todo. Recomiendo echarle un ojo a la página si las preguntas que nos rondan la cabeza son una o más de las siguientes:

• Will You Stay Conscious?
• Would Your Blood Boil?
• Would You Freeze?
• Has Anybody Ever Survived Vacuum Exposure in Real Life?
• How Fast Will A Spaceship Decompress If It Gets Punctured?