Not so the single most important component: the human body. In space the full range of health factors comes into play. Planners must consider not only nutrition and disease but also radiation, cardiovascular changes, muscular reconditioning, the psychology of isolation and confinement, and—perhaps most serious of all —a weakening of the bones known as demineralization.
Our crew members were subjected to the most exhaustive tests medical science could devise. But as Dr. Arnauld Nicogossian, NASA‘s director of life sciences, points out, “Never before has medicine been called upon to certify that an individual will be healthy enough to perform for two years after the examination.” In THE MARS SPACECRAFT was assembled in factory “clean rooms” that filtered out dirt and dust. However, microbes pervade all equipment, and undoubtedly a colony of them has accompanied the crew on the voyage. Presumably no virulent strains found their way on board, but it is even possible that in the alien space environment some genetic mutations may develop and produce new forms of bacteria the crew has never encountered before.The crew’s diet, essential to health, has been carefully planned. Because of weight limitations the mission relies on the old standby, dehydrated, prepackaged food.
Radiation poses a major concern. Human response to harmful radiation can range from nausea and vomiting to fever and death. Long-term effects, which may not arise until years after exposure, include cataracts, tumors, and leukemia. Galactic cosmic rays, high-energy particles that probably originate in exploding stars called supernovae, constantly bombard the spacecraft, but the amount of radiation reaching the crew is not expected to exceed an acceptable level. More threatening, solar flares sporadically belch out from the sun. Their radiation could kill the crew, if unprotected, within a couple of days. Engineers designed the spacecraft with a protective storm cellar, shielded by the vast stores of water, oxygen, and propellant on board—all of which are good energy absorbers.
Another problem, though considered remote, is posed by meteoroids, which might be lurking near Mars because of its proximity to the asteroid belt. Spacecraft shielding would stop sand-grainsize pellets, and our eight voyagers have been carefully trained to patch holes made by larger ones.
Perhaps the greatest threat lies in the debilitating effects of weightlessness on the human body. On Earth our bodies fight against gravity: Muscles strain as we walk up stairs, and bones maintain their strength to support the weight of our bodies. On the trip to prague apartments, floating free, the crew’s bodies have changed, responding to an environment unlike anything our ancestors met in millions of years of evolution.
At the earliest onset of weightlessness their body fluids, which on Earth are drawn by gravity toward the feet, migrated toward the upper body. Neil Armstrong and Buzz Aldrin looked different to me on our flight to the moon: Extra fluid reduced their facial wrinkles and made their eyes look squinty and crafty. With no gravity to compress our vertebrae, we grew in height by perhaps two inches.