Being weightless is unnatural and uncomfortable. The airplane that gives people a taste of zero g is called the Vomit Comet. About half of all visitors to space experience motion sickness, which may consist of nausea, vomiting, dizziness, headaches, and general malaise. It usually wears off after two or three days, but 10 percent of all astronauts suffer a long-term and debilitating form of space sickness that interferes with their ability to function normally. This has been known since the early days, but astronauts expected to have the "right stuff" were reluctant to report it, and often they were grounded if they did. U.S. Senator Jake Garn became the poster child for puking when he flew on the Shuttle in 1985, and astronauts since then have referred to the "Garn scale" to rate their own symptoms. Garn was essentially incapacitated during his entire flight. Oceanographer and NASA researcher Robert Stevenson said, "Jake Garn made a mark in the Astronaut Corps because he represents the maximum level of space sickness that anyone can ever attain, so the mark of being totally sick and totally incompetent is one Garn. Most guys will get maybe to a tenth Garn, if that high."
NASA's Weightless Wonder, more commonly known as the Vomit Comet. This is a modified Douglas DC-9 airliner. Click here for original source URL
A Dutch researcher did experiments where people were subjected to human centrifuges (often used for astronaut training) and observed that they suffered similar symptoms after leaving the centrifuge. So the trigger for space sickness is adapting to a different gravitational force, rather than the absence of gravity. Technically, astronauts are never subject to zero gravity — gravity is everywhere in the universe. But in Earth orbit, astronauts and their "container" free fall at the same rate as their forward motion, so they "float" inside the container. Microgravity is a more accurate term. Thanks to their Mir Space Station, Russians hold the records for the longest time in zero g. Valeri Polyakov spent 438 days on Mir in the mid-1980s and three other cosmonauts spent more than a year. By going up six times, Sergei Krikalev racked up 803 days in space. How these cosmonauts fared is providing vital insights into what to look for when we send humans to Mars.
The full set of physiological effects would give any potential spacefarer pause. A lack of gravity causes body shape to morph. Astronauts get 2 or 2.5 inches taller, but that extension (and subsequent compression when they return) is quite painful. Internal organs drift upward, faces get puffy, waists and legs shrink, and the result is a cartoonish image of a strongman. But this is an illusion; without gravity to fight against, muscles atrophy and bones get thin and brittle. Astronauts work out for two or three hours a day to combat these effects. The heart also weakens, and blood pressure may lower to the point where a person occasionally can pass out. Immune systems weaken in space, and the upward migration of body fluid leads to congestion and headaches. Glucose tolerance and insulin sensitivity vary wildly in space. Since they're not shielded by the Earth's atmosphere, cosmic rays cause low-level brain damage, and they may accelerate the onset of Alzheimer's disease. Eyes suffer, too; Russian cosmonaut Valentin Lebedev suffered progressive cataracts and went blind after spending eight months in orbit. The cosmic rays also create brilliant flashes of light in the eyeball, creating a kind of private disco ball.
Decent food combats physical discomfort, or at least boosts morale. Early astronauts had a fairly grim diet of flavored paste from a tube or bite-size, freeze-dried snacks. Floating crumbs and drops of liquid cause havoc with sensitive electronics, so they were avoided at all costs. Now the choice is much better. Astronauts can feast on pouches of shrimp cocktail, beef stroganoff, and cherries jubilee. Many of the technologies that NASA developed for preparing, sealing, sterilizing, and heating meals have been adopted by the food-service industry and are enjoyed by couch potatoes the world over. The Space Shuttle's fuel cells generated water, providing the side benefit that water to reconstitute the food was made in orbit, saving launch weight.
On the orbiting space stations, the scene is quite familiar. Skylab astronauts gathered around a table where they could "sit" using foot straps, and they each had a knife, a fork, and a spoon, plus a pair of scissors to cut plastic seals. The International Space Station uses an eight-day rotation of meals, which could become monotonous if you were up there a year. Half the meals are American and half are Russian, with crews getting to taste and vet the food of the other country in their training sessions. The diet of burgers and borscht has broadened as people from other countries have started to fly aboard the station. Astronauts get three meals and occasional snacks. Those having the midnight munchies must dip into the reserve supplies, which are brought in case landing is delayed for any reason. Raiding someone else's food is a major transgression; every astronaut's meals are customized according to their preferences and marked with a colored dot. Voyages have unraveled over less — the Caine mutiny over Captain Queeg's missing strawberries comes to mind. Getting balanced nutrition is tricky due to the limited range of food available. Vitamin D is cranked up, since there's no sunlight to help produce it and a deficiency would lead to excessive bone loss. Iron is dialed down because astronauts don't make enough red blood cells to absorb the usual amount. Calories stay about the same as on Earth.
What goes in must come out. Containing and processing waste is a real problem in the close confines of a spacecraft or space station. NASA makes astronauts use a "positional trainer" that teaches them how to guide their feces into a two-inch-diameter opening, all while watching a video shot from underneath looking up. Diapers are a thing of the past, but when the space toilet has a problem, astronauts must resort to even more primitive collection methods. In 2008, the International Space Station's lone toilet broke. TV satirist Stephen Colbert mocked NASA on his show for resorting to what they called "a bag-like collection system." When NASA held a write-in naming contest for its next-generation toilet, Colbert rallied his viewers to inundate the NASA website. He won. But NASA wimped out and declined to name the commode the Colbert, dubbing it instead Tranquility.
For the fewer than six hundred who've been up, the experience transcends any physical discomfort. What a sublime experience it must be — to traverse in ninety minutes what took Jules Verne's Phileas Fogg eighty days, to view the curved limb where sky shades into night, to glimpse beyond the horizon. And that's just the edge of space. Beyond that, a vast array of fascinating worlds beckons.