Surviving Space Card #1
The air quality on space expeditions is vital to the astronauts. Without oxygen, the crew would get fatigued, black out and die. There are two ways that oxygen can be furnished for space flight. Oxygen can be produced by electrolysis. In this process, solar-panel-generated electricity is used to split water into hydrogen and oxygen gas, just like photosynthesis occurs on Earth. The oxygen can be used by the crew while hydrogen can then be vented into space. The second way that oxygen can be produced is by a chemical oxygen generator. A chemical oxygen generator is a device that releases oxygen created by a chemical reaction. The oxygen source is usually an inorganic superoxide, chlorate or perchlorate. The generators are usually ignited mechanically, by a firing pin, and the chemical reaction is usually exothermic (heat is given off), making the generator a potential fire hazard. The generators are currently used as a backup system aboard the International Space Station and one canister can provide enough oxygen for one crew member for one day.
Chemical oxygen generators are used in aircraft as emergency oxygen for passengers to protect them from drops in cabin pressure. If a decompression occurs, the panels are opened either by an automatic pressure switch or a manual switch, and the masks are released. When the passengers pull down on the mask, they remove the retaining pins and trigger the production of oxygen. The supply of oxygen lasts for 15 to 20 minutes which is long enough for a pilot to descend to a more breathable altitude.
Chemical oxygen generators are used in aircraft, breathing apparatus for firefighters and mine rescue crews, submarines and everywhere compact emergency oxygen with a long shelf life (20 years) is needed. They usually contain a device for absorption of carbon dioxide.
Oxygen generator (inside above, outside
Electrolysis- splitting the hydrogen & oxygen in water
Surviving Space Card #2
Water is used by every living thing. Depending on body size, water makes up somewhere between 55 to 78 percent of the human body. To function properly, the body requires between one and seven liters of water per day to avoid dehydration; the precise amount depends on the level of activity, temperature, humidity, and other factors.
In space, Earth’s natural water cycle is missing. Water must be brought with space explorers and then recycled. In space, water rationing and recycling will be a part of everyday life. On the International Space Station, a Russian-built water processor takes the humidity and condensation from the air and turns it into drinking and bathing water. Waste water not only comes from the air but from the Space Shuttle’s fuel cells, from urine, from oral hygiene and hand washing. Without careful recycling, 40,000 pounds per year of water from Earth would be required to resupply a minimum of four crewmembers for the station.
On Earth, water that passes through animals’ bodies is made fresh again by natural processes. Microbes in the soil break down urea and convert it to a form that plants can absorb and use to build new plant tissue. The granular soil also acts as a physical filter. Bits of clay cling to nutrients in urine, purifying the water and providing nutrients for plants.
Water excreted by animals also evaporates into the atmosphere and rains back down to the Earth as fresh water—a natural form of distillation.
Water purification machines on the ISS partly mimic these processes, but they do not rely on microbes or any other living things. The machines cleanse the water in a three step process. The first step is a filter that removes particles and debris. Then the water passes through the multifiltration beds, which contain substances that remove organic and inorganic impurities. And finally, the catalytic oxidation reactor removes organic compounds that vaporize quickly and kills bacteria and viruses.
Even with intense conservation and recycling efforts, the Space Station gradually loses water because of inefficiencies in the life support system. No water reprocessing technology is currently available that is 100% efficient.
Water is lost by the Space Station in several ways: the water recycling systems produce a small amount of unusable brine; the oxygen generating system consumes water; air that’s lost in the air lock takes humidity with it; and the carbon dioxide removal systems remove some water out of the air, to name a few.
If the water recycling systems can be improved to an efficiency of greater than about 95 percent, the water contained in the Station’s food supply would be enough to replace the lost water.
When water evaporates from the ocean & surface
waters, it leaves behind impurities. In the absence
of air pollution, nearly pure water falls back to the
ground as precipitation.
Surviving Space Card #3
Throughout history, nutrition has played a crucial role in exploration, and space exploration is no exception. For current space expeditions, food prepared here on Earth must be taken with the astronauts. Diets are designed to supply each astronaut with 100 percent of the daily value of vitamins and minerals necessary for the environment of space.
The nutrients astronauts need in space are the same ones all people need, but the amounts of some differ. Astronauts need the same number of calories for energy and most of the vitamins and minerals they need are the same as on the ground. However, the amount of iron in an astronaut’s diet must be regulated to less than 10 milligrams per day for both men and women. Astronauts have fewer red blood cells while they are in space. Most of the iron absorbed from food goes into new red blood cells. If astronauts were to eat foods high in iron, the iron would be stored in their bodies and could cause health problems. In addition to iron, sodium must also be regulated. The amount of sodium in the astronauts’ diet is limited because too much can lead to bone loss as well as other health problems.
On Earth and in microgravity, people need vitamin D for healthy bones. The body usually makes vitamin D when exposed to sunlight but in space this option is not available. Vitamin D supplements are recommended for space travelers on the space station since the current space foods do not provide enough of this vitamin.
Two different food systems will be used for future long-duration missions to other planets, one for traveling to and from the distant body and one for use on the surface of the moon or Mars.
The transit food system will be similar to the space station food system with the exception that products with three-to five-year shelf lives will be needed, especially for a mission to Mars. Thus part of the trip will be similar to what occurs aboard space missions now—eating out of food packages and heating food items in a similar fashion.
The surface food system, be it lunar or planetary, will be quite different. It will be similar to a vegetarian diet that someone could cook on Earth – minus the dairy products. Once crewmembers arrive on the surface and establish living quarters, they can start growing crops. Possible crops that could be grown and harvested include potatoes (sweet and white), soybeans, wheat, peanuts, dried beans, lettuce, spinach, tomatoes, herbs, carrots, radishes, cabbage and rice. Once the crops are processed into edible ingredients, cooking will be done in the spacecraft’s galley to make food items.
Disposal of used food packaging will be an issue. Packaging materials will be used that have less mass but sufficient barrier properties for oxygen and water to maintain shelf life as those now in use.
Surviving Space Card #4
The more we lift and the faster we move, and the more often we do both, the stronger our bones and muscles become. Every time we stand, walk, or pick something up, our muscles work against gravity. With each gravity-defying activity, our bones react by triggering the formation of additional bone mass. But what would happen if we no longer had gravity to work against?
During space flight, astronauts experience microgravity, a force one millionth as strong as the gravitational force we feel on Earth. The human body, which adapted to thrive in Earth’s gravity, must adapt to this new environment. Bones that supported weight on the ground no longer have that load to bear. They begin to lose mass and strength, as do weight-bearing muscles in the lower body. Reduced physical activity and a shift of fluids into the upper body combine to reduce cardiovascular capacity. This process is known as de-conditioning.
While in space, these changes don’t present a problem, but gravity can be hard on a body no longer used to it. Whether returning to Earth or landing on some other planet, the body’s adaptation to microgravity increases the risk of broken bones, reduces work capacity, and can result in balance disorders and even blackouts when standing.
To minimize microgravity’s impact, NASA employs in-flight exercise as a countermeasure. Exercise maintains bone mass, muscle strength, and cardiovascular capacity, but microgravity makes it tricky. With a shoulder brace to keep the astronauts from floating away, the ergometer (like an exercise bike) is relatively easy to use in a weightless environment. The ergometer offers a good cardiovascular and leg muscle workout. What it doesn’t do so well is provide adequate loading forces to keep bones strong.
Treadmill running offers a superior workout for maintaining bone strength. The downside is that an elasticized harness must be used to simulate gravity by pulling the user against the running surface. This makes the process so uncomfortable that astronauts are forced to take breaks every five or ten minutes.
Resistive exercise is a relative newcomer to the in-flight workout. In the past, astronauts loaded their bones and muscles by working against a resistive force, usually by pulling against strong bungee cords which the astronauts found quite limiting and boring. The newest device is called the advanced Resistive Exercise Device and functions like a weight machine in a gym on Earth, except it has no conventional weights. Instead, it has vacuum cylinders –canisters with air that have had a vacuum applied—that provide workloads of up to 600 pounds. The device works somewhat like a bicycle pump, only in reverse. For example, if you are squatting, the vacuum gets pulled out as you stand up, and when you squat back down, the vacuum pulls the bar back to the normal position. Between the vacuum cans and the bar, there are small flywheels that spin in opposite directions, creating an artificial gravity when someone lifts the bar. Astronauts are able to do both upper and lower body workouts with the device.
For Space Station inhabitants, NASA requires two hours of exercise each day as a countermeasure to the de-conditioning effects of microgravity. In addition, drug therapy is also used.
As astronauts explore further into space, regular exercise will be important for reducing depression and anxiety as well as helping to reduce heart disease, diabetes and colon cancer.
Surviving Space Card #5
As the duration of space missions continues to increase, the detrimental effects of microgravity needs to be examined. In prior Surviving Space Cards, the issues of bone loss, muscle weakness (atrophy), and loss of red blood cells has been mentioned. This Surviving Space Card will address additional responses by the human body to microgravity.
One of the more serious adverse effects of weightlessness is fluid redistribution. The redistribution of body fluids occurs when these fluids shift from the lower body, where they normally abound due to the downward tug of gravity, to the head and upper body. The redistribution of fluids is coupled with fluid loss. When the brain senses the increased volume of fluid in the upper body, it interprets this as being an increase in the total volume of fluid in the body. The brain then responds by triggering the excretion of fluids, making astronauts prone to dehydration. In addition, fluid redistribution causes head congestion and puffy face in the upper body while shrinking the legs in the lower body.
Balance disorders can also result from extended exposure to zero gravity. Receptors in the inner ear allow humans to sense direction and gravity while on Earth. In space, however, these receptors do not receive the same cues. Hand-eye coordination, posture and balance are all affected by the disorientation that occurs in microgravity. Upon returning to Earth, astronauts are often overwhelmed by dizziness and are unable to maintain their balance.
The immune system is also affected by weightlessness. Astronauts become quite susceptible to illness when in space. The human immune response lowers and the quantity of infection-fighting cells in the immune system decreases after prolonged exposure to microgravity. Space adaptation syndrome often results from the weakening of the immune system and from the general stresses of a microgravity environment. Approximately half of all astronauts are affected by this unpleasant syndrome which is characterized by nausea, headache, lethargy and sweating. Fortunately, the sickness only lasts a few days.
In addition to the conditions mentioned above, there is a multitude of minor effects of weightlessness on the human body. Symptoms such as flatulence (farting or passing gas), weight loss, nasal congestion and sleep disturbance are usually only minor, yet common, annoyances.
Fortunately, most of the effects of zero gravity are reversible. Astronauts gradually recover from their voyages into space and their bodies return to their normal function.
Surviving Space Card #6
One of the major hazards of space exploration is that of radiation. Radiation is a form of energy that is emitted or transmitted in the form of rays, electromagnetic waves, and/or particles. In some cases, radiation can be seen (visible light) or felt (infrared radiation), while other forms like x-rays and gamma rays are not visible and can only be observed directly or indirectly with special equipment.
On Earth we are protected from much of the electromagnetic radiation that comes from space by Earth’s atmosphere and magnetic field. Most radiation is unable to reach the surface of the Earth except at limited wavelengths, such as the visible spectrum, radio waves, some ultraviolet wavelengths, and some high-energy ionizing radiation. As we rise through the atmosphere, climb a high mountain, take a plane flight or go to the International Space Station or to the Moon, we rapidly lose the protection of the atmosphere.
One of NASA’s goals is to enable human exploration of space without exceeding an acceptable level of risk from exposure to space radiation. Space radiation is different from common terrestrial forms of radiation. Radiation that is emitted from the sun is made up of fluctuating levels of high-energy protons. Space radiation consists of low levels of heavy charged particles. High-energy protons and charged particles can damage both shielding materials and biological systems. The amount, or dose, of space radiation is typically low, but the effects are cumulative (they add up over time). Solar activity varies, and so the risk of exposure increases with the amount of time spent in space. Therefore there is significant concern for long-term human space travel. Possible health risks include cancer, damage to the central nervous system, cataracts, risk of acute radiation sickness, and hereditary effects.
There are three main factors that determine the amount of radiation that astronauts receive. They include:
- Altitude above the Earth—at higher altitudes the Earth’s magnetic field is weaker, so there is less protection against ionizing particles, and spacecraft pass through the trapped radiation belts more often.
- Solar cycle—the sun has an 11-year cycle, which ends in a dramatic increase in the number and intensity of solar flares, especially during periods where there are numerous sunspots.
- Individual’s susceptibility—researchers are still working to determine what makes one person more susceptible to the effects of space radiation than another person.
For any future long-duration deep-space exploration, radiation levels will be so high that specially designed storm shelters will be needed to protect astronauts from receiving deadly doses of radiation during high coronal mass ejections, solar flares, and/or solar particle events (streams of protons and electrons). For safe operations on the Moon or when traveling to Mars, a coordinated system of satellites will be needed to monitor space weather to help warn astronauts when it is necessary to go into their shelters.
Countermeasures to combat radiation damage to astronauts include constructing shields, dietary supplements such as antioxidants like vitamins C and A, specific diets, and drugs such as Radiogardase which is designed to increase the rate at which radioactive substances are eliminated from the body.