Meeting basic needs in Space
We have seen different space vehicles and the various missions conducted for space exploration. All these missions require living in hostile environment of space. Therefore certain basic needs have to be fulfilled to provide astronauts with environment similar to that of earth.
• Breathing - Space is a vacuum and there is no air out there. For the survival of human beings a suitable composition of air is required. A continuous supply of oxygen is essential for respiration. A manned spacecraft uses a gas, which is a combination of oxygen and nitrogen. This gas is circulated with the help of fans in the cabin. A chemical called lithium-hydroxide absorbs carbon- dioxide, which is by-product of respiration.
• Pressure - human body must be enveloped by appropriate pressure .The lack of pressure causes changes in the cardiovascular system, the musclo-skeletal system and the nervous system. To accomplish this problem airtight enclosures or capsules where appropriate pressure can be artificially maintained must always surround the astronauts.
• Temperature control - the temperature of outer space varies drastically. Therefore the space vehicle is equipped with a temperature control system to maintain the temperature. The functions carried out by the system are:
• Distribute the heat evenly
• Get rid of the excess heat
The temperature aboard the spacecraft is maintained by active methods and passive methods.
• Active method involves the circulation of fluid to remove heat
• Passive methods use insulating materials and electrical heaters
• Eating and drinking - the food given to astronauts must be nutritious, easy to prepare and should not be perishable. Modern spacecrafts are equipped with facilities for heating frozen foods. Food comes in several forms (dehydrated, low moisture, heat-stabilized, irradiated, natural and fresh). The orbiter has a galley-style kitchen module, which is equipped with the following:
Water is an essential requirement. Water is made from liquid oxygen and hydrogen
• Eliminating body wastes - due to the micro gravity, collection and disposal of wastes poses a huge problem. A device resembling toilet seat is used for the collection of wastes. Airflow provides suction for collection of wastes under the toilet seat. On small aircrafts funnels are used for collection of liquid wastes and plastic bags are used for solid wastes. While working in space special equipments are worn for collection of wastes.
Bathing - the simplest way of bathing is sponge bath with the help of wet towels. A collapsible shower stall is also used where water is sprayed on astronaut's body. The stall is dried by vacuum.
• Sleeping - sleeping bags with pillows are used to fasten the astronauts to a soft surface and a pillow. Astronauts may wear blindfolds to block sunlight. Some astronauts prefer to float in air with few straps fastened to prevent bouncing.
• Recreation - to refresh the mind space station has collection of books, computer games and tapes. Exercise also helps mind to relax.
• Controlling inventory - keeping a track of the items used in space mission is a great challenge. Drawers are used to store materials and equipments are strapped to wall and ceilings. A list is stored on computer, which keeps a track of various items stored.
• Effect of weightlessness -Weight of any body is given by W = mg where m = mass of body & g = acceleration due to gravity.
Now why is it that a person feels his own weight? The answer is very simple. It is due to the earth's gravity. The earth's pull makes the man exert a force on a body supporting him and the support, by Newton 's third law, exerts an equal and opposite force back on the person. This gives us the feeling of weight.
If this support is not there and we are freely falling, then we get a feeling of weightlessness, as there is nothing to exert a force on us. This is what happens when we go into space. As the effect of gravity of earth in space is negligible, we get a feeling of weightlessness. The feeling of weightlessness does not have any drastic effect on humans, so long as it is experienced for a very short period of time, just nausea, vomiting etc.
If weightlessness is experienced for a long time then there could be some injuries caused to the human body. As explained earlier, the human body experiences a force towards the earth. So the muscles of the body have to work harder to move around. But in a state of weightlessness, most of the times, the muscles are in a state of inactivity.
In the absence of gravity, the functioning of organ of equilibrium, in the inner ear is also affected. However, it is possible for human body to adapt easily to tolerate the weightless state even in a psychological sense by training in zero gravity conditions.
• Change in behavior of objects due to absence of gravity- Humans can no longer walk due to absence of weight. Also there is no friction due to which the soles of the footwear do not stick to the roughest surface available. We have to pull ourselves with our hands by use of handles attached to the walls. Too much force applied to these handles can result in painful bumps. Hence the walls and in particular all corners and edges would have to be very well cushioned.
Let us see how the state of weightlessness affects the human body and the measures to be taken to counteract them.