How Astronauts Will Survive In Space

Oxygen for Respiration

Without oxygen, the human body cannot survive longer than three minutes. It is therefore imperative that that life support and survival systems provide adequate amounts. An average astronaut needs nearly two pounds of oxygen per day. This large amount cannot be brought along due to its heavy weight - oxygen and breathable gases must be recycled. Initially in space exploration, oxygen was provided through the use of perchlorate candles. The contents of these metallic canisters reacted and formed oxygen (O2) as a product. Now, the process known as electrolysis is used to separate water into its components of hydrogen and oxygen. The process is powered by battery or gathered electricity via solar panels. This process in much more sustainable as water can be recycled into oxygen and hydrogen. The oxygen that is generated fills the entire pressurized cabin for space crew to breathe. The cabin atmosphere is not pure and is mixed with other gases in ratios similar to the Earth's natural nitrogen/oxygen balance. While the removal of the diluent gases can reduce the pressure and weight required of a space craft's atmosphere, diluent gases are mixed in for safety. Inert gases such as argon may be added for stability and fire control. Pure oxygen is highly flammable and accidental explosions aboard space craft are a great concern. Pure oxygen is often times pumped to space suits for outside repairs and space walks via umbilical chord. The atmosphere in space suits is usually a purer oxygenated mix. A suit full of pure oxygen requires less pressure than a mixed breathing gas. This ensures that the suit is flexible and not rigid due to internal pressure. Cabin air must continually be filtered to prevent the build up of carbon dioxide, a product of respiration, and poisonous gases that the human body releases in small amounts. A chemical named zeolite is used to filter out both carbon dioxide and monoxide. Zeolite acts like a molecular coffee filter – breathable air passes through but poisonous gases such as carbon monoxide and dioxide are trapped within. Carbon monoxide can be fatal in small amounts. Activated carbon filters are used to remove other poisonous gases such as ammonia and methane.

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Using plants to recycle CO2 to oxygen has been studied and experimented with for sometime, but as of right now it is not a viable solution. The volume of plants and materials needed to recycle oxygen fast enough for a crew is simply incredible. Also, plants must be continually monitored and cared for. Plants must get enough water, nitrogen, and other essential nutrients. At this point, chemical solutions are simply faster and more reliable. The viable use of plants for CO2 to O2 conversion would require simulating a small ecosystem. Even controlled experiments such as the biosphere projects have failed to create a stable model of Earth's natural atmospheric processes. For now, scientist must find ways to improve chemical solutions such as electrolysis so that they can be used longer term and be more self sufficient. Using algae and phytoplankton as CO2 scrubbers is currently being investigated. A biochemical solution would help to eliminate mechanical and electrical reliance ensuring a longer term solution. A biochemical algae scrubber could potentially be far smaller and more portable than the electrolysis currently being used. Algae do not require electricity or regulating its use – just sunlight.