Living in space

Explore nature 200 1 August

Qiao aguang compiled

Since Soviet astronaut Gagarin first flew into space 40 years ago, human life in space is no longer a dream. Recently, the space travel of American billionaire Tito has aroused many space enthusiasts' yearning for space life. Many people want to follow Tito's footsteps, board the International Space Station, float in the cabin and overlook the earth.

However, life on the International Space Station is not as pleasant as expected.

Make your own oxygen

The first problem encountered by the space station is that there is almost no air at an altitude of more than 300 kilometers above the ground.

On earth, air contains 78% nitrogen, 2 1% oxygen and 1% other gases. In the space station, astronauts must have such air if they want to live and work normally. Nitrogen is transported by the space shuttle, while oxygen is made in the space station. Middle school students all know that two hydrogen atoms plus one oxygen atom make up water, and they have also done experiments to electrolyze water in test tubes to obtain oxygen. On the high-tech International Space Station, oxygen is obtained according to this basic chemical equation, and the obtained oxygen is stored in a pressure tank for later use. The generated hydrogen can only be discharged into space at present, and will be used to react with carbon monoxide to generate methane in the future as the power to maintain the orbital height of the space station.

Before the electrolytic water machine of the Russian-made "Star" service module on the space station was started, the astronauts breathed oxygen by burning "perchlorate candles". This is a metal can filled with perchlorate. Unplug the spark plug and it will burn, releasing oxygen until it burns completely.

Each tank can release one person's oxygen for one day. The chemical principle used here is also the experimental principle that middle school students have done to heat potassium perchlorate to obtain oxygen. But don't think that you can make this kind of "candle" after finishing middle school. There is a deeper scientific truth in this. For example,1On February 23rd, 997, this kind of "candle" on the Russian Mir space station caused a fire and almost reimbursed Mir. Afterwards, it took scientists two years to discover that the culprit of the fire was latex gloves-pieces of latex gloves worn by canning workers were mixed together during canning, and latex reacted with perchlorate, which triggered the fire.

In addition to obtaining oxygen, the space station must also eliminate gases harmful to human body. At present, the machines in the "Star" cabin of the space station use "zeolite" as a molecular sieve to filter air, and the carbon dioxide discharged from it can only be sent into space at present, so it will be recycled in the future.

In addition to carbon dioxide, people also emit a small amount of other gases, such as methane, ammonia decomposed from urea in urine, acetone, methanol and carbon monoxide, which are by-products of metabolism: urination and breathing. The space station uses an activated carbon filter to absorb these gaseous compounds from the air.

In order to ensure the air in the space station is safe, the pipe network on the space station collects air samples from different parts of the space station and sends them to the mass spectrometer for gas composition analysis. When the crew was working somewhere in the space station that day, they told the computer to collect more samples there to ensure the health of the crew.

Don't waste a drop of water

After a long journey to the space station, what I want to do most is to rush into the bathroom to wash my face, or even get into the bathroom to take a hot bath. But the reality is that you can only wipe it with a wet towel, and the water you use is the steam exhaled by your partner and the water in the tank. In high altitude areas far away from the earth, every drop of water is precious, so it should be recycled and used sparingly. Even urine should be recycled after treatment.

The original water was sent by the American space shuttle and the Russian cargo ship "Progress". One part of it is used to decompose to produce oxygen, and the other part becomes the initial water of the water circulation system of the space station. The orbital water processor developed by Russia can collect water vapor in the air of space station. The United States is building a recycling system that can recycle almost every drop of water. The system recovers water from the fuel tank, urine, mouthwash and hand washing water of the space shuttle, and even the animals in the laboratory can't escape the collection of the recovery system. Otherwise, in order to ensure the minimum water consumption standard of the four-person crew, it is too expensive to transport more than 1.8 thousand kilograms of water from the earth to the space station every year.

The water on the earth is also circulating, only through the natural processes of plants and animals. The water vapor exhaled by animals enters the air and then falls into the rain. Animal urine is decomposed by microorganisms for absorption by plants, and plants are eaten by people when they are mature. The water purification system of the space station simulates this process, but it does not depend on microorganisms, animals and plants, and adopts mechanical methods completely, which is technically reliable. First, primary filtration is carried out to remove impurities and particles, then organic and non-organic impurities are removed by multi-layer filtration, and finally volatile organic compounds are removed by catalytic oxidation reactor to kill bacteria and viruses. So the water in the space station is cleaner than the water from any household faucet on the earth.

On earth, as soon as you turn on the tap, water will flow out. But the water pressure in the space station is only half of that on the earth, so the towel can only be wetted by the shower head and then used to wipe your hands. Therefore, washing your hands in the space station only needs110 water on the earth. When you want to drink water, you should hook the water tank and put it in the water dispenser, select the required amount, and press the button to get the required amount of water, instead of turning on the tap to let the water flow out by itself. After recycling as much as possible, the water on the space station will still be lost and must be replenished by the space shuttle and the "Progress" spacecraft. The Russian "Dawn" cabin is equipped with standby emergency water tanks, each of which can hold about 4 1 kg of water.

Destroy microorganisms

Something got there before the first man boarded the International Space Station. This is an invisible but potentially dangerous thing, which has the ability to survive and regenerate in the worst environment and can attack the crew and the space station-this is microorganism.

In order to eliminate the threat of microorganisms to the health of astronauts, the water on the space station was disinfected by catalytic oxidation reactor, and the water was heated to 130. In this process, organic molecules in microorganisms are oxidized and almost all of them are killed. After disinfection, there are less than 100 microorganisms per 100 ml of water.

The growth of microorganisms on the surface of space station equipment will produce acid, which will lead to surface corrosion. In order to solve this problem, first of all, all anti-mildew materials should be used, and the surface should be coated with paint made of anti-mildew chemicals; Secondly, to control the humidity of the space station, it is impossible to provide an environment suitable for microbial breeding; Third, keep the surface clean so that microorganisms have no food.

Resist supercooling and overheating

Humans are only suitable for living in places that are neither too cold nor too hot, neither too bright nor too dark. On the earth, as long as it stays away from the South Pole, does not fall into the crater, and does not fall into the desert, it is suitable for human survival. However, mankind will explore space, not just as tourists, but as settlers. It is a great challenge for designers of space stations to create an environment suitable for human habitation.

If there is no temperature control on the space station, the sunny side will reach 12 1 and the back side will be-157, so there is only one place in the middle of the space station suitable for human habitation. However, considering the thermal balance of the space station, the designers of the space station assembled a thermal control system to make the "astronaut's home" cool and comfortable. Therefore, it is necessary to use all kinds of instruments to generate heat to deal with the influence of the cold from the outer space of the space station and the rising temperature inside the ultra-insulated orbital laboratory, because in a room completely isolated from the outside world and with air conditioning turned off, the energy generated by all wires will eventually become heat. On the space station, the energy of solar panels enters the space station, which makes all systems such as aerospace electronic instruments work, and they all generate heat. Therefore, measures must be taken to avoid exceeding the thermal limit that people can bear.

There are two ways to solve this problem. One of the passive methods is to use thermal insulation materials or coating on the surface to reduce the heat loss of each bulkhead. Polyester film can prevent the solar radiation from coming in. Using polyester fiber to separate each layer of polyester film can block the heat conduction between layers and ensure that radiation passes through this "blanket" to become the main heat transfer mode, which not only prevents the loss of solar radiation, but also prevents the cold current in space from penetrating the metal shell of the space station; The second is to heat all places with electric heating wires; The third is to balance the heat transfer with a pipeline filled with liquid.

Another method is the active method. It is a cold plate-a metal plate that directly transfers heat. The high heat generator is attached to the cold plate, and the cold water is circulated by a turbine with a speed of 1700 rpm. A heat exchanger is used to collect heat into liquid ammonia and then transfer the heat to water. Because the circulating water outside the space station will soon freeze, in order to make these liquid systems work, the waste heat should be exchanged to another cycle containing ammonia at the first time. Under normal atmospheric pressure, ammonia will not freeze until MINUS 77 degrees. The heated ammonia flows through a huge radiator installed outside the space station, releasing heat and cooling in the flow. Large thermal resistors similar to solar panels are used to radiate the collected heat into space. The external radiator of the space station adopts honeycomb aluminum plate, 14, with a total area of 156 square meters.

Finally, the air flow inside the space station must be balanced. Under the condition of zero gravity of the space station, hot air will not rise and cold air will not fall. We should try our best to create suitable air flow to prevent cold spots, because such cold spots will cause condensation, electric sparks, serious corrosion and even promote the growth of microorganisms. Corrosive mold appeared on the Russian Mir.

Taikong homemaking

Do astronauts need to pick up garbage or clean the kitchen? Are there domestic workers in space?

The space station with narrow space can only accommodate 3-7 people, and everyone is undertaking heavy scientific and technological work, and there are no idle people to do housework. Therefore, all the food in the space station is transported by the American space shuttle or the Russian cargo ship "Progress", and there is no need for the crew to make their own food. The crew can choose their favorite food from a rich menu. Most foods are processed and packed in small bags or cans. Some foods have been dehydrated, so you can eat them by heating water. Bagged and canned food can only be eaten by heating, and there are a small amount of raw vegetables and fruits. But these foods don't need to be put in the refrigerator, they just need to be stored at room temperature; There is a small refrigerator on the space station, but it can't be used continuously because of electricity.

There are stoves on the space station, originally a small food heater the size of a briefcase made in Russia or a portable food heater made in the United States, both of which are conductive stoves, not microwave ovens. Later, there was a microwave oven, but it was still not the final space furnace and needed to be improved.

When the space shuttle arrived, it brought new materials such as water and food. When it returned, it became the most expensive garbage truck in the world, transporting sealed garbage bins back to the earth. The Russian cargo ship "Progress" is even more magical, bringing new supplies and unloading after arrival. Then, the trash can was put into the "Progress" and sealed. After leaving the space station, it entered low orbit and re-entered the atmosphere under control. During this period, the "Progress" and garbage burned to ashes and fell into the ocean.

Complex pins and healds of pipeline system

On earth, turn on the faucet in the bathroom and water will flow out. After flushing the toilet, the water ran away. But in space, what about sanitation facilities? For example, how will water flow under zero gravity? Will the water that flushes the toilet automatically fall down?

Most of the time, the space station works like a ship in a bottle, completely isolated from the outside world. Only when the space shuttle and the Progress spacecraft bring air and water to the space station, and the Soyuz spacecraft replaces the crew and astronauts for spacewalking, the docking port or sealed chamber will be opened. The most important thing for the space station is to effectively prevent air leakage and ensure water recycling.

For this reason, the outer surface and inner wall of the space station are covered with complex pipeline networks. In these pipes, liquid and gas are necessary to ensure the health of the crew. Due to the special environment of space, the pipeline on the space station must be small in size, light in weight, corrosion-resistant, non-leaking, non-breeding microorganisms and very reliable. In order to meet these requirements, the pipelines on the space station are all made of expensive materials such as titanium, stainless steel or Teflon (PTFE) wound on metal mesh.

The pipes on the space station must work without the help of gravity. In the absence of gravity, fluids will only stay there unless there is pressure to push them. In order to make the liquid flow, there are dozens of pumps and fans in the pipeline system of the space station, which increases the pressure needed to transport the liquid and gas. It is conceivable that the toilets on the space station are obviously different from those on the ground. Toilets can't work without gravity, so the space station uses special straws to remove human excrement.

The communication of the International Space Station adopted the experience of Russian Mir Space Station, and the crew was encouraged to call home. Every crew member has a videophone and can call home every week. The crew can also send and receive emails every day, and no one will feel far away from their families.

Systems that ensure the safety of human life in space, such as making oxygen, recycling water and establishing temperature control systems, are called "life support systems". Scientists have begun to study the advanced life support system, that is, the micro-earth environment. One day, humans will finally be able to eat their own food in space, breathe the oxygen provided by space plants and drink the water purified by space plants.