Chapter 41 8.3 Humans are closely related to Chlorella

The next question is obviously: How big should this glass bottle that is isolated from the flow of the outside world be, and what kind of living things should be filled in it, so as to ensure the survival of people in it? When human daredevils venture through the soft bottle wall of the earth's atmosphere, the above-mentioned academic problems have practical significance.Can you keep humans alive in space like shrimp in a biosphere by keeping plants alive?Can you enclose men also in a sunlit bottle filled with living things, and let them use each other's breath?This is a question worth exploring.

Primary school students know that animals consume oxygen and food produced by plants, and plants consume carbon dioxide and nutrients produced by animals.It's a beautiful mirror image: one produces what the other needs, serving each other like shrimp and algae.Perhaps, by pairing plants and mammals together in the right way, as their counterparts require, they can support each other.Perhaps, people can also find a biological incarnation suitable for themselves in a closed container. The first person crazy enough to do this tentative experiment was a Russian researcher at the Moscow Institute of Biomedical Problems.In the early years of space research, Yevgeny Shevlev welded an iron box in 1961 big enough to contain his eight gallons of green algae.Shevlev's elaborate calculations show that 8 gallons of chlorella under a sodium lamp can produce enough oxygen for a person, and a person can exhale enough carbon dioxide for 8 gallons of chlorella.Both sides of the equation can cancel each other out to become one.So, theoretically speaking, it should work, at least it is balanced on paper, and the calculation on the blackboard is also perfect.

But in this airtight iron warehouse, the situation is completely different.You can't breathe theory.If the green algae grows poorly, the talented Shevlev will also be unlucky; on the contrary, if Shevlev is finished, the green algae will not survive.In other words, in this box, these two species are almost in a completely symbiotic relationship, and their own survival is completely dependent on the existence of the other, and no longer depends on the external world that is the responsibility of the entire planet, with oceans, air, and creatures of all sizes. constitute a huge security network.The people and algae enclosed in this cabin have actually been separated from the broad network woven by other life forms, forming a separate and closed system.It was out of faith in science that the capable Shevlev climbed into the cabin and sealed the door.

Chlorella and people persisted for a full day.Over a period of about 24 hours, the person inhales the chlorella's exhaled breath, and the chlorella inhales the person's exhaled breath.Then the corrupt air drove Shevlev out.Towards the end of the day, the concentration of oxygen initially provided by the green algae decreased rapidly.At the last moment, when Shevlev broke through the airtight door and crawled out, his colleagues were stunned by the sickening stench from his cabin.Carbon dioxide and oxygen exchanged harmoniously, but green algae and other gases from Shevlev, such as methane, hydrogen sulfide, and ammonia, gradually polluted the air.Like the happy frog in the fable being boiled slowly, Shevlev himself did not notice the stench.

Shevlev's risky work was taken seriously by other Soviet researchers in a secret laboratory far away in northern Siberia, who carried on Shevlev's work.Shevlev's own group was able to keep dogs and mice alive in the chlorella system for up to seven days.Unbeknownst to them, around the same time, the U.S. Air Force Academy of Aeromedicine locked a monkey for 50 hours in an atmosphere made of green algae.After that, Shevlev and the others put an 8-gallon barrel of chlorella in a larger airtight chamber, and adjusted the nutrients of the green algae and the intensity of the light, creating a person who can survive in this airtight chamber for 30 days. Day record!During this particularly long-lasting process, the researchers discovered that the green algae and human exhalation don't quite match up.Keeping the atmosphere in balance also requires the use of chemical filters to remove excess carbon dioxide.Scientists were encouraged, though, that levels of the stinky methane stabilized after 12 days.

In 1972, more than ten years later, the Soviet research team, under the leadership of Joseph Gitelson, established the third version of the small biological habitat that can support human survival.The Russians called it Biosphere 3.It was crowded inside and only three people could survive. Four small air-tight chambers filled with barrels of soilless plants were illuminated by xenon lamps.In these small rooms, the Boxers grow and harvest the crops that are native to Russia—potatoes, wheat, beets, carrots, kale, radishes, onions, and cumin.Half of their food comes from these harvests, including bread made from wheat.In this crowded, stuffy sealed greenhouse, people and plants live together for up to 6 months.

The box is actually not completely sealed.The air it seals has no gas exchange, but it only recirculates 95% of the water.Soviet scientists stored half of the food (meat and protein) in it beforehand.In addition, Biosphere 3 cannot recycle human waste or kitchen waste; Biosphere 3 residents have to discharge these items from the box, which also discharges certain trace elements and carbon. To keep all the carbon from being lost in the cycle, residents burn some of the inedible parts of the dead plants, turning it into carbon dioxide and ash.Over several weeks, the room accumulated trace amounts of gas from various sources: plants, building materials, and the residents themselves.Some of these gases are poisonous, and people at that time did not know how to recover this gas, so they had to use catalytic furnaces to "burn" these things.

Of course, NASA is also very interested in feeding and sheltering humans in space. In 1977, they initiated a program that continues to this day: the Controlled Ecological Life Support System. NASA's approach is parsimonious: looking for the simplest form of life that can produce the oxygen, proteins, and vitamins humans need to consume.In fact, it was in the process of fiddling with these basic systems that Cao Hengxin, a member of NASA, stumbled upon a shrimp/algae pairing that was interesting but not particularly useful in NASA's eyes. In 1986, NASA launched the breadboard program.The purpose of this program is to realize on a larger scale the experimental results obtained on the table.The administrators of the Breadboard Project found an abandoned cylinder left over from the Mercury spacecraft.The huge tubular container was once used as a pressure test chamber for the small space capsule atop the Mercury rocket. NASA added ventilation and plumbing to the exterior of the double-decker cylinder, and converted the interior into a bottle house complete with lamps, plants, and recirculation racks.

Like the Soviet Union's Biosphere 3 experiment, Breadboard plans to use higher plants to balance the atmosphere and provide food.The amount of green algae that a person can barely swallow in a day is really limited, and even if a person only eats green algae, the nutrients that chlorella can provide to humans every day are only one-tenth of what humans need.It is for this reason that NASA researchers have abandoned the green algae system and turned to plants that not only clean the air, but also provide food. Everyone seems to be thinking of ultra-intensive farming in unison.Ultra-intensive cultivation can provide something actually edible, such as wheat.The most feasible devices are all kinds of hydroponic devices, that is, to transmit water-soluble nutrients to plants in the form of mist and foam, or to use film drip irrigation to those green leaves such as lettuce covered with plastic supports. Plants deliver nutrients.This well-designed plumbing installation produces dense plants in tight spaces.Frank Salisbury of the University of Utah found a lot of precise control methods to control the light, humidity, temperature, carbon dioxide content and nutrients required for wheat growth in the best state, and expanded the planting density of spring wheat 100 times.Based on the results of field experiments, Salisbury estimated how many calories could be produced per square meter of super-densely sown wheat in a closed environment such as a moon base.He concluded that "a lunar farm the size of an American football field could support 100 Moon City residents".

100 people live on a vegetable farm the size of a football field!Isn't this the vision of Jefferson's agricultural utopia!You can imagine a neighboring planet populated by countless villages with oversized domes.Every village can produce food, water, air, people and culture for itself. Yet NASA's approach to creating closed living systems strikes many as overly cautious, suffocatingly slow, and unbearably simple.In fact, NASA's "controlled ecological life support system" can be described with a very appropriate word: "controlled". But what we need is a little bit of "out of control".