Peppers grown on the International Space Station have recently received a bumper harvest
What kind of plant can be selected as a space "vegetable garden"
Under the microgravity environment of the low-Earth orbit space station, those ready-to-eat fruits and vegetables that can be eaten should be planted because it is very difficult to cook and process food under microgravity conditions; in addition, the ease of cultivation and management of plants should also be considered, and Unit volume, unit energy consumption output rate, etc.
◎Reporter Tang Fang
Recently, Megan MacArthur, a female astronaut on the International Space Station, ate "space" peppers.
In July this year, this batch of peppers began to be planted on the International Space Station, and recently it has ushered in a bumper harvest.
MacArthur chopped up the peppers to make a taco, and posted pictures and texts on social media calling them "delicious."
How to provide fresh food to the astronauts staying in the space station for a long time has always been a headache.
Countries around the world have not stopped their experiments in space cultivation.
According to incomplete statistics, hundreds of plant seeds, including peppers and strawberries, have been sent to the International Space Station for cultivation.
Among them, chili is one of the most popular foods in space planting experiments.
Why are peppers so popular?
What kind of plants are suitable for space cultivation?
Does the food grown in space have radiation? Can it be eaten directly?
In this regard, a reporter from Science and Technology Daily interviewed Liu Hong, chief designer of "Yue Gong No. 1" and professor of Beijing University of Aeronautics and Astronautics.
Choose plants to grow in space carefully
"Chili has a relatively high vitamin C content. Sweet peppers, fruit peppers, vegetable peppers, etc., taste fresh; peppers can bloom, have a high degree of appreciation, and have a refreshing smell." Liu Hong told reporters that in addition, peppers also It is more suitable for planting in a space environment. The pepper seedlings have small plants, occupy less space, and have firmer branches. The plant type has better support under microgravity.
Not only that, peppers are also more "skin-skin", have better stress resistance and are easy to survive.
Of course, in addition to peppers, there are also many plants suitable for long-term cultivation in space.
Liu Hong pointed out that to cultivate plants in space to protect the lives of astronauts, we must first calculate the overall human demand for nutrients such as calories, vitamins, and trace elements in space, and then calculate which plants can meet these needs when matched together; secondly, Under the microgravity environment of the low-Earth orbit space station, those ready-to-eat fruits and vegetables that can be eaten should be planted because it is very difficult to cook and process food under microgravity conditions; in addition, the ease of cultivation and management of plants should also be considered, and Unit volume, unit energy consumption output rate, etc.
"Specifically, for manned deep-space exploration activities centered on the construction of lunar and Mars bases, it is necessary to ensure human caloric intake, and food crops such as wheat and soybeans need to be planted; vegetables should be diversified to meet human physiological and physical conditions. For psychological needs, lettuce, cabbage, small rapeseed, pepper, eggplant, tomatoes, etc. can be grown. Cucumber is a climbing plant, which takes up a lot of space, but is crisp and refreshing. If the planting needs to be firmly fixed to prevent the vines from filling the cabin; for fruits , It’s good to plant strawberries, it takes up less space and has more fruits.” Liu Hong said.
In the 60-year history of manned spaceflight in the world, hundreds of astronauts have entered space, and long-term space missions by astronauts have become the general trend.
The longest of these was the Russian astronaut Valery Polyakov, who stayed on the International Space Station for 437 consecutive days.
The issue of food supply for astronauts in space has always been the focus of attention.
"In the early days, space food was like toothpaste. Vegetables, fruits, and meat were all processed into a paste and squeezed out to eat. Later, it developed into a pre-processed whole piece of food, which can identify the type of food. Now, food on the ground can basically be taken. In space, except for fresh fruits, other foods are pre-processed compressed foods, canned foods, and packaged foods. Most of them need to be heated before eating." Liu Hong introduced.
"Only eat packaged food for long-term storage, it will inevitably be boring for a long time. For longer or farther detection tasks, carrying too much natural food may be broken, so another kind of life support is needed. System.” Liu Hong explained that the guarantee of human life is to ensure people’s needs for oxygen, water, food, etc. Therefore, planting plants in space is very important and you can kill three birds with one stone.
"Plant photosynthesis consumes carbon dioxide and produces oxygen. Astronauts produce a lot of waste water in their daily work and life. After the waste water is purified, plants can be irrigated. The transpiration of plants evaporates water into the air, which can be condensed into high-quality air condensate. After the water is purified, it is naturally fresh and safe, and people's psychological acceptance is also higher." Liu Hong said.
Watering "space plants" is a matter of university
The low-Earth orbit space environment is characterized by microgravity.
"The moment the elevator drops, it is close to the state of microgravity." Liu Hong said, "The space microgravity environment has a great influence on plant cultivation techniques. The necessary conditions for plant growth are light, temperature, water, gas, and fertilizer. Watering plants in space is a huge challenge."
Plants need water only when they are short of water, the same is true in space, but it is a technical task to grasp the timing of watering.
"On the ground, a sensor can be used to detect soil moisture and water in time; the space station is affected by microgravity, and water droplets will adhere to the sensor, causing the sensor to malfunction. It is clear that the substrate is lacking water, but the sensor may still show sufficient water." Liu Hong said that for watering the space station, all the water is first pumped out, then the gas and water are separated, and finally the water is pumped into the substrate, and this whole set of cyclic operations is carried out at regular intervals.
"This has led to the fact that although the planting area of the plant incubator is not large, the supporting water pumps, valves, pipes and other accessories are a huge set of devices."
"Now'space growing vegetables' is no longer a particularly high-tech and difficult thing. In addition to the troublesome water supply, the rest of the light, temperature, gas and fertilizer have better solutions." Liu Hong pointed out that the most current It is important to systematically study the scientific laws of plant growth in space.
Take wheat as an example. What is the difference between the yield of wheat grown in space and on the ground?
What is the law of photosynthesis in space to produce oxygen and absorb carbon dioxide?
What's the difference between the nutrient content of the produced substance and the earth?
These are all questions that scientists from all over the world are eager to explore.
It is reported that since the 1970s, scientists and astronauts have tried to grow vegetables in the space station, but due to various reasons, many attempts have failed.
After decades of unremitting efforts, Russian astronauts ate the lettuce grown in space for the first time in 2003, and in 2016 the International Space Station cultivated the first zinnia blooming in space.
In recent years, hundreds of planting experiments on space stations by countries all over the world have laid a solid foundation for opening up "space vegetable gardens."
The shape and taste of fruits produced in space are similar to those produced on earth
However, some netizens expressed concern about whether vegetables grown in space will be affected by radiation?
Can the grown food be eaten directly?
"The radiation in the space station cabin is within a safe value. Space plants are also grown under the conditions for plant growth. Therefore, the color, shape, and taste of the fruit are not essentially different from those on the earth. But the vitamin C content of solanaceous vegetables will be even higher. Higher, it may be that the cabin radiation is slightly higher than that on the earth, which stimulates plants to synthesize more antioxidants.” Liu Hong pointed out that in fact, the microgravity environment and radiation environment in space will have an impact on plants, and countries all over the world also Ongoing research.
Liu Hong pointed out that all food grown in space must be sampled.
Take a green pepper as an example. Its leaves, roots, or entire plant will be frozen and brought back to the ground for analysis.
The National Aeronautics and Space Administration (NASA) once brought lettuce back to the earth to test whether it contains microorganisms harmful to human health, and finally proved to be safe.
So, what is the difference between bringing seeds to space for direct planting, and bringing seeds back to earth for planting after space experiments?
Liu Hong explained that space mutation breeding takes seeds into space and exposes them to outer space cosmic rays.
Cosmic rays will "kill" most of the seeds, and the few that survived will be brought back to the earth for planting.
For example, my country's Chang'e 5 once carried a batch of seeds "to heaven". After returning from the "Journey to the Moon", some of the seeds of rice, alfalfa and oats have emerged in the laboratory, which is of great value for further scientific research.
However, even if it is "survived", most of these seeds are actually "disabled."
Only a few of them will produce traits that humans hope to see, such as a giant pumpkin once a "space seed" has grown.
"The plants planted in the space capsule are completely different. The space station cabin itself is well protected, so it will not cause the plants to mutate." Liu Hong said.