If we want more people to stay in space, what problems need to be solved?

On May 30, 2023, the Long March 2F rocket lifted the Shenzhou 16 manned spacecraft into space. With the Shenzhou 16 astronaut crew entering space, the total number of astronauts in the Chinese space station and the International Space Station in low-Earth orbit reached 17, setting a record for the highest number of astronauts in outer space at the same time in history. At the same time, space tourism is developing in full swing, and the construction of foreign commercial space stations is ready to go. It can be said that in the future, more and more people will work and live in orbit.

Shenzhou 15 and Shenzhou 16 crews, totaling 6 astronauts, "join forces in space"

In order to support more people in orbit, how many technical difficulties do researchers need to overcome?

More people achieve space careers

"The dream of flying will never lose weight, and the dream of science has unlimited tension." This is not only the "seed" of exploring the mysteries of the universe sown by space teachers to young people, but also a vivid portrayal of the work and life of professional astronauts in orbit. In addition to carrying out aerospace science popularization and education activities, they also pay close attention to rendezvous and docking, carefully walk in space, and widely carry out space physics experiments and aerospace medicine experiments. The reason why the number of people in orbit is increasing is largely due to the increasing complexity of space work tasks and the huge increase in the demand for personnel.

The International Space Station is designed to support a long-term stay of seven people, and has set a record of short-term accommodation of 13 people. Since it was fully built and put into operation in 2010, the International Space Station has received hundreds of visitors, many of whom are space science payload experts or aerospace engineers.

The International Space Station once set a record of accommodating 13 people for a short period of time

Some of them actively carry out biomedical experiments, study the life activities of animals, plants, microorganisms, and cells in space flight, and pay attention to the destruction and regeneration characteristics of biological tissues. Some study the impact of space flight on human chromosome telomeres, cognitive ability, gene expression, etc., and obtain cutting-edge results in the field of life sciences. Some cultivate food crops in space, strive to contribute to alleviating food shortages, and even bring several bottles of wine into space, claiming to the outside world that they are "studying the impact of weightlessness on brewing technology."

In addition, astronauts have also conducted a lot of engineering technology application research in orbit, such as replacing cooling and communication system components, maintaining and assembling space telescopes, etc. Although the space station is equipped with a mature automation system, astronauts are more capable of dealing with unexpected situations. In the past, there was a fire on the Mir space station, and it was all thanks to the astronauts that they put out the fire in time, restored the normal air composition and repaired some equipment.

Mir space station once encountered a fire hazard

In short, astronauts are needed to participate in complex affairs, and more astronauts will be working in new fields in the future. As space tourism becomes more and more popular, not only the number of people in orbit has reached new highs, but professional astronauts need to be responsible for more detailed and trivial affairs to ensure the safety and enjoyment of tourists.

Technical support meets high demands

If we want to maintain more people in orbit, the first condition is of course to have manned round trips between the earth and the sky, and the "safety" index is paramount. It is particularly important to note that once astronauts encounter an accident in space, the existing medical assistance conditions in orbit are limited after all. Therefore, the "safest" principle requires that the space station can return astronauts to the ground at any time.

As more and more astronauts are in orbit, more and more emergency rescue spacecraft need to be prepared on the ground. Ensuring their safety and reliability during standby is the key. At present, manned spacecraft generally adopts a rolling execution mode of rescue standby and normal flight missions to ensure that each spacecraft waits on the ground for a short time and is basically the same, avoiding a series of hidden dangers that may be caused by the long-term placement of spacecraft.

In addition, daily necessities and personal belongings are mainly delivered to the space station by cargo spacecraft. As the saying goes, "a gram of weight is worth a gram of gold" in the field of space launch, which shows that space transportation capacity is extremely precious.

There are many types of cargo spacecraft payloads, including daily necessities, space drinking water, gas supply, experimental payloads, and space station propellant replenishment. With the increase in the number of astronauts in orbit, the reliance on ground cargo supply is greater, so improving the transportation efficiency of cargo spacecraft has become a technical difficulty and an important direction for improvement.

The US Cygnus cargo spacecraft delivers goods with a malfunction

At present, cargo spacecraft of various countries widely adopt methods such as adding composite materials, optimizing hull structure and deadweight control, improving propellant energy conversion efficiency, and improving orbital insertion accuracy, so that cargo spacecraft can better complete their tasks in terms of uplink cargo ratio, rapid transportation, and propellant replenishment.

The most important technical guarantee for astronauts to work and live in orbit for a long time is the space station's environmental control and life support system. In the harsh space environment, the space station has multiple protection functions such as heat preservation, thermal insulation, collision protection, radiation protection, temperature regulation, and pressure regulation. It can resist the influence of space debris, cosmic rays, and abnormal radiation, and build a solid barrier for astronauts' life in space.

As more and more astronauts stay in orbit, higher requirements are placed on the life support system. It is necessary to produce several times more oxygen and water than before, remove more carbon dioxide, trace harmful gases, microorganisms, and dust, and adjust temperature, humidity, and air pressure more accurately and quickly.

In the current space station, electrolysis oxygen production technology can provide oxygen for astronauts, and carbon dioxide reduction technology can cleverly convert the carbon dioxide exhaled by astronauts into water, which after further processing can become drinkable water for daily use.

Astronauts install carbon dioxide reduction device in Chinese space station

It can be said that the efficient and reliable environmental control and life support system operates "endlessly", effectively reducing the dependence on cargo spacecraft for supplies. In order to serve more people on orbit, its expansion and upgrading is imperative.

Bright prospects for innovation in multiple fields

Traditionally, spacecraft and rockets are basically disposable, with high overall costs. The cost of each mission of the Russian Soyuz series of manned spacecraft is close to US$100 million, and the high price has become an important factor restricting human exploration of space.

With the advancement of science and technology, rocket or spacecraft recovery and reuse technology has become a hot topic in aerospace research and has gradually matured. After simple maintenance, more and more aerospace equipment can be used multiple times, significantly reducing the cost of launch. Once low-cost reusable technology achieves more extensive practical progress in the aerospace field, it will surely help more astronauts go to space.

Recyclable rockets and spacecraft will significantly reduce the cost of manned space missions

During operation, the space station is affected by the thin atmosphere resistance and solar wind, and its orbit is constantly lowered, which requires a lot of fuel to raise the orbit of the space station and maintain normal operation. In addition, during the operation of the space station, it is also necessary to cooperate with tasks such as rendezvous and docking, spacewalks, etc., to change orbits and adjust attitudes in a timely manner. Obviously, these orbital maneuvers consume precious space station propellant, and it is necessary to explore new technologies to drive spacecraft.

In recent years, grid ion thrusters and Hall thrusters have gradually become practical. The latest research results show that the conversion efficiency of electrodeless plasma thrusters using argon propellant has reached about 30%.

Plasma thrusters and Hall thrusters have been widely used in spacecraft

I believe that in the near future, more advanced propulsion technologies will be applied to space exploration, which will be more efficient and consume less energy, so that the same amount of propellant can support larger spacecraft and accommodate more astronauts in orbit for a long time.

Currently, astronauts rely mainly on cargo ships to deliver supplies in space. Although ground researchers try their best to feed astronauts and a wide variety of foods have been added to the astronauts' diet, it is still inevitable to eat canned and jelly-like foods frequently when living in space for a year or so.

But they don't have to worry - space planting experiments are constantly yielding results. Astronauts grow vegetables and fruits by themselves in space and often taste fresh ingredients, which will surely maintain better working and living conditions in space.

The growth process of rice on the Chinese space station

Of course, space planting and the presence of more astronauts in orbit place more stringent demands on environmental control and life support systems. Whether it is control accuracy, monitoring indicators, energy consumption levels, or working life, these are all directions for future improvement.

Moreover, as the number of people in orbit increases, the demands for temperature, humidity, lighting and even gravity will gradually become more diversified and personalized. The technical level of the environmental control and life support systems will inevitably be upgraded, and it is very likely that astronauts will be allowed to carry out maintenance and debugging work in orbit.

More and more professional astronauts and space tourists are staying in orbit, providing a large amount of raw data for space researchers, which is expected to accumulate valuable experience for future exploration of extraterrestrial bodies and deep space. In the future, as the "threshold" for flying into space is lowered, more people are expected to experience the beauty of space in person, and a more fulfilling work and life in space will also help human space exploration fly further.

The original title of this article is "With more and more people in orbit, how many technical difficulties are there?", published in the 2023 issue of Space Exploration magazine