Although humans successfully entered space decades and years ago, the scale of manned mission to mars is larger than any previous space project. At present, there is no rocket that can make a giant spacecraft carrying astronauts and all the materials and fuel necessary to reach Mars get rid of the gravity of the earth and reach space. It may be necessary to send parts into low-earth orbit by rockets in batches, and astronauts will assemble spacecraft and materials in space before flying to Mars.
At present, the largest equipment operating in space is the International Space Station, with a mass of over 4 0 0 tons. It was carried by 365,438+0 spacecraft.
The mass of an aircraft that can send humans to Mars is about 1250 tons. Using the existing rockets, it takes 7 0 to 8 0 flights to complete the task. It took more than 1 0 years to assemble the International Space Station, and it also took a very long time to assemble the Mars spacecraft.
Maybe this task will be much easier in the future. If the new space launch system SLS rocket is successfully developed in 2022, its carrying capacity is still considerable. Space Exploration Technology, a private space company in the United States, is developing a new Falcon heavy-duty launch vehicle with a slightly smaller carrying capacity than SLS rocket. NASA estimates that at least seven new SLS rockets need to be launched to send the materials and spacecraft needed to land on Mars into Earth orbit.
Fuel storage
Humans need many things to survive in space: food, oxygen, shelter and fuel. Propellants will account for 8 0% of the materials sent into space by manned Mars flight. The problem is that it is difficult to store such a large amount of fuel in space. When astronauts build a Mars spacecraft, they put materials into low-earth orbit, where objects orbit the earth about every 9 0 minutes. They spend half their time baking in the high temperature of the sun and the other half in the cold and dark space. This change can easily lead to the evaporation of liquid hydrogen and oxygen, and the fuel storage container may explode if it is not handled properly. There, the hydrogen in the container will evaporate by 4% within one month. If the Mars project stays in low earth orbit for 1 year, it will lose nearly 1/2 propellant. The cost of sending 1 kg hydrogen into space is about 1 10,000 dollars, and this leakage is a huge waste. Nasa is testing the technology of loading and converting propellant in large space at low temperature. If successful, NASA can build a long-term gas warehouse in space to refuel the rocket at any time.
Propulsion technology
NASA plans to send a spaceship to the surface of Mars first, and then send astronauts there. Advanced propulsion technology is very important for sending humans to Mars as soon as possible. Nasa is studying solar propulsion technology, which is a technology to propel the spacecraft by emitting ionized gas from the tail of the spacecraft. This technology has been used by NASA's Dawn spacecraft and Japan's Hayabusa spacecraft. Mars projects need solar electric thrusters larger than these existing projects. NASA currently has a plan to collect asteroids and drag them back to Earth, which will promote the research of solar electric propulsion technology.
Landing on Mars
The thin Martian atmosphere cannot open large parachutes quickly, so it is very difficult for large spacecraft to land on Mars. "Curious" weighs 1 ton and is the largest object that can be sent to the surface of Mars at present. NASA said that the manned Mars project needs to send at least 4 0 tons of objects to Mars. The "Mars 1" one-way manned Mars project also needs to carry nearly 1 0 tons of materials. Experts from NASA are developing a hypersonic inflation system. These are huge spherical objects that can help the plane slow down when deployed.
However, the key to human landing on Mars is supersonic re-propulsion technology. In 1960s and 1970s, NASA conducted wind tunnel experiments on supersonic re-propulsion technology, and not long ago, there was another one. The good news is that experiments show that supersonic re-propulsion technology is feasible in theory. The bad news is that NASA is no longer studying this project.
Now, some private space companies, such as Space Exploration Technology, are studying reusable rockets, which can return to the launch pad from low Earth orbit. The company may study supersonic re-propulsion technology later.
Health problems of astronauts
Space is a dangerous place for human body, with the most complicated system. The sun, which provides energy for life on earth, is a fatal threat to life in space travel. Once astronauts are outside the earth's magnetic field, the sun's rays will accumulate in their bodies, thus increasing their risk of cancer. The recent data obtained by the "Curious" Mars probe has quantified the radiation level and danger level on the surface of Mars. Big explosions such as solar flares and high-energy particles may produce deadly doses of radiation to spacecraft. Therefore, the American private manned Mars program-"Inspired Mars" was carried out in 2 0 1 8, when the solar activity was weak, and the possibility of solar particle explosion was the lowest. However, lower solar particle activity increases the radiation from galaxies, which is also harmful. A trip to Mars may take seven to nine months, and human beings should be protected during the whole process. At present, the most feasible scheme is to wrap the spacecraft with water. When encountering a solar storm, water can absorb light and provide some shelter. However, the quality of water is relatively large, and adding any weight in space projects will increase the cost. It is expected to develop a small magnetic field technology that can protect astronauts in the future, but it will take many years to realize it.
Besides radiation, the biggest challenge of manned trip to Mars is microgravity (also called zero gravity), which will lead to many strange diseases and a series of psychological problems. If you are in weightlessness for a long time, there will be problems such as bone calcium loss, muscle atrophy and optic nerve swelling. If not treated in time, you may be weak, brittle bones and even blind. Advanced medical technology and regular exercise are helpful to solve some physical problems in space travel. At present, NASA plans to let astronauts stay on the International Space Station for 1 year in order to better study these factors. However, in the process of flying to Mars, the psychological problems that astronauts have to face are largely unknown. The distance between the International Space Station and the Earth is relatively close, and astronauts can see the Earth, but the astronauts of the Mars program have to endure the pain of not being able to communicate with their families for a long time. In the 1990s, American scientists conducted the "Biosphere 2" experiment, which allowed eight people to stay in a large-scale simulation environment for nearly two years. Taber mccallum, an expert who participated in the "Biosphere 2" experiment, said: "Everyone who participated in the experiment said that psychological problems are the biggest problem." So far, the longest Mars travel simulation experiment is the international large-scale experimental project "Mars 5 0 0" organized by Russia and participated by many countries. From June 2065438 to June 2000, six volunteers stayed in a sealed room for 5 0 0 days. With the passage of time, the volunteers who participated in the experiment became listless in the room, and 1 of them became very depressed. Two of the six students have no problems, only 1 students remain active and busy, and their cognitive ability has not declined.
At present, the United States is carrying out a Mars program to test the limits of human tolerance for loneliness.
Mars resources
Mars is cold and dry, but it is rich in resources for astronauts to use.
Before the astronauts arrive, a machine will be sent to Mars in advance. It will use carbon dioxide in the Martian atmosphere to extract oxygen and separable elements from the soil, and then use them to make building materials and rocket fuel. Mars is rich in solid water, and there are enough ice crystals in the soil in some places, which robots can easily collect.
Although often discussed, on-site resource utilization technology has never been developed. NASA needs to prove that it is feasible to rely on the resources of other planets to survive.
Humans also need to plant plants on Mars, because astronauts need fresh fruits and farms, which can reduce the freeze-dried food they eat. But planting on another planet is a tricky and dangerous thing. American expert Taber mccallum said, "Nobody wants astronauts to live on their own food. Plants are very picky. If astronauts make mistakes, they may die. " After analyzing the input and output of plant planting, temperature control and other necessary system and technical requirements, mccallum estimated that it would take 1 5 to 2 0 years to get the output equivalent to the input of agricultural system.
Protect mankind and the earth.
Because of the possibility of extraterrestrial life, NASA and other major spacefaring countries agreed to abide by strict planet protection standards. 1 9 6 9, when three American astronauts successfully landed on the moon and returned to earth, NASA isolated them for three weeks to ensure that they did not bring terrible space viruses that might harm human beings. This kind of work has been repeated. It was not until the eighth manned mission to the moon was completed in 1 9 7 1 that scientists were convinced that astronauts did not bring harm from the moon.
Although there are no harmful bacteria on the moon, Mars is another environment. The possibility of life on Mars is really small, but it is not zero. There is evidence that Mars may once have the ability to give birth to life. These possible creatures may be harmful.
While considering that microbes on Mars may harm human beings, we should also pay attention to another opposite problem. Humans have their own microbial communities and fungi, but at present we can't stop these microorganisms and fungi from polluting Mars after landing on it. We need to improve our ability to protect human beings from the influence of Mars, and at the same time we need to protect Mars from the dangerous influence of human beings. In order to comply with the strictest planetary protection agreement, the best way is to carry out some unmanned exploration missions on the surface of Mars. Humans can camp in low-earth orbit or Mars satellites, and real-time remote control detectors and other robots on the surface of Mars. These robots will check whether there is evidence of life on the surface of Mars and look for safer landing sites. Future technology will also prevent astronauts from bringing human pollution when they land on Mars.
Mars dust
The arid Martian environment will produce a lot of harmful tiny dust. Living on the surface of Mars is like living in a huge salt field. Mars dust is corrosive, and astronauts' tools need to be particularly durable, otherwise they will be easily corroded.
More importantly, try not to expose astronauts to the dust environment on Mars, because the dust on Mars is considered toxic. After analyzing the Martian soil samples, Curiosity found that the Martian soil contained perchlorate. Perchlorate is a chemical substance that needs great attention in the earth's water supply system, which may lead to thyroid diseases.
Dust on Mars may also contain carcinogens, which may cause allergic reactions or lung diseases similar to those suffered by Apollo astronauts. The manned Mars program needs to know the humidity of Martian dust and human habitat, otherwise the dust may hurt human skin like lye or bleach. At present, NASA, S p a c e X and INSPARI I I O ON MARS all have Mars landing plans, and one of them will be selected as the final plan.
No one knows how much the manned Mars project will cost, which is estimated to be as high as hundreds or even hundreds of billions of dollars. It seems that such a project should be completed through international cooperation, which requires the participating countries to make everything through formal commitments. The world is complex, and the long-term task is to deal with political changes and economic recession.