What are the characteristics of manned spacecraft?

Manned spaceship is essentially a manned satellite. Compared with the satellite, its shape is simple, such as spherical and conical, but it is heavier. Satellites are diverse and irregular in shape and much lighter than spaceships.

Manned spacecraft and satellite systems are the same, except for structure, energy, attitude control and temperature control, there are also radio systems such as remote control, telemetry, communication and beacon tracking to ensure communication with the ground, transmit control instructions, transmit telemetry information, transmit data parameters and so on.

Manned spacecraft is characterized by manned, so it has different systems from satellites, including emergency rescue, return, life support and other systems. Manned spacecraft with rendezvous, docking and maneuvering flight capabilities are generally equipped with space rendezvous radar, computer and orbit change engine.

For example, as far as the manned spacecraft needs to return to the ground alone, the structure of the spacecraft is much more complicated than that of the satellite that does not return to the earth: first, it must deal with the ablation caused by aerodynamic heating, but also protect against meteors and cosmic rays, and so on. The so-called pneumatic heating means that when the manned spacecraft begins to return, it has considerable kinetic energy and potential energy because of its high height and high speed; After it entered the atmosphere, it slowed down sharply under the action of air resistance, and most of the energy of the spacecraft was converted into heat energy. If all this heat is conducted to the spacecraft, it can completely turn the spacecraft into ashes, which is the problem of pneumatic heating. The structural design of manned spacecraft must solve this problem. Reasonable selection of the aerodynamic shape of the spacecraft's return capsule can make about 80% of the heat generated during its return to the atmosphere spread to the surrounding atmosphere, and the remaining 20% of the heat must be solved by reliable heat prevention measures.

Another important technical problem is the life support system on manned spacecraft, which is not only complicated, but also absolutely reliable. The cabin should be airtight, the temperature and air pressure in the cabin should meet the needs of people's lives, and the control requirements are extremely high. In order to create a microclimate similar to that of the earth in manned spacecraft, we must first simulate the mixing ratio of the atmosphere, and supply oxygen by inflation or electrolysis, so that nitrogen accounts for 80% and oxygen accounts for 20% in the astronaut cockpit, ensuring that each astronaut needs 576~930 grams of oxygen every day; For about 1000 grams of carbon dioxide exhaled by each of them every day, molecular sieve adsorption method is adopted to control its concentration within 1%. It is also important to adjust the temperature and humidity in the spacecraft cabin. The heat source of the cockpit comes from 1/3 of human body, which usually produces about 3 13.5~627 kilojoules per person per day. The heat from solar radiation and various electronic instruments also accounts for 1/3 respectively. In addition to heat insulation measures for the shell, special heat exchangers are used in the cockpit to absorb and radiate excess heat, so as to keep the relative temperature at 18℃ ~25℃. The human body breathes and sweats every day, discharging about 1.5 liters of water, and forming water vapor in the cabin. Therefore, condensation and chemical absorption should be adopted to control the humidity at 30% ~ 70%. Because the cockpit is small and closed, there are more than 400 metabolites in the human body, which is easy to cause pollution in the cabin; In weightlessness, gas convection disappears, heat balance is difficult to maintain, and so on, all of which need to be solved well on the spacecraft.

In the process of space flight, manned spacecraft can study the influence of various special factors on human body and corresponding protective measures, as well as the necessary conditions and equipment for long-term survival in space environment.

When the spacecraft takes off sharply, the weight of the human body will increase accordingly, leading to overweight; When the spacecraft returns to the earth, it must brake, the speed will drop sharply, and it will be overweight in the opposite direction. After the spacecraft enters the orbit around the earth, it will get rid of the gravity of the earth to some extent. At this time, the human body will lose weight and enter a state of weightlessness. Overweight and weightlessness will have physiological effects on various organs of the human body. Therefore, when the manned spacecraft enters orbit and safely returns to the ground, we can study the reaction and ability of human beings in the process of space flight, and study how astronauts bear the influence of takeoff, orbital flight and gravity change after returning to the atmosphere.

The scientific application of manned spacecraft can be used in biology, medicine, astronomy, physical research and celestial observation, and can be used in various space science experiments and earth natural resources investigation.

At present, only the United States, the Russian Federation and China have developed manned spacecraft and fully mastered this manned space technology. But European countries and Japan are actively preparing to develop manned spacecraft.

In the past 30 years, the manned space program has been realized, including the Oriental, Ascension, Alliance, Salute and Equal Manned Space Program developed by the former Soviet Union. The United States has successively developed manned space programs such as Mercury, Gemini, Apollo, Skylab and Space Shuttle.

Learning point

Space rendezvous radar

Space rendezvous radar is a kind of radar used to guide spacecraft to rendezvous and dock in space orbit. The two manned spacecraft are in different orbits. Spacecraft A carries space rendezvous radar and guidance computer, while spacecraft B (target) carries (or does not carry) transponder. The function of rendezvous radar is to capture and track the target, measure the distance, distance change rate and angle between two spacecraft, and transmit them to the guidance computer and display. The parameters such as the rendezvous motion of spacecraft A, the best time to enter the transfer orbit, the injection point, and the speed change correction are calculated by the computer and displayed on the display. According to these data, the astronauts manipulated spacecraft A to make the distance and the rate of change between the two spacecraft approach zero, thus realizing the rendezvous.