The return cabin, also known as the cockpit, isastronautOf“cab”。It's a round trip for astronautsSpaceThe cabin section is a closed structure with a door at the front end.Return capsule andPropulsive cabinAfter disengaging, return cabin return, propulsion cabinIncinerate, andOrbital moduleIt is equivalent to a ground observationsatelliteorSpace laboratory, it will continue to work on the track for a period of time.
On October 31, 2023, the return capsule of Shenzhou 16 manned spacecraft landed successfully.[8][11]
In the afternoon of April 30, 2024, the return capsule of Shenzhou 17 manned spacecraft landed successfully at Dongfeng landing site.[13]
Generally, manned spacecraft can be divided into propulsion module, orbital module and re-entry module.
Propulsion cabin, also called instrument cabin, is usually equipped with propulsion system, power supply, track brake, and is provided for astronautsoxygenAnd water.The propulsion cabin is also equipped with a main structure with an area of more than 20 square meters on both sidesSolar cellSail wings.
The orbital module is the main activity area for astronauts. In addition to entering the re-entry module when launching and returning, astronauts are in the orbital module at other times. The orbital module integrates many functions such as working, eating, sleeping and washing.
The return capsule, also known as the cockpit, is the "cockpit" of astronauts.It is the compartment for astronauts to travel to and from space. It is a closed structure with a door at the front.After the re-entry module and the propulsion module are separated, the re-entry module returns, and the propulsion module is burned. The orbital module is equivalent to an earth observation satellite or space laboratory, and it will continue to work in orbit for a period of time.
Structural requirements
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Airtightness
AndairshipLike other manned segments, the return capsule has a high degree of tightness.However, unlike the orbital module, the return module still needs to be air tight under high temperature and pressure.
Anti ablation and easy to dissipate heat
In order to avoid burning through the bulkhead with high heat caused by severe friction with the atmosphere, the surface of the return tank is coated withAblative materialAnd heat dissipation by means of pyrolysis, melting and evaporation of materials.This material is a composite material formed by mixing asbestos, glass and phenolic resin.The Shenzhou re-entry capsule with a diameter of 2.5 meters has a surface area of 22.4 square meters, and the total weight of the thermal protection material is about 500 kilograms.In order to avoid local overheating, the return cabin has a rolling attitude adjustment engine, which will be heated evenly by rotation.
With so many protective measures, the possibility of cabin rupture should still be considered.At that time, astronauts in airtight spacesuits will take overAutopilotControl the emergency return of the spacecraft by manually operating the backup system.Safe entryatmosphereAfter that, it is necessary to further control the landing speed.
When the return capsule returns, it will re-enter the atmosphere under the effect of gravity. The ever-changing airflow will make it difficult for the high-speed return capsule to maintain a fixed posture. Therefore, the return capsule must be shaped like a tumbler, with a large bottom and a small head, and is not afraid of the turbulence of the airflow.The whole return capsule can be divided into three parts.
cockpit
In addition to the seats that can reduce the impact, the astronauts' emergency supplies and instruments, films, tapes, test samples, scientific data andremote sensingThe materials will be put here.
Shenzhou 9The seat in the re-entry module is very similar to the baby seat, because the astronauts must keep a crouching position when returning, which is a very safe position.The seat of the return capsule is like a baby chair, which experts say can reduce the impact.Before returning, the seat should also be raised to cushion the impact of the instant impact when landing.
Thermal barrier
Severe friction with the atmosphere will produce thousands of degrees of high temperature on the cabin surface. If the problem of heat protection is not solved, the spaceship will burn to ashes before landing.The surface of the return capsule has a layer of thermal protection layer, which is made of special ablative materials. The thermal protection principle is to take away the heat through the burning of materials. According to the experimental research of scientists, the shape of the big clock is relatively conducive to achieving the thermal protection goal.
In the world, there are three main ways to prevent and insulate the return capsule of spacecraft: one is endothermic heat protection. In some parts of the return capsule, metal heat absorbing materials with good thermal conductivity, high melting point and large heat capacity are used to absorb a lot of aerodynamic heat;The second is radiation type heat protection, which uses titanium alloy, ceramics and other composites with radiation properties to radiate heat;The third is ablation and heat prevention, which uses the method of melting, evaporation, sublimation or decomposition gasification of some materials on the surface of polymer materials to take away a lot of heat when heating at high temperature.[1]
ChineseShenzhou Series SpacecraftIt adopts the self-developed anti erosion heat protection mainly, supplemented by radiation heat protection and insulationThermal insulation materialSystem.The advanced thermal insulation material technology is used to put a 25mm thick "thermal coat" on the return capsule. Under the effect of huge heat flow, the thermal insulation material decomposes, melts, evaporates and sublimates itself, taking away a lot of heat while consuming the surface quality. The material decomposes to form a dense outer shell radiating heat outward, and the internal non ablated thermal insulation area,It can prevent heat from entering the return capsule.The above factors together determine that the ablative heat protection material has a good thermal protection function, which can control the internal temperature of the spacecraft at about 30 ℃.[1]
parachute
During the landing of the re-entry module, at least three parachutes - pilot parachute, deceleration parachute and main parachute - should be "opened".If necessary, there is a fourth umbrella - the backup umbrella.The main parachute of China's Shenzhou VI parachute covers an area of 1200 square meters, with a total length of more than 70 meters. The parachute jacket is more than 20 meters long, but it is only the size of a handbag when folded, and weighs only more than 90 kilograms.The power device return capsule itself has no power, but the appearance of the spaceship is composed of two parts. A smaller cone in the front is the return capsule, while a larger cylinder in the back can be called the service capsule. Where there is power, there are many devices.When it is time to return, the power plant can slow down the spacecraft to return to the ground in a spiral orbit.When entering the return orbit, the two parts will separate.
Landing mode
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The return capsule carries astronauts and a large number of precision test instruments. The successful recovery of the return capsule isManned Space EngineeringA crucial link in.The parachute is usually used to reduce the landing speed of the re-entry module when it returns to the ground.Due to the limitation of the designed landing speed of the parachute, the landing speed of manned space re-entry capsule on land is generally 6-7m/s, while that of unmanned re-entry capsule can reach 10-14m/s.When the re-entry module lands at such a high landing speed, it will have a great impact at the moment of landing, which will have a great impact on the astronauts and instruments in the module.[2]
The landing impact system of the re-entry module includes two parts: the re-entry module and the landing site ground.[3]The landing impact process of the re-entry capsule mainly draws the following conclusions:
(1) The time of reaching the peak stress value far from the landing point on the bottom of the re-entry capsule lags behind the landing point. At the same time, the stress value at the landing point changes slightly with the land speed, while the change amplitude of the position far from the landing point is larger with the land speed;(2) From the perspective of acceleration response, due to the buffering effect of the big bottom, the peak acceleration response on the big bottom of the girder is significantly reduced, and the acceleration response value is larger in the frequency range of 40-80Hz;(3) From the distribution of impact energy, it can be seen that the landing ground is the main body of impact energy absorption, and the big bottom is the most important part of energy absorption on the return capsule. In the structural design of the return capsule, the cushion role of the big bottom should be fully played.[2]
Sea landing
Apollo 11 return capsule
After returning to the cabin and entering the water, the dye will be automatically released to dye the surrounding sea water into fluorescent color and be sent out in timeGPS positioningSignal to facilitate rescue personnel to quickly find targets at sea.The landing return capsule can ensure the astronauts to live in it for a long time according to its technology and use characteristics (sealing, floating, carrying life support equipment, etc.).When the re-entry capsule splashes down on the sea, the astronauts' activities for survival include: selecting a suitable place and attitude for the re-entry capsule to stay;Use onboard radio system to communicate with the outside world;Use emergency supplies in the return cabin;Leave the return capsule with a spacesuit or diving suit.The activities carried out by astronauts during drifting after leaving the re-entry capsule include: building life rafts for the crew to act collectively;Inflate the diving suit;Eating food and water in portable emergency equipment;Use emergencyradioAnd optical signal equipment contact with the outside world;Search toRescue helicopterOr the ship approaches.When the return capsule floats on the water surface and the air exchange hole is closed, if the temperature and gas composition in the return capsule are within the allowable range, it is more appropriate for astronauts to stay in the return capsule to ensure safety.Unless absolutely necessary, the astronauts will not leave the re-entry module.Mercury“Gemini”Both the "Apollo" series manned spacecraft and the "Apollo" series manned spacecraft are recycled at sea.[3]
Ground landing
When the return capsule lands on the desert, astronauts should use the return capsule and parachute to build a shelter against wind and sand.In winter, when the re-entry capsule lands on forest swamp or frozen land, astronauts should use the re-entry capsule and other equipment to build a cold shelter.
Landing process
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After the manned spacecraft completes the scheduled mission, the return capsule with astronauts will return to the earth, and the whole return process needs to go through four stages, namely, braking off orbit, free descent, re-entry and landing.[4]
Brake off track section
Figure 1 Spacecraft composed of two compartments
The phase when the spacecraft enters the return orbit from the original flight orbit through attitude adjustment, braking and deceleration is called the braking off orbit section.Before returning, the spaceship must first adjust its attitude to make it rotate 90 ° counterclockwise in the horizontal direction, and change from the state of the orbital module in the front, the return module in the middle, and the propulsion module in the rear to the horizontal flight state, which is the first time for the spaceship to adjust its attitude.Then, the orbital module and the return module separated at a relative speed of 1 to 2 meters per second. The orbital module remained in space orbit and continued to operate. This is the orbital module separation.At this time, the spaceship becomes a combination of propulsion module and return module.As shown in Figure 1.The two module assembly continues to rotate 90 ° counterclockwise to become the flight state of the propulsion module in the front and the return module in the rear. At the same time, the pitch angle is adjusted to meet the braking requirements, which is the second attitude adjustment of the spacecraft.The ignition of the engine in the propulsion module of the spaceship produces a force opposite to the flight direction of the spaceship, which reduces the flight speed of the spaceship, thus leaving the original flight orbit and entering the return orbit. This braking process can be likened to "braking".[4]
Free Descent Section
From leaving the original orbit to entering the atmosphere, the air resistance of the spacecraft is very small, which is mainly due to the free flight state under the action of the gravity of the earth. Therefore, this stage is called the free descent phase or the transition phase.In this flight phase, the spacecraft will complete the separation of propulsion module, establish reentry attitude and other important flight events according to the plan.The propulsion module will be burned after entering the atmosphere after being separated from the return module.It is an important work to establish the correct reentry attitude angle (the angle between the velocity direction and the local horizontal plane) of the re-entry capsule. This angle must be accurately controlled within a certain range. If the angle is too small, the spacecraft will brush over the edge of the atmosphere and cannot return;If the angle is too large, the spacecraft will return too fast, and will be burned in the atmosphere like a meteor.[4]
Reentry section
The flight phase from the reentry capsule entering the dense atmosphere to the start of the recovery landing system is called reentry phase.When the spacecraft returns, it enters the atmosphere again from the vacuum environment when it leaves the orbit. This stage is called reentry phase.The altitude of reentry into the atmosphere is generally 80~100km.After entering the dense atmosphere, the re-entry capsule is subjected to aerodynamic heating and reentry overload, which is the worst stage of the re-entry process.With the reduction of altitude, the air density is getting higher and higher, and the return capsule is severely rubbed with the air, making its bottom temperature reach thousands of degrees Celsius, and the return capsule is surrounded by flames. Therefore, special heat protection measures should be taken for the return capsule.When the return capsule descends to a certain altitude, the radio signal sent by the ground cannot be received, nor can the ground receive the radio signal sent by the return capsule. Therefore, this area is called the radio "black barrier area".When the axial overload of the return capsule reaches the specified index, the return capsule implements lift control to make the overload of the return capsule not exceed the range that the astronauts can bear, and uses lift control to control the landing position of the return capsule, so that the return capsule returns to the scheduled landing site.[4]
Landing section
The process from opening the parachute to landing of the return capsule is called the landing phase.With the reduction of altitude and speed, the aerodynamic resistance of the re-entry capsule gradually balances with the gravity of the earth, and the re-entry capsule drops at an average speed of about 200 meters per second.However, if the return capsule rushes to the ground at this speed, the consequences will be unimaginable, so the return capsule must be further decelerated.At an altitude of about 10km from the ground, the recovery and landing system of the return capsule starts to work. The pilot parachute, deceleration parachute and main parachute are pulled out successively to make the speed of the return capsule slowly decline, and the heat proof bottom is thrown away. When the return capsule is about 1m from the ground, the reverse thrust engine is started to make the return capsule achieve soft landing.In order to increase the reliability of landing, in addition to the main parachute system, the re-entry module is also equipped with a smaller backup parachute system.Once the main parachute system fails, it can be activated in emergency at the specified altitude to make the return capsule land safely.[4]
Exhibition
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From September 15 to 21, 2022, the main event of National Science Popularization Day in Beijing will be held at the Beijing Science Center. At the "Light Year Deep" deep space exploration theme exhibition, the return capsule of Shenzhou XIII manned spacecraft will be displayed to the public for the first time after returning to the earth from space, and the return capsule parachute and the wreckage of Long March 3A carrier rocket will also be displayed together.[5]
Successful landing
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At 20:09 on December 4, 2022 (Beijing time), the return capsule of the Shenzhou XIV manned spacecraft landed successfully at the Dongfeng landing site. The on-site medical supervision and medical insurance personnel confirmed that the astronauts Chen Dong, Liu Yang and Cai Xuzhe were in good health, and the Shenzhou XIV manned flight mission was a complete success.[6-7]
At 06:33 on June 4, 2023, the return capsule of Shenzhou 15 manned spacecraft landed successfully.[8]
At 19:34 on October 26, 2023 (Beijing time), after the manned spacecraft and the space station assembly successfully achieved autonomous and rapid rendezvous and docking, the Shenzhou 17 crew entered the orbital module from the spacecraft's return capsule.The Shenzhou 16 crew successfully opened the "home" and welcomed the Shenzhou 17 crew to the "Tiangong".[9]
Shenzhou 16 manned spacecraft return capsule
On October 31, 2023, the return capsule of Shenzhou 16 manned spacecraft landed successfully.[8][10-12]
In the afternoon of April 30, 2024, the return capsule of Shenzhou 17 manned spacecraft landed successfully at Dongfeng landing site.[13]
