On April 25, the Shenzhou-18 spacecraft was launched, and on April 26, the Dongfeng landing site carried out the last system-wide comprehensive exercise of the Shenzhou-17 search and rescue recovery mission, which meant that the Dongfeng landing site was ready to welcome the triumphant return of Shenzhou-17.
However, the three astronauts of Shenzhou 17 did not return to Earth immediately, but needed to carry out an in-orbit handover with the astronauts of the Shenzhou 18 spacecraft. After completing the handover, the Shenzhou-17 spacecraft will also need to wait for a time window to return to Earth before evacuating from the Chinese space station.
On the morning of April 30, the Shenzhou-17 spacecraft was evacuated from the Chinese space station complex and began to return to Earth. As with previous missions, the fast return scheme continues this time. That is to use a 5-lap (7.5-hour) rapid return scheme, which is to return to Earth after 5 laps around the Earth after evacuation.
After completing the flight around the earth, the spacecraft will not land directly on the ground, because during the flight, the spacecraft still maintains the state of a three-module combination, that is, the orbital module, the return module, and the propulsion module. Before preparing to return to the Earth and re-enter the Earth's atmosphere, the spacecraft will successively separate the orbital module and the propulsion module, leaving only the spacecraft return module. It was in the re-entry capsule that the astronauts returned to Earth. After re-entering the Earth's atmosphere, the spacecraft return capsule also needs to adjust its flight attitude, and when it descends to 10 kilometers above the ground, it needs to open the parachute to slow down, and finally land safely.
When the spacecraft returns to the capsule and lands safely, the astronauts in the spacecraft will not leave the capsule immediately. This is because the attitude of the spacecraft landing is uncontrollable, and the astronaut's sitting posture in the seat in the return capsule may not be very good, if you are not sure about the astronaut's sitting position or do not adjust their sitting position, the seat restraint mechanism is removed, which may cause the astronaut to fall. Therefore, the first thing is to confirm the attitude of the astronauts.
After the preparations, these astronauts will go out of the capsule one by one, and the whole process of getting out of the capsule is also relatively complicated and time-consuming, generally lasting half an hour to an hour. Moreover, after the astronauts leave the capsule, they also need to go through a series of processes, one of which is to sit next to the return capsule and rest, and readjust to the gravitational environment on the ground.
After completing the extravehicular medical rescue and medical supervision and medical insurance work, the staff will also transfer the astronaut to the medical supervision and medical insurance carrier, and then examine the astronaut's body, and also help the astronaut change the flight suit, the whole process lasts about 160 minutes.
I believe that many friends have seen the picture of the astronauts when they leave the capsule, they are carried by the staff, and they are still wearing spacesuits in the cabin. In this case, not only the astronauts of the Shenzhou 17 spacecraft need to wear in-cabin spacesuits, but also the astronauts wear in-cabin spacesuits when the previous Shenzhou spacecraft returns, and foreign astronauts need to wear in-cabin spacesuits when they return to Earth in the Soyuz manned spacecraft and the Crew Dragon spacecraft. What the hell is going on here? Actually, there are lessons in history.
Soyuz-11 manned spacecraft
In the 60s of the last century, the United States and the former Soviet Union launched a space race, both sides wanted to become the first country in the world to achieve a manned lunar landing, and both were actively promoting the manned lunar landing program, but because the United States took the lead in realizing the first manned lunar mission in human history, the former Soviet Union's manned lunar landing program faced many difficulties. Under such circumstances, the former Soviet Union changed its direction and launched the world's first long-term orbital space station, which was Salyut 1.
On April 19, 1971, the Salyut 1 space station was successfully launched, according to the plan, the former Soviet Union planned to launch the Soyuz 10 manned spacecraft and the Salyut 1 space station to complete the rendezvous and docking, so that astronauts into the Salyut 1 space station, but it was unsuccessful. This was followed by the launch of Soyuz-11 mission.
On the morning of June 6, 1971, the Soyuz-11 manned spacecraft was successfully launched, sending three astronauts into space. On June 7, 1971, the Soyuz-11 spacecraft successfully completed the rendezvous and docking with the Salyut 1 space station, and the three astronauts successfully entered the space station, and then lived in the Salyut 1 space station for more than 23 days.
After completing a series of missions, the three astronauts took a spacecraft from the Salyut 1 space station on June 29, 1971 to prepare for the return to Earth.
In the early morning of June 30, 1971, the spacecraft was preparing to re-enter the atmosphere, and the separation of the re-entry module and the orbital module was carried out before re-entering the earth, when the pressure valve in the re-entry capsule was deployed, resulting in the sealing of the re-entry capsule being destroyed, and the spacecraft re-entry capsule quickly lost pressure. Three astronauts aboard the Soyuz-11 spacecraft died due to loss of pressure and lack of oxygen. Although the procedures for the return capsule of the Soyuz-11 spacecraft were carried out normally, and the return capsule landed safely on the ground, the three cosmonauts of the former Soviet Union were sacrificed.
This was one of the most tragic space accidents in the history of the Soviet Union, as it failed to launch a spacecraft to send astronauts to the Salyut 1 space station, which crashed over the Pacific Ocean.
After the Soyuz-11 accident, the former Soviet Union made improvements to the Soyuz spacecraft, not only installing a life support system, but also stipulating that the spacecraft must wear a spacesuit when launching and returning. This is why astronauts now wear in-cabin spacesuits when launching spacecraft and returning to Earth in spacecraft, whether it is our Shenzhou manned spacecraft, or Russia's Soyuz manned spacecraft, or the American Crew Dragon spacecraft, or the space shuttle before the United States.