Now that our space station has entered the stage of application and development, it has become a normal thing for astronauts to be stationed in the Chinese space station, and two Shenzhou manned spacecraft will go to the Chinese space station this year. Compared with the previous missions, since the Shenzhou 17 mission, some aspects have changed, and one of the changes is the adjustment of the cargo spacecraft.
Before the launch of the Shenzhou-12 spacecraft, we launched the Tianzhou-2 cargo spacecraft ahead of schedule for replenishment; before the launch of the Shenzhou-13 manned spacecraft, we launched the Tianzhou-3 cargo spacecraft ahead of schedule for replenishment; before the launch of the Shenzhou-14 spacecraft, we launched the Tianzhou-4 cargo spacecraft ahead of schedule for replenishment; before the launch of the Shenzhou-15 spacecraft, we launched the Tianzhou-5 cargo spacecraft ahead of schedule for replenishment; and before the launch of the Shenzhou-16 spacecraft, we launched the Tianzhou-6 cargo spacecraft ahead of schedule。
When the Shenzhou-17 spacecraft was launched, we did not launch the Tianzhou cargo spacecraft in advance, but carried out the launch mission almost three months later. The Shenzhou-17 spacecraft will be launched on October 26, 2023, and the Tianzhou-7 cargo spacecraft will be launched on January 17, 2024. Now the Shenzhou-18 spacecraft is about to be launched, and the Tianzhou-8 cargo spacecraft has not been launched in advance, and it is expected to be launched in the second half of the year. What the hell is going on?
Although the Tianzhou-7 and Tianzhou-8 cargo spacecraft were not launched ahead of schedule, the space station still has enough supplies to support astronauts to fly for a long time. Compared with the previous Tianzhou cargo spacecraft, the cargo capacity of the new batch of cargo spacecraft has increased from 6.9 tons to 7.4 tons, and the effective loading volume has increased from 18.1 cubic meters to 22.5 cubic meters, which is equivalent to an expansion of 20%, making it one of the most powerful cargo spacecraft in the world.
In the past, each cargo spacecraft can basically ensure that the astronaut crew of a Shenzhou manned spacecraft flies in orbit for 6 months, so it is necessary to launch 2 Tianzhou cargo spacecraft every year for replenishment, and the new batch of cargo spacecraft for upgrading carries more materials, and now the frequency of Tianzhou cargo spacecraft launch has also been adjusted, from 2 per year to 3 every 2 years. Therefore, before the launch of the Shenzhou 17 spacecraft, the Tianzhou-7 cargo spacecraft was not launched in advance, and the Tianzhou-8 cargo spacecraft was not launched in advance before the launch of the Shenzhou-18 spacecraft.
According to the plan, in 2024, our space station will carry out 4 launch missions, one of which is the launch of the Tianzhou-7 cargo spacecraft in January, and the second launch mission is the Shenzhou-18 that is about to go to the Chinese space station, in addition, in the second half of the year, we will also launch the Tianzhou-8 cargo spacecraft and the Shenzhou-19 manned spacecraft.
Shenzhou-18 is about to be launched
The rocket and ship assembly of the Shenzhou-18 mission arrived at the launch area on April 17, and on April 21, the launch area also carried out a system-wide joint exercise, and three astronauts boarded the Shenzhou-18 spacecraft to carry out a joint inspection and test of man, ship, arrow and ground, and completed all the key operations of the rocket's standby and take-off stages.
This actually means that the Shenzhou 18 spacecraft is about to be launched. It is reported that the Shenzhou-18 spacecraft is expected to be launched on the evening of April 25, and the launch mission still uses a fast rendezvous and docking method to go to the Chinese space station and dock to the radial port of the core module of the Chinese space station Tianhe.
When the Shenzhou-18 spacecraft arrives at the Chinese space station, our space station will once again form a combination of 3 cabins and 3 ships, that is, the Tianhe core module, the Wentian experimental module, the Mengtian experimental module, as well as the Shenzhou 17 manned spacecraft, the Shenzhou 18 manned spacecraft, and the Tianzhou 7 cargo spacecraft, with a total weight of more than 100 tons, and the space station will also be temporarily filled with 6 astronauts. When the Shenzhou-17 spacecraft returns to Earth at the end of this month, the space station assembly will return to the state of a three-cabin two-ship assembly.
As the launch time of the Shenzhou 18 spacecraft is getting closer and closer, the astronaut crew of this mission is about to make a public appearance, and the astronauts who participate in this mission have actually been selected, which are generally determined about a year in advance, and then begin to participate in mission training. After all, during the period in orbit, these astronauts will live and work in the Chinese space station for 6 months, which requires higher requirements for astronauts and needs to complete more complex tasks.
The return time of Shenzhou 17 has been determined
From the point of view of time, the launch of Shenzhou 18 is expected to be a matter of these days, when the Shenzhou 18 spacecraft is launched, the space station will be full of 6 astronauts again, but this state will not last long, generally at the same time in orbit to live, work for about a week, when the two astronaut crews complete the handover, the Shenzhou 17 spacecraft will return to Earth. Therefore, when the launch time of the Shenzhou 18 spacecraft is determined, the time for the Shenzhou 17 spacecraft to return to the earth is actually determined.
There is news on the Internet that the Shenzhou 17 spacecraft will return to Earth on April 30. Although this is not the official announcement time, judging from the arrangement of the mission, it is actually about this time. When the Shenzhou-17 spacecraft returns to Earth, the spacecraft will land at the Dongfeng landing site after a series of operations, and the entire return process can be said to be thrilling.
This is because when the manned spacecraft is evacuated from the space station assembly, the speed is still very fast, almost reaching the first cosmic speed of the earth at 7.9 kilometers per second, because only by reaching such a fast speed can the spacecraft maintain the state of flying around the earth without falling off.
Due to the high speed of the spacecraft, a series of braking decelerations, that is, a reduction in flight speed, are required on the way back to Earth. As the speed of the spacecraft decreases, so does its orbital altitude, from a circular orbit of almost 400 kilometers to an elliptical orbit of about 100 kilometers at perigee. Finally, the spacecraft needs to separate the various modules, and only the spacecraft return capsule can safely return to the surface.
Even if the re-entry capsule were able to land safely on the ground and not burn violently in the atmosphere and turn to ashes like other modules, the exterior of the re-entry capsule would still be burned black beyond recognition. This is due to the fact that the speed of the spacecraft's return capsule is very fast, and the Earth has a dense atmosphere, and when the return capsule breaks into the atmosphere at a very fast speed, the aerodynamic heating effect is strong, and the outside temperature rises sharply to one or two thousand ° C. Under the scorching heat, the exterior of the spacecraft's return capsule seemed to be surrounded by raging fire.
Of course, although the temperature outside the spacecraft return capsule is quite high, the spacecraft return capsule is still very comfortable because the outside of the spacecraft return capsule is coated with ablative materials and thermal insulation materials, which can protect the spacecraft return capsule from being burned out. It's just that under the scorching heat of such high temperatures, the outside of the return capsule will be burned black. There's really no way around it.