At 10.22 a.m. Moscow time on 24 July, a Changzheng-5B rocket with the first laboratory module of China's Tiangun space station took off from the Wenchang launch site.
Wenian is introducing a significant number of innovations to China's space station, in particular new experiments. Like the Tianhae main module already in orbit, Wenian has an estimated mass of 22 tons. However, it will be slightly longer than the last, 17.9 m compared to 16.6 m, while maintaining a maximum diameter of 4.2 m.
Wenian represents eight "stores", i.e. the spaces inside a leaky standard size module containing scientific instruments. A marked increase over the two only people present on Tianhae. The space for science is also outside the module; in fact, there will be 22 slots in the central building for experiments that will be shown in direct contact with the space environment. Experiments focused mainly on the study of materials and life sciences.
Ventian is also equipped with a 5-metre robotic hand developed by HIT. It is smaller than the 10-metre main on Tianha. However, this new manipulator can be directly connected to the previous one, forming a single device.
An important addition to the module is the three new accommodations, which will allow them to be used as a reserve in case of emergency, but first of all to bring the total number of permanent tacono-vehicles at the station to six. The pressure portion is the first cylindrical section on the left of the figure above. The central part is a new lock that will now be used to enter space for off-ship activities. The last part, on the right, is fuel tanks and solar batteries, which are shown in blue on this image.
After leaving Changzhen-5B, Wentyan will open the antenna and only partially deploy the solar panels. The latter will be fully deployed only after the module is docked in Tianhe. During a journey that lasts a few days, Wentyan will launch four main engines several times to adjust and raise orbit. The remaining 32 engines will also be used for orbital control in preparation for the meeting with Tianhae.
In order to facilitate the docking, the station already in orbit will turn 180 degrees around the horizontal axis and then return to its original configuration after the arrival of Wentyan. The module will remain at the port parallel to Tianhe and will be set to its final position in September only, perpendicular to Tianhae, in order to make room for the arrival of the second module of the Manthian laboratory, which will perform a similar manoeuvre. When the Mentian module will also be moved perpendicularly to Tianhe, the Tiangun will take the final T-shaped form.
Changjeng-5 is now the most powerful launcher available in China: the Martian Tianwen-1 mission and the last lunar Chan ' e-5 mission in 2020 also reached space with this launch vehicle. Changjeng 5B is a version of this launch vehicle modified to operate without a second stage. This is done to increase the flow of the leak, i.e. the space on board the missile.
Without the second stage, the loading capacity is decreasing, especially in high orbits, but since the Wenian module is very large and will have to rise to a height of only 350 km, such a single-stage configuration is ideal.
The consequence of this, however, is that the first stage must remain on longer, because it is the only stage of propulsion. As a result, the first stage itself goes into orbit. It goes into orbit in 8 minutes and 20 seconds and goes into low orbit. This will lead to constant friction with the atmosphere, which will cause the stage to re-enter the atmosphere in a few days. Unfortunately, because the effect of atmospheric friction is unpredictable, because it depends on weather conditions, atmospheric density, the amount of radiation and other factors, we cannot predict exactly where this phase will occur.
However, despite its size, it is not a particularly dangerous wreck. At the time of the re-entry into the atmosphere of the first stage of the Changjeng-5B rocket, which launched the Tianhe module in 2021, several parts of the engines and a long pipe to transport fuel along the missile hit the Earth.