Hausjärvi, FINLAND – China is gearing up to send a second module to its under-construction space station later this month with a launch from the coastal city of Wenchang.
A Long March 5B heavy-lift missile will launch the approximately 22-ton Wentian experiment module around 2:20 a.m. ET (0620 UTC) on July 24, according to recently announced clearance reports corresponding to such a launch.
The 53.7-meter-long 837.5-ton rocket will be rolled out to the pad in Wenchang in the coming days.
Wentian is expected to converge and join Tianhe, the similar-sized core module for the Tiangong space station launched in April 2021. Tianhe made orbital adjustments earlier this month to prepare for the arrival of Wentian.
The new module has a length of 17.9 meters and a maximum diameter of 4.2 meters. It features crew quarters and an airlock cabin which, once operational, will become the main entry point for extravehicular activities (EVAs), replacing the role now played by the Tianhe docking hub.
The new crew facilities will enable China to conduct a first crew transfer. This will take place as the current crew of the Shenzhou-14 greets three new astronauts who will fly aboard the Shenzhou-15 in December. Tiangong will then house six astronauts over a period of days.
Its main role is to host experiment racks for science experiments while also providing backups for Tianhe’s life support and control functions. Wentian carries a five-meter-long robotic arm, complementing the 10-meter-long Tianhe arm. The two arms can also be linked together.
Wentian is also coming up with 30-meter-long solar panels, increasing the power available to Tiangong. Wentian wants host a new round of live science lectures, following on from that presented by the Shenzhou-13 crew aboard Tianhe.
“Wentian is a critical stage in the construction of China’s space station,” said Brian Harvey, author of China in Space: The Great Leap Forward. “The Tianhe crew has overseen numerous disconnections and feedbacks, so such maneuvers are well practiced, but nothing can be taken for granted, especially not for the first time.”
The Shenzhou-14 astronauts aboard Tianhe have undergone a training program that includes meeting and docking operations and the use of Tianhe’s mechanical arm in preparation for Wentian’s arrival.
Tianzhou-2, a freighter initially used to deliver supplies to Tianhe for the first crew, Shenzhou-12, was used for a conversion test to verify procedures for moving a module from the forward docking port to a lateral port.
Tianhe has so far been visited by three separate three-man crews. The most recent, Shenzhou-14, arrived on June 5 and will oversee the arrival of Wentian and Mengtian, another 22-ton experiment module slated for launch in October.
The arrival of the latter will complete the planned T-shaped Tiangong space station, although China has suggested it could later expand the complex to six modules.
“The real work of the station, which we can expect to fly in the 2040s, will begin,” Harvey said, once Mengtian is docked in position.
The Chinese space station was first designed in 1992 with the approval of Project 921, which called for the development of human spaceflight capabilities. The project was delayed due to problems with the development and implementation of the Long March 5B, but could also be expanded to six modules and most commercial and tourism missions.
The country also plans to launch an orbiting optical telescope module called Xuntian by the end of 2023. It will be able to link to Tianhe for repairs, maintenance, refueling and upgrades, and aims to survey 40 percent of the sky in a decade.
Xuntian has an aperture two meters in diameter and a field of view more than 300 times larger than the 32-year-old Hubble Space Telescope. NASA plans a new research mission, the Nancy Grace Roman Space Telescope, around 2027.
Notably, the two previous launches of Long March 5B, which carried a prototype next-generation crew spacecraft and the Tianhe module, respectively, saw the rocket’s large first stage enter orbit and return unchecked.
Attention will be paid to whether or not to change the start profile or to add deorbiting options, such as restarting engines. If not, the mission may see another uncontrolled return. Exceptionally, the Long March 5B includes a core stage and boosters.
Usually, smaller second or further stages do the final work of putting a spacecraft into orbit, with the larger first stage cutting off before reaching orbital speed and falling within a calculated, safe area.
China’s Foreign Ministry spokesman Wang Wenbin said last year that “it is common throughout the world for the upper stages of rockets to burn as they enter the atmosphere.” In this case, the large first stage is also the top stage.
While such an event would involve particularly large and massive spacecraft, the self-contained threat of the rocket stage used causing damage or damage will be very low. Most of the stage will burn up in the atmosphere and will likely land in the oceans or uninhabited areas.
However, there is a greater cumulative risk, according to academics, of uncontrolled reentry due to space launch activities.
Area eviction notices provide: drop zones for the boosters and fairings for the upcoming Wentian launch, but no indication of a zone for the first phase.