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China’s Long March 5B heavy rocket rolls out with new space station module

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The Long March-5V rocket, designed to launch the Wentian module to the Chinese space station, leaves the assembly shop at the Wenchang launch base on Hainan Island on Monday. 1 credit

On Monday, China moved a heavy Long March 5B rocket to the launch pad in preparation for launching this weekend with a 22-tonne module for the country’s Tiangong space station, a mission that could end in another uncontrolled re-entry of the Long March 5B. large main stage.

On Monday, the powerful launcher left the assembly shop for the launch pad at the Wenchang Space Center on Hainan Island in southern China. The Wentian module for the Chinese space station is enclosed within a rocket payload fairing.

The Long March 5B missile is due to launch around 2:20 am EST (0620 GMT) on Sunday, July 24, according to mission-related airspace warnings. This is also the approximate time that the Tiangong space station’s orbital plane flies over the Wenchang Launch Center.

The Wentian module, with a launch weight of around 44,000 pounds (20 metric tons), will dock with the main Tianhe module at China’s Tiangong station in low Earth orbit. Chinese astronauts Chen Dong, Liu Yang and Cai Xiuzhe, who live in the Tiangong complex, will monitor Wentian’s arrival and then become the first crew members to enter the station’s new module.

This weekend’s launch will add the second of three large pressurized modules needed to complete the initial construction of the Tiangong space station. The Tianhe core module was launched on a Long March 5B rocket in April 2021, and Chinese ground teams are preparing the Mengtian module for launch on a Long March 5B rocket in October.

The Wentian module carries a small robotic arm designed for more precise movements than the larger arm located outside the main Tianhe module. The Wentian Module will primarily conduct biological experiments and biological experiments, according to Chinese officials.

A Long March 5V rocket carrying a module from China’s Wentian space station takes off on Monday for a launch pad at the Wenchang Space Center on Hainan Island. 1 credit

The Wentian module will initially dock with the axial port on the Tianhe module, a docking mechanism that was recently cleared following the departure of the no longer needed Tianzhou cargo ship. The Tianhe’s mechanical arm will move the module to its final position on the side of the main section of the space station.

The Mengtian module, scheduled to launch later this year, will arrive at the Tiangong space station in a similar fashion. Once Wentian and Mengtian are in their final positions, the Chinese station will have a distinctive T-shape with three main pressurized elements.

With the launch of the Long March 5B to the launch pad to send the Wentian module into orbit, the Chinese teams in Wenchang will complete the final pre-flight checks and tests before loading kerosene, liquid hydrogen and liquid oxygen into the rocket in the final hours before launch. Sunday.

Ten engines will be fired to propel a 176-foot (53.7-metre) Long March 5B rocket into the sky with a thrust of 2.4 million pounds.

The Long March 5V rocket is a variant of the Long March 5, China’s most powerful launch vehicle, which flies without the upper stage needed to launch payloads into high orbits or send spacecraft to the Moon or Mars. On the Long March 5B, the upper stage has been replaced with an increased payload capacity to accommodate the large modules of the Chinese space station.

This means that the Long March 5V rocket can reach low orbit using four kerosene-fuelled strap-on boosters and a hydrogen-fueled main stage. On two previous Long March 5B flights, including the launch of the Tianhe main module last year, the main stage remained in low orbit after the payload deployed.

The mission patch for launching the Wentian module shows the lab element being docked to the axial port of the main Tianhe module before being moved to the side port with the robot arm. 1 credit

Major stages of previous Long March 5B missions re-entered the atmosphere about one to two weeks after launch. The Long March 5B main stage is about 100 feet (30 meters) long and has an empty mass of about 23.8 tons (21.6 metric tons), making it one of the largest and most massive man-made objects ever to re-enter the atmosphere. in an uncontrolled way.

Following the last launch and re-entry of Long March 5B last year, NASA administrator Bill Nelson said China was “not meeting responsible standards for its space debris.”

“Space powers must minimize the risks to people and property on Earth associated with the re-entry of space objects and maximize the transparency of these operations,” Nelson said in a statement last year.

Wang Wenbin, a spokesman for China’s foreign ministry, told a press conference last year that it was “common practice” to burn up rocket upper stages on re-entry. He incorrectly referred to the body of the Long March 5V missile as an upper stage and said that “most of its parts will burn up during re-entry, making the probability of damage to aircraft or ground objects extremely low.”

But no other launch vehicle in the world leaves such a massive component in orbit to return to Earth. Dead satellites and old rocket stages regularly return to the atmosphere, but objects weighing more than a few tons rarely return.

An artist’s illustration of China’s Tiangong space station as it appears when completed. 1 credit

The larger upper and main stages used on other rockets typically fall back to Earth before reaching orbit, usually in unmanned areas below the launch pad.

Like most space debris that re-enters the atmosphere, most of the Long March 5B rocket burns up when temperatures reach thousands of degrees upon re-entry. But some debris can reach the Earth’s surface intact.

There is little risk of any rocket fragment injuring anyone or damaging property, with objects likely to fall into the ocean or into uninhabited areas. But the uncontrolled re-entry of the first main stage of Long March 5B in 2020 scattered debris across the Ivory Coast. The re-entry of Long March 5B occurred over the Indian Ocean last year.

Without any design changes, the Long March 5B rockets used to launch the Wentian module on Sunday and the Mengtian module in October will suffer a similar fate with unguided re-entry. Airspace warning messages issued to pilots for the Wentian launch this weekend show no re-entry zone for the main stage, suggesting it will remain in orbit for an uncontrolled descent for days or weeks after launch.

The Chinese space station orbits about 236 miles (380 kilometers) above the Earth at an angle of 41.5 degrees to the equator. The orbit means that a spent Long March 5B main stage could fall somewhere between 41.5 degrees north and south latitude.

Write to the author.

Follow Stephen Clark on Twitter: @StephenClark1.


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