China moved its heavy Long March 5B rocket to the launch pad on Monday in preparation for takeoff this weekend with a 22-ton unit to the country’s Tiangong space station, a mission that could end with another uncontrolled return of the Long March 5B rocket. The major stage.
The powerful launch pad rolled from its assembly building to the launch pad on Monday at the Wenchang Launch Center on Hainan Island in southern China. The Wentian module of the Chinese space station is enclosed within the payload hull of the rocket.
The Long March 5B missile is scheduled to launch at approximately 2:20 a.m. EDT (0620 GMT) on Sunday, July 24, according to airspace warning notices associated with the mission. This is also the approximate time that the orbital plane of the Tiangong space station passes over the Wenchang launch center.
The Wentian module, which has a launch weight of about 44,000 pounds (20 metric tons), will stick to the Tianhe base unit at China’s Tiangong Station in low Earth orbit. Chinese astronauts Chen Dong, Liu Yang and Kai Zhuzhi who live in the Tiangong complex will monitor the arrival of Wentian, then become the first crew members to float in the new station module.
The launch this weekend will add the second of three large pressurized modules required to complete the initial construction of the Tiangong space station. The Tianhe base unit was launched on the Long March 5B rocket in April 2021, and Chinese ground teams are preparing the Mengtian unit for launch on the Long March 5B rocket in October.
The Wentian unit carries a small robotic arm designed for more precise movements than the larger arm placed outside the Tianhe base unit. Chinese officials said the Wentian unit will mainly host life sciences and biological experiments.
The Wentian unit will initially dock with a pivot port on the Tianhe Unit, a docking mechanism that was recently cleared by leaving the no longer needed Tianzhou cargo ship. Tianhe’s mechanical arm will move the unit to its final position on the side of the space station’s core section.
The Mengtian module, scheduled to launch later this year, will arrive at the Tiangong Space Station in a similar fashion. Once Wentian and Mengtian reach their final positions, the Chinese station will have a distinct “T” shape with its three main elements compressed.
With Long March 5B on the launch pad to send the Wentian module into orbit, Chinese teams at Wenchang will complete final pre-flight checks and tests before loading kerosene, liquid hydrogen and liquid oxygen fuel into the rocket in the final hours before launch Sunday.
Ten engines will ignite to propel the 176-foot (53.7-meter) Long March 5B rocket into the sky with a thrust of 2.4 million pounds.
The Long March 5B rocket is a version of the Long March 5, China’s most powerful launcher, that flies without the upper stage required to put payloads into high-altitude orbits or send spacecraft to the Moon or Mars. On Long March 5B, the upper stage was replaced with an expanded payload volume to accommodate large modules of the Chinese space station.
This means that the Long March 5B rocket can reach a low-altitude orbit using four kerosene-fueled boosters and a hydrogen-fueled core stage. On two previous Long March 5B flights, including the launch of the Tianhe core module last year, the core stage remained in low orbit after deploying its payloads.
Key stages on previous Long March 5B missions returned to the atmosphere one to two weeks after launch. Long March 5B’s core 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 that could ever re-enter the atmosphere. in an uncontrollable way.
After the most recent launch and re-entry of Long March 5B last year, NASA Administrator Bill Nelson said China “failed to meet responsible standards with respect to space debris.”
“Space-faring nations should reduce the risks to people and property on Earth from the re-entry of space objects and increase transparency regarding these operations,” Nelson said in a statement last year.
Wang Wenbin, a spokesman for China’s Foreign Ministry, said at a press conference last year that it was a “common practice” for the upper stages of missiles to burn up as they re-enter the atmosphere. He incorrectly referred to the Long March 5B missile’s body as an upper stage and said that “most of its parts will burn up on re-entry, making the potential for damage to aviation or ground-based facilities and activities extremely low.”
But no other launcher in the world leaves such a massive component in orbit to return to Earth. Dead satellites and old rocket stages return to the atmosphere regularly, but objects over a few tons in mass are rare to re-enter.
The larger boosters and main stages used in other rockets usually fall to Earth without reaching orbit, and are usually in areas far from the launch site and empty of people.
Like most space junk that returns to the atmosphere, much of the Long March 5B rocket burns up as temperatures reach thousands of degrees during re-entry. But some debris can reach the Earth’s surface intact.
The risk of any missile debris harming someone or damaging property is low, with objects potentially falling into the ocean or into uninhabited areas. But the uncontrolled return of the first primary stage of Long March 5B in 2020 led to debris scattering over Ivory Coast. The return of Long March 5B occurred last year over the Indian Ocean.
Without any design changes, the Long March 5B missiles used to launch the Wentian unit on Sunday and the Mengtian unit in October would face a similar fate with an unguided return. The airspace warning messages issued to pilots for the Wentian launch this weekend show no return zone for the primary stage, indicating that it will remain in orbit for an uncontrolled landing in the days or weeks following launch.
The Chinese space station orbits about 236 miles (380 kilometers) above Earth, at an inclination of 41.5 degrees to the equator. The orbit means that the primary phase expended at Long March 5B could fall anywhere between 41.5 north and south latitude.
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