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The Chinese rocket stage is expected to re-enter the atmosphere around May 8

Rollout of the first Long March 5B to the trail in We changed, South China in April 2020. Credit: CASC

HELSINKI – A large rocket stage that launched China’s first space station last week is likely to re-enter the atmosphere around May 8, according to early space tracking predictions.

US Department of Defense spokesman Mike Howard said in a statement May 4 that “US Space Command is aware of and is tracking the location of China’s Long March 5B in space, but its exact entry point into Earth’s atmosphere.

cannot be determined until a few hours after its return, which is expected around May 8. Until then, the 18th Space Control Squadron will provide daily updates on the location of the rocket body from May 4 at www.space-track.org .

We will provide additional information as it becomes available, ”the statement said. The launch of the Long March 5B at the end of April 28 Eastern successfully put the 22.5-metric ton Tianhe core module into orbit.

however, the approximately 30 meters high Long March 5B with a diameter of 5 meters also reached orbital velocity instead of falling within a predetermined area.

The empty rocket body is now in orbit of 162 by 306 kilometers. According to space tracking by the US 18th Space Control Squadron, lower than an initial orbit of 170 by 372 kilometers.

Without the ability to restart the engines, the core phase will be dragged to Earth by increasing collisions with molecules in Earth’s atmosphere.

Atmospheric fluctuations and other variables and the high speed of the stage mean that accurate predictions of when and where the stage will re-enter are not possible until a few hours before the event.

The Long March 5B core’s orbital slope of 41.5 degrees means that the missile body will pass slightly further north than New York, Madrid and Beijing, and as far south as southern Chile and Wellington, New Zealand, and could make its return at any point. within this area.

A May 4 update from the Aerospace Corporation predicts the return will occur on May 9 at 12:37 a.m. Eastern Time (4:37 a.m. Universal Time), with a margin of error of plus or minus 28 hours.

The Russian space agency Roscosmos also stated on May 4 that its Automated Warning System on Hazardous Situations in Outer Space (ASPOS OKP) indicated that the Long March 5B would follow an uncontrolled reentry.

Calculations by Russian experts indicate a return window of 9 p.m. May 7 – 4:00 pm May 9 East, with more refined forecasts over the next few days. China has not yet commented on the status of the Long March 5B.

The country plans 10 more launches from various spacecraft and launchers by 2022 to build its three-module space station. China is currently preparing to send the Tianzhou-2 cargo spacecraft to Tianhe with a Long March 7 missile in the coming weeks.

A first manned mission, Shenzhou-12, is expected to send three astronauts to the new orbital outpost in June. Notably, two more launches of the Long March 5B are expected in 2022 to send the Wentian and Mengtian experiment modules to orbit Tianhe.

It is not known whether the China Academy of Launch Vehicle Technology (CALT), which designed and manufactures the Long March 5B, has planned changes to the missile or launch profile that would allow the core platform to either deorbit or on a ballistic trajectory to Earth. fall .

The Long March 5B is specially designed to launch modules for the Chinese space station in low Earth orbit. During a test flight in 2020, the nuclear stage also reached an orbital speed. That incident saw a reentry over the Atlantic with local reports suggesting that debris from that 20-ton podium appears to have survived the reentry and landed in the African nation of Ivory Coast.

Parts of the Long March 5B (Y2) to launch the Chinese space station’s core module at a facility in Tianjin. Credit: CMSA

Holger Krag, head of the European Space Agency’s Space Safety Program Office, told SpaceNews that an average mass of about 100 tons each year enter the atmosphere in an uncontrolled manner.

“It is always difficult to judge the amount of mass remaining and the number of fragments without knowing the design of the object, but a reasonable” rule of thumb “is about 20-40% of the original dry mass,” said Krag.

Unlike older Long March series missiles, the Long March 5B nuclear stage uses liquid hydrogen and liquid oxygen as fuel. Older generation Long March 2, 3 and 4 series missiles use a poisonous hypergolic propellant combination of hydrazine and nitrogen tetroxide, creating reentry debris that would be potentially dangerous to anyone approaching the wreckage.

Debris from Chinese rocket launches from inland spaceports occasionally falls into populated areas. China is expected to take precautions against causing injuries through security announcements, evacuations and calculation of rocket stage fall zones, and by experimenting with technologies such as grid fins and parafoils.

While much attention has been paid to the threat to people on the ground and aircraft in flight from the return of satellite and missile components, the Aerospace Corporation raised the issue of pollution from reentry last year.