A Chinese rocket is set to make an uncontrolled re-entry as it heads back to Earth sometime in the next dew days, with concerns that it could rain heavy pieces of spacecraft on populated areas.
The 21-ton object is the core stage of China's Long March 5B rocket, which launched from the Wenchang Spacecraft Launch Site in south China's Hainan Province on Wednesday.
The core module successfully separated from the rocket and entered the predetermined orbit, but the 100ft booster started circling Earth, uncontrolled, rather than falling into a designated spot in the ocean - as is common for used rockets.
According to SpaceNews, the core stage's orbital inclination of 41.5 degrees means the rocket body passes 'a little farther north than New York, Madrid and Beijing and as far south as southern Chile and Wellington, New Zealand', and could 'make its re-entry at any point within this area'.
Jonathan McDowell, an astronomer who tracks objects orbiting Earth, told the outlet: "I think by current standards it's unacceptable to let it re-enter uncontrolled."
McDowell added: "Since 1990 nothing over 10 tons has been deliberately left in orbit to re-enter uncontrolled."
When the rocket falls out of orbit, it may just burn up in Earth's atmosphere.
However, large chunks of debris could still survive the fall, and rain down on inhabited areas if they miss the ocean.
Holger Krag, the head of the Space Safety Programme Office for the European Space Agency, told SpaceNews: "It is always difficult to assess the amount of surviving mass and 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."
China previously launched the Long March 5B - which is designed for launching space-station modules - once before, in May last year.
That time, the rocket's core stage also fell to Earth uncontrolled, six days after launch - re-entering the atmosphere over the Atlantic Ocean.
Despite the obvious issues, the most recent launch has been deemed a success, and is considered a strong first step for China's space station construction.
Li Dong, chief designer of Long March-5 rockets at China Academy of Launch Vehicle Technology, said: "I'm thrilled that China has made the perfect first step in building its space station.
"The Long March-5B Y2 rocket completed its mission.
"I wish all the best for the following in-orbit tests, all the following tasks can be finished in success, and that our astronauts can enter China's own space station at an early date."
Liao Guorui, the commander responsible for signaling the ten-second countdown and the blast-off order, added: "For such an important task that allows no missteps, we made preparations on personnel training, documents and contingency plans.
"We withstood the test in the launching process."
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