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Uncontrollable China rocket hurtles towards re-entry

The long Chinese rocket blasts off into a cloudy sky with a burst of fire beneath it.

April 29, 2021, liftoff of the Long March 5B rocket carrying the Tianhe core module for the Chinese Space Station. The core stage is due to re-enter Earth’s atmosphere in early May. Image via CCTV/ SpaceNews.

China’s 100-foot (30-m) Long March 5B rocket successfully launched the Tianhe space station module last Thursday, April 29, 2021. That module will become the living quarters of the future Chinese Space Station. It’s currently in its correct orbit after separating from the core stage of the rocket as planned. The core stage, however, also reached orbit and is now descending again, on a path to be one of the largest-ever pieces of space debris to make an uncontrolled re-entry back into Earth’s atmosphere. It’s not yet clear exactly where or when the debris will hit our planet (we’re seeing a prediction of “around May 8” from experts). No one knows whether, when it falls, it’ll land on an uninhabited – or inhabited – part of Earth.

According to SpaceNews, the object’s orbital inclination, or tilt, of 41.5 degrees means it passes a little farther north than cities at about 40 degrees north latitude, including New York City, Madrid and Beijing. It passes as far south as southern Chile and New Zealand. The core stage could make its reentry at any point within this wide area. Of course, most space debris tends to burn up in the atmosphere, meaning only the largest pieces will come down to the ground. But mission engineers also generally try their best to point a returning piece of debris back to Earth and give estimates as to where it may fall.

Astrophysicist Jonathan McDowell of Harvard University (@planet4589 on Twitter) has been regularly tweeting about the descending core stage. The following tweets are from last night (May 5). Perigee is an orbiting body’s closest point to Earth. Apogee is an orbiting body’s farthest point from Earth. What’s happening here is that the rocket body’s perigee is getting closer and closer. As it reenters Earth’s atmosphere, it becomes subject to more and more atmospheric drag.

With all of the above said, the most likely possibility is the core stage will fall in an uninhabited area. After all, Earth’s oceans cover 70% of our planet, and thus most returning space debris does fall into the ocean. It’s possible, though, that some debris will fall on land. According to Mark Matney, a scientist in the Orbital Debris Program Office at NASA’s Johnson Space Center in Houston, the odds that you will be hit by falling space debris are one in several trillion.

Even for experts, plotting the precise trajectory of a large piece of falling space debris is difficult, if not impossible. There are many uncertainties involved in calculating the effect of atmospheric drag on China’s core module, for example. The high speed of the rocket body means it orbits Earth roughly every 90 minutes, and so a change of just a few minutes in reentry time results in a reentry point hundreds of miles away. Plus, the sun is now in a relatively active phase of its 11-year cycle, and Earth’s atmosphere can expand or contract with solar activity. All of these factors make it hard to estimate exactly when and where the rocket will come down.

In a separate statement, McDowell predicted some pieces of the rocket will survive reentry and that it would be the:

… equivalent of a small plane crash scattered over 100 miles … Last time [China] launched a Long March 5B rocket, they ended up with big long rods of metal flying through the sky, damaging several buildings in the Ivory Coast.

A slightly elongated bright spot on an otherwise blank gray field, with text below.

The image above comes from a single half-second exposure, remotely taken with the Elena robotic unit of the Virtual Telescope on May 6, 2021. The telescope tracked the exceptionally fast (0.3 deg/second) apparent motion of the object. Gianluca Masi of Virtual Telescope Project wrote: “At the imaging time, the rocket stage was at about 700 km [about 400 miles] from our telescope, while the sun was just a few degrees below the horizon, so the sky was incredibly bright: these conditions made the imaging quite extreme, but our robotic telescope succeeded in capturing this huge debris.” Image via Gianluca Masi/ Virtual Telescope.

Interestingly, regardless of when the falling debris strikes soil (or ocean), the return of China’s Long March 5B will come just days after the new Spaceflight Assets bill was affirmed by Florida’s legislature. That happened last week, on April 26, 2021. The bill, which had the support of SpaceX, is now awaiting the signature of Florida governor Ron DeSantis. When enacted, the law will go into effect on July 1, and require that anyone who finds “reasonably identifiable” spacecraft parts – in and around Florida at least – must report them to local law enforcement and that the authorities must then make a “reasonable effort” to notify the hardware’s owner. The bill grants entities involved in launching rockets and spacecraft, such as SpaceX, access to private property, if necessary, to recover discarded space-related artifacts. Anyone failing to surrender such artifacts could be charged with “misappropriation of a spaceflight asset,” a first-degree misdemeanor, punishable by up to a year in prison or a $1,000 fine. Violators may even pay additional restitution if the hardware is lost or damaged.

Read more from EarthSky: Florida bill says companies like SpaceX retain ownership of fallen hardware

A hexagonal white panel is displayed, battered and worn, with the writing SpaceX faintly visible.

The parachute cover from SpaceX’s Demo-2 Crew Dragon was recovered by a fishing boat in the Gulf of Mexico, and now sits in a private memorabilia collection belonging to a SpaceX investor. Image via Steve Jurvetson.

China, our world’s most populous country, hopes to have the new station operational by 2022. The only space station currently in orbit is the International Space Station (ISS); China is not an ISS partner, and no Chinese nationals have been aboard. The Chinese government sat out the famous 1960s space race between the Soviet Union and the U.S., which ultimately launched the first humans to the moon in 1969. But, in recent years, China has been making up for lost time. It’s launched several robotic missions to the moon and Mars, as well as successfully landed on the moon’s far side, and made history with its lunar sample return mission.

Meanwhile, Tianwen-1 is a Chinese probe that entered Mars orbit on February 10, 2021. It’s set to land a rover on Mars’ surface this month or in June.

Read more from EarthSky: Chinese rover Zhurong to attempt a Mars landing this month

Bottom line: China’s Long March 5B rocket successfully launched the Tianhe space station module last Thursday, April 29, 2021. That module will become the living quarters of the future Chinese Space Station, and is currently in its correct orbit after separating from the core stage of the rocket as planned. The core stage, however, also reached orbit, and is now on a path to be one of the largest ever pieces of debris to make an uncontrolled re-entry back into Earth’s atmosphere.

Via SpaceNews

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