Explained: Why a China rocket crashing in Indian Ocean has drawn NASA flak

Debris from a Chinese rocket Sunday made an uncontrolled re-entry into the Earth’s atmosphere and disintegrated over the Indian Ocean, with remnants falling at a location to the west of Maldives.

The debris came from the upper stage of a Long March 5B rocket– China’s largest– that had been launched into space on April 29 for putting into orbit a core module of the new Tianhe space station, which is expected to become operational in 2022.

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For days, there had been speculation on whether the debris would hit a populated area on the Earth’s surface, leading NASA to criticise China on Sunday over lack of transparency and for “failing to meet responsible standards”.

Why did the Chinese rocket spark worry?

When a rocket is launched, its discarded booster stages re-enter the atmosphere soon after liftoff and harmlessly fall into the ocean– a standard practice. In this case, however, a 10-floor large vehicle of the rocket weighing 18 metric tonnes went into orbit along with the section of the under-construction space station that it was carrying.

While in orbit, this vehicle kept rubbing against the air at the top of the atmosphere, and the resulting friction caused it to start losing altitude. The piece hurtled through a low-Earth orbit at roughly 25,490 km/hr, traced by the US military, Live Science reported.

An “uncontrolled re-entry” thus became inevitable, but China did not admit this fact to the world until Sunday, when it said the debris had entered the Earth’s atmosphere over the Mediterranean, flown over the Arabian peninsula and crashed near the Maldives at 72.47° East and 2.65° North.

Few expected the debris to harm humans, mainly due to most of it burning up in the atmosphere, as well as the fact that large parts of the Earth are covered by oceans and massive land areas lie uninhabited.

Still, the incident has raised questions about the space technology that China is developing, and the probability of harm being caused to populated areas in the future.

In May last year, pieces from another Long March rocket of the same 5B variant had crashed on Ivory Coast in what became the largest uncontrolled debris fall since the collapse of the former Soviet space station Salyut 7 in 1991. While no injuries were reported in the crash, many buildings were damaged, according to Reuters.

So, what caused the rocket piece to enter into orbit?

When rockets carry their payload into space, their booster stages that reach orbit fire the engine again after completing their job so as to drop back to Earth and not remain in orbit. Space agencies plan this process to ensure that such rocket parts end up in uninhabited areas, such as the middle of the ocean.

According to a New York Times report, China chose not to do this for its Long March rocket, leading to its vehicle crashing back uncontrollably. China’s plan to launch 10 more missions like this until 2022 to complete the Tianhe has thus sparked worry that pieces from its rockets could end up causing injuries.

Have such out-of-control crashes taken place before?

In March this year, a SpaceX rocket stage made an uncontrolled landing on a farm in Washington state in the US, but this happened due to a malfunction in the engine tasked to bring it down, and not by choice.

Even before this, in 1979, when the NASA space station Skylab was brought down, some of the debris ended up in Australia, leading to an apology from then-US President Jimmy Carter.

In 1978, when a nuclear-powered Soviet satellite crashed in Canada, Moscow was forced to bear a part of the expense gone into cleaning the radioactive debris, the NYT report said.

How has the US reacted?

As reports emerged of the rocket part’s re-entry, US Defence Secretary Lloyd Austin ruled out shooting it down, but blamed China for being negligent in allowing it to fall out of orbit.

The Chinese Communist Party-run newspaper Global Times, however, dismissed criticism of the rocket being “out of control” and potentially dangerous as “Western hype”.

After the debris re-entry on Sunday, NASA Administrator Bill Nelson said in a statement, “Spacefaring nations must minimize the risks to people and property on Earth of re-entries of space objects and maximize transparency regarding those operations,” adding, “It is clear that China is failing to meet responsible standards regarding their space debris.”