Space Programme

Hard landing

Did Long March rocket launch go to plan?

Long-March-5B-w

Long March 5B: pre-launch

What counts as a successful rocket launch? Simply getting into space? Presumably any astronauts on board are interested in getting home safely too. But it seems fair to expect that parts of the rocket shouldn’t come crashing back to Earth in an uncontrolled manner, at least?

Going by these criteria, the launch of the Long March 5B carrier rocket on May 5 wasn’t quite the success that China’s space agency has claimed. On May 11, part of its staging – sections normally jettisoned before the spacecraft achieves orbit – came hurtling back to Earth, narrowly missing Los Angeles and New York, before finally coming down somewhere over the Atlantic on Monday morning US eastern time.

Weighing almost 18 tonnes and measuring thirty metres in length, it was one of the largest piece of space debris to make an uncontrolled re-entry since a Soviet space station fell back to Earth in 1991.

Pictures posted to Twitter appeared to show some debris had careered into the Ivory Coast. Seismic and infrasound monitoring stations in the area picked up the impact.

What happened was that the staging components made it into very low orbit and hurtled through space for almost a week. “This rocket stage was just left in low-Earth orbit until friction brought it down. That’s definitely not best practice by international standards,” Jonathan McDowell an astronomer at the Harvard-Smithsonian Center for Astrophysics, told NBC News.

The launch of the Long March 5B came after two other failures to get into orbit earlier this year. This time the rocket managed to leave the Earth’s atmosphere, delivering a cargo vessel and an empty version of a manned spacecraft. The spacecraft returned on May 8 in a landing celebrated as a “complete success”. But the cargo vessel came back to Earth two days earlier in a deorbiting process described by China’s Manned Space Agency as “abnormal”. No further details were given about its descent.

A congratulatory message sent by the Communist Party’s Central Committee, the State Council and the Central Military Commission had hailed the launch as “a good beginning for the country’s space station programme”.

But as WiC went to press on Friday, there was no comment on the uncontrolled plunge of the staging section.

McDowell said it is common for pieces of rockets or satellites to fall back to Earth, though they rarely weigh more than a couple of tonnes and largely disintegrate on re-entry.

Larger objects are less likely to break-up or burn up entirely, which is why is it better to control their re-entry process.

On its last orbit of Earth the staging – including spent fuel tanks and engines – passed directly above Los Angeles and New York. What if it had hit? “It wouldn’t be enough to wipe out New York,” McDowell explained. “It might take out a floor of a building, but either way, that is still more than we need right now.”

Fair point, that sort of thing might have complicated the next round of trade talks with Washington…

The 18 Space Control Squadron – a unit of the US Air Force that tracks objects moving in the Earth’s orbit, confirmed the de-orbiting of the staging section on May 11 and tagged the Tweet #spaceflightsafety and #spacedebris.

Parts of Chinese rockets have landed in populated areas before. Last November sections of a Long March 3B, launched in Sichuan, bashed into a local village, causing a house to catch fire. That’s why many of the international space programmes launch over oceans, in a bid to make cases like these less dangerous.

The Chinese send up more of their rockets over land. In most cases its space agency also plans for the scattering of rocket debris and evacuates the designated landing zones ahead of time. It tells residents – typically in rural and sparsely inhabited areas – not to approach the debris if they find it because it often contains toxic or flammable chemicals.

But in the case of the most recent launch and re-entry, China’s space agency doesn’t seem to have given similar warnings, suggesting that the later events were largely unplanned.


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