Scientists estimate the risk of human casualties due to falling rocket debris

(ORDO NEWS) — While the chances of space rocket fragments “coming back” to Earth, injuring or killing someone are slim, and most are likely to fall into the ocean or somewhere safe, researchers warn risks increase over time.

There is a 10% chance that fragments of a rocket launched into space will fall to Earth after its uncontrolled re-entry into the atmosphere, a study by scientists from the University of British Columbia (Vancouver, Canada) showed.

According to the authors of the work, in 2020, after at least 60% of launches into low Earth orbit, rocket bodies remained there for several days, months or even years, eventually presenting a risk of collision with satellites, falling and killing people on land, sea and in airplanes.

For a long time, this was not given importance, but space launches are becoming more and more, as well as space debris.

You don’t have to look far for examples: in May 2020, the 18-ton main stage of the Chinese Long March -5B rocket entered the dense layers of our planet’s atmosphere uncontrollably after launching a prototype of a new generation of manned spacecraft into orbit. The wreckage of the hull fell on two villages in West Africa, damaging several buildings.

A year later, in the spring of 2021, Beijing launched the heavy Long March 5: it successfully launched the first module of China’s new Tiangong space station into LEO. Fragments fell into the Indian Ocean, although most burned.

According to scientists, these two stages were the heaviest objects that returned uncontrollably to our planet since the Soviet Salyut-7 station in 1991, when it entered the Earth’s atmosphere at a speed of over 30 thousand kilometers. Of course, in the case of Chinese launches, the United States hastened to immediately blame the Celestial Empire.

“But there is no international consensus on an acceptable level of risk, and other spacefaring nations, including the US, are making similar choices regarding uncontrolled re-entries,” the researchers noted, recalling 2016, when a SpaceX rocket entered the atmosphere over Indonesian territory.

In the United States, standard Orbital Debris Prevention ( ODMSP ) practices apply to space launches: the risk of accidents from a rocket re-entry must be below the 1 in 10,000 threshold (yet scientists describe it as meaningless in an era when there are the ability to create reusable media).

And sometimes they close their eyes to the demands. Thus, the US Air Force abandoned ODMSP in 37 launches of 66 conducted on their order from 2011 to 2018.

The argument was that it was too expensive to replace non-compliant missiles. NASA, in turn, ignored the requirements seven times from 2008 to 2018, including during the launch of Atlas V in 2015, when the risk of accidents was estimated at 1 in 600.

“Launch consequences depend on the carrier model. Some have “boosters” that are dropped suborbitally and usually into the ocean.

If the main stage reaches the orbit, it is either left there (as in the case of the Long March-5V), or returned back in a controlled manner. When a stage exits at a sufficiently low perigee, gas drag gradually reduces its altitude and eventually leads to an uncontrolled re-entry into the atmosphere, which can occur at any point in the flight path.

On the contrary, during controlled re-entry from orbit, the engine is activated to send the stage to a remote area of ​​\u200b\u200bthe ocean or other safe zone, ”the article says.

The authors used 30 years of publicly available data on population densities, rocket launches, orbital inclination and space debris to calculate an approximate number of casualties due to falling debris of this kind.

From May 1992 to May 5, 2022, more than one and a half thousand man-made objects descended from orbit: over 70% of them did it uncontrollably. Reentry was considered unmanageable if the time interval between launch and reentry dates was more than a week.

Scientists have focused on carrier fragments that remain partially intact and pose a danger to humans. Calculations have shown that if each uncontrolled reentry results in debris scattered over an area of ​​ten square meters, over the next decade with a probability of 10% there will be one or more related accidents – directly on the ground, at sea or in a flying aircraft. .

Jakarta and Dhaka, the capitals and largest cities of Indonesia and Bangladesh, respectively, as well as Lagos, the sea gates of Nigeria, were at particular risk.

The chances of rocket debris falling on their inhabitants were three times higher than for New York, Beijing. However, as the authors of the study note, both estimates are conservative, as the number of launches is growing rapidly.

Since the technologies for re-entry and thus controlled descent already exist, the only thing we lack is the collective will to use such developments due to the costs associated with them.

“Recent advances in technology and mission design make most uncontrolled re-entries unnecessary, but governments and launch companies don’t want to incur costs.

Therefore, governments whose populations are at risk should demand that the major space powers act in concert by authorizing controlled reentry of rockets into the atmosphere, and non-compliance with the requirements should have meaningful consequences, ”the scientists concluded.


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