What are the odds of a free-fall missile killing someone somewhere in the world? There is about a 10 percent chance within the next decade if current practices in the space industry remain the same, according to the authors of a new research paper published in the journal natural astronomy.
While this is not a significant risk, the threat is much greater in some parts of the world than in others. In particular, many countries in The global south is likely to handle a larger share of space waste even though they are not responsible for it, according to the analysis. It could become an even bigger problem as rockets are launched into space frequently to transmit an increasing number of satellites.
“It’s a statistically low risk, but it’s not insignificant, and it’s increasing — and completely avoidable,” says Michael Byers, lead author of the analysis and professor in the University of British Columbia’s Department of Political Science. So, should we take available measures to eliminate the risk of injuries? I think the answer should be yes.
When rockets propel themselves into space, they usually drop deadly weights – launching “stages” or rocket bodies containing empty fuel tanks and engines that are no longer useful for launch. Some rockets drop boosters before reaching orbit and can target the oceans with some precision (this helps the oceans cover most of the Earth’s surface).
If a rocket has already reached orbit, that equipment can be safely guided back to Earth, back into the ocean, using engines that can re-ignite. SpaceX has also become famous for the landing parts of its Falcon 9 rocket so they can be reused again, and the company also performs controlled orbital eliminators for the parts it can’t memorize.
Some rocket stages are still left in orbit after launch – which is what this new paper focuses on.
To date, there have been no documented deaths from uncontrolled missile entry into the atmosphere. But in 2020, a 12-meter tube and other debris from a Chinese Long March 5B rocket fell into two villages in Ivory Coast.
There was another nail-biting last year when the stage of a 100-foot-high, nearly 20-metric-ton Chinese rocket sank to the ground. It finally fell into the Indian Ocean after scaring cities like New York and Madrid under its path. This was the spark for research that Byers led, with the help of his son, an undergraduate at the University of Victoria who is another author on the paper.
Looking back at the past 30 years of rocket launches, Byers and colleagues found that Jakarta, Indonesia, Mexico City, Mexico, Lagos, and Nigeria are at least three times as likely to see an unattended missile object re-enter the atmosphere above them than Washington. , Capital and New York City in the United States.
“The risk on an individual level is really small… [but] “If you live in a densely populated city at 30 degrees north latitude, that should be your biggest concern,” Byers said. That’s because much of the debris from uncontrolled reentries comes from rockets that launch net payloads into geosynchronous orbit, which roughly follows the equator and allows the satellite to match the Earth’s rotation. There is also a “significantly increased risk” about 30 degrees north of the equator due to population density at that latitude, according to Byers.
If governments impose changes and the space industry is willing to incur the additional costs, that risk may disappear. The newly published paper points to international agreements that could serve as an example, such as the 1987 Montreal Protocol that phased out much of the ozone-depleting substances previously used as refrigerants in air conditioners and refrigerators. This could mean carrying smaller payloads so that there is enough fuel left to safely guide the discarded rocket stage back to Earth. Fortunately, it appears that the industry is already starting to adapt.
The current common practice still stands, ‘Well, that’s too bad. We will leave the rocket stage in the geographical transfer orbit and make it re-enter uncontrollably. And that is starting to change, particularly in the United States,” says Jonathan McDowell, an astrophysicist at Harvard University. Space Force, for example, now Deorbit missile launch providers require missile stages. SpaceX is designing a next-generation rocket called the Starship that is supposed to be completely reusable.
“General practice with respect to flight is to maximize safety. And we think the same approach should be taken for space launches,” Byers says. So while it’s still not likely that pieces of a free-fall rocket will land on anyone’s head, he believes Byers says there is more that can be done to make spaceflight as safe as possible.
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