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Space & Astronomy

How likely are you to be killed by falling space junk ?

July 26, 2022 | Comment icon 11 comments



Earth's orbit is full of space junk, but just how dangerous is it ? Image Credit: NASA
Scientists have calculated exactly how likely you are to be injured or killed by space debris in the next ten years.
The chance of someone being killed by space junk falling from the sky may seem ridiculously tiny. After all, nobody has yet died from such an accident, though there have been instances of injury and damage to property. But given that we are launching an increasing number of satellites, rockets and probes into space, do we need to start taking the risk more seriously?

A new study, published in Nature Astronomy, has estimated the chance of causalities from falling rocket parts over the next ten years.

Every minute of every day, debris rains down on us from space - a hazard we are almost completely unaware of. The microscopic particles from asteroids and comets patter down through the atmosphere to settle unnoticed on the Earth's surface - adding up to around 40,000 tonnes of dust each year.

While this is not a problem for us, such debris can do damage to spacecraft - as was recently reported for the James Webb space telescope. Occasionally, a larger sample arrives as a meteorite, and maybe once every 100 years or so, a body tens of metres across manages to drive through the atmosphere to excavate a crater.

And - fortunately very rarely - kilometre-sized objects can make it to the surface, causing death and destruction - as shown by the lack of dinosaurs roaming the Earth today. These are examples of natural space debris, the uncontrolled arrival of which is unpredictable and spread more or less evenly across the globe.

The new study, however, investigated the uncontrolled arrival of artificial space debris, such as spent rocket stages, associated with rocket launches and satellites. Using mathematical modelling of the inclinations and orbits of rocket parts in space and population density below them, as well as 30 years' worth of past satellite data, the authors estimated where rocket debris and other pieces of space junk land when they fall back to Earth.

They found that there is a small, but significant, risk of parts re-entering in the coming decade. But this is more likely to happen over southern latitudes than northern ones. In fact, the study estimated that rocket bodies are approximately three times more likely to land at the latitudes of Jakarta in Indonesia, Dhaka in Bangladesh or Lagos in Nigeria than those of New York in the US, Beijing in China or Moscow in Russia.

The authors also calculated a "casualty expectation" - the risk to human life - over the next decade as a result of uncontrolled rocket re-entries. Assuming that each re-entry spreads lethal debris over an area of ten square metres, they found that there is a 10% chance of one or more casualties over the next decade, on average.

To date, the potential for debris from satellites and rockets to cause harm at the Earth's surface (or in the atmosphere to air traffic) has been regarded as negligible. Most studies of such space debris have focused on the risk generated in orbit by defunct satellites which might obstruct the safe operation of functioning satellites. Unused fuel and batteries also lead to explosions in orbit which generate additional waste.

But as the number of entries into the rocket launch business increases - and moves from government to private enterprise - it is highly likely that the number of accidents, both in space and on Earth, such as that which followed the launch of the Chinese Long March 5b, will also increase. The new study warns that the 10% figure is therefore a conservative estimate.
What can be done

There are a range of technologies that make it entirely possible to control the re-entry of debris, but they are expensive to implement. For example, spacecraft can be "passivated", whereby unused energy (such as fuel or batteries) is expended rather than stored once the lifetime of the spacecraft has ended.

The choice of orbit for a satellite can also reduce the chance of producing debris. A defunct satellite can be programmed to move into low Earth orbit, where it will burn up.

There are also attempts to launch re-usable rockets which, for example, SpaceX has demonstrated and Blue Origin is developing. These create a lot less debris, though there will be some from paint and metal shavings, as they return to Earth in a controlled way.

Many agencies do take the risks seriously. The European Space Agency is planning a mission to attempt the capture and removal of space debris with a four-armed robot. The UN, through its Office of Outer Space Affairs, issued a set of Space Debris Mitigation Guidelines in 2010, which was reinforced in 2018. However, as the authors behind the new study point out, these are guidelines, not international law, and do not give specifics as to how mitigation activities should be implemented or controlled.

The study argues that advancing technologies and more thoughtful mission design would reduce the rate of uncontrolled re-entry of spacecraft debris, decreasing the hazard risk across the globe. It states that "uncontrolled rocket body reentries constitute a collective action problem; solutions exist, but every launching state must adopt them."

A requirement for governments to act together is not unprecedented, as shown by the agreement to ban ozone layer-destroying chlorofluorcarbon chemicals. But, rather sadly, this kind of action usually requires a major event with significant consequences for the northern hemisphere before action is taken. And changes to international protocols and conventions take time.

In five years, it will be 70 years since the launch of the first satellite into space. It would be a fitting celebration of that event if it could be marked by a strengthened and mandatory international treaty on space debris, ratified by all UN states. Ultimately, all nations would benefit from such an agreement.

Monica Grady, Professor of Planetary and Space Sciences, The Open University

This article is republished from The Conversation under a Creative Commons license.

Read the original article.

Source: The Conversation | Comments (11)


Recent comments on this story
Comment icon #2 Posted by acute 16 days ago
The other day..... as I was walking into Greggs for a Chicken Bake and a Sausage Roll, I was hit from above by a 2.5mm plasterboard screw!  None of the builders renovating the flat above were visible, so I'm suing NASA for $5m.    
Comment icon #3 Posted by jethrofloyd 15 days ago
If the Skylab didn't hit me in the head when I was a boy, I'm not afraid of the space junk anymore.
Comment icon #4 Posted by Portre 15 days ago
Great. Something else to keep me up at night worrying 
Comment icon #5 Posted by L.A.T.1961 15 days ago
Debris from massive Chinese booster rocket could fall to Earth early next week The 23-ton Long March 5B rocket which carried the Wentian laboratory module, took off from Hainan Island at 2:22 p.m. local time Sunday, July 24, and the module successfully docked with China's orbital outpost. Its job completed, the rocket has gone into an uncontrolled descent toward Earth's atmosphere and it's not clear where it will land. The uncontrolled descent marks the third time that the country has been accused of not properly handling space debris from its rocket stage. https://edition.cnn.com/2022/07/26/c... [More]
Comment icon #6 Posted by psyche101 6 days ago
If this hit you, it wouldn't be pretty.   https://www.google.com/amp/s/amp.abc.net.au/article/101277542 I wonder if Elon wants it back?
Comment icon #7 Posted by openozy 6 days ago
What the space junk or the stout farmer? 
Comment icon #8 Posted by psyche101 6 days ago
Good one! Still laughing while I write this... 
Comment icon #9 Posted by Grim Reaper 6 6 days ago
The odds are much better that you may get killed by falling US Army Airborne Soldier, or his Tracked Vehicle !  Whose main Parachute fails and his Reserve Parachute is released and tangles in the main because he didn't release or cut it lose before deploying the reserve parachute, which would cause the poor soldier or his Vehicle to Roman Candles from 10,000 ft! Bo diddley Bo diddley have you heard"" I'm going to jump from a big bird"" Standup Hookup Shuffle to the door and jump right out on the count of 4""  If my main don't open I have a reserve by my side"" If that one should fail me too lo... [More]
Comment icon #10 Posted by psyche101 6 days ago
Whoa!!! That's an incident worth mentioning! Lol, I have to admit, I watched the A Team on the telly a couple nights ago. This instantly reminded me of the scene where they leave the plane in a tank..... Cheers mate, you have the most interesting stories to tell!!
Comment icon #11 Posted by Grim Reaper 6 6 days ago
Well honestly that’s not my photo, I down loaded, because of the comments in the Thread. However, in 1985 when I was stationed at Ft. Stewart, Georgia we went to the Nation Training Center in the Mohave Desert in California! I was assigned to the 24th Infantry Division at the time. It was February 1982 when we arrived at the Mohave Desert for Operation Gallant Eagle which was one of the largest training exercises in close to15 years and with the largest Airborne Operation since WWII carried out by the 82nd Airborne Division. The concept was simple the 82nd was a Light Davison that could Air in... [More]


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