The unpredictable risk of Space Junk
It may seem absurd that somebody could be killed by space debris that fell from the sky. After all, although there have been incidents of injury and property damage, no one has yet died in such an accident. But do we need to start taking the risk more seriously now that we send more satellites, rockets, and spacecraft into orbit?
A recent study in Nature Astronomy calculates the likelihood of fatalities falling rocket pieces over the next ten years.
We are exposed to the danger of debris falling from space on us every minute. Around 40,000 tonnes of dust are produced annually by the minuscule fragments from asteroids and comets that hover through the atmosphere and land unnoticed on the Earth's surface.
Although we are not affected by this, spacecraft can be harmed by this debris, as was recently reported with the James Webb space telescope. A body ten of meters wide occasionally manages to drive through the atmosphere to create a crater, and occasionally a more significant sample enters the atmosphere as a meteorite.
Additionally, albeit extremely infrequently, kilometre-sized objects can reach the surface and cause death and destruction, as seen by the absence of dinosaurs from the planet today. These are a few examples of natural space debris whose unexpected arrival is unpredictable and dispersed relatively evenly worldwide.
However, the current study focused on the unexpected influx of manufactured space debris from satellites and rocket launches, including discarded rocket stages. The authors calculated the locations of rocket debris and other space junk when they fall back to Earth using mathematical modelling of rocket part inclinations and orbits in space and population density below them, as well as 30 years' worth of preliminary satellite data.
They discovered a slight but significant chance of parts returning in the next ten years. However, this is more likely to occur across southern latitudes than northern ones.
The study calculated that Jakarta in Indonesia, Dhaka in Bangladesh, or Lagos in Nigeria is about three times more likely to have rocket bodies land than New York in the US, Beijing in China or Moscow in Russia.
The authors also estimated the risk to human life from uncontrolled rocket re-entries during the following ten years. They discovered an average 10% risk of one or more casualties during the following ten years, assuming that each re-entry disperses fatal debris across an area of ten square metres.
To date, it has been believed that there is very little chance that satellite and rocket debris will harm the surface of the Earth or air traffic in the atmosphere. Most research on this type of space debris has concentrated on the danger posed in orbit by abandoned satellites that could interfere with the safe operation of active satellites. Explosions in orbit caused by unused fuel and batteries also produce more waste.
However, it is pretty expected that the number of mishaps, both in space and on Earth, like the one that occurred after the launch of the Chinese Long March 5b, will also climb as the number of entries into the rocket launch sector rises and shifts from government to private enterprise. According to the current study, the 10% figure is a modest estimate.
How can organisations Proceed
Regulating debris re-entry is possible thanks to various technologies, but doing so is expensive. For instance, spacecraft can be "passivated," where any remaining energy (such as fuel or batteries) is used up rather than saved after the mission's completion.
A satellite's chosen orbit can potentially lessen the likelihood of junk formation. Instructing a retired satellite to fly into low Earth orbit, where it will burn up, is possible.
Additionally, there have been attempts to launch reusable rockets, such as those developed by Blue Origin and SpaceX. As they return to Earth in a controlled manner, these produce much less debris, but there will be some from paint and metal shavings.
The UN published a set of Space Debris Mitigation Guidelines, which was updated in 2018. These guidelines are not international law and do not specify how Countries should carry out mitigation activities. The European Space Agency is preparing to use a four-armed robot to gather and remove space junk.
Further studies showed that improving technology and more careful mission design would lower the uncontrolled re-entry of spacecraft debris, reducing the danger of hazards worldwide. Uncontrolled rocket body reentries are a collective action issue; solutions are available, but each launching state must embrace them.
Government cooperation is not unusual, as evidenced by the agreement to outlaw ozone-depleting chlorofluorocarbon compounds. Additionally, international agreements and protocol modifications take time. But unhappily, before taking such action, there must be a significant incident with ramifications for the northern hemisphere.
It has been seventy years since NASA sent the first satellite into orbit in five years. It would be appropriate if all UN member states could sign a more vital and binding international treaty on space debris to commemorate that occasion. In the end, such an agreement would be advantageous to all countries.