When you gaze at the starry sky, you may have already noticed bright points moving quickly. These are satellites, whose numbers are constantly increasing. But what happens when these spacecraft fall back to Earth? A recent study provides unexpected answers, revealing potential risks for populations on the ground.
Canadian researchers examined eleven satellite megaconstellations, representing over 73,000 spacecraft. Their calculations show that if these satellites do not completely disintegrate during their atmospheric reentry, the collective risk of injury or death on the ground, thus taking into account all spacecraft, could reach 40%. This estimate takes into account the materials used in satellite construction, with major implications for public safety.
Materials like aluminum tend to melt entirely, but others, such as stainless steel or titanium, better resist intense heat. These components are often found in fuel tanks and reaction wheels (flywheels). During reentry, aerodynamic forces break up the satellites, and heat ablates the materials into fine particles. However, many satellites, especially the larger ones, do not burn up completely, leaving debris that can reach the ground.
Uncertainty remains about the ability to guarantee total disintegration. If debris withstands, it can scatter over a wide area during an uncontrolled reentry. Currently, safety standards often do not take into account the cumulative effect of thousands of satellites. This poses a risk not only for people on the ground but also for aircraft in flight and infrastructure, requiring increased attention.
Researchers mention in their analysis the possibility of designing constellations with fewer satellites, but with greater capacity and lifespan. This approach would reduce risks and potential damage. Their study, published in the journal
Space Policy, demonstrates the need for thorough reflection on current space practices and their long-term consequences.
From the International Space Station, SpaceX's Starlink satellites are visible as bright trails above Earth, accompanied by lightning and city lights. Credit: Don Petit/NASA
To mitigate these dangers, the team recommends several measures. States and regulators should require independent verification of claims about complete disintegration. It is important to assess risks not on a single satellite but on the entire fleet and to work towards a controlled reentry regime, applicable globally.