How and why space debris are already an hazard
Earth’s radius is more than 6 thousand kilometers (something around a mean of 6370, depending on latitude). Can you imagine a such a big sphere in your mind? Well, let’s now surround that sphere with more than 20 thousand objects. Here what it would look like:
We’ll leave to you the pleasure of discovery by searching on the internet what is the damage that a small object of one centimeter of diameter can do by traveling at 50 thousand kilometers per hour of relative speed and hitting another object, maybe a telecomm satellite, or maybe a module of the ISS or an astronaut performing an EVA…
They clearly appear in the 1960s with the first space missions and the trend is increasing reaching the count of 20,000 objects in the last years.
If you are wondering, those objects are not yet trackable by today’s technology. «Space object catalogues, as generated and maintained by space surveillance networks, are limited to larger objects, typically greater than 10 cm in low-Earth orbits (LEO, below about 2000 km) and greater than 0.3–1 m at geostationary orbits (GEO, about 36 000 km). These sensitivity thresholds are a compromise between system cost and performance», reports ESA on its website. Indeed, only a very small part of the total space debris can be tracked by in-situ impact detectors, like satellites.
What cannot be done through the self-deorbiting of a satellite or leaving the gravity to take down the objects, could be down by actively removing objects, starting from the most critical ones. Active removal can be more efficient in terms of the number of collisions prevented versus objects removed. Studies at ESA and NASA show that with a removal sequence planned according to a target selection based on mass, area, or cumulative collision risk, the environment can be stabilized when on the order of 5–10 objects are removed from LEO per year.
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